Factors Affecting Spatial and Temporal Variability in Nutrient and Pesticide Concentrations in the Surficial Aquifer on the Delmarva Peninsula

Hydrophysical and Hydrochemical Controls of Cyanobacterial Blooms in Coursey Pond, Delaware (USA)

“…During the study period, mean SC in Coursey Pond was 185 μS and varied between 100 and 235 μS (Fig. 3), values that are within the previously reported range for Coursey Pond (Water Quality Portal Station ID: 21DELAWQ_WQX‐206451) and regional groundwater (Debrewer et al, 2005; Ator, 2008). Variations in SC clearly reflect the importance of hydrologic forcing of gross pond chemistry.…”

“…As such, groundwater quality and local, primarily agricultural land‐use practices heavily influence the biogeochemistry of Coastal Plain streams and ponds. Given the quartzose sand composition of the Columbia aquifer, the relatively shallow depth to groundwater (Martin and Andres, 2008), and the dominance of agricultural land uses, the limited groundwater quality data in the watershed (https://waterdata.usgs.gov/de/nwis/qw) show the expected elevated concentrations of NO 3 − and total dissolved solids but very little NH 4 + (Debrewer et al, 2005; Ator, 2008). …”

Wetland Restoration and Creation for Nitrogen Removal: Challenges to Developing a Watershed-Scale Approach in the Chesapeake Bay Coastal Plain

“…Image produced by the US Geological Survey, Hamilton et al (1991) with modification by Denver et al (2004). and elevated nitrate concentrations are found even near the base of the surficial aquifer (Hamilton et al, 1993;Debrewer et al, 2007). Seventy percent of the nitrogen flux in headwater streams is attributable to base-flow nitrate flux .…”

“…Seventy percent of the nitrogen flux in headwater streams is attributable to base-flow nitrate flux . Debrewer et al (2007) reported that median nitrate concentrations in groundwater are greater than 5 mg L À1 and often higher than 10 mg L À1 in wells placed at a median depth of 6 m below the surface in agricultural areas. Similar nitrate concentrations in deeper groundwater (14 m below surface) reflect recharge in upgradient agricultural land (Hamilton et al, 1993;Debrewer et al, 2007).…”

“…Debrewer et al (2007) reported that median nitrate concentrations in groundwater are greater than 5 mg L À1 and often higher than 10 mg L À1 in wells placed at a median depth of 6 m below the surface in agricultural areas. Similar nitrate concentrations in deeper groundwater (14 m below surface) reflect recharge in upgradient agricultural land (Hamilton et al, 1993;Debrewer et al, 2007). Mitigating nitrate loss is further complicated by the long travel time required for deep groundwater to move through the surficial aquifer; nitrate may remain in groundwater for decades to centuries before discharging into streams (Bohlke and Denver, 1995).…”