EFFECTS OF BEDROCK GEOLOGY AND ANTHROPOGENIC ACTIVITIES ON THE FATE AND TRANSPORT OF TRACE ELEMENTS WITHIN AN AGRICULTURAL WATERSHED OF LEBANON, NORTHEASTERN USA

Rock weathering resulting in soil formation is an important geological process associated with the release of trace elements into the environment. However, the geochemical enrichments withing the agricultural watersheds are often due to a combination of both rock weathering and anthropogenic activities. This project examined the source, concentrations, spatial distributions, as well as fate and transport of major and trace elements in soil and bedrock of Lebanon, an agricultural watershed, northeastern USA. To address these objectives, a total of sixteen exposed rock samples along with the weathered fragments were collected from seven rock formations that include Hebron Gneiss, Brimfield Schist, Scotland Schist, Lebanon Gabbro, Tatnic Hill, Waterford Group, and Canterbury Gneiss. In addition, a total of eighty-seven (87) soil samples were collected within the agricultural watershed, and analyzed for acid, and soluble extractable elements, basic soil parameters such as particle size distribution, organic matter contents, and soluble salts. Results of geochemical analysis of soil showed spatial variability, which are mostly correlated with OM and fine particles sizes. Calculation of chemical index of weathering (CIA) of bedrocks showed a weak to intermediate weathering. The mass-transfer coefficient (T_r) values showed a combination of anthropogenic and lithogenic release of trace elements within the watershed. Despite this, calculation of geoaccumulation index (Igeo) and pollution load index (PLI) of agricultural soils showed no enrichments with respect to As (63 %), Cd (71%), Cu (93%), Mn (99%), Ni (99%), Pb (51 %) and Zn (97%), attributable to high sand fractions, and low pH values of agricultural soils, as well as the influence of the use of poultry litter as soil amendment. Results have implication on the fate and transport of trace elements to underlying horizons within an agricultural watershed area.