Atmospheric Deposition of Pesticides, PCB, PAH, Nutrients and Metals to Texas Coastal Estuaries

Long term atmospheric deposition monitoring was established by Coastal Bend Bays and Estuaries Program (CBBEP) from April 22, 1997 to August 31, 1999 at Texas A&M University Corpus Christi (TAMUCC) and from June 3, 1997 to August 31, 1999 at Whites Point (Phase I). Wet only rain samples were collected every week on Tuesday from January 2, 2002 until December 26, 2006 at TAMUCC as part of the National Atmospheric Deposition Program (NADP). Samples were collected once a week and represented an integration of all the individual rain events that occurred during the sampling period. The results indicate that atmospheric deposition is an important source of nutrient nitrogen, trace element and organic contaminants to the Coastal Bend Bays. The yearly average pH of the rain from 2002 through 2006 ranged from 5.09 to 5.21 (average of 5.14) which is slightly acidic but comparable to pre-industrial revolution natural pH (5.0). Some of the major ions detected in the wet and dry deposition (Cl, Na, Mg) are derived from sea salts as anticipated for a site located on the coast. The majority of sulfate in rain and dry deposition is of anthropogenic origin. Potassium and calcium can have marine and anthropogenic sources. Forty-six percent (46%) of the nutrient nitrogen entering the Bays is from atmospheric deposition to the Bay and watershed. While contaminant inputs have significant seasonal variability, the long term inputs are consistent when integrated over longer temporal intervals (e.g., years). Trace elements Zn, Pb, As, Cu and Cd have anthropogenic sources. Organic contaminants including polycyclic aromatic hydrocarbons (PAH), pesticides, and PCB are deposited and removed from the Coastal Bend Bays by atmospheric deposition and gas exchange. These data provide a robust estimate of atmospheric deposition that can be applied to the Coastal Bend Bays ecosystem. Further research is required to determine how the timing of nutrient inputs to the Coastal Bend Bays system from atmospheric deposition affects phytoplankton species and abundance and their role in harmful alga blooms, hypoxia and sea grass abundance.