The reduced sulfur content of coastal sediment is a proxy for the organic carbon deposition rate. As such, it is an important parameter in environmental monitoring. Some reduced sulfur occurs in the form of pore water solutes such H2S, HS− and S2−, which can be measured in situ with potentiometric or amperometric microsensors. The majority of the reduced sulfur, however, accumulates in solid phases such as FeS that are responsible for the distinct black colouration of organic-rich sediment. Most of these sulfides convert to H2S when treated with acid, these are known as the acid volatile sulfides (AVS). To measure the sediment AVS content with this technique, a sediment sample has to be removed from the field and treated in the laboratory. We have developed a method to map the micro-scale (10−3–10−6 m) spatial distribution of sediment AVS in the field. Our method uses high-resolution sediment profile images created in situ and a site-specific correlation between sediment colour and AVS concentration. We believe that this method will open new opportunities for experimental studies of the functioning of soft-sediment ecosystem.