Bioaccumulation of Organic Anthropogenic Wastewater Indicators in Earthworms

Land application of biosolids as a source of nutrients for crops is an important source of terrestrial contaminants. Biosolids are known to contain a complex mixture of organic and inorganic contaminants. Organic contaminants present in biosolids include detergent metabolites, pharmaceuticals, synthetic fragrances, hormones, and more, which are collectively referred to as anthropogenic wastewater indicators (AWIs). Individual concentration of AWIs in biosolids can range from parts per trillion to parts per million levels. Earthworms are predominant consumers of organic matter in terrestrial environments and thus, represent a sentinel organism for detecting the presence AWIs. Bioaccumulation of AWIs by earthworms was previously observed in field and laboratory studies. Research from multiple locations across the United States with varying histories of biosolid applications (ranging from first time to repeated applications), has documented that following land application select AWIs (e.g. pharmaceuticals, synthetic fragrances, detergent metabolites, disinfectants, and plasticizers) are rapidly transferred from the biosolid into earthworm tissue. Similar bioaccumulation of AWIs by earthworms exposed to biosolids was also observed in controlled laboratory exposure experiments. Such laboratory results indicate that the presence of biosolids can influence earthworm (Eisenia fetida) survival and reproduction. While concentrations of select AWIs were below detection levels in soil samples, their detection in earthworm tissue suggestion bioaccumulation and biomagnifications is an important process taking place. Thus, earthworms may serve as a valuable tool for identifying terrestrial AWI contamination. Because earthworms represent a substantial fraction of biomass in many terrestrial environments and are primary consumers of soil organic matter, they also may serve as a pathway for introducing AWIs into the food web. Research currently in progress will determine the ability of earthworms to not only bioaccumulate select AWIs, but also to metabolize such contaminants, making them a potential valuable tool to mitigate the AWI content of biosolids.