Langdon Caroline J, Meharg Andrew A, Feldmann Jörg, Balgar Thorsten, Charnock John, Farquhar Morag, Piearce Trevor G, Semple Kirk T, Cotter-Howells Janet
Institute of Environmental & Natural Sciences, Lancaster University, Lancaster, Lancs., UK LA1 4YQ.
J Environ Monit. 2002 Aug;4(4):603-8. doi: 10.1039/b201366p.
Arsenic speciation was determined in Lumbricus rubellus Hoffmeister from arsenic-contaminated mine spoil sites and an uncontaminated site using HPLC-MS, HPLC-ICP-MS and XAS. It was previously demonstrated that L. rubellus from mine soils were more arsenate resistant than from the uncontaminated site and we wished to investigate if arsenic speciation had a role in this resistance. Earthworms from contaminated sites had considerably higher arsenic body burdens (maximum 1,358 mg As kg-1) compared to the uncontaminated site (maximum 13 mg As kg-1). The only organo-arsenic species found in methanol/water extracts for all earthworm populations was arsenobetaine, quantified using both HPLC-MS and HPLC-ICP-MS. Arsenobetaine concentrations were high in L. rubellus from the uncontaminated site when concentrations were expressed as a percentage of the total arsenic burden (23% mean), but earthworms from the contaminated sites with relatively low arsenic burdens also had these high levels of arsenobetaine (17% mean). As arsenic body burden increased, the percentage of arsenobetaine present decreased in a dose dependent manner, although its absolute concentration rose with increasing arsenic burden. The origin of this arsenobetaine is discussed. XAS analysis of arsenic mine L. rubellus showed that arsenic was primarily present as As(III) co-ordinated with sulfur (30% approx.), with some As(v) with oxygen (5%). Spectra for As(III) complexed with glutathione gave a very good fit to the spectra obtained for the earthworms, suggesting a role for sulfur co-ordination in arsenic metabolism at higher earthworm arsenic burdens. It is also possible that the disintegration of As(III)-S complexes may have taken place due to (a) processing of the sample, (b) storage of the extract or (c) HPLC anion exchange. HPLC-ICP-MS analysis of methanol extracts showed the presence of arsenite and arsenate, suggesting that these sulfur complexes disintegrate on extraction. The role of arsenic speciation in the resistance of L. rubellus to arsenate is considered.
利用高效液相色谱-质谱联用仪（HPLC-MS）、高效液相色谱-电感耦合等离子体质谱联用仪（HPLC-ICP-MS）和X射线吸收光谱（XAS），对采自受砷污染的矿渣场和未受污染场地的红正蚓（Lumbricus rubellus Hoffmeister）体内的砷形态进行了测定。此前已有研究表明，来自矿土的红正蚓比来自未受污染场地的红正蚓对砷酸盐具有更强的抗性，我们希望研究砷形态在这种抗性中是否起作用。与未受污染场地（最高13毫克砷/千克）相比，来自受污染场地的蚯蚓体内砷的负荷量要高得多（最高1358毫克砷/千克）。在所有蚯蚓种群的甲醇/水提取物中发现的唯一有机砷物种是砷甜菜碱，使用HPLC-MS和HPLC-ICP-MS进行了定量分析。当以总砷负荷的百分比表示时，来自未受污染场地的红正蚓体内砷甜菜碱浓度较高（平均23%），但砷负荷相对较低的受污染场地的蚯蚓体内也有较高水平的砷甜菜碱（平均17%）。随着砷体内负荷的增加，砷甜菜碱所占百分比呈剂量依赖性下降，尽管其绝对浓度随着砷负荷的增加而升高。文中讨论了这种砷甜菜碱的来源。对来自砷矿的红正蚓进行的XAS分析表明，砷主要以与硫配位的As(III)形式存在（约30%），还有一些与氧配位的As(V)（5%）。与谷胱甘肽络合的As(III)的光谱与蚯蚓获得的光谱非常吻合，这表明在蚯蚓体内砷负荷较高时，硫配位在砷代谢中起作用。也有可能由于（a）样品处理、（b）提取物储存或（c）HPLC阴离子交换，As(III)-S络合物发生了分解。文中考虑了砷形态在红正蚓对砷酸盐抗性中的作用。
