Department of Earth Sciences and Research Center on Natural Resources, Health and the Environment, University of Huelva, Campus 'El Carmen', Fuerzas Armadas s/n, 21071, Huelva, Spain.
Department of Earth Sciences and Research Center on Natural Resources, Health and the Environment, University of Huelva, Campus 'El Carmen', Fuerzas Armadas s/n, 21071, Huelva, Spain.
Environ Pollut. 2020 Dec;267:115506. doi: 10.1016/j.envpol.2020.115506. Epub 2020 Aug 27.
Metal pollution in estuaries represents a serious environmental challenge, especially in areas affected by industrial and mining activities. This study investigates the metal partitioning and availability of rare earth elements (REE), Y and other trace metals (Ag, Tl, U and Cs) in the Ria of Huelva estuary (SW Spain), strongly affected by mining and industrial activities. A 30 h monitoring campaign was performed collecting periodic water samples and deploying diffusive gradient in thin films (DGTs) devices to determine the main factors controlling metal availability. The dissolved concentrations of U (3118-3952 ng/L) and Cs (284-392 ng/L) were in the same order of magnitude than those reported in other estuaries and coastal waters worldwide, however, REE (26-380 ng/L), Y (15-109 ng/L), Ag (14-307 ng/L) and Tl (29-631 ng/L) concentrations exceeded these values for the same salinities. Unlike most metals (i.e. Ag, Tl, U, Cs), which were mainly found in the dissolved form (87-100% of total), REE and Y were found in the particulate phase (22-36% of total). Metal lability was mainly related to the concentration in the water column following this order: U>REE>Y>Ag>Tl. A similar binding mechanism was observed for Tl and Cd, due to its chemical affinity. This relationship between chemical properties and absorption by DGT-resin was also observed for REE (and Y), Rb and Sr, which may cause bioaccumulation upon persistent exposure, considering the ability of these metals to cross the biological membranes. The lability of metals predicted by geochemical codes did not coincide with absorption of labile metals by DGTs due probably to the instability of complexes in contact with the DGT membranes, the inability of metals to form thermodynamically stable complexes or the absorption of colloids. From this work it can be concluded that DGT passive sampling should complement traditional sampling to monitor metal availability in aquatic environments.
河口的金属污染是一个严重的环境挑战，特别是在受工业和采矿活动影响的地区。本研究调查了西班牙西南部胡尔瓦河口（Huelva estuary）受采矿和工业活动强烈影响的稀土元素（REE）、Y 和其他痕量金属（Ag、Tl、U 和 Cs）的金属分配和可用性。进行了一项 30 小时的监测活动，定期采集水样并部署扩散梯度薄膜（DGT）装置，以确定控制金属可用性的主要因素。U（3118-3952ng/L）和 Cs（284-392ng/L）的溶解浓度与世界其他河口和沿海水域报告的浓度处于同一数量级，然而，REE（26-380ng/L）、Y（15-109ng/L）、Ag（14-307ng/L）和 Tl（29-631ng/L）的浓度在相同盐度下超过了这些值。与大多数金属（即 Ag、Tl、U、Cs）主要以溶解形式存在（总浓度的 87-100%）不同，REE 和 Y 存在于颗粒相中（总浓度的 22-36%）。金属的生物可利用性主要与水柱中的浓度有关，其顺序为：U>REE>Y>Ag>Tl。由于化学亲和力，Tl 和 Cd 也表现出类似的结合机制。REE（和 Y）、Rb 和 Sr 也观察到了这种化学性质与 DGT-树脂吸收之间的关系，由于这些金属能够穿过生物膜，因此它们可能在持续暴露时导致生物积累。基于地球化学编码预测的金属生物可利用性与 DGT 对生物可利用金属的吸收不一致，可能是由于与 DGT 膜接触时络合物的不稳定性、金属形成热力学稳定络合物的能力不足或胶体的吸收。综上所述，DGT 被动采样应该与传统采样相结合，以监测水生环境中的金属生物可利用性。
