Black carbon slick and SML sampling. Example of a black slick observed in Halong Bay during the dry season (left), and sea surface microlayer (SML) sampling (right) using the glass plate technique within such highly BC-impacted slicks. Note the color of the SML sample; although visually resembling an oil slick in situ, analyses confirmed these black slicks were due to BC. DOI: https://doi.org/10.1525/elementa.255.f2