ABSTRACT The origin of a resurgent hexavalent chromium contamination in groundwater from a phreatic aquifer in the Friuli Venezia Giulia Region plain was investigated by chromium isotopic systematics. The area underwent a severe Cr(VI) contamination by industrial effluents in 1997, when Cr(VI) concentration in groundwater reached 4500 µg/L. In subsequent years the contamination naturally attenuated, totally disappearing in 2003. A renewal of water contamination was observed in 2008, Cr(VI) reaching 1560 µg/L. The δ53Cr value in groundwater and extracts from sediments was measured in 2009–2011, and it ranges between −3.21 and +0.21‰ and between −4.71 and +1.26‰, respectively. Due to the lack of geogenic Cr-sources, these data are interpreted as evidence of the subsequent oxidation through Mn-oxides of the Cr(III) hosted in the aquifer and originated by the reduction of the original industrial chromates. Cr(III) is characterized by negative δ53Cr, starting from the δ53Cr value around zero of Cr(VI) in industrial effluents. Oxidation liberates soluble Cr(VI) which is transported by groundwater and permeated soils. The complex Cr-isotopic vs. concentration distribution reflects both the new Cr(VI) reduction and dilution processes in the aquifer system. From an environmental point of view, the data raise concerns regarding the potential impact of past Cr(VI)-contamination.

中文翻译：

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铬同位素追踪意大利北部弗留利威尼斯朱利亚地区过去受污染地区的六价铬污染的死灰复燃

摘要 利用铬同位素系统学研究了弗留利威尼斯朱利亚地区平原潜水含水层地下水中六价铬污染的起因。该地区在 1997 年受到工业废水的严重 Cr(VI) 污染，当时地下水中的 Cr(VI) 浓度达到 4500 µg/L。在随后的几年中，污染自然减弱，2003 年完全消失。2008 年观察到水污染重新出现，Cr(VI) 达到 1560 µg/L。地下水和沉积物提取物中的δ53Cr值是在2009-2011年测量的，分别在-3.21和+0.21‰之间以及-4.71和+1.26‰之间。由于缺乏地质成因的 Cr 源，这些数据被解释为随后通过含水层中 Cr(III) 的 Mn 氧化物氧化的证据，该氧化源自原始工业铬酸盐的还原。Cr(III) 的特征是负 δ53Cr，从工业废水中 Cr(VI) 零附近的 δ53Cr 值开始。氧化释放出可溶的 Cr(VI)，由地下水和渗透土壤输送。复杂的 Cr 同位素与浓度分布反映了含水层系统中新的 Cr(VI) 还原和稀释过程。从环境的角度来看，这些数据引起了人们对过去 Cr(VI) 污染的潜在影响的担忧。氧化释放出可溶的 Cr(VI)，由地下水和渗透土壤输送。复杂的 Cr 同位素与浓度分布反映了含水层系统中新的 Cr(VI) 还原和稀释过程。从环境的角度来看，这些数据引起了人们对过去 Cr(VI) 污染的潜在影响的担忧。氧化释放出可溶的 Cr(VI)，由地下水和渗透土壤输送。复杂的 Cr 同位素与浓度分布反映了含水层系统中新的 Cr(VI) 还原和稀释过程。从环境的角度来看，这些数据引起了人们对过去 Cr(VI) 污染的潜在影响的担忧。