Atmospheric deposition of organochlorine contaminants to Galveston Bay, Texas

Atmospheric monitoring of PCBs and chlorinated pesticides (e.g., HCHs, chlo rdanes, and DDTs) in Galveston Bay was conducted at Seabrook, Texas. Air an d wet deposition samples were collected from 2 February 1995 and continued through 6 August 1996. Vapor total PCB (tPCB) concentrations in air ranged from 0.21 to 4.78 ng m(-3) with a dominance of tri-chlorinated PCBs. Dissol ved tPCBs in rain ranged From 0.08 to 3.34 ng l(-1), with tetra-chlorinated PCBs predominating. The predominant isomers found in air and rain were alp ha- and gamma -HCH, alpha- and gamma -chlordanes, 4,4 ' -DDT, and dieldrin, The concentrations of PCBs and pesticides in the air and rain revealed no clear seasonal trend. Elevated levels of PCBs in the air occurred when temp eratures were high and wind came from urban and industrialized areas (S, SW , NW, and W of the site). Concentrations of HCHs were elevated in April. Ma y, and October, perhaps due to local and:or regional applications of gamma -HCH (lindane). Other pesticides showed no notable temporal variation. When winds originated From the G ulf of Mexico (southeasterly), lower concentra tions of organochlorines were detected in the air. The direct deposition ra te (wet + dry) of PCBs to Galveston Bay (6.40 mug m(-2) yr(-1)) was signifi cantly higher than that of pesticides by a factor of 5-10. The net flux fro m gas exchange estimated for PCBs was from Galveston Bay water to the atmos phere (78 mug m(-1) yr(-1)). Gas exchange of PCBs from bay water to the atm osphere was the dominant flux. (C) 2001 Elsevier Science Ltd. All rights re served.