AN INVESTIGATION OF WATER QUALITY IN ROCK CREEK, ADAMS COUNTY, PA: IMPACT OF TREATED WASTEWATER, AGRICULTURE, URBANIZATION, AND RIPARIAN BUFFERS

This study focuses on the effects of treated wastewater, agricultural and urban runoff, and riparian buffers on the water quality of Rock Creek, Gettysburg, PA. Samples were collected at six sites along Rock Creek and one site in a tributary to Rock Creek, Stevens Run. Samples were collected daily from each site for ten days in mid-May 2022, as well as weekly from each site throughout the month of June 2022. At each site, temperature, pH, electrical conductivity, and total dissolved solids were measured and a 300 mL sample was collected for future laboratory analysis. Nitrate-N, phosphate, and ammonia concentrations were measured for each sample using colorimetry kits. Iron, zinc, phosphorus, and arsenic concentrations were measured for samples from five specific dates using inductively-coupled plasma atomic emission spectroscopy (ICP-AES). Average temperature was highest at Stevens Run, likely due to the low discharge and lack of riparian buffer, and lowest at the site with the largest riparian buffer. Average pH was consistent across sites along Rock Creek, but more basic in Stevens Run due to limestone rock composition used as an erosion control measure lining the stream. Average electrical conductivity and total dissolved solids increases as distance downstream increases, suggesting an accumulation of sediment from run-off. Average nitrate-N and ammonia concentrations were highest in the site along Rock Creek that lacked a riparian buffer, suggesting that the riparian buffers limit agricultural runoff in the other sites along the creek. The sites upstream and downstream of the Gettysburg Municipal Authority (GMA) wastewater treatment effluent discharge point did not differ significantly in average concentrations of nitrate-N, ammonia, and phosphate, suggesting that the GMA wastewater effluent does not significantly discharge these pollutants. Zinc and phosphorus concentrations were higher downstream of the GMA effluent point compared to upstream, suggesting that these elements may come from the GMA wastewater effluent. The site underneath a major road did not have a significantly higher average concentration of zinc compared to the other sites, suggesting minimal impact from urban runoff. There was no arsenic detectable within the limits of the ICP-AES at any of the sites.