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利用常规气象观测资料、探空资料、污染物浓度及AQI资料、NCEP再分析资料等,对2018年11月24日至12月3日夜间常州持续11 d的强浓雾和严重霾天气过程进行了分析。结果表明：（1）此次雾-霾过程持续时间长、范围广、强度大、污染重。（2）中纬度地区高层持续纬向环流控制、中低层暖脊稳定存在,地面持续受均压场或弱倒槽顶部、弱冷锋前部影响,是这次持续性雾-霾过程的重要天气条件。（3）边界层内弱辐散、负涡度及弱的下沉气流是此次雾-霾天气得以长时间维持、发展的动力因子。近地层长时间水汽饱和且维持小风速利于雾-霾的长时间维持。（4）近地面高强度的贴地逆温长时间维持和持续较低的混合层高度是此次雾-霾形成、发展和长时间维持的重要热力条件。雾比霾的平均混合层高度明显偏低且霾等级越高混合层高度越低,混合层高度的变化先于能见度变化,对雾-霾临近预警有较好的指导作用。（5）弱冷空气渗透、风速适当增加、混合层高度的先期快速下降、负净辐射曝辐量绝对值的明显增大是雾爆发性增强的主要原因。 相似文献
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《Applied Geochemistry》2003,18(9):1373-1386
The Baccu Locci stream catchment (Sardinia, Italy) is affected by serious As contamination as a consequence of past mining. The presence of both point and widespread sources of contamination (waste-rock dumps and flotation tailings, respectively) strongly affects surface water chemistry, and produces high As concentrations (hundreds of μg l−1) in stream waters. Water chemistry of the Baccu Locci stream changes considerably over a distance of about 10 km as a consequence of various, locally concomitant, processes acting along the stream course: (1) mixing with metal-rich SO4 waters; (2) dissolution/precipitation of metal-bearing phases; (3) mixing with HCO3-dominated lake waters; (4) gypsum dissolution coupled with calcite precipitation; (5) mixing with dilute surface and/or ground waters. In contrast to metals (e.g. Pb, Cu, Zn and Cd), whose dissolved concentrations rapidly decrease downstream of the mined area through (co-)precipitation/adsorption mechanisms, As concentrations tend to gradually increase (up to 0.9 mg l−1) along the stream course as far as the alluvial plain, though significant variations are locally observed. This behaviour is mainly due to the higher mobility of As than metals under the near neutral-oxidative conditions occurring in the Baccu Locci stream waters. Results of a leaching test indicate that part of the As contained in the flotation tailings occurs as As(III), which is more mobile and less strongly sorbed than As(V). The As released to the waters by various mechanisms (i.e. release/desorption from the Fe(III)-hydroxides coatings of silicate grains, oxidation of residual arsenopyrite, decomposition of scorodite) tends to remain in solution and to be transported long distances. As a consequence of the widespread presence of highly As-contaminated flotation tailings all over the medium-lower Baccu Locci stream catchment, long-term As contamination is expected. 相似文献
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利用2016—2018年常州市区环境空气细颗粒物数据,结合同期地面气象资料,分析了常州市区PM2.5以及气象因素的变化特征,并统计分析气象因素对PM2.5浓度的影响。结果表明：常州市区PM2.5、降水量、相对湿度和气温等具有明显季节性,呈夏季较高冬季较低,而气压夏季较低冬季较高的特征。相对湿度与PM2.5呈正相关,即随着相对湿度的增加PM2.5超标率和平均浓度均增加;降水对PM2.5具有一定的清除作用,清除率与降水前PM2.5浓度、降水量、降水强度有关,降水量、降水强度越大,则降水清除效果越好,而降水前PM2.5浓度较小,则清除率不明显;常州市区偏西风时PM2.5的超标率和平均浓度较其他风向较高;风速对常州市区PM2.5的影响呈负相关,即风速越大PM2.5超标率和平均浓度均减小;常州市区地面天气形势可以分为两种类型,第一种类型表现为气压较低气温较高,PM2.5超标率以及平均浓度相对较低,而第二种类型表现为气压较高气温较低,PM2.5超标率以及平均浓度相对较高。 相似文献
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