Seasonal variation of polycyclic aromatic hydrocarbons in soil and air of Dalian areas, China: an assessment of soil-air exchange.
Seasonal variation of polycyclic aromatic hydrocarbons in soil and air of Dalian areas, China: an assessment of soil-air exchange.
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DOI：
10.1039/b805840g
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发表时间：
2008-08
期刊：
影响因子：
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通讯作者：
De-gao Wang;Meng Yang;Hongliang Jia;Lei Zhou;Yifan Li
中科院分区：
文献类型：
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作者：
De-gao Wang;Meng Yang;Hongliang Jia;Lei Zhou;Yifan Li
2007年对大连市城乡土壤和大气中多环芳烃的浓度进行了季节性监测。在土壤中，夏季各PAHs的平均浓度均大于冬季，而重质PAHs的浓度冬季大于夏季。冬季/夏季PAHs浓度比值（R（W/S））随土壤中PAHs分子量的增加而增加，说明分子量大的PAHs在冬季比夏季更容易沉积到土壤中。空气中各PAHs的平均浓度冬季均大于夏季。与土壤中的R（W/S）相比，空气中的R（W/S）值均大于1，说明冬季总体上单个PAH浓度大于夏季。土壤和大气样品中各多环芳烃化合物的平均浓度组成测定结果表明，多环芳烃剖面的季节变化很小。结果表明，冬夏季土壤和大气中的多环芳烃有相同或相似的来源。利用土壤和空气浓度计算土壤和空气之间的逸度系数，评估了土-气平衡的方法。计算的土壤-空气逸度系数表明，无论冬夏，大连地区土壤对轻质量多环芳烃（2 ~ 3环）均为二级源，对重质量多环芳烃（5 ~ 6环）仍为汇.中重PAHs（4 ~ 5环）接近土-气平衡，随季节或功能区的变化，有在土-气间转移的趋势。夏季（平均温度298 K）多环芳烃的逸度系数大于冬季（平均温度273 K），表明夏季多环芳烃从土壤向大气迁移的趋势大于冬季。温度、降雨量等环境条件的变化会影响多环芳烃在土壤和空气之间的移动。冬季和夏季城市样点中多环芳烃的逸度系数均大于农村样点。这种现象可能与城市热岛效应导致城市站点的温度高于农村站点有关。
The seasonal variations of concentrations of PAHs in the soil and the air were measured in urban and rural region of Dalian, China in 2007. In soil, mean concentrations of all PAHs in summer were larger than those in winter, whereas the concentrations of heavier weight PAHs in winter were larger than those in summer. Winter/summer concentration ratios for individual PAHs (R(W/S)) increased with the increase of molecular weight of PAHs in soil, indicating that PAHs with high molecular weight were more easily deposited to soil in winter than summer. In air, mean concentrations of all PAHs in winter were larger than those in summer. In comparison with the R(W/S) in soil, all the values of R(W/S) in air were larger than one indicating that the entire individual PAH concentrations in winter were larger than those in summer. The average concentration composition for each PAH compound in soil and air samples was determined and the seasonal change of PAH profile was very small. It was suggested that PAHs in soils and air had the same or similar sources both in winter and summer. The approach to the soil-air equilibrium was assessed by calculating fugacity quotients between soil and air using the soil and air concentrations. The calculated soil-air fugacity quotients indicated that soil acted as a secondary source to the atmosphere for all lighter weight PAHs (two-three rings) and it will continue to be a sink for heavier weight PAHs (five-six rings) in the Dalian environment, both in winter and summer. Medium weight PAHs (four-five rings) were close to the soil-air equilibrium and the tendency shifted between soil and air when season or function region changed. The fugacity quotients of PAHs in summer (mean temperature 298 K) were larger than those in winter (mean temperature 273 K), indicating a higher tendency in summer than winter for PAHs to move from soil to air. The variation of ambient conditions such as temperature, rainfall, etc. can influence the movement of PAHs between soil and air. Most of the fugacity quotients of PAHs for the urban sites were larger than that for the rural site both in winter and summer. This phenomenon may be related with that the temperatures in urban sites were higher than those in the rural site because of the urban heat island effect.