Influence of calcareous soil particulates on acid rain: belo horizonte metropolita region, Brazil

摘要

This paper describes the characteristics ofacid rain in the Belo Horizonte Metropolitan Region/RMBH,Brazil, a region influenced by sulfur dioxide andnitrogen oxides emitted by industries and automotivevehicles. The region also receives the prevailing windsfrom the large karstic area where an intensivecalcareous exploitation occurs. The supply of alkalinecalcareous dust to neutralize anthropogenic acids in theatmosphere can control the acidity of the RMBHprecipitation. Rainfall was collected from 3 monitoringstations, on a daily basis, using bulk collectors, fromOctober 1993 to February 1994. The volume-weighted meanpHs ranged from 4.98 to 5.27. the dominating ion followedby SO42-, NH4+ and NO3-. Acidity in precipitation was wellcorrelated with SO42-: Ca2+ and NO3-: Ca2+ ratios. In thedry periods, these calcium particles are continuouslyemitted to the atmosphere and as a result the acidityof the first rain that passes through this bufferedatmosphere is lower. However, in a continuous rainyperiod the rain acidity tends to increase progressively.The results showed the great acid neutralizing capacityof the RMBH atmosphere by calcium particles.