午夜欧美大片免费观看,欧美激情综合五月色丁香,亚洲日本在线视频观看,午夜精品福利在线

Characteristics and variation trends of acid rainfall in Chengdu are analyzed using the historical observation data of acid rains combined with the concentrations of air pollutants and other surface meteorological data such as precipitation amount and winds at Wenjiang and Jianyang stations from 2006 to 2017. Results show that the average pH of precipitation and the frequency of acid rains were 4.74 and 51.6% at Wenjiang, respectively, while the corresponding values were 5.64 and 27.2% at Jianyang, implying that the frequency of acid rains was not distributed uniformly across the geographical area. Seasonal variations of pH and K values of precipitation were significant, with high pH values in summer and low in winter. In contrast, the high K values were observed in winter and low values in summer. The annual variation trends of pH of precipitation increased during the observation periods, corresponding to the decreasing trends of frequency and intensity of acid rains. In addition, the K values decreased dramatically, with a decrease rate of 3.5 and 3.7 μS〖DK〗·cm-1〖DK〗·a-1 at Wenjiang and Jianyang, respectively. The pH of precipitation showed negative correlations with SO2 and NO2 with a correlation coefficient of -0.488, and sulfur oxides contributed less to acid rain pollution; while K values exhibited highly positive correlations with the above pollutants with a correlation coefficient of 0.657. The relationship between pH and K values for SO2 and NO2 were stronger than that of PM10 and PM2.5. Additionally, the concentrations of atmospheric particulate had an significant impact on the K values. The pH varied insignificantly with precipitation amount, while K values decreased with the increase of precipitation amount. Winds showed a positive correlation with pH but negative correlation with K values of precipitation.