Do Chemically Contaminated Subaqueous Soils Present a Challenge for Classification?.

Subaqueous soils that have been heavily contaminated with synthetic chemicals such as oils, greases, and tars may present a challenge to soil classification and taxonomy. While the concentration of these chemicals may be reduced quickly after initial contamination, a refractory fraction can remain that will affect soil properties for decades or longer. These pollutants can coat particles, fill pore space, or occur as layers either on top of or within a soil profile. Soil Taxonomy is unclear as to whether or not such fluid contaminants meet the definition of artifacts. Even if they do, their presence would not result in the classification of an anthropic epipedon in many subaqueous soils because an anthropic epipedon must have an n value less than 0.7, a requirement that many subaqueous soils do not meet. Unless these contaminants are considered to be soil material or parent material, they do not fall clearly within the definition of human-transported materials. No extragrade subgroups exist that adequately describe such a contaminated soil. Present Soil Survey Manual description of such contamination is limited to noting a petrochemical smell or including general notes on observed contaminants. These contaminants can be both chemically and physically hazardous to human health and the health of aquatic organisms, and their presence is one of the most significant features of any soil in which they occur. Their presence may indicate a broad history of other pollution in a subaqueous landscape, as is the case in Bear Creek, a heavily urbanized tributary of the Patapsco River near Baltimore, MD. It is reasonable to expect that some other industrialized regions will contain such contaminated subaqueous soils. For the time being, we have no appropriate way to capture some of the most significant features of these soils in their taxonomic names.