江苏省里下河地区富硒土壤元素地球化学特征及其成因机制

Elemental geochemical characteristics and genetic mechanisms of Se-rich soils in the Lixiahe area in Jiangsu Province

基于江苏省里下河平原区所积累的有关生态地球化学调查数据,通过元素分布对比、相关分析、R型聚类分析、主成分分析等,系统探讨了该区富硒土壤的元素地球化学特征和成因机制,为合理开发利用第四纪沉积类型的富硒土地资源等提供了依据或线索。研究结果显示:里下河富硒土壤为典型的第四纪沉积成因,富有机质、偏还原的封闭的潟湖相沉积环境是形成局地富硒土壤的基础;富硒土壤特征元素组合为Se-OM-N-K-Fe-Co,主要位于地表30 cm以上深度,Se含量多为(0.3~0.4)×10^(-6),分布均匀;土壤中大多数元素之间有显著正相关性,Se-OM、Se-CEC的相关系数r分别为0.74、0.66,Se和pH之间有较显著负相关性,相关系数为-0.35;富硒土壤形成要经历成土母质初始富集、成土期间再富集和成土后表生富集3个富Se阶段,以及非潟湖相沉积物(如海相沉积等)的干扰,有机质吸附、胶体吸附和生物地球化学作用是导致土壤Se富集的主要原因;富硒土壤中还伴有Cu、Pb、Zn、Ni、Co、V等相对富集,但相关重金属未超标。

Based on relevant eco-geochemical survey data collected fromthe Lixiahe plain area in Jiangsu Province,this study systematically explored the geochemical characteristics of elements in Se-rich soils and the genetic mechanism through elemental distribution contrast,correlation analysis,R-type cluster analysis,and principal component analysis.This study can be referenced for the rational production and utilization of Se-rich land resources of the Quaternary sedimentary type.Key findings are as follows:(1)Se-rich soilsin the Lixiahe area are typical Quaternary sediments,and the closed lagoon facies sedimentary environment characterized by rich organic matter and slightly reducing conditions plays a foundational role in the formation of local Se-rich soils;(2)Typical element association,Se-OM-N-K-Fe-Co,in Se-rich soils is primarily located within a depth of 30 cm from the surface,with Se content ranging mostly from 0.3×10^(-6)to 0.4×10^(-6)in a uniform distribution;(3)Significant positive correlations between Se and some other elements can be observed in the soils,with the correlation coefficients(r)between Se and OM,and Se and CEC being 0.74 and 0.66,respectively.In contrast,Se exhibits a significant negative correlation with pH,with a correlation coefficient of-0.35;(4)The formation of Se-rich soilsmight have experienced three Se enrichment stages:the initial enrichment in soil parent materials,the re-enrichment during soil formation,and the supergene enrichment after soil formation,accompanied by interference from non-lagoon facies sediments(such as marine sediments).Organic matter adsorption,colloid adsorption,and biogeochemistry constitute the main causes of Se enrichment in the soils;(5)The Se-rich soils are also relatively enriched in heavy metal elements like Cu,Pb,Zn,Ni,Co,and V,which are within the national limit standards.