混合暴露条件下菲律宾蛤仔不同组织对几种重金属的富集与释放特征

The characteristics of heavy metal accumulation and release in Ruditapes philippinarum tissues and organs during the exposure of mixed heavy metals

应用双箱动力学模型模拟了菲律宾蛤仔在Pb、Zn、Cu、Cd、Cr、Hg和As 7种重金属混合暴露条件下,内脏团、鳃、斧足及基部和外套膜组织对重金属的生物富集与释放实验,并通过非线性拟合得到菲律宾蛤仔各组织对7种重金属的富集速率常数k1、排出速率常数k2、生物富集系数BCF、生物半衰期B1/2、富集平衡时生物体内重金属含量CAmax等动力学参数。结果表明,1)重金属在菲律宾蛤仔不同组织器官中的富集具有选择性,理论平衡状态下,Cu、Cd、As、Pd在各组织的含量分布(CAmax):内脏团>斧足及基部>鳃>外套膜;Cr分布规律(CAmax):内脏团>鳃>斧足及基部>外套膜;Hg分布规律(CAmax):斧足及基部>外套膜>鳃>内脏团;Zn分布规律(CAmax):斧足及基部>鳃>外套膜>内脏团。2)菲律宾蛤仔对不同重金属的富集系数存在显著差异(P<0.05),对Cu富集程度最高,其富集系数范围为1514.0-4818.0;其次是Cd和Hg,富集系数范围分别为104.5-975.4,255.9-447.4;As、Cr、Pb、Zn离子在菲律宾蛤仔体内富集程度较低,其富集系数均在300以内。3)菲律宾蛤仔对重金属的释放能力较差,双箱动力学模型可较好地反映混合暴露条件下菲律宾蛤仔对重金属的富集特征,但不适合对其释放特征进行描述。

Biological accumulation and release of heavy metals in Ruditapes philippinarum have been observed in previous studies. However the specific process in individual tissues remained unclear. In this study, we used two-compartment bio-concentration model to evaluate the kinetic parameters of the biological accumulation and release of seven heavy metals （ Pb, Zn, Cu, Cd, Cr, Hg, and As） in different tissues and organs of Ruditapes philippinarurn, including visceral mass, gill, foot part and mantle tissues. In the experiments R. philippinarum was exposed to water containing all seven heavy metals. The uptake rate constant （kl）, elimination rate constant （k2 ）, bio-concentration factor （BCF）, biological half-lives （B1/2 ）, and equilibrium concentration in vivo （CAmax） of heavy metals were determined with non-linear curve fitting method. The results were summarized below： （ 1 ） Different heavy metals were accumulated with a preference in major organs and tissues of R. philippinarum. The CAmax of Cu, Cd, As and Pb in R. philippinarum followed the order： visceral mass 〉 foot part 〉 gill 〉 mantle tissues; the CAmax of Cr： visceral mass 〉 gill 〉 foot part 〉 mantle tissues; Hg （CAmax） ： foot part 〉 mantle tissues 〉 gill 〉 visceral mass; Zn （CA ） ： foot part 〉 gill 〉 mantle tissues 〉 visceral mass. （2） BCFs of seven heavy metals in R. philippinarum were significantly different （ P 〈 0. 05 ）. Cu was the most accumulated heavy metal in R. philippinarum with a BCF range of 1514. 0 -4818.0, followed by Cd and Hg with a BCF range of 104. 5 -975.4 and 255.9 -447.4, respectively. As, Cr, Pb and Zn were accumulated at a lower level with the BCF values below 300. The weakest accumulation was observed for As, and the BCF values in foot part, gill and mantle tissues were 56. 0, 53.1, and 47.4 respectively. The BCF of Zn in visceral mass was 61.9. （3） After 25 days, concentrations of heavy metals in the major organs and tissues of R. philippinarum were still at high levels, which indicated R. philippinarum had weak ability to release heavy metals. Although the two-compartment kinetic model efficiently described the accumulation of heavy metals in R. philippinarum with most fitting indicators （R） above 0. 9, it was not suitable for the simulation of the release phase, for example, the R values of Pb and Cu were only 0. 110 and 0. 230 respectively.