中文摘要：

于2011年冬季使用SASS采样器在清华大学采集PM2.5样品,并对其中重金属和水溶性重金属（As、Cd、Cr、Cu、Mn、Pb和Zn等）以及无机离子进行了分析.结果表明,采样期间水溶性重金属浓度较高,As、Cd、Cr、Cu、Mn、Pb 和 Zn 平均浓度依次为8.42,3.18,1.99,7.84,30.82,49.27,412.81ng/m^3.Cd和水溶性As平均浓度超过《环境空气质量标准》中建议浓度限值.水溶性重金属在重污染期间易出现富集,灰霾和采暖期间As、Cd、Cr、Cu、Mn、Pb和Zn平均浓度都有增加趋势.水溶性重金属的逐日变化趋势与重金属和PM2.5有较好的一致性.水溶性重金属在重金属中比重：50%≤Zn和As；20%〈V、Mn、Se、Sr、Cd、Sb≤50%；其他元素≤20%.Zn水溶性比例高达66.8%,鉴于其浓度高、毒性强,应成为重点研究对象.受不同污染状况的影响时,Cd、Mn和Pb的水溶性稳定,As、Cr、Cu和Zn的水溶性较稳定.采样期间北京市PM2.5中Cd、Cr、Cu、Mn、Pb和Zn的水溶性随中和比率（NR）的变大而增强,As水溶性随NR变大而减弱.

英文摘要：

PM2.5 samples were collected at Tsinghua University by SASS sampler in winter 2011. Heavy metals and water-soluble heavy metals of As, Cd, Cr, Cu, Mn, Pb and Zn, as well as water inorganic soluble ions were analyzed. The results indicated that the concentrations of water-soluble heavy metals were at high levels during the sampling period. The average concentrations of water-soluble heavy metals of As, Cd, Cr, Cu, Mn, Pb and Zn were 8.42, 3.18, 1.99, 7.84, 30.82, 49.27 and 412.81ng/m^3, respectively. The average concentrations of Cd and water-soluble As exceeded the National Proposed Standard of Ambient Air Quality Standard, more attention should be paid to these two elements. Water-soluble heavy metals were enhanced during heavily polluted episodes. Compared with non-haze and non-heating period, water-soluble As, Cd, Cr, Cu, Mn, Pb and Zn increased during haze days and heating period. The variations of water-soluble heavy metals tracked well with those of total heavy metals and PM2.5. The fractions of water-soluble heavy metals in total heavy metals were≥50%for Zn and As;〈20%and≤50%for V, Mn, Se, Sr, Cd, Sb;and≤20%for the rest elements. The water-soluble Zn contributing up to 66.8% of the total Zn was of particular concern due to its high concentration level and toxicity. The water-solubility of Cd, Mn and Pb was stable during different pollution conditions,whereas it was less stable for As, Cr, Cu and Zn. During the study period, the water-solubility of Cd, Cr, Cu, Fe, Mn, Pb and Zn increased as a function of neutralization ratio （NR）, whereas, As showed an opposite trend.