Water column sampling for forensics

After a spill, oil is present in water as both dissolved and particulate (oil-droplet) phases due to entrainment and dissolution/weathering processes. The two phases, capable of physically separating and remixing in a body of water, complicate forensic evaluations but also contribute information on waterborne fate and transport. Identifying and tracking each phase in field samples has high forensic value in developing interpretive scenarios of weathering and exposure processes and for providing data germane to modeling and toxicology studies in damage assessments. Samples can be parsed into phase components either physically in the field using portable filtration equipment or later with data evaluation methods developed to parse out unfiltered samples using a weathered particulate-oil reference series generated from a few field-filtered samples. If done properly, sampling the water column for oil hydrocarbons during or after an oil spill can be highly insightful but the task is challenging and technically demanding with multiple opportunities to get it wrong, especially without feedback until weeks or months later when the data come back from the lab. This chapter presents water-sampling issues (and solutions), methods of forensically assessing quantified data, and adaptive sampling strategies that prove effective in tracking a deep submerged plume.