冻融周期对棕壤性质及砷吸附解吸特性的影响

Effects of Freeze-thaw on Soil Characters and Arsenate Adsorption and Desorption

冻融是北方地区常见的自然现象,是作用于土壤的非生物应力,会对土壤中的矿物、电荷、有机物质的数量和种类以及有机物质的形态产生影响。本文以棕壤为试验材料,采用室内模拟培养的方法研究了不同冻融情况下土壤对砷吸附解吸特性的影响及其与土壤理化性质之间的关系。结果表明:朗格缪尔(Langmuir)方程可以很好地拟合各处理土壤对砷的吸附,当平衡液砷质量分数为15 mg·kg^(-1)时,土壤对砷的吸附趋于平衡状态,且未冻融土壤对砷的吸附能力明显大于冻融土壤,这与Langmuir方程中MBC的变化趋势一致。土壤中砷的解吸量随土壤吸附砷数量的增加而增加;与未冻融土壤相比,冻融土壤对砷的解吸率随冻融周期的增加而逐渐增大,说明冻融能够促进砷的解吸,增加土壤中砷的生态环境风险。冻融土壤砷的最大缓冲容量(MBC)与土壤p H、有机质、阳离子交换量和可变电荷量均具有显著或极显著的正相关关系,而冻融对土壤可变电荷量的影响可能是导致不同冻融条件下土壤砷吸附解吸差异的主要原因。探讨冻融对砷在土壤中的吸附解吸特性的影响,可为冻融区砷污染土壤的修复及生态环境风险评价提供数据参考和理论依据,具有重要的理论和现实意义。

Freeze-thawing is the common natural phenomena in northern China whichis the role of abiotic stress in soil. Freeze-thawing could influence the minerals, charge and organic material quantity, it also could influence the kind of charge and organic material form in soil. This study was based on brown soil test materials. Indoor experiment were employed to investigate the effects of arsenate adsorption and desorption ability in soils under different freeze-thawing treatments and its influencing factors. The results showed that the arsenate adsorption ability on soils could be well-described by the Langmuir equation.When the arsenic content in liquid balance was 15mg·kg-1, arsenic adsorption was tended to equilibrium state in soil. The amount of arsenate adsorption tened to increase with the the increasing of arsenate concentration. Compared with the no freeze-thaw treatments samples, arsenate adsorption capability of soils was significantly greater than unfreeze-thaw treatments samples. The amount of arsenate desorption of soils tended to decline when the amount of arsenate adsorption of soils were declined. The amount of arsenate desorption tened to increase with the the increasing of the amount of arsenate adsorption. Compared with the no freeze-thaw treatments samples, the amount of arsenate desorption of freeze-thaw treatments tened to increase with the rising cycles of freeze-thaw. The Arsenate maximum buffer capacity (MBC) of freeze-thaw soils closely related to pH, organic matter (OM), cation exchange capability (CEC), negative variable charge (CECv) and the degree reached 0.01 or 0.05 significance level. Meanwhile, the effects of CECv in freeze-thaw soils could be the main reason for the difference of soils arsenate adsorption and desorption under different freeze-thaw treatments. Explore the effects of arsenate adsorption and desorption ability in soils under different freeze-thawing treatments and its influencing factors could provide data reference and theoretical basis for restoration and ecological environment risk evaluation of the soil pollution under freeze-thawing area of arsenic which has important theoretical and realistic significance.