On-site evaluation of the effects of carbonaceous amendments on the bioavailability of aged organochlorine pesticide residues in soil

Authors: ANDERSON, M.O. - University Of Maryland; YANG, Z. - University Of Maryland; Hapeman, Cathleen; MCCONNELL, L.L. - University Of Maryland; Green, Carrie; JACKSON, DANA - Collaborator; EVANS, M.N. - University Of Maryland; TORRENTS, A. - University Of Maryland

Submitted to: Environmental Pollution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/8/2021
Publication Date: 10/16/2021
Citation: Anderson, M., Yang, Z., Hapeman, C.J., Mcconnell, L., Green, C.E., Jackson, D., Evans, M., Torrents, A. 2021. On-site evaluation of the effects of carbonaceous amendments on the bioavailability of aged organochlorine pesticide residues in soil. Environmental Pollution. 6:100126. https://doi.org/10.1016/j.envadv.2021.100126.
DOI: https://doi.org/10.1016/j.envadv.2021.100126

Interpretive Summary: Historical orchards can contain high levels of pesticides that are now banned such as the organochlorine insecticides DDT and dieldrin. These compounds do not degrade readily and can present a risk to indigenous organisms. However, the required remediation of the soil can be quite costly. Previous laboratory studies showed that the use of composts which is much less costly can limit the amount of DDT and dieldrin available to organisms. This is known as bioavailability. Decreasing the bioavailability of contaminants will decrease the amount of the contaminant consumed by an organism and limit the effects on the indigenous food chain. Results from a field study showed that compost may be a viable remediation method, but the more important finding is that better methods are needed for assessing the risks to indigenous organisms in areas where the contaminant concentrations are highly variable. This study will lead to more robust methods for conducting ecological risk assessments and more effective remediation techniques.

Technical Abstract: Reducing the bioavailability of persistent organic contaminants in soil by incorporating carbonaceous material (CM) has been investigated and confirmed by numerous laboratory studies. However, the efficacy of these methods under more complex field conditions needs exploration. We conducted an 18-month, small-scale plot study (n = 7) to evaluate the ability of two CMs, a compost aged for four months and a compost aged for two years, to reduce the bioavailability of the organochlorine pesticides (OCPs) dichlorodiphenyltrichloroethane (DDT), its metabolites (together as DDx), and dieldrin. The study was carried out in a historical orchard where OCPs were applied routinely until they were banned. Soil and earthworms were collected, contaminant concentrations were measured, and bioaccumulation factors (BAFs) were calculated for the 28 subplots at multiple timepoints. A decrease in the uptake and bioaccumulation of the OCPs was observed with increasing soil concentration, i.e., the relationship between soil and worm concentrations was non-linear. In addition, substantial spatial variability in the soil and earthworm concentrations was observed which gave rise to variability in BAF. Although this study showed some evidence that CM amendments may reduce bioaccumulation over time, the results were not statistically significant due to the spatial variability. This study suggests that more robust methods are needed in calculating ecological risk assessments for indigenous animals, particularly for sites with large contaminant concentrations and with substantial spatial variability, as well as the challenges of extrapolating laboratory results to the field.