广西岩溶区石漠化程度对土壤颗粒中汞分布的影响

Effect of rocky desertification on mercury distribution in soil particles from karst area of Guangxi

石漠化是广西岩溶地区最为严重的生态问题之一,部分石漠化地区的土壤汞污染问题比较突出。为深入了解广西岩溶区石漠化土壤中汞(Hg)的变化特征及与土壤粒径的关系,采集广西环江县汞地质背景较高的不同石漠化程度(潜在石漠化、轻度石漠化、中度石漠化、重度石漠化)的表层土样,运用筛分法研究不同石漠化土壤粒级组成及汞在不同粒级土壤中的分布特征。结果表明,整个石漠化样地以>0.25 mm粒级土壤为主(84.3%~89.2%),其次是0.25~0.053 mm(10.1%~14.5%),而<0.053 mm粒级土壤所占比例最少(0.38%~0.83%)。随着石漠化程度的加剧,>2 mm粒级土壤所占比例减少,<2 mm粒级土壤所占比例增加。相关性分析表明,不同石漠化程度土壤汞含量与>2 mm粒径呈负相关,与<2 mm粒径呈正相关,重度石漠化反之。汞含量具有显著的粒级效应,随着粒级的减少而增大,在<0.053 mm粒级达到最大值且累积系数较高,汞在不同粒级上的累积效应与粒级上的含量一致。汞在不同粒级土壤质量累积效应所占比例不同,粗颗粒质量累积效应比例比细颗粒高。

Rocky desertification is one of the most serious ecological problems in karst areas in Guangxi,and mercury pollution in some rocky desertification areas is more prominent.In order to understand the variation characteristics of mercury(Hg)in rocky desertification soils and the relationship between Hg and soil particle size in in Guangxi karst area,surface soil samples with different degrees of rocky desertification(potential rocky desertification,light rocky desertification,moderate rocky desertification and severe rocky desertification)with high geological background of mercury were collected in Huanjiang,Guangxi.The sieve method was used to study the sized composition of different rocky desertification soils and the distribution characteristics of mercury in different sizes.The results showed that the whole rocky desertification plot was dominated by >0.25 mm sized soil(84.3%-89.2%),followed by 0.25-0.053 mm(10.1%-14.5%),and the proportion of <0.053 mm sized soil is the least(0.38%-0.83%).With the increase of rocky desertification degree,the proportion of >2 mm sized soil decreases,and the proportion of <2 mm sized soil increases.Correlation analysis shows that soil mercury content of different rocky desertification degrees is negatively correlated with >2 mm particle size,and positively correlated with <2 mm particle size,and vice versa for severe rocky desertification.The mercury content has a significant grain-level effect,which increases with the decrease of sized soil,reaches the maximum at the <0.053 mm particle size and has a high cumulative coefficient.The cumulative effect of mercury on different particle sizes is consistent with the content at the grain level.Mercury has a different proportion of soil mass accumulation effects at different grain sizes,and the coarse particle mass cumulative effect ratio is higher than that of fine particles.