Identifying Metals Contamination in Groundwater Using Geochemical Correlation Evaluation

Thorbjornsen, Karen; Myers, Jonathan

doi:10.1080/15275920601180529

Cited by 6 publications

(6 citation statements)

References 12 publications

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“…Geochemical trace metal/reference metal loglog associations are usually illustrated with Fe, Al, or Mn as the representative soil reference metal. Similar trace metal associations have consistently been observed for Fe (Hamon et al 2004;Myers and Thorbjornsen 2004;Thorbjornsen and Myers 2007a), Al (Klassen 1998;Myers and Thorbjornsen 2004;Thorbjornsen and Myers 2007b), and Mn (Hamon et al 2004;Sterckeman et al 2006;Thorbjornsen and Myers 2007b;Tongtavee et al 2005). In fact, little discussion in the literature is given regarding compositional differences in Fe, Al, and Mn among soils in geochemical evaluations.…”

Section: Resultssupporting

confidence: 58%

Evaluation of geochemical associations as a screening tool for identifying anthropogenic trace metal contamination

Anderson

Kravitz

2009

Environ Monit Assess

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Geochemical association plots are used as a screening tool for environmental site assessments and use empirical log-log relationships between total trace metal concentrations and concentrations of a major (i.e., reference) soil metal constituent, such as iron (Fe), to discern sites with naturally elevated trace metal levels from sites with anthropogenic contamination. Log-log relationships have been consistently observed between trace metal and reference metal concentrations and are often considered constant. Consequently, we used a regional geochemistry data set to evaluate background trace metal/Fe log-log associations across soils with highly diverse composition. Our results indicate that, although geochemical associations may be proportional, they significantly differ across predominant United States Department of Agriculture (USDA) soil orders. This suggests that highly complex interactions between soil-forming factors and variable secondary clay mineral composition affect the ratio of trace metals to Fe concentrations in soils. Also, intra-order variability in trace metal/Fe ratios generally ranged multiple orders of magnitude which suggest that the order level of the USDA soil taxonomic system is insufficient to reasonably classify background trace metal concentrations. Consequently, geochemical association plots are a useful screening tool for environmental site assessments, but ubiquitous application of generic background metal data sets could result in erroneous conclusions. Because significantly different ratios were observed across predominant USDA soil orders, an agglomerative clustering technique was used to elucidate hierarchical patterns of association. We present these results as a mechanism to aid environmental assessors in screening candidate background metal data sets for their applicability to site-specific soil composition; although site-specific background metal data should be utilized if ample pristine reference sites with similar (i.e., sub-order) soil composition can be identified and sampled.

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Section: Resultssupporting

confidence: 58%

Evaluation of geochemical associations as a screening tool for identifying anthropogenic trace metal contamination

Anderson

Kravitz

2009

Environ Monit Assess

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“…Geochemical ratio analysis is frequently used to assess if metal concentrations in groundwater are naturally occurring (Thorbjornsen & Myers 2007, 2008; U.S. Navy [USN] 2004). Typically this entails assessing the correlation between two elements, a trace element of interest (typically the COPC) against a major element such as aluminium or iron.…”

Section: Evaluation Of Background Concentration Thresholds Of Constitmentioning

confidence: 99%

Key considerations that can make or break a closure-focused groundwater-monitoring program

Gemson¹,

Weaver²,

Heemink³

2019

Proceedings of the International Conference on Mine Closure

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Potential long-term water quality impacts present one of the main challenges for effective closure of mine sites. As such, groundwater-monitoring programs form an inherent part of closure. At many mine sites, groundwater-monitoring programs develop organically over time, in response to specific issues that may arise during the life of the mine. When transitioning from operational to closure-focused groundwater monitoring the programs often undergo greater scrutiny by stakeholders. This transitioning also offers the opportunity to re-evaluate the fundamentals underpinning the program, allowing for the alignment of monitoring efforts with the site and scenario-specific monitoring and closure objectives. If gotten right significant efficiencies can be gained in achieving outcomes that support closure, but if not, quite the opposite. This paper presents key considerations for a closure-focused groundwater-monitoring program. These include: 1) thorough assessment and confirmation of the constituents of potential concern (COPCs); 2) background concentration thresholds for COPCs that occur naturally (especially important in mineralised areas); 3) the setting of appropriate assessment criteria for water quality monitoring taking into account background concentrations and water uses; 4) developing the program within a source-pathway-receptor framework that clearly considers the environmental setting and potential changes in hydrodynamics following closure; 5) regulatory requirements; and 6) consideration of sampling frequency and temporal trends to develop trigger levels and actions to increase or decrease monitoring effort, to maintain flexibility within the program and to assist with the setting of reasonable end-points.

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“…Iron oxides become soluble as the redox potential drops below a threshold value, and this increases the dissolved concentrations of iron and the dissolved concentrations of trace elements that were adsorbed on the iron oxide surfaces. Detailed discussion of the effects of suspended particulates and reductive dissolution on elemental concentrations, as well as the methodology for evaluating these effects, is provided in Thorbjornsen and Myers (2007).…”

Section: Introductionmentioning

confidence: 99%

“…Elemental correlation plots serve an important role during evaluation of groundwater metal data, when such plots are used in conjunction with a careful consideration of site-specific geochemical conditions and the known behavior of the elements under those conditions (Thorbjornsen & Myers, 2007). Other researchers have suggested evaluating plots of element concentrations versus the corresponding total suspended solids concentrations, or normalizing trace element concentrations against aluminum or iron concentrations (US EPA, 1993), but do not discuss the processes responsible for the observed correlations.…”

Section: Introductionmentioning

confidence: 99%

“…These evaluations can also be used in support of risk assessments to determine if metals in site groundwater are naturally occurring and can be removed from lists of chemicals of concern. They are also effectively used as a screening step during background studies to identify samples that reflect metal contamination and justify their removal from the background data set, such that the remaining background samples reflect only naturally occurring element concentrations (Thorbjornsen & Myers, 2007). This article discusses two other applications of geochemical evaluations: (1) to determine if metals of concern should be retained in or deleted from the list of chemicals analyzed during long-term monitoring (LTM) programs and (2) at active remediation sites, to document the effects of organics remediation on metals and identify the processes controlling the metal concentrations.…”

Section: Introductionmentioning

confidence: 99%

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Geochemical evaluation of metals in groundwater at long‐term monitoring sites and active remediation sites

Thorbjornsen¹,

Myers²

2008

Remediation Journal

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At many sites, long-term monitoring (LTM) programs include metals as chemicals of concern, although they may not be site-related contaminants and their detected concentrations may be natural. At other sites, active remediation of organic contaminants in groundwater results in changes to local geochemical conditions that affect metal concentrations. Metals should be carefully considered at both types of sites, even if they are not primary contaminants of concern. Geochemical evaluation can be performed at LTM sites to determine if the monitored metals reflect naturally high background and, hence, can be removed from the analytical program. Geochemical evaluation can also be performed pre-and post-treatment at active remediation sites to document the effects of organics remediation on metals and identify the processes controlling metal concentrations.Examples from both types of sites are presented in this article. O c 2008 Wiley Periodicals, Inc. INTRODUCTIONMetal concentrations in groundwater samples can be natural, reflect anthropogenic input, or be indirectly affected by organic contaminants and/or their treatment. The mechanisms controlling metal concentrations under natural conditions are well established (Appelo & Postma, 2005;Drever, 1997;Hem, 1985;Stumm & Morgan, 1996). One mechanism of particular importance is trace-element adsorption on suspended minerals. In neutral-range pH waters lacking high concentrations of complexing anions (such as fluoride), detections of aluminum above approximately 1,000 micrograms per liter (µg/L) indicate the presence of suspended clay minerals; similarly, under neutral-range pH and oxic conditions, detections of iron above approximately 1,000 µg/L indicate the presence of suspended iron oxide minerals (Hem, 1985). Trace elements have affinities to adsorb on the surfaces of these suspended clay and oxide minerals, depending in part on the charges of the element species and sorptive surfaces.In the absence of contamination, the concentrations of the trace element versus aluminum (representing clays) or trace element versus iron (representing iron oxides) usually covary in a given data set, when adsorption of the trace element on suspended particulates is the dominant process. Under reducing conditions, however, such covariance is not always observed, at least for iron and associated trace elements that are 99Geochemical Evaluation of Metals in Groundwater at Long-Term Monitoring Sites and Active Remediation Sites redox active. Iron oxides become soluble as the redox potential drops below a threshold value, and this increases the dissolved concentrations of iron and the dissolved concentrations of trace elements that were adsorbed on the iron oxide surfaces. Detailed discussion of the effects of suspended particulates and reductive dissolution on elemental concentrations, as well as the methodology for evaluating these effects, is provided in Thorbjornsen and Myers (2007).Iron oxides become soluble as the redox potential drops below a threshold value, and this increases the di...

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Identifying Metals Contamination in Groundwater Using Geochemical Correlation Evaluation

Cited by 6 publications

References 12 publications

Evaluation of geochemical associations as a screening tool for identifying anthropogenic trace metal contamination

Evaluation of geochemical associations as a screening tool for identifying anthropogenic trace metal contamination

Key considerations that can make or break a closure-focused groundwater-monitoring program

Geochemical evaluation of metals in groundwater at long‐term monitoring sites and active remediation sites

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