泥鳅扰动对稻田土壤孔隙水中砷的影响

Effects of loach disturbance on arsenic in soil pore water of paddy field

为探究不同养殖密度(低密度、中密度、高密度)泥鳅扰动对土壤孔隙水中砷(As)含量的影响,采集湖南浏阳稻田表层土,以泥鳅为扰动生物,对泥鳅扰动土壤孔隙水中As含量变化进行研究,为进一步开展土壤-水环境中As循环研究提供基础数据。结果表明:泥鳅扰动后,土壤pH随时间先升高后降低,扩散层变宽,并逐渐向深层土壤扩散,泥鳅组土壤pH表现为:中密度组>低密度组>高密度组,低密度组和中密度组土壤溶解氧(DO)显著高于对照组和高密度组(P<0.05),中密度组土壤DO略高于低密度组,推测中密度组的扰动能力较其他密度组强;土壤-水界面pH和DO梯度变化明显,低密度组和中密度组土壤-水界面DO变化梯度较高密度组大,分层现象明显,各处理土壤体系DO表现为:土壤上覆水>土壤-水界面>土壤;泥鳅扰动促进了As由土壤向土壤上覆水迁移释放,显著增加了土壤上覆水As含量,其中低密度组促进效果较中密度组和高密度组显著;各处理土壤孔隙水As含量随时间逐渐减小(淹水期除外),从土壤深处向土壤-水界面迁移,总体呈现为土壤表层小于深层,泥鳅扰动能显著减少土壤孔隙水As含量,尤其对低密度组和中密度组土壤孔隙水As含量减少具有一定促进作用,同时也促进了土壤中As向土壤-水界面迁移释放;第7天时,泥鳅组土壤孔隙水As含量变化最显著,贯穿于整个土壤深度,低密度组As含量显著小于中密度组和高密度组,说明低密度组促进效果较中密度组和高密度组显著,这与土壤上覆水结果一致。研究表明,泥鳅扰动显著减少了土壤孔隙水As含量,其中低密度组和中密度组对不同深度土壤孔隙水As含量减少具有一定的促进作用,同时也促进了土壤中As向土壤-水界面迁移释放。

In order to explore the effects of loach disturbance of different stocking densities(low density,medium density and high density)on the arsenic(As)content in soil pore water,the surface soil of paddy field in Liuyang,Hunan Province was collected,and the changes of As content in soil pore water disturbed by loach were studied using loach As disturbance organism,providing basic data for further research on As cycling in soil-water environment.The results showed that after the disturbance of loach,soil pH first increased and then decreased with time,the diffusion layer widened,and gradually spread to the deep soil.The soil pH of loach group was as follows:medium density group>low density group>high density group,soil dissolved oxygen(DO)in low density group and medium density group was significantly higher than that in control group and high density group(P<0.05),and soil DO in medium density group was slightly higher than that in low density group,suggesting that medium density group had stronger disturbance ability than other density groups.The pH and DO gradients at the soil-water interface changed significantly.The DO gradients at the soil-water interface in low-density and medium-density groups were larger than those in the high-density group,and the stratification was obvious.The DO of each treated soil system was:overlying soil water>soil-water interface>soil.Loach disturbance promoted the migration and release of As from soil to overlying water and significantly increased the content of As in overlying water.The promotion effect of low density group was more significant than that of medium density group and high density group.The As content of soil pore water in each treatment gradually decreased with time(except in the flooding period),and migrated from the deep soil to the soil-water interface,showing that the surface soil was less than the deep soil.The disturbance of loach could significantly reduce the As content of soil pore water,especially in the low density group and the medium density group.It also promoted the migration and release of As from soil to soil-water interface.On day 7,the content of As in soil pore water of the loach group showed the most significant change throughout the entire soil depth.The content of As in the low-density group was significantly lower than that in the medium-density and high-density groups,indicating that the promotion effect of the low-density group was more significant than that in the medium-density and high-density groups,which was consistent with the results of soil overlying water.The study shows that the disturbance of loach significantly reduces the As content in soil pore water,in which the low density group and the medium density group promote the reduction of As content in soil pore water at different depths,and also promote the migration and release of As in soil to the soil-water interface.