Water samples from the Rhode River, an estuary situated on the western shore of the Chesapeake Bay, were analyzed for atrazine residues twice a week for 2 yr. Precipitation samples, which included dryfall, rainfall, and snowfall were collected with wide-mouth stainless steel collection pans situated about 20 m above ground in an open space. A total of 68 precipitation samples was collected from December 1976 to February 1979. Atrazine residues were detectable in estuarine water and in rainwater year-round. Atrazine residues in estuarine water were generally 6 to 190ng/l, atrazine residues in rainwater (bulk precipitation) were 3 to 2190ng/l. Atrazine residues in rainwater samples collected during the winter season (January to April 1977) were unexpectedly high (e.g. 3 to 970ng/l). The highest atrazine concentration of 2190ng/l was detected from a 0.76 cm rainfall event collected on May 19, 1977. Intermittent spraying operations of atrazine within the cornfields were generally done during May of each year. Rain samples collected during May of 1978 also showed higher atrazine residues than the rest of the 1978 growing season, but at levels much less than those detected in 1977 rainwater. Although high attrazine concentrations were detected in winter rainfall, these did not result in similarly higher atrazine concentrations in estuarine receiving waters. Our data showed a decline of atrazine concentrations in estuarine water in October and November which continued until a rainfall following Spring herbicide applications. Atrazine is enriched at the microsurface layer of estuarine water, but direct atmospheric input of atrazine did not seem to contribute significantly to the enrichment mechanism. Atrazine is believed to be transported long distances in polluted air masses. The estuarine microsurface layer could be a source of atmospheric atrazine, but the importance of the source is yet to be determined. Atrazine was quantitatively determined by GC using a nitrogen specific electrolytic detector and was confirmed by GC/Mass.

Element mass balance estimates for South Carolina Coastal Plain watersheds indicate that fertilizers and liming materials are the major sources for inputs of Ca, Mg, K, Cl, and HCO(,3) whereas precipitation is the major input for Na and SO(,4). Stream flow is the chief mode of output for all of these elements. A balance between input and output is evident only for Cl. Retentions of 50% or more are shown by Ca, Mg, K, HCO(,3), and SO(,4) whereas Na shows an apparent net loss. The retention of Ca, Mg and HCO(,3) suggests that less than 25% of the dolomitic liming materials applied to the landscape actually dissolve and that the carbonate chemistry of Lower Coastal Plain streams is therefore probably largely controlled by seepage of groundwaters from underlying calcareous aquifers. The retention of K and the loss of Na may be due to cation exchange reactions on soil clays whereas the apparent retention of SO(,4) is probably due to reduction to H(,2)S in floodplain environments and soil adsorption.