Contaminants and excess nutrients from atmospheric deposition and non-point sources contribute to water quality impairment in the Chesapeake Bay watershed. Assessment of landscape metrics and air and water quality data have provided insight into the fate, delivery, and transport mechanisms of pollutants, particularly those associated with agriculture. Three cases studies will be presented. 1) Riparian areas are known to decrease nutrient contamination from agricultural runoff and can capture pesticide spray drift. In some cases, however, the riparian tree canopy can also provide a direct conduit to local streams for pesticide residues. 2) MESA {2-[2-ethyl-N-(1-methoxypropan-2-yl) -6-methylanilino]-2-oxoethanesulfonic acid}, a metabolite of the extensively-used herbicide metolachlor, was used to track nitrate-N concentrations within the mainstem of the Choptank River, a Chesapeake Bay tributary. Very little nitrate-N consumption was observed in the estuary suggesting that excessive eutrophication was due to an alternative nitrogen source, most likely ammonia-N deposition. Furthermore, conservation practices should focus on reducing nitrate-N loads and enhancing denitrification further upstream in the cropland areas (headwaters) prior to entry into the estuary. 3) Polybrominated diphenyl ethers (PBDEs), frequently found in waste water treatment effluent, were detected in significantly higher concentrations in air samples collected downwind from sprayfields utilized for wastewater disposal. Examination of land use data, physio-chemical properties of PBDEs, and back-trajectory analysis revealed that the PBDEs were volatilized from spray droplets and may be an important source of these contaminants in the region.

Determining contaminate sources to the Chesapeake Bay to discern the effectiveness of conservation practices

246th National Meeting (2013)

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