Acidic precipitation: considerations for an air-quality standard

摘要: Acidic precipitation, wet or frozen precipitation with a H+ concentration greater than 2.5 μeq l−1, is significant air pollution problem in the United States. The chief anions accounting for rainfall are nitrate and sulfate. Agricultural systems may derive net nutritional benefits from increasing inputs of acidic rain do forest when soils alone considered. benefit because high N S requirements agricultural plants. Detrimental effects to result if atmospheric significantly add exceed production by soils. Acidification fresh waters southern Scandinavia, southwestern Scotland, southeastern Canada, northeastern States caused acid deposition. Areas these regions which this acidification occurs have common, highly volume weighted mean annual concentrations 25 l−1 higher slow weathering granitic precambrian bedrock thin deficient minerals would provide buffer capacity. Biological detectable below pH 6.0. As lake stream levels decrease 6.0, many species plants, invertebrates, vertebrates progressively eliminated. Generally, fisheries severely impacted 5.0 completely destroyed 4.8. At present time studies documenting on terrestrial vegetation insufficient establish an quality standard. It must be demonstrated that current acidity injure vegetation. For aquatic ecosystems, research indicates establishing maximum permissible value at protect most sensitive areas permanent acidification. Such standard probably other as well.