Spatial and temporal variations of atmospheric deposition in interior and coastal Connecticut

Abstract

Both wet and dry deposition fluxes of sulfur, nitrogen, and phosphorus were estimated at three monitoring stations in Connecticut, one inland near the Connecticut-Massachusetts border and two along the Connecticut coastline of Long Island Sound. Three years of data, from 1991 through 1993, were analyzed and are reported in this paper. The total annual deposition ranged from 1.27 to 1.58 gm-2 for sulfur, 0.8 to 0.85 gm-2 for nitrogen, and 3.81 to 4.69 mg m-2 for phosphorus. More than 90% of the phosphorus and about two-thirds of the sulfur and nitrogen were deposited in wet form. The estimated wet deposition quantities were all higher in summer, indicating a higher scavenging efficiency of rainfalls. The dry deposition quantities were higher for particles but lower for gases during the summer seasons. While there were no significant differences in wet deposition among the three monitoring stations, spatial gradients in atmospheric concentration and dry deposition, especially for sulphur, were detected with higher values to the southwest industrial area. Although more sites might be needed to pinpoint the sources of the pollutants, one station is sufficient for a reliable estimation of the overall deposition. The strong episodic nature of the deposition quantities, however, demands more frequent than denser sampling in the area for long-term monitoring. Also, since the weekly deposition quantities were all strongly positively skewed, more descriptive statistics in addition to the mean values are recommended in data reports.