SARS-CoV-2 concentrations in a wastewater collection system indicated potential COVID-19 hotspots at the zip code level.

Wastewater based epidemiology (WBE) has been successfully applied for SARS-CoV-2 surveillance at the city and building levels. However, sampling at the city level does not provide sufficient spatial granularity to identify COVID-19 hotspots, while data from building-level sampling are too narrow in scope for broader public health application. The objective of this study was to examine the feasibility of using wastewater from wastewater collection systems (WCSs) to monitor COVID-19 hotspots at the zip code level. In this study, 24-h composite wastewater samples were collected from five manholes and two wastewater treatment plants (WWTPs) in the City of Lincoln, Nebraska. By comparing to the reported weekly COVID-19 case numbers, we identified different hotspots responsible for two COVID-19 surges during the study period. One zip code was the only sampling locations that was consistently tested positive during the first COVID-19 surge. In comparison, nearly all the zip codes tested exhibited virus concentration increases that overlapped with the second COVID-19 surge, suggesting broader spread of the virus at that time. These findings demonstrate the feasibility of using WBE to monitor COVID-19 at the zip code level. Highly localized disease surveillance methods can improve public health prevention and mitigation measures at the community level.

Modeling the vertical transport of antibiotic resistance genes in agricultural soils following manure application.

Antibiotic resistance genes (ARGs) may be introduced to agricultural soil through the land application of cattle manure. During a rainfall event, manure-borne ARGs may infiltrate into subsurface soil and leach into groundwater. The objective of this study was to characterize and model the vertical transport of manure-borne ARGs through soil following the land application of beef cattle manure on soil surface. In this study, soil column experiments were conducted to evaluate the influence of manure application on subsurface transport of four ARGs: erm(C), erm(F), tet(O) and tet(Q). An attachment-detachment model with the decay of ARGs in the soil was used to simulate the breakthrough of ARGs in leachates from the control column (without manure) and treatment (with manure) soil columns. Results showed that the first-order attachment coefficient (ka) was five to six orders of magnitude higher in the treatment column than in the control column. Conversely, the first-order detachment and decay coefficients (kd and µs) were not significantly changed due to manure application. These findings suggest that in areas where manure is land-applied, some manure-borne bacteria-associated ARGs will be attached to the soil, instead of leaching to groundwater in near terms.

Climate change impacts the subsurface transport of atrazine and estrone originating from agricultural production activities.

Climate change will impact soil properties such as soil moisture, organic carbon and temperature and changes in these properties will influence the sorption, biodegradation and leaching of trace organic contaminants to groundwater. In this study, we conducted a modeling case study to evaluate atrazine and estrone transport in the subsurface under current and future climate conditions at a field site in central Nebraska. According to the modeling results, in the future, enhanced evapotranspiration and increased average air temperature may cause drier soil conditions, which consequently reduces the biodegradation of atrazine and estrone in the water phase. On the other hand, greater transpiration rates lead to greater root solute uptake which may decrease the concentration of atrazine and estrone in the soil profile. Another consequence of future climate is that the infiltration and leaching rates for both atrazine and estrone may be lower under future climate scenarios. Reduced infiltration of trace organic compounds may indicate that lower trace organic concentrations in groundwater may occur under future climate scenarios.

Fate and transport of antibiotics and antibiotic resistance genes in runoff and soil as affected by the timing of swine manure slurry application.

Land application of swine manure slurry is a common practice to supplement nutrients to soil for crop production. This practice can introduce antibiotic residues and antibiotic resistance genes (ARGs) into the environment. Field testing is critical in identifying manure management practices effective in minimizing the environmental impacts of manure-borne antibiotic and ARGs. The objective of this study was to determine how the timing of swine manure application relative to rainfall events impacts the fate and transport of antibiotics and ARGs in surface runoff and manure-amended soil. Swine manure slurry was either broadcast or injected on test plots in the field. A set of three 30-min simulated rainfall events, 24 h apart, were initiated on manured plots 1 day, 1 week, 2 weeks, or 3 weeks after the manure application. Results showed that an interval longer than 2 weeks between application and rainfall often significantly reduced the levels of antibiotics and ARGs tested in runoff with the exception of tet(X). For soil samples from broadcast plots, concentrations of two of the three antibiotics tested (lincomycin and tiamulin) decreased substantially in the first two weeks after manure application. In contrast, concentrations of most of the ARGs tested (tet(Q), tet(X), and erm(A)) in soil did not change significantly during the test period. Information obtained from the study can be beneficial in designing manure management practices and estimating the environmental loading of antibiotics and ARGs resulting from manure application.

Enhanced biodegradation of atrazine at high infiltration rates in agricultural soils.

The objective of this study was to assess the persistence and transport of atrazine at high infiltration rates expected from higher intensity precipitation associated with climate change scenarios in the midwestern U.S. The transport and transformation of atrazine was monitored in column experiments at high infiltration rates (64-119 mm d-1) associated with increased precipitation intensity. The optimum linear sorption and the lumped Monod biokinetic parameters were determined by inverting observed break-through curves (BTCs) using the advection-dispersion-sorption-degradation model. Batch microcosm studies were also conducted to examine the effect of moisture content (5%, 15% and 25%) on atrazine degradation and support the column results. BTCs from both soil types with continuous atrazine input showed a characteristic pattern of a pulse input i.e. lag phase prior to rapid atrazine degradation. The rate of atrazine leaching at higher infiltration rates was not fast enough to counteract the effect of enhanced degradation. Higher infiltration rates enriched the distribution of hydroxyatrazine in the soil profile for sandy loam, but their effect was minimal in loam soil. The pattern of degradation obtained in batch microcosms agreed with the column results. In both soils, mean half-life of atrazine was lower (4-8 days) at high soil moisture contents. Under future climate change scenarios, where more intense precipitation is likely to result in higher infiltration rates and increased soil moisture, the potential for groundwater pollution from atrazine may be reduced, especially in areas with a long history of atrazine application to soil.