Rasa Kimmo, Peltovuori Tommi, Hartikainen Helinä
Department of Applied Chemistry and Microbiology, University of Helsinki, P.O. Box 27, FIN-00014, University of Helsinki, Finland.
Sci Total Environ. 2006 Aug 1;366(2-3):819-25. doi: 10.1016/j.scitotenv.2005.08.007. Epub 2005 Sep 12.
Excessive use of sodium chloride (NaCl) as de-icing chemical causes environmental problems, such as elevated chloride concentrations in groundwater. On vulnerable sites, this can be avoided by using alternative organic de-icing chemicals, such as potassium formate (KHCOO). The environmental impacts of KCHOO are, however, not well known. This study reports the potential effects of NaCl and KCHOO on mechanisms controlling the mobility of cadmium (Cd) in roadside soils as a result of vehicular traffic. Changes in the solubility of Cd in a coarse mineral soil treated with these two de-icing chemicals were studied in a 50-day incubation experiment under four different moisture and temperature combinations and an initial soil Cd concentration of 3 mg kg(-1). After incubation, the distribution of soil Cd into different fractions was analyzed using a sequential extraction method. Soil pH and soil redox potential were recorded and the occurrence of Cd-Cl complexes in the soil was estimated using published stability constants. During incubation, KCHOO lowered the soil redox potential, but this was not accompanied by a decrease in the sorption capacity of oxides and the release of oxide-bound Cd into soil solution. On the other hand, elevated pH (from 4.3 to 6.7-8.5) in the formate treatments increased the sorption of Cd onto the oxide surfaces (up to 80% of total sorbed Cd). In the NaCl treatments, cation competition and formation of Cd-Cl complexes increased the water-soluble Cd fraction. Consequently, the amount of bioavailable Cd was 3.5 times smaller in the KCHOO than in the NaCl treatments.
过量使用氯化钠（NaCl）作为除冰化学品会引发环境问题，比如地下水中氯化物浓度升高。在易受影响的地区，可通过使用替代有机除冰化学品，如甲酸钾（KHCOO）来避免这种情况。然而，甲酸钾对环境的影响尚不为人所知。本研究报告了由于车辆交通，氯化钠和甲酸钾对控制路边土壤中镉（Cd）迁移机制的潜在影响。在一项为期50天的培养实验中，研究了在四种不同的水分和温度组合以及初始土壤镉浓度为3毫克/千克（-1）的条件下，这两种除冰化学品处理过的粗粒矿物土壤中镉溶解度的变化。培养后，采用连续提取法分析土壤镉在不同组分中的分布。记录土壤pH值和土壤氧化还原电位，并利用已发表的稳定常数估算土壤中镉 - 氯络合物的存在情况。在培养过程中，甲酸钾降低了土壤氧化还原电位，但这并未伴随着氧化物吸附能力的下降以及氧化物结合态镉向土壤溶液中的释放。另一方面，甲酸盐处理中pH值升高（从4.3升至6.7 - 8.5）增加了镉在氧化物表面的吸附（高达总吸附镉的80%）。在氯化钠处理中，阳离子竞争和镉 - 氯络合物的形成增加了水溶性镉组分。因此，甲酸钾处理中生物可利用镉的量比氯化钠处理中小3.5倍。
