Sherwood John E, Barnett Darlene, Barnett Neil W, Dover Kylie, Howitt Julia, Ii Hiroyuki, Kew Peter, Mondon Julie
School of Life and Environmental Sciences, Deakin University Warrnambool Campus, Victoria 3280, Australia.
Anal Chim Acta. 2009 Oct 12;652(1-2):215-23. doi: 10.1016/j.aca.2009.06.009. Epub 2009 Jun 9.
Measurements of total, filterable and DGT-labile concentrations of nine metals (Al, Cd, Cr, Cu, Fe, Pb, Mn, Ni and Zn) have been made at five sites up to 4.2km from a deep sea tailings outfall operated by Lihir Gold Ltd. at Lihir Island, Papua New Guinea. At each site, pairs of DGT units (one containing a 0.4mm and the other a 0.8mm diffusive gel layer) were deployed at three depths (50-70; 105-130; 135-155m) for 4-7 days. Comparison of predicted water column DGT-labile metal concentrations in field deployments showed the 0.8mm DGT units were relatively enriched in metals, with the effect being greatest closer to the outfall for Pb and Mn and least for Fe, Cr, Ni and Zn. The most likely explanation for this is that in addition to simple ion diffusion, kinetic factors associated with ageing or desorption processes govern release of metals from iron and aluminium oxyhydroxide colloids which diffuse through the gels. The thicker gels have a longer residence time over which metals can be released for adsorption. This model explains why enrichment is most pronounced near the outfall; more distant sites have lower colloid concentrations because of the longer time for coagulation to increase particle sizes to the extent they cannot enter the gels. Total and filterable metal (FM) concentrations were frequently below the limits of detection (LOD) achievable by conventional ICP-AES (1-52microgL(-1)) and this limited their usefulness for assessing environmental risk and for metal speciation determination. Because of its pre-concentration step DGT gave metal concentrations above their LODs and these decreased exponentially with distance from the outfall. Concentrations of DGT-labile metal fell below Australian water quality guidelines for protection of 99% of marine organisms within 0.13km of the outfall for Cd, Cr and Ni and below that for protection of 95% of marine organisms within 0.4, 0.7 and 3.6km for lead, zinc and copper, respectively.
在巴布亚新几内亚利希尔岛，对利希尔黄金有限公司运营的深海尾矿排放口4.2公里范围内的五个地点的九种金属（铝、镉、铬、铜、铁、铅、锰、镍和锌）的总量、可过滤量和DGT活性浓度进行了测量。在每个地点，将一对DGT装置（一个含有0.4毫米扩散凝胶层，另一个含有0.8毫米扩散凝胶层）部署在三个深度（50 - 70米；105 - 130米；135 - 155米），放置4 - 7天。现场部署中预测的水柱DGT活性金属浓度比较表明，0.8毫米的DGT装置金属相对富集，铅和锰在靠近排放口处这种效应最大，铁、铬、镍和锌最小。对此最可能的解释是，除了简单的离子扩散外，与老化或解吸过程相关的动力学因素控制着金属从通过凝胶扩散的铁和铝的羟基氧化物胶体中的释放。较厚的凝胶有更长的停留时间，在此期间金属可以释放以供吸附。该模型解释了为什么在排放口附近富集最为明显；更远的地点胶体浓度较低，因为凝聚时间更长，颗粒尺寸增大到无法进入凝胶的程度。总金属和可过滤金属（FM）浓度经常低于传统ICP - AES可达到的检测限（LOD）（1 - 52微克/升），这限制了它们在评估环境风险和金属形态测定方面的用途。由于其预浓缩步骤，DGT给出的金属浓度高于其检测限，并且这些浓度随与排放口距离的增加呈指数下降。对于镉、铬和镍，排放口0.13公里范围内DGT活性金属浓度低于澳大利亚保护99%海洋生物的水质准则，对于铅、锌和铜，分别在0.4公里、0.7公里和3.6公里范围内低于保护95%海洋生物的水质准则。
