A TALE OF TWO STREAMS: CHLORIDE, CONDUCTIVITY, AND TRACE METALS IN STREAMS ON THE HCC CAMPUS

The purposes of this study are three-fold: (1) to provide an authentic research experience in environmental geoscience for undergraduate students at Howard Community College (HCC) as part of the URSC program, (2) to contribute to the growing body of research documenting the impact of de-icing salt application to ecosystems in the northeastern United States, and (3) to provide water quality and trace metal data detailing the year-round impact of de-icing salts and other anthropomorphic effects on two streams in Howard County, Maryland during 2022 and to offer specific suggestions to reduce negative impacts. Water quality has been assessed by measuring the following parameters: water temperature, dissolved oxygen, pH, conductivity, turbidity, chloride, nitrate and phosphate levels. In addition, concentrations of manganese (Mn), cadmium (Cd), and nickel (Ni), have been measured using an Atomic Absorption Spectrophotometer (AAS). A method for analyzing Cd using the AAS has been developed and tested. Samples with Cd concentrations as low as 0.08 ppb have been successfully analyzed using a 500 mg/L Pd-citric acid solution as a matrix modifier. Both Ni and Cd concentrations generally decreased from winter to summer and were below the chronic EPA Aquatic Life Criteria for Cd (0.72 μg/L) and Ni (52 μg/L) year-round. Data through November show a strong positive correlation between chloride levels and conductivity, with both being lower in the summer, particularly after rain events. The highest chloride and conductivity values were measured in winter and likely result from input of runoff laden with road salt. Chloride levels in the streams remain above the EPA chronic limit of 230 mg/L for most of the year; degradation of the freshwater stream ecosystem can be expected since chloride concentrations remain above this level. Elevated chloride levels, in turn, appear to produce a “cascade effect,” mobilizing elements such as Mn from soil and sediment into ground water as evidenced by a significant positive correlation between Mn and Cl concentrations through November. Based on the results of this study, more targeted and judicious application of road salts to the college’s sidewalks and roadways during the winter months is recommended in order to address chronically high conductivity and chloride levels in the campus streams.