Spatial and seasonal variations in pH rainwater, Bahía Blanca - Argentina

CAMPO, A.; ZAPPERI, P.

Los Angeles

Congreso; 2013 AAG Annual Meeting; 2013

The Association of American Geographers

The city of Bahia Blanca is in the southwest of the Buenos Aires province, Argentina, its coastal location makes it an important settlement of petrochemical industries. Also, most of the grain production of the country is exported through this harbor system. Although natural rains are generally considered as being weakly acid, the area is characterized by alkaline precipitation since mean pH of rain falling on different sites of the city ranged from 7,6 y 8,2. We have registered maximum values of 9,7 and minimum of 5,8. Therefore, the purposes of this study are to characterize the spatial and seasonal variations in precipitation pH for Bahía Blanca and to examine the relationship between synoptic scale meteorology factors and rain pH. To analyze weather conditions we used the synoptic charts from the National Weather Service and we set up a network of eleven rain gauges in the city. We registered the amounts of precipitation and measured the rainwater pH with digital pH testers. We have discovered that the directions of the air mass approach affects the values of pH. Most events of high pH values have relation with the "Westerlies" circulation pattern that influences over the city. These winds carry calcium rich sediments that soils in the region lost through wind erosion. Lowest pH rainwater is under the influence of southeastern winds. Due to the circulation pattern the advection of the maritime air mass over the continent can carry Clˉ and Na+ ions injected to the atmosphere by “spray” processes.