酸化方式对土壤中铜的形态及生物有效性的影响

为了探明不同土壤酸化方式对土壤中Cu的形态及生物有效性的影响,采集了湖北黄棕壤和山东寿光潮土两种不同程度Cu污染土壤,采用直接酸化(硫酸、T1)、模拟施肥(硫酸铵酸化、T2)和模拟人工酸雨(T3)三种土壤酸化措施,研究不同酸化方式对土壤中Cu的形态变化及芥蓝对Cu吸收、转化的影响。试验结果表明:在两种土壤中,随着土壤酸化程度的加剧,芥蓝生物量均显著降低(P0.05),而茎叶中Cu含量显著增加;在潮土中芥蓝植株Cu浓度最大值是最小值的1.43倍,黄棕壤中则为1.50倍。随土壤酸化程度增加,土壤中0.1 mol-Mg Cl2可交换态Cu的含量显著增加:潮土中,随着p H降低,交换态铜含量最大增加10.7%,比对照增加了451.5%;黄棕壤中,随着p H降低,土壤中可交换态Cu含量从2.33%增加到12.07%,比对照增加了418.0%。芥蓝茎叶中Cu含量与土壤交换态Cu间呈极显著的正相关关系,相关系数达0.763以上;在两种土壤中,不同酸化措施的土壤中Cu有效态含量与土壤p H呈显著的线性负相关lg(EXC)=-alg(p H)+b],线性方程的斜率在-0.314~-0.352之间,基于方程斜率可知,在降低相同p H值条件下,各酸化措施对土壤中Cu的活化顺序为T3T2T1,由此可以推断,降低相同p H值条件下,由酸雨导致的土壤中重金属的活化程度大于施肥和工业废水的酸化作用。

Effects of Different Acidification Methods on Forms and Bioavailability of Cu in Soils

The influence of soil acidification on forms and bioavailability of heavy metals in soils has not been understood well. In this study, two types of Cu polluted soils collected from Daye, Hubei(yellow brown soil) and Shouguang, Shandong(alluvial soil) were used to examine the changes of forms and availability of soil Cu under three different acidification treatments, i.e. direct acidification--sulfuric acid(T1), fertilizer acidification--ammonium sulfate(T2) and simulated acid rain(T3). Acidification treatments decreased the biomass of Brassica oleracea L., but increased the shoot Cu concentrations(P<0.05). In alluvial soil, the maximum concentration of the shoot Cu was 1.43 times as much as the minimum, and 1.50 times in yellow brown soil. Soil exchangeable Cu increased significantly with increasing acidification. Compared with the control, 0.1 mol·L^-1 MgCl₂-exchangeable Cu was up to 10.7%, an increment of 451.5%, in the alluvial soil; while it was up to 12.07%, an increase of 418% in the yellow brown soil. Significant positive correlation was observed between soil exchangeable Cu and the shoot Cu of Brassica oleracea L. with correlation coefficient above 0.80. However, soil exchangeable Cu had a significant negative linear correlation with soil pH lg(EXC)=-alg(pH)+b], with the slope of -0.314~-0.352.The increase of soil Cu bioavailability by soil acidification followed the order:T3>T2>T1, showing that the bioavailability of heavy metals would be greater in soils acidified by acid rain than in those by fertilizers and industrial wastewater.