Earthworms: Diagnostic Indicators of Wastewater Derived Anthropogenic Organic Contaminants in Terrestrial Environments

Analysis of earthworms for anthropogenic organic contaminants (AOCs) offers a potential diagnostic tool for assessing the presence and transfer of AOCs from wastewater sources into terrestrial environments and biota. Earthworms and soil samples were collected from one minimally affected agricultural field (soybean, Site 1) with no known history of biosolids or manure amendment and three agricultural locations amended with municipal biosolids. The biosolid-amended sites consisted of a soybean field amended for the first time with municipal biosolids (Site 2), a hay field with an extended history of amendment with municipal biosolids (Site 3), and a grassland pasture used for cattle grazing (Site 4) with an extended history of biosolids amendment with municipal biosolids from the same source as Site 3. Forty-two of the 72 AOCs monitored in this study were detected in quantifiable concentrations in one or more of the biosolids, soil, or earthworm samples. In most of these samples, the biogenic sterols had the highest concentration among measured AOCs, but the biosolids and biosolid-amended samples contained a variety of AOCs indicative of human use such as the disinfectant triclosan, detergent metabolites, and the synthetic fragrances galaxolide and tonalide. A number of AOCs were detected in the earthworm tissue samples, some of which bioaccumulated to concentrations greater than found in the soils from which were collected. Unexpectedly, some AOCs were detected in the soil and earthworms from the minimally impacted Site I. However, the relative abundance of uniquely anthropogenic contaminants, such as personal care products, is much less in the earthworms from Site 1 compared to those from the biosolids amended sites. When possible, bioaccumulation factors (BAFs) on a dry mass basis were calculated for the AOCs detected in the earthworms. Triclosan and monoethoxy-nonylphenol detergent metabolites were measured to have BAFs as high as 41.0 and 21.7, respectively. Many of the AOCs measured in the earthworm tissue samples were below detectable concentrations in the corresponding soil samples. This study documents that some AOCs present in land-applied biosolids can be transferred to earthworms and that earthworms may serve as a diagnostic tool for assessing the presence of AOCs in terrestrial environments.