红树林表层沉积物老化过程中铅的赋存形态

Speciation of Lead in Mangrove Surface Sediments during Aging Process

采用3种不同类型的东寨港红树林表层沉积物,通过室内沉积物老化培养试验和改进的BCR提取法,分析了3种沉积物中铅的各赋存形态随不同老化时间与可溶性外源污染铅浓度变化的特征。结果表明,老化时间对红树林表层沉积物可还原态铅的影响不显著,对酸可提取态铅、可氧化态和残渣态铅的影响会因沉积物类型的不同而呈差异显著。随老化时间延长,沉积物A中酸可提取态铅含量先增加再降低(除1000 mg·kg^-1)、可氧化态铅含量在0,25,250 mg·kg^-1时增加;沉积物B中酸可提取态铅含量增加、残渣态铅含量降低(除500 mg·kg^-1);沉积物C中残渣态铅含量在0,25,250,500 mg·kg^-1时增加。此外,当老化时间为30,60,120 d时,添加较低外源铅浓度(25,250,500 mg·kg^-1)的沉积A和B中,酸可提取态铅和可还原态铅占总量的比例增加,残渣态铅占比减少;在沉积物C中,老化30 d后,随浓度增加,酸可提取态铅含量降低,残渣态铅含量增加,老化60 d和120 d后,可氧化态铅含量的比例呈现增加趋势。可见,外源铅进入沉积物经老化后的主要赋存形态是残渣态和可还原态,外源铅初始浓度会影响铅赋存形态达到稳定的时间,并且铅的赋存形态受到沉积理化特征的影响。结果揭示了红树林沉积物中铅的环境化学行为,可为红树林湿地修复重金属污染提供参考依据。

Three types of surface sediments in Dongzhai Harbor mangroves were collected for analysis of the changes of lead speciation patterns in the sediments with different aging time and soluble exogenous lead concentration by using indoor aging incubation experiment and modified BCR sequential extraction procedure.The results showed that the aging time had no significant effect on the reducible lead,but the effects of the aging time on the acid extractable lead,oxidizable lead and residual lead varied significantly with the types of the sediments.In the sediment A with aging,the acid extractable lead fraction increased and then decreased under all the concentrations of the soluble exogenous lead except 1000 mg·kg^-1 and the oxidizable lead fraction increased under the soluble exogenous lead concentrations of 0,25,250 mg·kg^-1;in the sediment B the acid extractable lead fraction increased while the residual lead fraction decreased(except under 500 mg·kg^-1);in the sediment C the residual lead fraction decreased under the soluble exogenous lead concentrations of 0,25,250,500 mg·kg^-1.In addition,the acid-extractable lead and reducible lead fractions increased in proportion but the residual lead fraction decreased in proportion in the sediments A and B for 30,60 and 120 days of aging with lower concentrations of exogenous lead(25,250,500 mg·kg^-1).In the sediment C the acid-extractable lead fraction decreased and residual lead fraction increased in proportion with increasing concentrations of exogenous lead after 30 days of aging.After 60 and 120 days of aging,the oxidizable lead fraction increased in proportion.Obviously,the lead mainly occurred in residual and reducible fractions in the sediments after aging.The initial concentration of exogenous lead had an effect on the time of lead speciation,and,the lead speciation was affected by the physiochemical properties of the sediments.The results reveal the environmental behavior of lead in mangrove sediments and provide a reference for remediation of heavy metal lead pollution in mangrove wetlands.