RESUMEN
>44 million United States residents depend on private drinking water wells that are federally unregulated. Maintaining a clean groundwater supply for populations without access to public water systems is essential to supporting public health and falls to state regulators and private well owners. Yet, monitoring practices do not reflect the fact that groundwater pollution risk varies seasonally and with proximity to nearby surface-contaminated sites. Examination of nearly 50,000 well water samples across North Carolina, ranked second nationally in domestic well dependence and swine production, from 2013 to 2018 reveals a uniform sampling schedule but a variable risk of bacterial contamination within each calendar year. We document a threshold of 32.2 °C (90 °F) where total coliform bacteria and Escherichia coli (E. coli) detection in private well water spikes near swine lagoons but is absent from "upstream" wells and otherwise unexplained by a variety of other known contamination sites. Closing the gap between perceived and actual risks of drinking water contamination has potential to improve public health. State regulations and federal guidelines should consider coordinating domestic well sampling with seasonally and spatially fluctuating risks of groundwater contamination. Findings from this study are generalizable, having implications for other parts of the world with water sources that have the potential to get contaminated by nearby surface sources of human and animal waste, such as manure applications and leaching septic systems.
Asunto(s)
Agua Potable , Agua Subterránea , Porcinos , Animales , Humanos , Agua Potable/microbiología , Escherichia coli , Temperatura , Pozos de Agua , Abastecimiento de Agua , Agua Subterránea/microbiología , BacteriasRESUMEN
Air and water quality at a concentrated animal feeding operation (CAFO) in Eastern North Carolina that uses a covered lagoon and anaerobic digester was evaluated for 2 weeks in August 2020. Real-time PM2.5 mass concentrations were determined using a reference ADR-1500 nephelometer and high-frequency measurements of dissolved inorganic nitrogen (DIN) were evaluated using autonomously logging sensors. Air and water quality parameters were assessed before, during and after wastewater from the lagoon was irrigated onto adjacent spray fields. Reference measurements were conducted alongside a HOBO weather station to collect real-time wind speed and direction, temperature, and humidity measurements. PM2.5 concentrations varied between 0 and 159 µg/m3 with an average concentration of 11 µg/m3, below EPA standard for secondary aerosols of 15 µg/m3. Higher PM2.5 concentrations were observed when wind originated from swine barns but not from covered lagoons. Water quality data showed that DIN concentrations downgradient from the CAFO were elevated relative to upstream concentrations. A groundwater seep that drains a spray field contained the highest average DIN concentration (31.0 ± 12.8 mg L-1), which was 25 times greater than upstream DIN concentrations (1.2 ± 0.8 mg L-1). Average DIN concentration at the downstream station was lower than the seep concentration (8.6 ± 16.2 mg L-1), but approximately 8 times greater than upstream. Air quality data show that the lagoon cover was effective at mitigating air quality degradation, whereas DIN concentrations in water were similar to previous studies on CAFOs using open lagoons. In addition, air and water quality parameters were significantly (p < 0.001) higher after irrigation, indicating possible influence due to ammonia and nitrate elevation. Additional research is needed to compare high-frequency data collected from swine CAFOs using capped and uncapped lagoon systems to better understand spatiotemporal air and water quality trends of this practice.