沉积物中颗粒态镉的赋存形态对文蛤富集效性的影响

Influence of Speciation on the Bioavailability of Particle-bound Cadmium in Sediments

利用颗粒物悬浮系统研究了沉积物中Cd的特定赋存形态(如氢氧化铁结合态、氢氧化铝结合态、二氧化锰结合态)对其在文蛤体内富集速率的影响.结果表明,结合于沉积物中不同组分Cd的生物有效性存在明显差异.在Cd浓度为70 mg/kg时,22 d富集实验中氢氧化铁结合态和氢氧化铝结合态Cd在文蛤体内均没有明显的积累,而二氧化锰结合态Cd在文蛤体内有明显的富集,其富集速率为(0.009 4±0.001 0)μg/(g.d)(r2=0.853 9,p<0.000 1).在Cd浓度为140 mg/kg时,氢氧化铁结合态Cd仍然无法被文蛤吸收,氢氧化铝和二氧化锰结合态Cd则可以被文蛤富集,其富集速率分别为(0.016 6±0.001 7)μg/(g.d)和(0.024 8±0.001 7)μg/(g.d).不同赋存形态Cd的生物有效性表现为:Cd-MnO2>Cd-Al(OH)3>Cd-Fe(OH)3.对于不同赋存形态的Cd,吸收效率(AE)和摄食率(IR)的差异导致了其生物有效性的不同.

In the present work,the impact of speciation on the bioavailability of cadmium in sediments was investigated.Bioaccumulation of cadmium adsorbed on various（hydr）oxide minerals,i.e.ferric hydroxide,aluminum hydroxide and manganese dioxide,by bivalve Meretrix meretrix Linnaeus,was measured using a suspending system.The results showed that the bioavailability of cadmium was significantly different for different minerals.At Cd concentration of 70 mg/kg,the accumulation of Cd by clams in Cd-Fe（OH）3 and Cd-Al（OH）3 system was not detectable after 22 days of exposure.In comparison,the clams absorbed appreciable amount of Cd from 70 mg/kg of Cd-MnO2 system.An average uptake rate of（0.0094±0.0010） μg/（g·d） for 70 mg/kg Cd-MnO2 was obtained by linear fitting curve（r^2=0.853？9,p〈0.0001）.When Cd concentration was increased to 140 mg/kg,bioaccumulation of Cd from Cd-Fe（OH）3 system was still not observed,while for the clams cultivated in Cd-Al（OH）3 and Cd-MnO2 systems,Cd was apparently as.similated in the body of the animals.The uptake rates were determined to be（0.0166±0.0017） μg/（g·d） for Cd-Al（OH）3 and（0.0248±0.0017） μg/（g·d） for Cd-MnO2.Generally,The bioaccumulation sequence of the Cd-（hydr）oxides is Cd-MnO2 〉 Cd-Al（OH）3 〉 Cd-Fe（OH）3.The type of minerals determines both assimilation efficiency and ingestion rate,consequently controls the bioaccumulation of adsorbed cadmium.