Geochemical baselines based on stream waters: applications to environmental studies, Central Chile as a case study

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Title: Geochemical baselines based on stream waters: applications to environmental studies, Central Chile as a case study
Authors: Jorquera Zuniga, Carmina Olivia
Item Type: Thesis or dissertation
Abstract: Increasing environmental regulation has resulted in mining companies monitoring levels of toxic trace elements in the environment. However, little research has been done to identify the sources of such elements as natural or manmade. Whilst the mining industry has traditionally used hydrogeochemical baselines for exploration, this study has evaluated the use of such baselines for environmental assessments of drainage systems, particularly the identification and quantification of natural and anthropogenic sources. The results are discussed in the context of water quality regulation and guideline values. The research generated the first systematic regional geochemical baseline of Central Chile including the classic Andean copper mineral province and the Andina – Los Bronces mining district. The study area included three major catchments flowing from the Andean Cordillera into inhabited valleys, with the potential for contamination from agriculture and the urban environment. Waters were sampled at a density of 1 per 100 sq. km. over 20000 sq. km. in five seasons over three years. Multi-element chemistry and stable isotopes were determined. The geochemical baseline was prepared using high quality geochemical data. The distribution patterns of the anomalously high geochemistry showed strong relationships with bedrock geology, including the presence of evaporites, sulphide mineralisation and hydrothermally altered rocks (differentiated using isotopes in sulphate). High concentrations of nitrate and phosphate were identified in agricultural areas reflecting pollution from fertilisers and sewage (distinguished using isotopes in nitrate). Areas affected by fertilisers and sewage were significantly greater than those affected by mining. Waters draining unmined Cu-mineralisation had much higher Cu and Ni levels and lower pH than Cu-mine area waters. Most regional geochemistry was below international guidelines and Chilean regulatory levels and where elevated it reflected natural sources and seasonal variations. The study demonstrates that geochemical baselines have considerable potential for distinguishing between natural and anthropogenic pollutant sources in environmental assessments.
Content Version: Open Access
Issue Date: Aug-2013
Date Awarded: Dec-2013
Supervisor: Voulvoulis, Nikolaos
Plant, Jane
Sponsor/Funder: Anglo American Chile
Department: Centre for Environmental Policy
Publisher: Imperial College London
Qualification Level: Doctoral
Qualification Name: Doctor of Philosophy (PhD)
Appears in Collections:Centre for Environmental Policy PhD theses

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