Lakes are sensitive recorders of anthropogenic activities, as human society often develops in their vicinity. Lake sediments thus have been widely used to reconstruct the history of environmental changes in the past, anthropogenic, or otherwise, and radiocarbon dating provides chronological control of the samples. However, specific values of radiocarbon in different carbon reservoirs due to the different pathways of radiocarbon from the upper atmosphere to the lake, called the radiocarbon reservoir age, is always difficult to evaluate because of dynamic processes in and around lakes. There are few systematic studies on radiocarbon reservoir ages for lakes owing to the complex radiocarbon transfer processes for lakes. Here, we investigate lake waters of the Fuji Five Lakes with monthly monitoring of the radiocarbon reservoir effects. Radiocarbon from dissolved inorganic carbon (DIC) for groundwater and river water is also measured, with resulting concentrations (Δ14C) at their lowest at Lake Kawaguchi in August 2018 (–122.4 ± 3.2‰), and at their highest at Lake Motosu in January 2019 (–22.4 ± 2.5‰), despite a distance of 25 km. However, winter values in both lakes show similar trends of rising Δ14C (about 20‰). Our lake water DIC Δ14C results are compared to previously published records obtained from sediments in Lake Motosu and Lake Kawaguchi. These suggest that total organic carbon and compound-specific radiocarbon found in sediments are heavily influenced by summer blooms of aquatic organisms that fix DIC in water. Thus, future studies to conduct similar analyses at the various lakes would be able to provide further insights into the carbon cycle around inland water, namely understanding the nature of radiocarbon reservoir ages.

Reconstructing past terrestrial environments is vital for a comprehensive understanding of the Anthropocene. Various techniques have been employed to this end, including the utilization of speleothems and tree-ring archives (e.g., Sakashita et al., 2017; Cheng et al., 2020), but lake sediments are unique as they are distributed widely in many parts of the world. In some lakes, annual varve counting techniques can be used to establish sediment chronology and quantify the timing of past environmental changes (e.g., Bronk Ramsey et al., 2012), but the majority of lake sediment studies rely on radiocarbon dating (e.g., Nakamura et al., 2016; Yamamoto et al., 2018; Ghazoui et al., 2019; Safaierad et al., 2020). Radiocarbon (14C) measurements require careful consideration of the local radiocarbon reservoir effects (e.g., Jull et al., 2013; Yokoyama et al., 2019a). The radiocarbon reservoir effect is a phenomenon in which the 14C ages of water and sediments have an older 14C age than the ambient atmospheric radiocarbon ages due to the exchange of 14C-depleted carbon stored in soil or host rock (Ascough et al., 2010). Although freshwater ecosystems fix carbon from the atmosphere, dissolved carbon can also enter the lake water via groundwater. If the dissolved inorganic carbon (DIC) is derived from eroded carbonaceous bedrock, it may have very low amounts of 14C and lead to a reservoir age in the catchment or basin area (Broecker and Walton, 1959).

Since radiocarbon reservoir ages reflect hydrosphere dynamics, there are many studies that consider changes in seawater radiocarbon in the ocean with time (e.g., Hirabayashi et al., 2017, 2019; Ota et al., 2019; Servettaz et al., 2019). However, few systematic lake water reservoir age studies have been reported. The radiocarbon reservoir effect of lakes has been reported in many areas, with some areas having a sediment radiocarbon reservoir age of more than 1,500 years (e.g., Nakamura et al., 2016, Schneider et al., 2019). One source of atmospheric 14C to consider is bomb-derived 14C produced in the atmosphere during the nuclear weapons tests in the 1950s. “Bomb-14C” increased rapidly during the decade of weapons testing (Broecker and Walton, 1959), then decreased due to exchange between the atmosphere and other carbon reservoir such as the oceans and biosphere (Sweeney et al., 2007). Subsequently, usage of fossil fuels has been increasingly important to reduce atmospheric 14C level (Suess effect; Suess, 1955). In addition to atmospheric 14C, groundwater and/or river water may be the source of lake 14C (Brady et al., 2009). Yu et al. (2007) constructed a mass balance model considering variations in 14C due to changes in atmospheric, groundwater, and river water inflow or outflow. It has been suggested that the contribution of 14C from these sources may vary due to environmental changes including anthropogenic forcing, such as the use of fossil fuels (Graven, 2015; Blattmann et al., 2018). However, few studies mention the time scale of the variation of radiocarbon reservoirs in lake water. Therefore, systematic sampling and analysis are needed to estimate reliable radiocarbon reservoir ages of lake water, including measurements on groundwater and river water.

The Fuji Five Lakes were selected for this study in order to monitor DIC radiocarbon fluctuations in lake water. Their proximity to each other allows us to collect water monthly from each of the lakes. The lakes are situated within 40 km from the flank of Mount Fuji. It is a unique research setting to understand lake dynamics because the size and depths of each lake are different (Table 1). Water stored in the Fuji Five Lakes is sourced from precipitation, groundwater, and surface water. Geological and hydrological surveys were conducted in the mid-1940s and 1960s for groundwater resource development (Hamano, 1976), and the regional hydrology was studied by Hayashi and Tsuboi (2005), reporting the source distribution of groundwater by utilizing hydrogen and oxygen isotope ratios. In recent years, chlorofluorocarbons (CFCs) and tritium measurements have been used to estimate groundwater ages (Asai and Tsujimura, 2010). However, the degree of groundwater contribution has not been determined due to limitations in the earlier studies (e.g., Ochiai, 1995).

Table 1.

Summary of sizes, depth, altitude, and retention time of Fuji Five Lakes (Geospatial Information Authority of Japan and Yamanashi Prefecture, 1993). DOI: https://doi.org/10.1525/elementa.2020.00149.t1

LakeMotosuShojiSaiKawaguchiYamanaka
Area (km24.7 0.5 2.1 5.7 6.8 
Altitude (m) 900 900 900 831 981 
Maximum depth (m) 121.6 15.2 71.7 14.0 13.3 
Average depth (m) 67.9 3.7 34.8 9.8 9.2 
Retention time (year) 7.9 0.11 2.3 0.37 0.52 
LakeMotosuShojiSaiKawaguchiYamanaka
Area (km24.7 0.5 2.1 5.7 6.8 
Altitude (m) 900 900 900 831 981 
Maximum depth (m) 121.6 15.2 71.7 14.0 13.3 
Average depth (m) 67.9 3.7 34.8 9.8 9.2 
Retention time (year) 7.9 0.11 2.3 0.37 0.52 

In this study, DIC radiocarbon was measured monthly for the Fuji Five Lakes. The results are discussed in regard to local hydrological dynamics. Previously measured sediment total organic carbon (TOC) and compound-specific radiocarbon data were compared to DIC radiocarbon data for Lake Motosu and Lake Kawaguchi in order to examine local reservoir ages in the context of paleo environmental studies using lake sediment.

The Fuji Five Lakes are dammed lakes formed by the volcanic activity of Mt. Fuji. They are surrounded to the north by the Misaka and Tanzawa Mountains and to the south by Mt. Fuji (Takeuchi et al., 1995). The groundwater stream boundary 50 m underground was found by a survey conducted previously at altitudes of 900 m to 1,000 m at the foot of Mt. Fuji (Hamano, 1976). Most of the lake water in the Fuji Five Lakes is considered to be derived from the Mikasa or Tanzawa Mountains, and groundwater from Mt. Fuji is thought to rarely flow into the lake (Hamano, 1976). The section below 50 m is an impermeable layer, and groundwater has been shown to move along the buried fossil valley through the permeable upper layer (Ogata et al., 2014; Yamamoto et al., 2017a).

The map, water level, elevation, and water depth of the Fuji Five Lakes are shown in Figure 1 and Table 1. Lakes Motosu, Shoji, and Sai are situated at around 900 m above sea level, whereas Lake Kawaguchi, on the east side of Lake Sai, is 831 m above sea level. Lake Yamanaka is the most eastern lake in the five lakes area and has an altitude of 981 m. There are no rivers that constantly discharge to or from the lakes, other than for Lakes Kawaguchi and Yamanaka. However, lake water is artificially released from Lake Motosu to the Fuji River, from Lake Sai to Lake Kawaguchi, and from Lake Kawaguchi to the Katsura River.

Figure 1.

Figures showing (a) map of Japan, (b) locations of Mount Fuji and the Fuji Five Lakes, and (c) west to east schematic cross section of Fuji Five Lakes (modified from Yamamoto, 1971). DOI: https://doi.org/10.1525/elementa.2020.00149.f1

Figure 1.

Figures showing (a) map of Japan, (b) locations of Mount Fuji and the Fuji Five Lakes, and (c) west to east schematic cross section of Fuji Five Lakes (modified from Yamamoto, 1971). DOI: https://doi.org/10.1525/elementa.2020.00149.f1

Lakes Motosu, Sai, and Shoji are located to the northwest of Mount Fuji (Figure 1). Lava flows cover the southern side of the Lakes Sai and Shoji from the surface to 135 m in depth (Chiba et al., 2010), and at the eastern side of Lake Motosu, a lava flow of 167 m thick was reported (Koshimizu et al., 2007). This characterizes the high underwater flow velocity (Ochiai, 1995). The other 3 sides are surrounded by the steep Misaka mountains of 1,000 m to 1,800 m, and there is no constant river inflow or outflow. Hamada et al. (2012) conducted a yearlong vertical survey of water temperature and water quality, noting that precipitation dominated the water balance.

Lake Kawaguchi is the lowest of the Fuji Five Lakes at an altitude of 831 m, with the southern shore of Lake Kawaguchi covered by lava from Mount Fuji (Takada et al., 2016). The other 3 sides are surrounded by Misaka Mountains with an altitude of 1,400 m to 1,700 m. The inflowing water from Rivers Tera and Oku from the Misaka Mountains is considered to be mainly underground water (Yoshizawa and Mochizuki, 2005; Yamamoto et al., 2017a). Groundwater resources have been investigated by Hamano (1976), and the outflow from the lake is suggested to be due to the underground valley structure in the southeastern part of Lake Kawaguchi (Yoshimura and Kawada, 1942; Kanno et al., 1986; Hayashi and Tsuboi, 2005; Ogata and Kobayashi, 2015; Yamamoto et al., 2017b). Mt. Fuji lava does not contain rocks such as limestone that reduce Δ14C, but calcareous rock layers have been reported in the Misaka Mountains to the northern side of the Fuji Five Lakes (Matsuda, 2007).

To the southwest of Lake Yamanaka, sediments of gently sloping volcanic foot fans from Mt. Fuji overlap, and from the north to the east, the Tanzawa mountains with an altitude of 1,200 m to 1,400 m of mountains. The Tanzawa Mountains around Lake Yamanaka are classified as impervious layers. The groundwater level of the Ichinosuna and Ohori rivers that inflow into the lake is higher than that of the western parts of the lake (Susuki and Taba, 1994).

Sampling

Lake water was collected each month from June 2018 to April 2019 at the surface (0.5 m) of each lake for Δ14C measurements (Figure 2b). A 250-ml glass bottle shaded with aluminum was used for water sampling, and 56 lake water samples were collected. Various other water samples were also analyzed to compare Δ14C values, including groundwater (wells: n = 11) and river water (n = 6). For Lake Shoji, we were unable to collect lake water samples because we did not receive sampling approval in time, but we hope to measure lake water from Lake Shoji in the future. Groundwater was collected from drinking water wells in Fujikawaguchiko town and Narusawa and Yamanakako village. We chose sampling sites for each lake from at least 2 locations to identify the sources of lake water, namely, one for the Mt. Fuji side and the other close to the Misaka Mountains. River water was collected in the autumn when the average flow rate was at a high. Water samples from the Tera and Oku Rivers in the Misaka Mountains around Lake Kawaguchi were collected in October and November 2019. For Lake Yamanaka, river water from the Ohori River and Ichinosuna River were collected in November and December 2019.

Figure 2.

Figures showing (a) time-series analytical results of lake water radiocarbon and (b) sampling sites of water and spatial distributions of radiocarbon results. Lake water was sampled monthly from Lakes Motosu, Sai, and Yamanaka, from Lake Kawaguchi Central, and Lake Kawaguchi eastern side (Funatsu) from June 2018 to April 2019. Groundwater was collected to assess water sources on either the Mt. Fuji side of the watershed and on the Misaka mountains side. River water was sampled during October 2019 and November 2019. DOI: https://doi.org/10.1525/elementa.2020.00149.f2

Figure 2.

Figures showing (a) time-series analytical results of lake water radiocarbon and (b) sampling sites of water and spatial distributions of radiocarbon results. Lake water was sampled monthly from Lakes Motosu, Sai, and Yamanaka, from Lake Kawaguchi Central, and Lake Kawaguchi eastern side (Funatsu) from June 2018 to April 2019. Groundwater was collected to assess water sources on either the Mt. Fuji side of the watershed and on the Misaka mountains side. River water was sampled during October 2019 and November 2019. DOI: https://doi.org/10.1525/elementa.2020.00149.f2

Method

A few drops of mercurous chloride (HgCl2) were added to each sample to suppress biological activity after water collection. The samples were processed using the bubbling method (McNichol et al., 1994); 4 ml of phosphoric acid were added to 250 ml of lake water, and bubbling was carried out for 15 min in a glass tube filled with 60 mPa of helium gas to strip CO2 liberated from DIC. During this process, water vapor is released along with the CO2 gas, so 2 cryogenic traps containing ethanol cooled to –120°C were used to remove the water vapor. The CO2 was captured in a liquid nitrogen trap (Servettaz et al., 2019). The CO2 collected was processed under the protocol described in Yokoyama et al. (2007): CO2 was injected into a quartz tube together with 4 mg of iron powder pre-reduced at 450°C and graphitized by heating at 630°C for 6 h. The samples were measured using a single-stage accelerator mass spectrometer at the University of Tokyo Atmosphere and Ocean Research Institute (Yokoyama et al., 2019b).

Throughout this study, we report Δ14C using Equation 1, where x is the year of the sample measurement, and F is the fraction modern carbon as was defined in a previous study (Stuiver and Polach 1977).

Δ14C=Fe1950x/82671 × 1000 ‰,
1

where radiocarbon age and F can be written as follows (Donahue et al., 1990):

 14C age = 8033 ln F.
2

The radiocarbon reservoir age (R) expresses the difference in the age of the lake DIC and the contemporary atmosphere, in radiocarbon years. R can be written as follows:

R=radiocarbon agelake DICradiocarbon age atmosphere.
3

Substituting Equations 1 and 3, the following relationship between R and F can be obtained:

R=8033lnFlake8033lnFatm=8033lnFlakelnFatm
4
R=8033lnFlakeFatm=8033lnFatmFlake.

Solving Equation 1 for F, and substituting into Equation 4, we get a relationship between R and ▵14C:

R=8033ln(Δ14Catm/1000)+1(Δ14Clake/1000)+1.
5

Thus, the 14C offset between the lake water and the ambient atmosphere is presented in the current study, and the younger (smaller) the Δ14C provides the older (larger) the radiocarbon reservoir ages (e.g., Yokoyama et al., 2000; Hirabayashi et al., 2019; Fukuyo et al., 2020).

Radiocarbon measurement in lake water

The results of radiocarbon measurements are listed in Table 2 and Figure 2. The Δ14C in Lake Motosu was at its highest value in January (–22.4 ± 2.5‰), and the lowest was recorded in June (–53.8 ± 4.3‰). Winter average values were calculated to be around –20‰, but the values from summer to autumn, that is, between July and November, showed average values of around –30‰. It was not possible to measure the radiocarbon content of the lake water sample obtained in December from Lake Motosu due to the extremely small concentration of CO2 gas in the sample.

Table 2.

Radiocarbon results of lake water, groundwater, and river water dissolved inorganic carbon radiocarbon. DOI: https://doi.org/10.1525/elementa.2020.00149.t2

Lab. No.LocationDateΔ14C (‰)Error (±)14C Age (yBP)Error (±)
Lake Water 
YAUT-051526 Motosu 06/06/2018 –53.8 4.3 377 37 
YAUT-047429 Motosu 11/07/2018 –33.2 2.6 204 22 
YAUT-047431 Motosu 01/08/2018 –31.7 3.0 192 25 
YAUT-047432 Motosu 10/09/2018 –28.9 2.8 168 23 
YAUT-047433 Motosu 03/10/2018 –30.4 2.4 181 20 
YAUT-047436 Motosu 07/11/2018 –36.6 2.5 233 21 
N/A Motosu 05/12/2018 N/A N/A N/A N/A 
YAUT-047437 Motosu 09/01/2019 –22.4 2.5 115 21 
YAUT-047438 Motosu 06/02/2019 –22.7 3.0 118 24 
YAUT-047439 Motosu 06/03/2019 –22.6 2.6 117 22 
YAUT-046617 Sai 05/06/2018 –47.3 5.9 322 50 
YAUT-046618 Sai 03/07/2018 –35.9 5.3 226 44 
YAUT-046619 Sai 06/08/2018 –38.7 4.1 250 34 
YAUT-046623 Sai 11/09/2018 –25.3 2.3 139 19 
YAUT-046817 Sai 02/10/2018 –32.5 2.4 198 20 
YAUT-046818 Sai 06/11/2018 –41.6 2.0 275 17 
YAUT-046819 Sai 04/12/2018 –35.7 2.3 225 19 
YAUT-046936 Sai 08/01/2019 –43.4 2.9 289 24 
YAUT-046937 Sai 05/02/2019 –37.3 3.1 238 26 
YAUT-046938 Sai 05/03/2019 –34.3 5.5 213 46 
YAUT-046939 Sai 16/04/2019 –32.0 2.7 194 22 
YAUT-046219 Kawaguchi Funatsu 05/06/2018 –95.1 4.0 735 35 
YAUT-046223 Kawaguchi Funatsu 03/07/2018 –101.4 2.0 792 18 
YAUT-046224 Kawaguchi Funatsu 06/08/2018 –104.8 4.8 822 43 
YAUT-046225 Kawaguchi Funatsu 11/09/2018 –118.3 2.4 944 22 
YAUT-046226 Kawaguchi Funatsu 02/10/2018 –120.7 3.1 966 29 
YAUT-046119 Kawaguchi Funatsu 06/11/2018 –105.9 3.2 833 29 
YAUT-046828 Kawaguchi Funatsu 04/12/2018 –114.8 2.8 913 26 
YAUT-046829 Kawaguchi Funatsu 08/01/2019 –92.8 2.0 715 18 
YAUT-046831 Kawaguchi Funatsu 05/02/2019 –90.3 2.0 693 18 
YAUT-046832 Kawaguchi Funatsu 05/03/2019 –85.8 2.0 654 18 
YAUT-046833 Kawaguchi Funatsu 16/04/2019 –90.8 2.0 697 18 
YAUT-046402 Kawaguchi Center 05/06/2018 –109.1 4.1 861 37 
YAUT-046403 Kawaguchi Center 03/07/2018 –114.7 4.0 912 36 
YAUT-046404 Kawaguchi Center 06/08/2018 –122.4 3.2 982 29 
YAUT-046405 Kawaguchi Center 11/09/2018 –122.4 3.3 981 30 
YAUT-046406 Kawaguchi Center 02/10/2018 –119.6 4.1 956 38 
YAUT-046409 Kawaguchi Center 06/11/2018 –114.6 2.9 910 26 
YAUT-046823 Kawaguchi Center 04/12/2018 –99.4 2.8 774 25 
YAUT-046824 Kawaguchi Center 08/01/2019 –87.8 3.6 671 32 
YAUT-046825 Kawaguchi Center 05/02/2019 –93.1 2.8 718 25 
YAUT-046826 Kawaguchi Center 05/03/2019 –88.7 2.4 679 21 
YAUT-046411 Yamanaka 06/06/2018 –58.7 3.5 419 30 
YAUT-046412 Yamanaka 04/07/2018 –53.4 2.9 373 25 
YAUT-046413 Yamanaka 01/08/2018 –60.6 4.9 435 42 
YAUT-046415 Yamanaka 05/09/2018 –36.8 5.3 234 44 
YAUT-046416 Yamanaka 03/10/2018 –65.9 7.5 481 64 
YAUT-046417 Yamanaka 07/11/2018 –41.8 4.2 276 35 
YAUT-046836 Yamanaka 05/12/2018 –52.5 2.3 366 19 
YAUT-046837 Yamanaka 15/01/2019 –41.2 2.4 271 20 
YAUT-046838 Yamanaka 06/02/2019 –41.7 2.9 275 24 
YAUT-046839 Yamanaka 06/03/2019 –43.9 3.1 294 26 
YAUT-046816 Yamanaka 17/04/2019 –37.9 2.1 244 18 
Lab. No. Sample Location Date Δ14C (‰) Error (±) 14C Age (yBP) Error (±) 
Groundwater 
YAUT-050826 Koan Northwest of Motosu 21/10/2019 –7.1 2.2 –10 18 
YAUT-050815 Motosu Southeast of Motosu 11/11/2019 –246.0 1.9 2201 20 
YAUT-050812 Shojikyoson North of Shoji 11/11/2019 –45.5 2.3 307 20 
YAUT-050813 Shojiaokigahara South of Shoji 11/11/2019 –165.9 2.0 1390 20 
YAUT-050811 Shinhonsawa North of Sai 11/11/2019 9.8 2.3 –145 18 
YAUT-050809 Aoki South of Sai 28/10/2019 –38.9 2.5 251 21 
YAUT-050805 Goto North of Kawaguchi 11/11/2019 –62.2 3.1 449 26 
YAUT-050806 Wakahiko Northwest of Kawaguchi 11/11/2019 –256.1 1.9 2310 20 
YAUT-050804 Okune South of Kawaguchi 11/11/2019 –74.6 2.5 556 21 
YAUT-050803 Yamanaka South of Yamanaka 21/10/2019 4.0 2.6 –99 21 
YAUT-050802 Hirano North of Yamanaka 21/10/2019 –53.6 2.9 376 25 
Lab. No. Sample Location Date Δ14C (‰) Error (±) 14C Age Error (±) 
River Water 
YAUT-050816 Ichinosuna Yamanaka 21/10/2019 –6.5 2.2 –15 18 
YAUT-050817 Ohori Yamanaka 21/10/2019 –137.4 2.0 1120 19 
YAUT-050818 Tera Kawaguchi 01/10/2019 –48.3 2.2 331 19 
YAUT-050819 Tera Kawaguchi 05/11/2019 –45.2 2.2 304 19 
YAUT-050823 Oku Kawaguchi 01/10/2019 –106.3 2.3 836 21 
YAUT-050824 Oku Kawaguchi 05/11/2019 –94.7 2.5 732 22 
Lab. No.LocationDateΔ14C (‰)Error (±)14C Age (yBP)Error (±)
Lake Water 
YAUT-051526 Motosu 06/06/2018 –53.8 4.3 377 37 
YAUT-047429 Motosu 11/07/2018 –33.2 2.6 204 22 
YAUT-047431 Motosu 01/08/2018 –31.7 3.0 192 25 
YAUT-047432 Motosu 10/09/2018 –28.9 2.8 168 23 
YAUT-047433 Motosu 03/10/2018 –30.4 2.4 181 20 
YAUT-047436 Motosu 07/11/2018 –36.6 2.5 233 21 
N/A Motosu 05/12/2018 N/A N/A N/A N/A 
YAUT-047437 Motosu 09/01/2019 –22.4 2.5 115 21 
YAUT-047438 Motosu 06/02/2019 –22.7 3.0 118 24 
YAUT-047439 Motosu 06/03/2019 –22.6 2.6 117 22 
YAUT-046617 Sai 05/06/2018 –47.3 5.9 322 50 
YAUT-046618 Sai 03/07/2018 –35.9 5.3 226 44 
YAUT-046619 Sai 06/08/2018 –38.7 4.1 250 34 
YAUT-046623 Sai 11/09/2018 –25.3 2.3 139 19 
YAUT-046817 Sai 02/10/2018 –32.5 2.4 198 20 
YAUT-046818 Sai 06/11/2018 –41.6 2.0 275 17 
YAUT-046819 Sai 04/12/2018 –35.7 2.3 225 19 
YAUT-046936 Sai 08/01/2019 –43.4 2.9 289 24 
YAUT-046937 Sai 05/02/2019 –37.3 3.1 238 26 
YAUT-046938 Sai 05/03/2019 –34.3 5.5 213 46 
YAUT-046939 Sai 16/04/2019 –32.0 2.7 194 22 
YAUT-046219 Kawaguchi Funatsu 05/06/2018 –95.1 4.0 735 35 
YAUT-046223 Kawaguchi Funatsu 03/07/2018 –101.4 2.0 792 18 
YAUT-046224 Kawaguchi Funatsu 06/08/2018 –104.8 4.8 822 43 
YAUT-046225 Kawaguchi Funatsu 11/09/2018 –118.3 2.4 944 22 
YAUT-046226 Kawaguchi Funatsu 02/10/2018 –120.7 3.1 966 29 
YAUT-046119 Kawaguchi Funatsu 06/11/2018 –105.9 3.2 833 29 
YAUT-046828 Kawaguchi Funatsu 04/12/2018 –114.8 2.8 913 26 
YAUT-046829 Kawaguchi Funatsu 08/01/2019 –92.8 2.0 715 18 
YAUT-046831 Kawaguchi Funatsu 05/02/2019 –90.3 2.0 693 18 
YAUT-046832 Kawaguchi Funatsu 05/03/2019 –85.8 2.0 654 18 
YAUT-046833 Kawaguchi Funatsu 16/04/2019 –90.8 2.0 697 18 
YAUT-046402 Kawaguchi Center 05/06/2018 –109.1 4.1 861 37 
YAUT-046403 Kawaguchi Center 03/07/2018 –114.7 4.0 912 36 
YAUT-046404 Kawaguchi Center 06/08/2018 –122.4 3.2 982 29 
YAUT-046405 Kawaguchi Center 11/09/2018 –122.4 3.3 981 30 
YAUT-046406 Kawaguchi Center 02/10/2018 –119.6 4.1 956 38 
YAUT-046409 Kawaguchi Center 06/11/2018 –114.6 2.9 910 26 
YAUT-046823 Kawaguchi Center 04/12/2018 –99.4 2.8 774 25 
YAUT-046824 Kawaguchi Center 08/01/2019 –87.8 3.6 671 32 
YAUT-046825 Kawaguchi Center 05/02/2019 –93.1 2.8 718 25 
YAUT-046826 Kawaguchi Center 05/03/2019 –88.7 2.4 679 21 
YAUT-046411 Yamanaka 06/06/2018 –58.7 3.5 419 30 
YAUT-046412 Yamanaka 04/07/2018 –53.4 2.9 373 25 
YAUT-046413 Yamanaka 01/08/2018 –60.6 4.9 435 42 
YAUT-046415 Yamanaka 05/09/2018 –36.8 5.3 234 44 
YAUT-046416 Yamanaka 03/10/2018 –65.9 7.5 481 64 
YAUT-046417 Yamanaka 07/11/2018 –41.8 4.2 276 35 
YAUT-046836 Yamanaka 05/12/2018 –52.5 2.3 366 19 
YAUT-046837 Yamanaka 15/01/2019 –41.2 2.4 271 20 
YAUT-046838 Yamanaka 06/02/2019 –41.7 2.9 275 24 
YAUT-046839 Yamanaka 06/03/2019 –43.9 3.1 294 26 
YAUT-046816 Yamanaka 17/04/2019 –37.9 2.1 244 18 
Lab. No. Sample Location Date Δ14C (‰) Error (±) 14C Age (yBP) Error (±) 
Groundwater 
YAUT-050826 Koan Northwest of Motosu 21/10/2019 –7.1 2.2 –10 18 
YAUT-050815 Motosu Southeast of Motosu 11/11/2019 –246.0 1.9 2201 20 
YAUT-050812 Shojikyoson North of Shoji 11/11/2019 –45.5 2.3 307 20 
YAUT-050813 Shojiaokigahara South of Shoji 11/11/2019 –165.9 2.0 1390 20 
YAUT-050811 Shinhonsawa North of Sai 11/11/2019 9.8 2.3 –145 18 
YAUT-050809 Aoki South of Sai 28/10/2019 –38.9 2.5 251 21 
YAUT-050805 Goto North of Kawaguchi 11/11/2019 –62.2 3.1 449 26 
YAUT-050806 Wakahiko Northwest of Kawaguchi 11/11/2019 –256.1 1.9 2310 20 
YAUT-050804 Okune South of Kawaguchi 11/11/2019 –74.6 2.5 556 21 
YAUT-050803 Yamanaka South of Yamanaka 21/10/2019 4.0 2.6 –99 21 
YAUT-050802 Hirano North of Yamanaka 21/10/2019 –53.6 2.9 376 25 
Lab. No. Sample Location Date Δ14C (‰) Error (±) 14C Age Error (±) 
River Water 
YAUT-050816 Ichinosuna Yamanaka 21/10/2019 –6.5 2.2 –15 18 
YAUT-050817 Ohori Yamanaka 21/10/2019 –137.4 2.0 1120 19 
YAUT-050818 Tera Kawaguchi 01/10/2019 –48.3 2.2 331 19 
YAUT-050819 Tera Kawaguchi 05/11/2019 –45.2 2.2 304 19 
YAUT-050823 Oku Kawaguchi 01/10/2019 –106.3 2.3 836 21 
YAUT-050824 Oku Kawaguchi 05/11/2019 –94.7 2.5 732 22 

The results of Lake Sai show the lowest Δ14C values in June (–47.3 ± 5.9‰), with peak values in September (–25.3 ± 2.3‰). The values fall between –30‰ and –45‰ after October. When comparing the values between the Lake Sai and the Lake Motosu, similar Δ14C values in both lakes are observed from June to November, but the Lake Sai values drop after December by as much as 10‰.

The Δ14C trend at Lake Kawaguchi follows a similar trajectory as that of Lake Motosu, namely lower values in summer and higher values in winter. However, actual values are distinctly lower than the other lakes, where Δ14C observed at a site in the center of the lake is –122.4 ± 3.2‰ in August and –87.8 ± 3.6‰ in January.

The Δ14C values in Lake Yamanaka were below –60‰ in August and October, which is about 20‰ less than the value in September (–36.8 ± 5.3‰). The Δ14C fluctuated more than 20‰ per month from August to October.

Radiocarbon values of groundwater (wells) and river water

Table 2 shows the radiocarbon results for 11 groundwater (wells) and 6 river water samples. Groundwater sampling was conducted from October to November 2019, whereas 2 separate sampling campaigns (October and November 2019) were made for the Tera River and the Oku River. At least 2 ground water sampling sites were designed to collect waters for each lake, considering the incoming water routes from either the northern mountain ranges (e.g., Misaka Mountains) or southern mountain (i.e., Mt. Fuji). In the case of Lake Motosu, the groundwater from the Mt. Fuji side (YAUT-05815) had extremely low Δ14C (–246.0 ± 1.9‰). The groundwater Δ14C values from Koan (on the Misaka Mountains side: YAUT-050826) were measured at –7.1 ± 2.2‰, which was higher than that of surface lake water (Figure 2). For Lake Shoji, groundwater Δ14C was as low as –165.9 ± 2.0‰ from Shojiaoki, on the Mt. Fuji side (YAUT-050813), with higher values measured from Shojikyoson (–45.5 ± 2.3‰: YAUT-050812), on the Misaka Mountains side. At Lake Sai, Δ14C values of –38.9 ± 2.5‰ were obtained from Aoki (on the Mt. Fuji side: YAUT-050809), while Δ14C values in Shinhonsawa were 9.8 ± 2.3‰ (on the Misaka Mountains side: YAUT-050811), which is equivalent to, or higher, than the corresponding lake water Δ14C value.

Results from 2 other lakes, Lake Kawaguchi and Lake Yamanaka, show different features than the other 3 lakes described above. At Okune, located on the southern (Mt. Fuji) side of Lake Kawaguchi, Δ14C values of –74.6 ± 2.5‰ were obtained, whereas values of –62.2 ± 3.1‰ were measured from the sample collected from Goto (YAUT-050805). The values from Wakahiko, located further north on the Misaka mountains side are considerably higher, with Δ14C values of –256.1 ± 1.9‰ (YAUT-050806). The 2 rivers flowing into Lake Kawaguchi, namely the Tera and Oku Rivers, had water Δ14C values of –106.3 ± 2.3‰ to –94.7 ± 2.5‰ and –48.3 ± 2.2‰ to –45.2 ± 2.2‰, respectively.

At Lake Yamanaka, Δ14C values of 4.0 ± 2.6‰ were obtained (on the Mt. Fuji side: YAUT-050803), whereas the value obtained from Hirano was –53.6 ± 2.9‰ (northern side: YAUT-050802). They are similar to the Δ14C values of 2 river waters flowing into the lake: Ichinosuna and Ohori of –6.5 ± 2.2‰ and –137.4 ± 2.0‰, respectively.

Factors controlling the radiocarbon reservoir ages of lake waters

Systematic Δ14C analyses and reservoir ages for Fuji Five Lakes show seasonal variations depend on their setting. As all the lakes are located within 40 km of the northern flank of Mt. Fuji, climate conditions including precipitations and evaporations are similar for the Fuji Five Lakes. Monthly precipitation is preeminent in the summer months, with the maximum in September 2018. However, the value of lake water Δ14C did not show a significant change in September, except for Lake Yamanaka. Thus, the specific hydrological dynamics of each lake are likely responsible for the fluctuations in Δ14C.

The results can be categorized into 2 groups: The first includes lakes that show seasonal variations in Δ14C, such as Lake Motosu and Lake Kawaguchi. Their Δ14C values are relatively low (i.e., older reservoir ages) in summer but high (i.e., younger reservoir age) in winter. The second group, such as Lake Sai and Lake Yamanaka, does not show clear seasonality.

Two possible causes can explain the Δ14C fluctuations (i.e., reservoir ages) for these lakes. The first is that the decrease in Δ14C is due to the changes in retention time of each lake. However, since a previous study revealed that the retention time of lake water in Lake Motosu is typically 7.9 years and the retention of each lake is significantly different (Table 1), it is unlikely that seasonal Δ14C fluctuations are due to retention time. If there is an effect of retention time, the longer the retention time, the lower the Δ14C value. However, Lake Motosu has the longest retention time of 7.9 years, yet the Δ14C value in Lake Motosu is the highest of the five lakes.

The second possible cause could be changes in contributions of waters with low Δ14C flowing into the lake. Since the groundwater Δ14C values around the Fuji Five Lakes are sufficiently low compared to the ambient atmospheric values, it is likely that groundwater supplies water with lower Δ14C to the lake waters. In Lakes Motosu and Kawaguchi, Δ14C tended to increase during winter (Figure 2, Table 2), while no seasonal Δ14C variation was observed at Lakes Sai and Yamanaka. In the following section, hydrological dynamics changes are discussed in the view of the mixtures of low Δ14C water that enter each lake.

At Lake Motosu, the water is heated from the surface, which leads to the development of a thermocline during spring and summer. In contrast, the lake waters do not stratify during winter because of the U-shaped lake basin with a maximum depth of 121.6 m. Hamada et al. (2012) suggested the possibility of meteoric water accumulation at the surface layer of the lake during the stratified period based on seasonal changes from electric conductivity measurements. However, the lake water Δ14C showed relatively lower values from spring to autumn compared to winter, suggesting contribution from groundwater with low Δ14C. Although the groundwater from the Misaka Mountains side (YAUT-050826) has high Δ14C in October 2018, the data may not be indicative of average values of the groundwater because the water was sampled just after a typhoon passed through. It could be explained by higher hydrostatic pressure caused by precipitation during summer to autumn and snowmelt in spring (Figure 3).

Figure 3.

Schematic figures of lacustrine radiocarbon reservoir system and carbon transport (black arrows, solid line: DIC, dotted line: CO2, double arrow; OC). The Δ14C values of Lakes Motosu and Kawaguchi is larger in summer than in winter (red arrow). DOI: https://doi.org/10.1525/elementa.2020.00149.f3

Figure 3.

Schematic figures of lacustrine radiocarbon reservoir system and carbon transport (black arrows, solid line: DIC, dotted line: CO2, double arrow; OC). The Δ14C values of Lakes Motosu and Kawaguchi is larger in summer than in winter (red arrow). DOI: https://doi.org/10.1525/elementa.2020.00149.f3

The Δ14C value during the summer at the eastern site (Funatsu) is around –122‰, which is lower than the site where water is collected at the center of Lake Kawaguchi (Central site: Δ14C is around –100‰). Groundwater samples collected from Wakahiko, located further north and situated on the Misaka mountains side, have Δ14C of –256.1 ± 1.9‰ (YAUT-050806). The water temperature of Funatsu is higher than that of the lake center in summer (Horiuchi et al., 1992), suggesting that the subsurface water or groundwater influx is more significant during summer (July–October).

Unlike the above lakes, no seasonal variation was observed at Lakes Sai and Yamanaka. The Δ14C increase of around 20‰ in September in Lake Yamanaka is attributed to the increase in precipitation due to a typhoon (Typhoon #21), which directly hit the region on September 4 and 5, 2018. The typhoon resulted in 200 mm of precipitation, causing the surface lake water Δ14C to rise. This typhoon also caused lake level to rise by up to +24 cm. An increased amount of low Δ14C groundwater flowed into the lake due to an increase in groundwater pressure during October 2018, or lake water was diluted by precipitation around September 2018.

The DIC Δ14C value in lake waters is considered to be a function of groundwater, precipitation, and carbon retained in the lake water. A combination of these factors causes Δ14C fluctuations in the lake waters. In this paragraph, we conducted a 2-box model simulation to estimate relative contributions of groundwater and precipitation for the Fuji Five Lakes surface waters (Figure 4). Previous studies have suggested that the main sources of water for the lakes are either groundwater or precipitation; however, groundwater is abundant in Lake Yamanaka (see Hamada and Kitagawa, 2010; Hamada et al., 2012). In fact, 3 lakes: Lake Motosu, Lake Shoji, and Lake Sai, have no rivers that constantly discharge to or from the lakes. Although Tera and Oku Rivers are flowing into Lake Kawaguchi, and Ichinosuna and Ohori Rivers flow into Lake Yamanaka, we cannot confirm the effects of river water due to the lack of flow rate data. Although the case mentioned above exists only under limited conditions, semiquantitative analysis of the hydrology of the lakes is useful in evaluating the mechanisms for understanding Δ14C changes in the lake surface water. Newly obtained groundwater Δ14C values by this study are employed, and an atmospheric Δ14C value of each month ranged from 7.0 ± 1.9‰ to –9.98 ± 1.5‰ (ICOS RI, 2019) at station Saclay was used in the following equation. The calculation formula is described below.

Δ14Clake=1f×Δ14Catm+f×Δ14Cgroundwater.
6
Figure 4.

Results of groundwater 14C contribution (%) in the Fuji Five Lakes compared to actual Δ14C values. Percentage of ground water 14C in lake water 14C (gray bar), lake water DIC 14C (black: Motosu, red: Sai, yellow: Kawaguchi Funatsu, gray: Kawaguchi Center, and blue: Yamanaka). DOI: https://doi.org/10.1525/elementa.2020.00149.f4

Figure 4.

Results of groundwater 14C contribution (%) in the Fuji Five Lakes compared to actual Δ14C values. Percentage of ground water 14C in lake water 14C (gray bar), lake water DIC 14C (black: Motosu, red: Sai, yellow: Kawaguchi Funatsu, gray: Kawaguchi Center, and blue: Yamanaka). DOI: https://doi.org/10.1525/elementa.2020.00149.f4

Here, f is the proportion (%) of groundwater Δ14C in the lake, whereas Δ14Clake DIC is the lake water Δ14 C, and Δ14Catm is the atmospheric Δ14C value observed in 2018. Groundwater also originates from precipitation, but Δ14C in groundwater decreases before reaching the lake because it is isolated from the atmosphere (e.g., Bente, 2013). Although the lake water in the Fuji Five Lakes is considered to be mainly derived from the Mikasa and Tanzawa Mountains (Hayashi, 2020), Δ14Cgroundwater DIC values obtained from wells around the Fuji Five Lakes are employed for Lakes Motosu and Sai where the Δ14Cgroundwater DIC values of the Misaka Mountain are higher than the lake DIC Δ14 C values. The values obtained from the Misaka Mountains side (i.e., Northern Sites) are used to calculate the proportion of groundwater 14C for Lakes Kawaguchi and Yamanaka. The proportion of groundwater contribution to DIC14C for the surface lake water in Lake Motosu is about 20%. This is consistent with the chemical measurements of waters reported in Hamada et al. (2012). Water in Lake Kawaguchi is largely influenced by groundwater, as the proportion is approximately 50%. For the Lakes Sai and Yamanaka, more than 80% of the lake water is derived from groundwater DI14C, including months when lake water Δ14 C values are smaller than groundwater DI14C value of each lake. Since the groundwater collected in this study is very limited in this area, further investigation is needed to clarify the origin of the lake water.

Implications for reservoir ages of Lake Motosu and Lake Kawaguchi

Previous studies collected sediment cores from Lake Motosu to study past environmental changes in the region (Lamair et al., 2018, 2019; Obrochta et al., 2018). Obrochta et al (2018) measured radiocarbon in TOC from sediments, and they reported a Δ14C surface value of Δ14C of –41 ± 2.5‰. Our observed lake water Δ14C in Lake Motosu from this study between July and November is similar with values around –30‰. This suggests that the carbon produced in the lake due to carbon fixation during spring to summer by phytoplankton living in the lake surface water is the dominant source of carbon for the sediments in the lake. As a result, it is considered that the DIC in the lake water from spring to summer is comparable to the TOC Δ14C of the sediments. Thus, the Δ14C of lake water DIC in spring to summer can be utilized to estimate the reservoir age of the sediments.

We also compared lake water DIC Δ14C with compound-specific Δ14C reported for Lake Kawaguchi sediments (Yamamoto et al., 2020). Compound-specific Δ14C extracted from fatty acids from Lake Kawaguchi sediments were reported for each fraction. The results show that C16 fatty acid Δ14C (–124 ± 6‰), chlorophyll a Δ14C (–133 ± 6‰), and lake water DIC Δ14C (–117 ± 2‰) are consistent with each other for the samples collected in June 2017. Our study revealed that the seasonal magnitude of Δ14C changes was around 35‰ from August 2018 (–122.4 ± 3.2‰) to March 2019 (–88.7 ± 2.4‰); thus, an increase in Δ14C could have occurred between the summer and winter in 2017 when Yamamoto et al. (2020) collected samples. If so, the value of DIC Δ14C observed from the current study is close to the values of C24 fatty acid (Δ14C = –77 ± 6‰) or C28 fatty acid (Δ14C = –75 ± 7‰). Both C24 and C28 fatty acids are considered to be derived from higher plants, soil-derived compounds (Gagosian et al., 1981; Simoneit 1977), and/or aquatic macrophytes (Ficken et al., 2000). Hence, the Δ14C of these fatty acids could be partly affected by additional aquatic sources in addition to terrestrial plant materials.

Further systematic studies are needed to clarify the relationship between lake water and organic matter produced by living organisms. To elucidate the origin of organic matter, δ13C measurements would be able to provide clear pathways of carbon transported from lake water to organic matter.

Monthly Δ14C measurements on the Fuji Five Lakes surface water DIC revealed the following:

  1. Δ14C values of Lake Motosu and Lake Kawaguchi decreased in summer, as compared to winter, whereas relatively low Δ14C values were observed in Lake Sai. Δ14C values decrease in June–August and October at Lake Yamanaka.

  2. Reservoir ages of sediment may reflect lake water DIC in spring to summer. Lake water DIC is likely to be fixed as organic matter and supplied to sediments due to the expansion of aquatic organisms that are active from spring to summer.

  3. Seasonal variations of lake water Δ14C are mainly driven by groundwater amount and also suggest that Δ14C of lake seasonality was shown to be useful for improving the accuracy of lake hydrology and radiocarbon dating.

The following datasets were generated:

  • Sizes, depth, altitude, and retention time of Fuji Five Lakes: Geospatial Information Authority of Japan (https://www.gsi.go.jp/), and Yamanashi Prefecture (1993) [The water quality of the Fuji Five Lakes over 21 years (1971–1991)] Yamanashi Prefectural Environment Bureau.

  • Radiocarbon data: uploaded as Table 2.

  • Atmospheric Δ14C value data: ICOS RI (2019) [ICOS Atmospheric Greenhouse Gas Mole Fractions of CO2, CH4, CO, 14CO2, and Meteorological Observations September 2015–April 2019 for 19 stations (49 vertical levels), final quality controlled Level 2 data], dataset. DOI: doi.org/10.18160/CE2R-CC91.

We would like to express our gratitude to the Fuji Healing Forest Laboratory of the University of Tokyo, Yamanakako Village, Narusawa Village, Fujikawaguchiko Town, Motosu Kohan Koan, Yamanashi Prefectural Air Quality Protection Division, and the Yamanashi Institute of Public Health and Environment for providing water samples. We would like to thank Dr. T. Aze and Dr. C. Sawada (AORI) for their support on AMS measurements, and W. Wong for a part of sample preparation. Discussions with E. Tam, B. Behrens, and A. D. Sproson were also appreciated. We thank Prof. G. Burr (National Taiwan University) and an anonymous reviewer for constructive comments which improved the manuscript.

A part of this research was supported by JSPS KAKENHI Grant Numbers 18K03769 and JP20H00193.

The authors have no competing interests to declare.

Contributed to conception and design: YY, KO.

Contributed to acquisition of data: KO, YY, YM, SY.

Contributed to analysis and interpretation of data: KO, YY, YM, SY, TM.

Drafted and/or revised the article: KO, YY, SY, TM.

Approved the submitted version for publication: YY, KO.

Asai
,
K
.,
Tsujimura
,
K
.
2010
.
Dating method for young groundwater using environmental tracers – Application of CFCs dating method to spring in volcanic areas
.
Journal of Japanese Association of Hydrological Sciences
39
:
67
78
. DOI: http://dx.doi.org/10.4145/jahs.39.67.
Ascough
,
PL
,
Bird
,
MI
,
Meredith
,
W
,
Wood
,
RE
,
Snape
,
ME
,
Brock
,
F
,
Higham
,
TFG
,
Large
,
DJ
,
Apperley
,
DC
.
2010
.
Hydropyrolysis: Implications for radiocarbon pretreatmenrt and characterization of black carbon
.
Radiocarbon
52
:
1098
1112
. DOI: http://dx.doi.org/10.1017/S0033822200046427.
Bente
,
P
.
2013
.
The freshwater reservoir effect in radiocarbon dating
.
Heritage Science
1
:
24
. DOI: http://dx.doi.org/10.1186/2050-7445-1-24.
Blattmann
,
MT
,
Wessels
,
M
,
McIntyre
,
PC
,
Eglinton
,
WT
.
2018
.
Projections for future radiocarbon content in dissolved inorganic carbon in Hardwater lakes: A retrospective approach
.
Radiocarbon
60
(
3
):
791
800
. DOI: http://dx.doi.org/10.1017/RDC.2018.12.
Brady
,
AL
,
Slater
,
G
,
Lavel
,
B
,
Lim
,
DS
.
2009
.
Constraining carbon sources and growth rates of freshwater microbialites in Pavilion Lake using 14C analysis
.
Geobiology
7
:
544
555
. DOI: http://dx.doi.org/10.1111/j.1472-4669.2009.00215.x.
Broecker
,
WS
,
Walton
,
A
.
1959
.
The geochemistry of C14 in fresh-water systems
.
Geochimica et Cosmochimica Acta
16
:
15
38
. DOI: http://dx.doi.org/10.1016/0016-7037(59)90044-4.
Bronk Ramsey
,
C
,
Staff
,
RA
,
Bryant
,
RL
,
Brock
,
F
,
Kitagawa
,
H
,
van der Plicht
,
J
,
Schlolaut
,
G
,
Marshall
,
MH
,
Brauer
,
S
,
Lamb
,
HF
,
Payne
,
RL
,
Tarasov
,
PV
,
Haraguchi
,
T
,
Gotanda
,
K
,
Yonenobu
,
H
,
Yokoyama
,
Y
,
Tada
,
R
,
Nakagawa
,
T
.
2012
.
A complete terrestrial radiocarbon record for 11.2 to 52.8 kyr B.P
.
Science
338
(
6105
):
370
374
. DOI: http://dx.doi.org/10.1126/science.1226660.
Cheng
,
H
,
Zhang
,
H
,
Spötl
,
C
,
Baker
,
J
,
Sinha
,
A
,
Li
,
H
,
Bartolome
,
M
,
Moreno
,
A
,
Kathayat
,
G
,
Xhao
,
J
,
Dong
,
X
,
Li
,
Y
,
Ning
,
Y
,
Jia
,
X
,
Xong
,
B
,
Brahim
,
YA
,
Pérez-Mejias
,
C
,
Cai
,
Y
,
Novello
,
VF
,
Cruz
,
CW
,
Severinghaus
,
JP
,
An
,
Z
,
Edwards
,
RL
.
2020
.
Timing and structure of the Younger Dryas event and its underlying climate dynamics
.
Proceedings of National Academy of Science, USA
.
117
:
23408
23417
. DOI: http://dx.doi.org/10.1073/pnas.2007869117.
Chiba
,
T
,
Suzuki
,
Y
,
Arai
,
K
,
Tomita
,
Y
,
Koizumi
,
S
,
Nakashima
,
K
,
Ogawa
,
K
.
2010
.
The measurement of magma discharge volume of the “Jogan” eruption in Aokigahara on Fuji volcano, based on the micro topography by LiDAR and result of the drilling
.
Journal of Erosion Control Engineer
63
(
1
):
44
48
. DOI: http://dx.doi.org/10.11475/sabo.63.1_44.
Donahue
,
DJ
,
Linick
,
TW
,
Jull
,
AJT
.,
1990
.
Isotope-ratio and background corrections for accelerator mass spectrometry radiocarbon measurements
.
Radiocarbon
32
(
2
):
135
142
. DOI: http://dx.doi.org/10.1017/S0033822200040121.
Ficken
,
KJ
,
Li
,
B
,
Swain
,
DL
,
Eglinton
,
L
.
2000
.
An n-alkane proxy for the sedimentary input of submerged/floating freshwater aquatic macrophytes
.
Organic Geochemistry
31
(
7–8
):
745
749
. DOI: http://dx.doi.org/10.1016/S0146-6380(00)00081-4.
Fukuyo
,
N
.,
Clark
,
G.
,
Purcell
,
A
,
Parton
,
P
,
Yokoyama
,
Y
.
2020
.
Holocene sea level reconstruction using lagoon specific local marine reservoir effect and geophysical modeling in Tongatapu, Kingdom of Tonga
.
Quaternary Science Reviews
244
:
106464
. DOI: http://dx.doi.org/10.1016/j.quascirev.2020.106464.
Gagosian
,
RB
,
Peltzer
,
ET
,
Zafiriou
,
OC
.
1981
.
Atmospheric transport of continentally derived lipids to the tropical North Pacific
.
Nature
291
:
312
314
. DOI: http://dx.doi.org/10.1038/291312a0.
Ghazoui
,
Z
,
Bertrand
,
S
,
Vanneste
,
K
,
Yokoyama
,
Y
,
Nomade
,
J
,
Gajurel
,
AP
,
van der Beek
,
P
.
2019
.
Potentially large post-1505 AD earthquakes in western Nepal revealed by a lake sediment record
.
Nature Communications
10
:
2258
. DOI: http://dx.doi.org/10.1038/s41467-019-10093-4.
Graven
,
HD
.
2015
.
Impact of fossil fuel emissions on atmospheric radiocarbon and various applications of radiocarbon over this century
.
Proceedings of the National Academy of Sciences of the United States of America
112
(
31
):
9542
9545
. DOI: http://dx.doi.org/10.1073/pnas.1504467112.
Hamada
,
H
,
Katsumata
,
D
,
Oyagi
,
H
.
2012
.
Investigation of seasonal change of water temperature and water quality and water balance on Lake Motosu-ko
.
Bulletin of Faculty of Education, Chiba University
60
:
459
468
.
Hamada
,
H
,
Kitagawa
,
Y
.
2010
.
Investigation of Seasonal change of Water temperature and Water quality and Water balance on Lake Yamanaka-ko
.
Bulletin of Faculty of Education, Chiba University
58
:
371
380
.
Hamano
,
K
.
1976
.
Groundwater of north ridge of Mount Fuji
.
Yamanashi University Faculty of Liberal Arts Research Report
27
:
59
66
.
Hayashi
,
T
.
2020
.
Understanding the groundwater flow system at the northern part of Mt. Fuji: Current issues and prospects
.
Journal of Geography (Chigaku Zasshi)
129
(
5
):
677
695
.
Hayashi
,
T
,
Tsuboi
,
T
.
2005
.
Interchange between mountain groundwater and lake at the foot of Mt. Fuji
.
Journal of Ground Water Technology
47
(
11
)
3
14
.
Hirabayashi
,
S
,
Yokoyama
,
Y
,
Suzuki
,
A
,
Miyairi
,
Y
.
2019
.
Insight into western pacific circulation from South China sea coral skeletal radiocarbon
.
Radiocarbon
61
(
6
):
1923
1937
. DOI: http://dx.doi.org/10.1017/RDC.2019.145.
Hirabayashi
,
S
,
Yokoyama
,
Y
,
Suzuki
,
A
,
Miyairi
,
Y
Aze
,
T
.
2017
.
Short-term fluctuations in regional radiocarbon reservoir age recorded in coral skeletons from the Ryukyu Islands in the north-western Pacific
.
Journal of Quaternary Science
32
(
1
):
1
16
. DOI: http://dx.doi.org/10.1002/jqs.2923.
Horiuchi
,
S
,
Lee
,
Y
,
Watanabe
,
M
,
Fujita
,
E
.
1992
.
Some limnological characteristics of Mt. Fuji
.
Proceedings of the Institute of Natural Sciences, Nihon University
27
:
45
56
.
ICOS
RI
.
2019
.
ICOS Atmospheric greenhouse gas Mole Fractions of CO2, CH4, CO, 14CO2 and meteorological observations September 2015 - April 2019 for 19 stations (49 vertical levels), final quality controlled Level 2 data
.
Integrated Carbon Observation System
. DOI: http://dx.doi.org/10.18160/CE2R-CC91.
Jull
,
AJT
,
Burr
,
GS
,
Hodgins
,
GWL
.
2013
.
Radiocarbon dating, reservoir effects, and calibration
.
Quaternary International
299
:
64
71
. DOI: http://dx.doi.org/10.1016/j.quaint.2012.10.028. 
Kanno
,
T
,
Ishii
,
T
,
Kuroda
,
K
.
1986
.
Study on groundwater flow in the northern foot area of Mt. Fuji and water level changes of Lake Kawaguchi, based on the hydrogeological structure
.
The journal of the Japanese Association of Groundwater Hydrology
28
:
25
32
. DOI: http://dx.doi.org/10.5917/jagh1959.28.25.
Koshimizu
,
S
,
Uchiyama
,
T
,
Yamamoto
,
G
.
2007
. Volcanic history of Mt. Fuji recorded in borehole cores from Fuji Five Lakes surrounding Mt. Fuji, in
Aramaki
,
S
,
Fujii
,
T
,
Nakada
,
S
,
Miyaji
,
N
eds.,
Fuji volcano
(pp.
365
374
).
Yamanashi, Japan
:
Yamanashi Institute of Environmental Sciences
.
Lamair
,
L
,
Hubert-Ferrari
,
A
,
Ouahabi
,
ME
,
Yamamoto
,
F
,
Schmidt
,
S
,
Auwera
,
JV
,
Lepoint
,
S
,
Boes
,
E
,
Fujiwara
,
O
,
Yokoyama
,
Y
,
Batist
,
MD
,
Heyvaert
,
V.MA
.
2019
.
Late holocene changes in erosion patterns in a lacustrine environment: Landscape stabilization by volcanic activity versus human activity
.
Geochemistry, Geophysics, Geosystems
20
(
4
),
1720
1733
. DOI: http://dx.doi.org/10.1029/2018GC008067.
Lamair
,
L
,
Hubert-Ferrari
,
A
,
Shinya Yamamoto
,
S
,
Ouahabi
,
M. E
,
Auwera
,
JV
,
Obrochta
,
S
,
Boes
,
E
,
Nakamura
,
A
,
Fujiwara
,
O
,
Shishikura
,
M
,
Schmidt
,
S
,
Siani
,
G
,
Miyairi
,
Y
Yokoyama
,
Y
,
Batist
,
MD
,
Heyvaert
,
VMA
,
QuakeRecNankai Team
,
2018
.
Volcanic influence of Mt. Fuji on the watershed of Lake Motosu and its impact on the lacustrine sedimentary record
.
Sedimentary Geology
363
:
200
220
. DOI: http://dx.doi.org/10.1016/j.sedgeo.2017.11.010.
Matsuda
,
T
.
2007
. Geology and geohistory of the Tertiary basement of Mt. Fuji, in
Aramaki
,
S
,
Fujii
,
T
,
Nakada
,
S
,
Miyaji
,
N
eds.,
Fuji volcano
.
Yamanashi, Japan
:
Yamanashi Institute of Environmental Sciences
:
45
57
.
McNichol
,
AP
,
Jones
,
GA
,
Huton
,
DL
,
Gagno
,
AR
.
1994
.
The rapid preparation of sea water ΣCO2 for radiocarbon analysis at the national ocean science facility
.
Radiocarbon
36
:
237
246
. DOI: http://dx.doi.org/10.1017/S0033822200040522.
Nakamura
,
A
,
Yokoyama
,
Y
,
Maemoku
,
H
,
Yagi
,
H
,
Okamura
,
M
,
Matsuoka
,
H
,
Miyake
,
N
,
Osada
,
T
Pani Adhikari
,
D
,
Dangol
,
V
,
Ikehara
,
M
,
Miyairi
,
Y
Matsuzaki
,
H
.
2016
.
Weak monsoon event at 4.2 ka recorded in sediment from Lake Rara, Himalayas
.
Quaternary International
397
(
18
):
349
359
. DOI: http://dx.doi.org/10.1016/j.quaint.2015.05.053.
Obrochta
,
SP
,
Yokoyama
,
Y
,
Yoshimoto
,
M
,
Yamamoto
,
S
,
Miyairi
,
Y
Nagano
,
G
,
Nakamura
,
A
,
Tsunematsu
,
K
,
Lamair
,
L
Hubert-Ferrari
,
A
,
Lougheed
,
BC
.
2018
.
Mt. Fuji Holocene eruption history reconstructed from proximal lake sediments and high-density radiocarbon dating
.
Quaternary Science Reviews
200
:
395
405
. DOI: http://dx.doi.org/10.1016/j.quascirev.2018.09.001.
Ochiai
,
T
.
1995
. East Mount Fuji groundwater analysis.
Tokyo, Japan
:
Liebel Publishing
.
Ogata
,
M
,
Kobayashi
,
H
.
2015
.
Chronological change of water level of Lake Kawaguchi and that of ground water level around south east area of Lake Kawaguchi
.
Y-CROST Research Report
10
:
91
94
.
Ogata
,
M
,
Kobayashi
,
H
,
Koshimizu
,
S
.
2014
.
Concentration of fluorine in groundwater and groundwater table at the northern foot of Mt. Fuji
.
The Journal of the Japanese Association of Groundwater Hydrology
56
(
1
):
35
51
. DOI: http://dx.doi.org/10.5917/jagh.56.35.
Ota
,
K
,
Yokoyama
,
Y
,
Miyairi
,
Y
,
Hayakawa
,
J
Satoh
,
N
,
Fukuda
,
H
,
Tanaka
,
K
.
2019
.
Northeast pacific seawater radiocarbon recorded in abalone shells obtained from Otsuchi Bay, Japan
.
Radiocarbon
. DOI: http://dx.doi.org/10.1017/RDC.2019.95.
Safaierad
,
R
,
Mohtadi
,
M
,
Zolitschka
,
B
,
Yokoyama
,
Y
,
Vogt
,
C
,
Schefuß
.
2020
.
Elevated dust depositions in West Asia linked to ocean–atmosphere shifts during North Atlantic cold events
.
Proceedings of the National Academy of Sciences of the United States of America
117
(
31
):
18272
18277
.
Sakashita
,
W
,
Miyahara
,
H
,
Yokoyama
,
Y
,
Aze
,
T
,
Nakatsuka
,
T
,
Hoshino
,
Y
,
Ohyama
,
M
,
Yonenobu
,
H
,
Takemura
,
K
.
2017
.
Hydroclimate reconstruction in central Japan over the past four centuries from tree-ring cellulose δ18O
.
Quaternary International
455
:
1
7
. DOI: http://dx.doi.org/10.1016/j.quaint.2017.06.020.
Schneider
,
L
,
Pain
,
FC
,
Haberle
,
S
,
Blong
,
R
,
Alloway
,
VB
,
Fallon
,
JF
,
Hope
,
G
,
Zawadzki
,
A
,
Heijnis
,
H
.
2019
.
Evaluating the radiocarbon reservoir effect in Lake Kutubu, Papua New Guinea
.
Radiocarbon
61
(
1
):
287
308
. DOI: http://dx.doi.org/10.1017/RDC.2018.49.
Servettaz
,
APM
,
Yokoyama
,
Y
,
Hirabayashi
,
S
,
Kienast
,
M
,
Miyairi
,
Y
,
Mohtadi
,
M
.
2019
.
Dissolved inorganic radiocarbon content of the Western Coral sea: Implications for intermediate and deep water circulation
.
Radiocarbon
61
(
6
):
1685
1696
. DOI: http://dx.doi.org/10.1017/RDC.2019.122.
Simoneit
,
BRT
.
1977
.
Organic matter in eolian dusts over the Atlantic Ocean
.
Marine Chemistry
5
:
443
464
. DOI: http://dx.doi.org/10.1016/0304-4203(77)90034-2.
Stuiver
,
M
,
Polach
,
HA
.
1977
.
Discussion Reporting of 14C data
.
Radiocarbon
19
(
3
):
355
363
. DOI: http://dx.doi.org/10.1017/S0033822200003672.
Suess
,
HE
,
1955
.
Radiocarbon concentration in modern wood
.
Science
122
:
415
417
. DOI: http://dx.doi.org/10.1126/science.122.3166.415-a.
Susuki
,
H
,
Taba
,
Y
.
1994
.
A study on the mechanism of exchange between lake waters of FUJI-GOKO (five lakes) and the groundwater around the lakes
.
Bulletin of the Institute of Natural Science, Nihon University
29
:
4
60
.
Sweeney
,
C
,
Gloor
,
E
,
Jacobson
,
AR
,
Key
,
RM
,
McKinley
,
G
,
Sarmiento
,
JL
,
Wanninkhof
,
R
.
2007
.
Constraining global air-sea gas exchange for CO2 with recent bomb 14C measurements
.
Global Biogeochemical Cycles
21
:
GB2015
. DOI: http://dx.doi.org/10.1029/2006GB002784.
Takada
,
R
,
Yamamoto
,
T
,
Ishizuka
,
Y
,
Nakano
,
R
,
2016
.
Geological Map of Fuji Volcano
.
Geological survey of Japan
.
Available at
https://www.gsj.jp/Map/JP/geology5.html#misc_12.
Takeuchi
,
K
,
Kiriishi
,
F
,
Imamura
,
H
.
1995
.
The water balance analyses of the Five Lakes of Mt. Fuji
.
The Journal of Japan Society of Civil Engineers
39
:
31
36
.
Yamamoto
,
S
.
1971
.
Hydronic study of volcano Fuji and its adjacent areas
.
Mount Fuji Comprehensive Academic Research Report
1
:
151
208
.
Yamamoto
,
S
,
Miyairi
,
Y
,
Yokoyama
,
Y
,
Suga
,
H
,
Ogawa
,
ON
,
Ohkouchi
,
N
.
2020
.
Compound-specific radiocarbon analysis of organic compounds from Mount Fuji proximal lake (Lake Kawaguchi) sediment, central Japan
.
Radiocarbon
62
(
2
):
439
451
. DOI: http://dx.doi.org/10.1017/RDC.2019.158.
Yamamoto
,
S
,
Nakamura
,
T
,
Uchiyama
,
T
.
2017
a.
Newly discovered lake bottom springs from Lake Kawaguchi, the northern foot of Mount Fuji, Japan
.
Journal of Japanese Association of Hydrological Sciences
47
(
2
):
49
59
. DOI: http://dx.doi.org/10.4145/jahs.47.49.
Yamamoto
,
S
,
Uchiyama
,
T
,
Miyairi
,
Y
,
Yokoyama
,
Y
.
2018
.
Volcanic and environmental influences of Mt. Fuji on the δ13C of terrestrially-derived n-alkanoic acids in sediment from Lake Yamanaka, central Japan
.
Organic Geochemistry
199
:
50
58
. DOI: http://dx.doi.org/10.1016/j.orggeochem.2018.02.002.
Yamanashi Prefecture
.
1993
. The water quality of the Fuji Five Lakes over 21 years (1971–1991).
Tokyo, Japan
:
Yamanashi Prefectural Environment Bureau
.
Yokoyama
,
Y
,
Esat
,
TM
,
Lambeck
,
Y
,
Fifield
,
LK
.
2000
.
Last ice age millennial scale climate changes recorded in Huon Peninsula Corals
.
Radiocarbon
42
:
3838
4401
. DOI: http://dx.doi.org/10.1017/S0033822200030320.
Yokoyama
,
Y
,
Hirabayashi
,
S
,
Goto
,
K
,
Okuno
,
J
,
Sproson
,
AD
,
Haraguchi
,
T
,
Ratnayake
,
N
,
Miyairi
,
Y
.
2019
a.
Holocene Indian Ocean sea level, Antarctic melting history and past Tsunami deposits inferred using sea level reconstructions from the Sri Lankan, Southeastern Indian and Maldivian coasts
.
Quaternary Science Reviews
206
:
150
161
. DOI: http://dx.doi.org/10.1016/j.quascirev.2018.11.024.
Yokoyama
,
Y
,
Miyairi
,
Y
,
Aze
,
T
,
Yamane
,
M
,
Sawada
,
C
,
Ando
,
Y
,
de Natris
,
M
,
Hirabayashi
,
S
,
Ishiwa
,
T
,
Sato
,
N
,
Fukuyo
,
N
.
2019
b.
A single stage accelerator mass spectrometry at the atmosphere and ocean research institute, The University of Tokyo
.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions With Materials and Atoms
455
:
311
316
. DOI: http://dx.doi.org/10.1016/j.nimb.2019.01.055.
Yokoyama
,
Y
,
Miyairi
,
Y
,
Matsuzaki
,
H
,
Tsunomori
,
F
.
2007
.
Relation between acid dissolution time in the vacuum test tube and time required for graphitization for AMS target preparation
.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
259
(
1
):
330
334
. DOI: http://dx.doi.org/10.1016/j.nimb.2007.01.176.
Yoshimura
,
S
,
Kawada
,
S
.
1942
.
Research of Fuji five lakes (2), physicochemical properties of Lakes Kawaguchi and Shoji in summer
.
Geographical Review of Japan
22
(
11
). DOI: http://dx.doi.org/10.4157/grj.18.441.
Yoshizawa
,
K
,
Mochizuki
,
E.
2005
.
Water quality of bottom layer water in Lake Kawaguchi during the summertime
.
Yamanashi Prefectural Institute of Public Health Annual Report
49
:
54
59
.
Yu
,
S-Y
,
Shen
,
J
,
Colman
,
SM.
2007
.
Modeling the radiocarbon reservoir effect in lacustrine systems
.
Radiocarbon
49
(
3
):
1241
1254
. DOI: http://dx.doi.org/10.1017/S0033822200043150.

How to cite this article: Ota, K, Yokoyama, Y, Miyairi, Y, Yamamoto, S, Miyajima, T. 2021. Lake water dissolved inorganic carbon dynamics revealed from monthly measurements of radiocarbon in the Fuji Five Lakes, Japan. Elementa: Science of the Anthropocene 9(1). DOI: https://doi.org/10.1525/elementa.2020.00149

Domain Editor-in-Chief: Steven Allison, University of California Irvine, Irvine, CA, USA

Guest Editor: Chuan-Chou Shen, Department of Geosciences, National Taiwan University, Taipei, Taiwan

Knowledge Domain: Ecology and Earth Systems

Part of an Elementa Special Feature: Pan-Pacific Anthropocene

This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International License (CC-BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. See http://creativecommons.org/licenses/by/4.0/.