Garfield Mason


Project title: Chloride Concentrations in agricultural, forested and urban streams: Risk of freshwater salinization?

Mentors: Kelly Addy and Dr. Art Gold


Adding excess road salt applications can salinize streams. Water with chloride concentrations higher than 250 mg/l will give a salty taste and likely contain elevated concentrations of sodium and toxic impurities from road salt. We assessed chloride levels in three streams with different dominant land uses that discharge into drinking water reservoirs which are concerned about salt because it can be harmful to the health of some individuals (e.g., those with high blood pressure). Specific conductivity was measured by in-stream sensors every 30 mins in these streams during most non-winter months over the past year. The specific conductivity data was converted to chloride concentration by finding a linear relationship between lab chloride concentrations and in situ specific conductivity.  After analyzing the large chloride dataset, we found that urban site had the highest overall chloride concentrations, likely due to the higher impervious cover it had in its watershed. Most samples from all streams were less than half of the EPA recommended concentration for aquatic life (250 mg/l). Surprisingly, the forested site had a higher proportion of elevated chloride samples than the agricultural site. The urban site was the only site to have chloride concentrations over 250 mg/l, which occurred twice during the sampling period. Although grab samples were taken during the winter months there is not enough sensor data during these months to conclude that chloride concentrations are below the EPA’s recommended values. However this study does suggest that seepage of road salts during the non-winter months does not contain high values of chloride concentrations at all three sites.