Abstract

Fishermans Bend is an urban redevelopment precinct situated on the Yarra River estuary in Melbourne, Australia. Understanding the hydrogeological system is important for characterising the impacts from legacy contamination and for monitoring the effects of urbanisation on groundwater flow systems and quality. Stable isotopes of water (δ¹⁸O, δ²H) and carbon (δ¹³C), radioisotopes (³H, ¹⁴C) and other geochemical indicators were used to assess sources of water and salinity in the shallow groundwater. Groundwater in the upper aquifer was predominantly Ca-HCO₃⁻ dominant, with fresh to brackish salinity—189–3,680 mg/L total dissolved solids (TDS). Localised areas of Ca-SO₄²⁻ and Na-HCO₃⁻ dominant groundwater were impacted by industrial activities and legacy landfills, respectively. Stable isotopes (e.g. δ¹⁸O −5.7 to −2.9‰) and tritium activities (1.75–2.45 TU) within the aquifer indicate meteoric water recharged by modern rainfall with short residence times. Carbonate dissolution from shell material, and decay of organic waste and methanogenesis in landfill-leachate-impacted bores were shown to enrich δ¹³C values up to −4.2‰. In contrast, groundwater in the adjacent/lower aquitard was Na-Cl dominant and saline (19,600–23,900 mg/L TDS), with molar ratios reflective of ocean water, indicating relict emplaced salts. This is consistent with ¹⁴C dating of shell material, indicating deposition in a Holocene marine environment. The presence of tritium above background levels (0.20–0.35 TU) in the groundwater, however, suggests a component of modern recharge. Salinity fluctuations within the aquitard at times of peak river level suggest the modern water source is ingress from the adjacent Yarra River.

中文翻译：

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环境同位素可作为澳大利亚沿海城市重建区地下水补给，停留时间和盐度的指标

摘要

渔人弯是一个城市重建区，位于澳大利亚墨尔本的亚拉河河口。了解水文地质系统对于表征遗留污染的影响以及监测城市化对地下水流量系统和质量的影响非常重要。的水稳定同位素（δ ¹⁸ O，δ ² H）和碳（δ ¹³ C），放射性同位素（³ H，¹⁴ C）和其他地球化学指标被用来评估在浅层地下水的水和盐度的来源。地下水在上层含水层是主要的Ca-HCO ₃ ^-占优势，用新鲜到微咸水盐度-189-3,680 mg / L的总溶解固体（TDS）。Ca-SO的局部区域₄ ^2-和Na-HCO ₃ ^-主导地下水由工业活动和遗留堆填区分别的影响，。稳定同位素（如δ ¹⁸含水层内Ø-5.7至-2.9‰）和氚活动（1.75-2.45 TU）表示由现代降雨具有短停留时间充电雨水。从壳材料碳酸盐溶解，并在垃圾填埋渗滤液影响孔的有机废物和产甲烷衰变显示出丰富δ ^13个C值达到-4.2‰。相比之下，邻近/较低的水族箱中的地下水以NaCl为主，盐水为19,600-23,900 mg / L TDS，摩尔比反映出海水，表明遗留了盐类。这与¹⁴一致壳材料的C年代，表明在全新世海洋环境中的沉积。但是，地下水中存在高于背景水平（0.20–0.35 TU）的suggests表明了现代补给的一个组成部分。最高河水位时，水族箱内的盐度波动表明现代水源是从相邻的亚拉河流入的。