采集北京2018年、2019年和2021年的大气降水样品,研究主要金属元素和水溶性离子的浓度和变化;重金属的湿沉降通量,水溶性离子,溶解的无机氮,大气降水中的硫及其对生态环境的影响;以及研究期间典型降水对大气污染物的清除机制。结果表明,研究期间北京地区降水以中性或碱性为主,酸雨发生的频率非常低,仅占3.06%。2018年、2019年和2021年主要金属元素总浓度分别为(4787.46±4704.31),(7663.07±8395.05),分别为(2629.13±2369.51)μg·L-1。2018年、2019年和2021年的离子总当量浓度分别为(851.68±649.16),(973.98±850.94),和(644.31±531.16)μeq·L-1。主要金属元素和离子的年际变化遵循2019年的顺序;2018年&2021年。春季主要金属元素的季节平均总浓度,夏天,秋天,和冬季(9624.25±7327.92),(4088.67±5710.14),(3357.68±3995.64),和(6203.19±3857.43)μg·L-1,和春季离子的季节性平均总当量浓度,夏天,秋天,冬季为(1014.71±512.21),(729.83±589.90),(724.35±681.40),和(1014.03±359.67)μeq·L-1,都呈现了春天>冬天>夏天>秋天的顺序。NO3-和SO42-是沉淀中的主要酸离子,而NH4+和Ca2+是主要的酸中和离子。重金属Cd的湿沉降通量很低[(0.05±0.01)mg·(m2·a)-1]。仅占主要金属元素湿沉积通量总量的(0.13±0.04)%;它的土壤安全年是291年,显著低于其他重金属,显示其生态风险相对最高。水溶性离子NH4+的总湿沉淀通量,Ca2+,NO3-,SO42-占总离子湿沉淀通量的(85.72±2.18)%,这表明它们对生态环境的综合影响可能更高。DIN湿沉积通量主要表征为NH4+-N,对夏季生态环境产生了积极影响。夏季SO42--S湿沉积通量较高,因此其对生态环境的积极影响也更大。大气降水对大气中污染物的清除作用受到各种因素的影响,这些因素的协同作用可直接影响降水对污染物的清除机制。
Atmospheric precipitation samples were collected in 2018, 2019, and 2021 in Beijing to study the concentrations and changes of the main metal elements and water-soluble ions; the wet deposition fluxes of heavy metals, water-soluble ions, dissolved inorganic nitrogen, and sulfur in the atmospheric precipitation and their impacts on the ecological environment; and the scavenging mechanisms of the typical precipitation to atmospheric pollutants during the study period. The results showed that the precipitation in Beijing during the study period was mostly neutral or alkaline, and the frequency of acid rain occurrence was very low, only accounting for 3.06%. The total concentrations of major metal elements in 2018, 2019, and 2021 were (4 787.46 ±4 704.31), (7 663.07 ±8 395.05), and (2 629.13 ±2 369.51) μg·L-1, respectively. The total equivalent concentrations of ions in 2018, 2019, and 2021 were (851.68 ±649.16), (973.98 ±850.94), and (644.31 ±531.16) μeq·L-1, respectively. The interannual changes in major metal elements and ions followed the order of 2019 > 2018 > 2021. The seasonal average total concentrations of major metal elements in spring, summer, autumn, and winter were (9 624.25 ±7 327.92), (4 088.67 ±5 710.14), (3 357.68 ±3 995.64), and (6 203.19 ±3 857.43) μg·L-1, respectively, and the seasonal average total equivalent concentrations of ions in spring, summer, autumn, and winter were (1 014.71 ±512.21), (729.83 ±589.90), (724.35 ±681.40), and (1 014.03 ±359.67) μeq·L-1, respectively, all presenting the order of spring > winter > summer > autumn. NO3- and SO42- were the main acid-causing ions in precipitation, whereas NH4+ and Ca2+ were the main acid-neutralizing ions. The wet deposition fluxes of the heavy metal Cd were very low [(0.05 ±0.01) mg·(m2·a)-1], only accounting for (0.13 ±0.04)% of the total wet deposition fluxes of main metal elements; however, its soil safety years were 291 years, significantly lower than those of other heavy metals, displaying that its ecological risk was relatively the highest. The total wet precipitation flux of water-soluble ions NH4+, Ca2+, NO3-, and SO42- accounted for (85.72 ±2.18)% of the wet precipitation flux of total ions, suggesting that their comprehensive impact on the ecological environment might have been higher. DIN wet deposition flux was mainly characterized by NH4+-N, which had a positive impact on the ecological environment in summer. SO42--S wet deposition flux was higher in summer, so its positive impact on the ecological environment was also greater. The scavenging effects of atmospheric precipitations to pollutants from the air were impacted by various factors, and the synergism effects of these factors could directly influence the scavenging mechanisms of precipitation to pollutants.