湘西黑色页岩关键带铅的分布及活动特征  

Distribution and mobility characteristics of lead in critical zones of black shales in Western Hunan

作　　者：胡弘桀 彭渤[1,2] 邬思成 吴能球 谢淑容[1,2] 杨霞[1,2] HU Hongjie;PENG Bo;WU Sicheng;WU Nengqiu;XIE Shurong;YANG Xia(College of Geographical Sciences,Hunan Normal University,Changsha,410081,China;Key Laboratory of Environmental Heavy-Metal Contamination and Ecological Remediation,Hunan Normal University,Changsha,410081,China)

机构地区：[1]湖南师范大学地理科学学院,长沙410081 [2]湖南师范大学环境重金属污染机理与生态修复重点实验室,长沙410081

出　　处：《环境化学》2024年第8期2728-2740,共13页Environmental Chemistry

基　　金：湖南省“十四五”重点学科地理学建设项目(地理学-5010002);湖南省发育生物与生育物种优势特色学科群建设项目(2022XKQ0207);湖南省教育厅重点项目(18A012);湖南省自然科学基金(2022JJ30030)资助~~

摘　　要：本研究对湘西一带发育于下寒武统黑色页岩关键带上的新鲜黑色页岩、风化黑色页岩和黑色页岩土壤进行系统采样和元素地球化学分析,探讨黑色页岩关键带铅(Pb)的分布和循环活动特征.结果表明,该区黑色页岩相对富集SiO_(2)、Al_(2)O_(3)、Fe_(2)O_(3)等惰性组分和Pb、Zn、Cu、Cd等重金属,而亏损MgO、Na_(2)O、K_(2)O等活性组分.黑色页岩关键带上Pb含量变化在2.3—80 mg·kg^(−1)之间,分布不均匀.且Pb富集不明显(EF<1.5),自新鲜黑色页岩→风化黑色页岩→黑色页岩土壤,其富集程度趋于降低.质量平衡计算表明,黑色页岩风化过程中,赋存于硫化物矿物中的Pb等重金属活动性较强,Pb随黄铁矿等硫化物氧化分解而淋滤释出,淋滤释出率平均达−21.9%(n=36);Pb等重金属在黑色页岩风化的淋滤释出后,于成土作用过程中进一步被淋滤释出,淋滤释出率平均达−29.8%(n=36).黑色页岩风化-成土过程中Pb的淋滤释出与黑色页岩中钙质含量低,硫化物氧化分解产生的酸难于被中和等因素有关.This paper reports the results of a geochemical study on the so-called black shale critical zones by analyzing the concentrations of major elements and heavy metals lead and others in fresh black shales,weathered black shales,and soils derived from black shales of the Lower Cambrian in western Hunan province of China.The results showed that the black shales in this area was relatively rich in major elements SiO_(2),Al_(2)O_(3)and Fe_(2)O_(3),and heavy metals Pb,Zn,Cu,Cd and others;and depleted in mobile elements in MgO,Na_(2)O,and K_(2)O and others.Concentrations of Pb in the black shale critical zones varied from 2.3-80(mg·kg^(−1)),suggesting Pb was heterogeneously distributed in the rocks of the critical zones,and the enrichment of Pb in the critical zones was insignificant(EF<1.5).The enrichment degrees of Pb decreased from those in the fresh black shales,to the weathered black shales,and then to soils derived from black shales.Results of the mass balance calculation showed that Pb and other metals that were enriched within sulfide minerals of the black shales displayed a strong mobility,for which Pb and other metals were released form the critical zones during the oxidization of sulfide minerals(e.g.,pyrite),with release proportion in average of−21.9%(n=36).Moreover,Pb and other metals were further strongly released out from the system during the pedogenesis followed the weathering processes,with a release proportion in average of−29.8%(n=36).The release of Pb during weathering and soil formation processes was associated closely with the low contents of CaO in the black shales,because such a low concentration of CaO in black shales would hardly lead to the neutralization of the acids produced during sulfide oxidization during weathering.

关 键 词：黑色页岩关键带 主量元素 风化-成土作用 PB 的活动性 湘西. 

分 类 号：X-1[环境科学与工程] O6[理学—化学]