New study highlights the role of wastewater and landscape sources contributing to pesticide contamination in the Potomac River watershed
Wastewater treatment plant discharges can be a source of organic contaminants, including pesticides, to rivers. Pesticide concentrations were predicted based on wastewater percentages in stream water using a modeling tool, and verified with measured concentrations to identify other potential landscape sources.
Issue
Pesticides can be introduced to the aquatic environment from a variety of landscape sources such as agricultural and urban runoff, as well as wastewater effluent. Human and environmental health partners can work together to identify streams that may be more susceptible to pesticide contamination and exceed toxicity thresholds for freshwater invertebrates.
USGS Study
An existing model (Faunce et al., 2023) was expanded to estimate concentrations from fourteen different pesticides in each stream segment of the Potomac River Watershed, based on the amount of wastewater present in stream water (Interactive Map: Potomac Wastewater Mapper). Measured samples were collected from 32 stream sites to verify predictions, and additional water quality information and landscape variables were used to infer other possible sources of pesticides to surface water.
Primary Findings
- Analysis of accumulated wastewater effluent and land use data can accurately screen for the presence of pesticides in streams.
- Treated sewage wastewater, urban runoff, and agricultural lands were associated with different types of insecticides, herbicides, and fungicides (Fig. 1).
- 14% of the stream segments in the Potomac River watershed received direct or accumulated wastewater effluent from sewerage wastewater treatments.
- Most stream sites (72%) had measured concentrations from pesticide mixtures that indicated freshwater invertebrates could be potentially at risk from chronic exposure, driven primarily by the presence of the insecticides imidacloprid and fipronil.
Management Implications
- Many impaired streams in the Potomac River watershed lack healthy invertebrate communities and require management implementation plans to improve conditions.
- Pesticides that exceed chronic aquatic toxicity thresholds for freshwater invertebrates pose a potential threat to stream health.
- Implementation plans that do not address sources of pesticide contamination may fall short of efforts to remediate invertebrate communities.
- Pesticide management strategies that address both wastewater and landscape sources from agricultural and urban runoff may improve the health of aquatic ecosystems.
How does wastewater affect pesticide concentrations in the Potomac River?
Graphical depiction of study approach, pesticide sources identified, and potential impacts to freshwater invertebrates.
Wastewater treatment plant discharges can be a source of organic contaminants, including pesticides, to rivers. Pesticide concentrations were predicted based on wastewater percentages in stream water using a modeling tool, and verified with measured concentrations to identify other potential landscape sources.
Issue
Pesticides can be introduced to the aquatic environment from a variety of landscape sources such as agricultural and urban runoff, as well as wastewater effluent. Human and environmental health partners can work together to identify streams that may be more susceptible to pesticide contamination and exceed toxicity thresholds for freshwater invertebrates.
USGS Study
An existing model (Faunce et al., 2023) was expanded to estimate concentrations from fourteen different pesticides in each stream segment of the Potomac River Watershed, based on the amount of wastewater present in stream water (Interactive Map: Potomac Wastewater Mapper). Measured samples were collected from 32 stream sites to verify predictions, and additional water quality information and landscape variables were used to infer other possible sources of pesticides to surface water.
Primary Findings
- Analysis of accumulated wastewater effluent and land use data can accurately screen for the presence of pesticides in streams.
- Treated sewage wastewater, urban runoff, and agricultural lands were associated with different types of insecticides, herbicides, and fungicides (Fig. 1).
- 14% of the stream segments in the Potomac River watershed received direct or accumulated wastewater effluent from sewerage wastewater treatments.
- Most stream sites (72%) had measured concentrations from pesticide mixtures that indicated freshwater invertebrates could be potentially at risk from chronic exposure, driven primarily by the presence of the insecticides imidacloprid and fipronil.
Management Implications
- Many impaired streams in the Potomac River watershed lack healthy invertebrate communities and require management implementation plans to improve conditions.
- Pesticides that exceed chronic aquatic toxicity thresholds for freshwater invertebrates pose a potential threat to stream health.
- Implementation plans that do not address sources of pesticide contamination may fall short of efforts to remediate invertebrate communities.
- Pesticide management strategies that address both wastewater and landscape sources from agricultural and urban runoff may improve the health of aquatic ecosystems.
How does wastewater affect pesticide concentrations in the Potomac River?
Graphical depiction of study approach, pesticide sources identified, and potential impacts to freshwater invertebrates.