TY - JOUR
T1 - Deployment of DGT units in marine waters to assess the environmental risk from a deep sea tailings outfall
AU - Sherwood, John
AU - Barnett, Darlene
AU - Barnett, Neil
AU - Dover, Kylie
AU - Howitt, Julia
AU - Ii, Hiroyuki
AU - Kew, Peter
AU - Mondon, Julie
N1 - Imported on 12 Apr 2017 - DigiTool details were: month (773h) = October 2009; Journal title (773t) = Analytica Chimica Acta. ISSNs: 0003-2670;
PY - 2009/10
Y1 - 2009/10
N2 - 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 4.2 km 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 0.4 mm and the other a 0.8 mm diffusive gel layer) were deployed at three depths (50'70; 105'130; 135'155 m) for 4'7 days. Comparison of predicted water column DGT-labile metal concentrations in field deployments showed the 0.8 mm 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 (1'52 'g L'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 0.13 km of the outfall for Cd, Cr and Ni and below that for protection of 95% of marine organisms within 0.4, 0.7 and 3.6 km for lead, zinc and copper, respectively.
AB - 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 4.2 km 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 0.4 mm and the other a 0.8 mm diffusive gel layer) were deployed at three depths (50'70; 105'130; 135'155 m) for 4'7 days. Comparison of predicted water column DGT-labile metal concentrations in field deployments showed the 0.8 mm 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 (1'52 'g L'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 0.13 km of the outfall for Cd, Cr and Ni and below that for protection of 95% of marine organisms within 0.4, 0.7 and 3.6 km for lead, zinc and copper, respectively.
KW - Colloid
KW - Environmental risk
KW - Lihir Island
KW - Oxyhydroxides
KW - Sub-surface plumes
KW - Trace metals
U2 - 10.1016/j.aca.2009.06.009
DO - 10.1016/j.aca.2009.06.009
M3 - Article
SN - 0003-2670
VL - 652
SP - 215
EP - 223
JO - Analytica Chimica Acta
JF - Analytica Chimica Acta
IS - 1-2
ER -
