Investigative Strategies for Lead-Source Attribution at Superfund Sites Associated with Mining Activities (2017) / Chapter Skim
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4 Investigative Strategies for Lead-Source Attribution
4 Investigative Strategies for Lead-Source Attribution
Pages 42-78
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From page 42... ...
Given the highly variable nature of lead contamination near and Before a detailed chemical or mineralogic analysis is adjacent to Superfund sites, not all the methods that are conducted, a basic site characterization and history should listed in the strategies will be applicable to all sites. In be developed that leads to a site conceptual model that can some cases, additional methods not cited in the strategies guide investigations toward likely lead sources; potential might be useful.
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From page 43... ...
The following Disturbance by human activities is likely to alter spatial discussion of depth sampling and spatial analysis is for and depth trends in lead concentrations and might have led soil developed in place without active deposition where to the direct incorporation of anthropogenic lead into the diagnostic vertical distributions tend to be retained as opsoil. In Southeast Missouri, for example, coarse-grained posed to soils that are subject to recent alluvial deposits (active floodplains)
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. It is gener No Soil Lead Concentration > Threshold Yes Site Characterization and History Spatial and Depth Sampling and Analysis No Unique Signatures Yes Evidence Used to Identify Sources Lead Isotopic Analysis No Unique Signatures Yes FIGURE 4-1 Example of an investigative strategy for attributing sources of lead in soil.
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From page 45... ...
Lead Isotopic Analysis Most commonly, the magnitude of anthropogenic lead is assessed by comparing concentrations in the sur- Measurement of lead isotopic composition can potenface materials with those in deeper horizons, including tially identify a lead source rapidly if the isotopic signaparent material. The analyses can be complicated by the ture is unique.
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From page 46... ...
models, the researchers attributed the added lead to atmo Studies conducted over the last several decades dem- spheric deposition between the 1850s and 1920s, when onstrate that lead isotopes are often effective in deter- lead was emitted to the atmosphere from coal-burning and mining lead sources in soils if the isotopic values of the ore-smelting in the area (Ma et al.
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From page 47... ...
The combined use of tree cores to determine and Benicia, California; their work illustrates the benefits temporal trends with spatial and depth profiles of soils and limitations of isotopic analysis for source attribution. to determine lead concentrations and isotopic signatures In the majority of sites examined from St.
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(2010) , and chemical composition to distinguish lead sources be- who found that lead concentrations within 2 km of mining tween automotive exhaust and paint chips, and Sobanska and smelting activities in Mount Isa, Queensland, Austraet al.
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From page 49... ...
Thus, they were able to argue that their presence in local soils was a clear indicator of airborne Source-Associated Tracers contamination from the nearby lead smelters. The final source-attribution approach for soils encom Lead Chemical Speciation passes a wide array of methods, including multielement analysis and methods that involve stable isotopes other Lead speciation can provide additional means for than lead; they have been used to determine the contribusource attribution, but chemical speciation of lead in soils tion of lead from multiple sources on the basis of compocan be challenging because lead can be dispersed or poor- sition of the geologic materials with which lead is assoly crystallized or be associated with small particles, all of ciated.
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From page 50... ...
(1995) ; they simple conduits, however, they are highly dynamic feaused scaled deposition estimates from atmospheric dis- tures in which water is continuously eroding and depositpersion to develop a statistical model that characterized ing sediment in the river channel and on the floodplain observed soil-lead concentrations and attributed sources during floods.
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From page 51... ...
parison of the lead isotopic composition of the sediment The primary objective of analyzing a river's ero- mixture with the isotopic composition of the suspected sional and depositional history is to identify, character- sources allows an estimation of the relative contribution ize, and map the distribution of distinct, time-correlated of lead to the sediments from each potential source. The sedimentary deposits along the river valley.
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From page 52... ...
First, the isotopic composition of river deposits lead concentrations increased. The decrease in 208Pb/206Pb of known age can be determined and compared with sus- ratios presumably reflected the influx of mine waste from pected lead sources in the basin for that time.
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From page 53... ...
in lead concentrations in channel sediments along the Big River to assess lead sources. Figure 4-6A shows that lead Spatial Analysis concentrations increase abruptly downstream of river mile 110, presumably in response to the influx of mining-relat One of the most extensively used methods for deter- ed waste materials as the river passes through the St.
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From page 54... ...
fraction, as shown in Figure 4-6B, which is associated with a known lead source, such as tailings. • Multiple sources might exist in a specific area, • The resolution of the downstream trends in lead and it might not be possible to differentiate inputs between concentrations reflects the number of samples that are multiple overlapping sources by using lead concentration collected along the river and the location from which the data alone.
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From page 55... ...
Sites should be selected to enthropogenic lead in floodplains and terraces often extends sure that all potential lead sources will be reflected in the to depths measured in meters. The spatial distribution of constructed chronology and to minimize the number of sediment-associated lead in these alluvial deposits reflects locations needed to differentiate inputs between all potenthe depositional processes responsible for floodplain for- tial lead sources.
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. The disruption of stream flow and sediment transings piles, the atmospheric deposition of lead might also port by a dam typically results in higher rates of nearly complicate vertical trends in lead concentrations.
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. As presented earlier, comparison of the changes in the lead isotopic composition of the sediments can often be linked to suspected lead sources.
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The es. As noted above, particles emitted from smelters are geochemical composition of the mixture depends on the often spherical; that knowledge combined with an under- composition of the source materials and the relative prostanding of their composition can determine their source.
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The occurthe modeling results, recent studies have explored the use rence of lead in mineralized soils, which are eroded and of an increasing suite of statistical approaches, including delivered to a river during runoff events, might be particuthe use of Monte Carlo sampling frameworks and Bayes- larly important in Superfund sites associated with mining ian methods (Franks and Rowan 2000; Small et al. 2002, districts.
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From page 60... ...
In some cases, be available. Various factors can influence the integrity of such a hydrogeologic assessment might lead to a confi- a groundwater sample, and such characteristics as well No Lead Concentration > Threshold Yes Site Characterization and Hydrogeologic Conceptual Model No Unique Source Yes Evidence Used to Identify Sources Groundwater or Surface Water Sampling FIGURE 4-8 Example of an investigative strategy for attributing sources of lead in Lead Isotopic Analysis water at a Superfund site.
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From page 61... ...
If total concentrations are desired, unfiltered and acid-digested samples are analyzed. Given As discussed above, lead isotopic abundances have the generally low lead concentrations in surface waters been used extensively to determine the potential sources and groundwater, all sampling and filtration equipment of lead in a wide array of media, including water.
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From page 62... ...
Multivariate statistical methods, such as Measurements and Modeling principal-components analysis or factor analysis, might be used to identify correlations or characteristic patterns Modeling of River Samples among elements or species. Mixing models use differ ences in chemical or isotopic composition among the po Analysis of synoptic samples and temporal varia- tential sources to determine whether the composition of tions in lead concentrations can help to identify sources a specific water can be represented by a mixture of the along rivers (Kimball 1997; Boughton 2001; Nimick and potential water-source compositions.
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From page 63... ...
. Chemi- begins by conducting chemical speciation on archived filcal equilibrium calculations, particularly ones that include ter remnants after lead analysis has been conducted, Tier sorption reactions, can help to elucidate possible chemical II includes field sampling to develop site-specific source reactions that lead to mobilization of lead from sources or signatures for input into receptor modeling, and Tier III how lead might be attenuated along a flow path.
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, stable in Chapter 3, high airborne lead concentrations in total lead isotopes (204Pb, 206Pb, 207Pb, and 208Pb) that can be suspended particles (TSP)
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pended. Additional bulk-material sampling and analysis of storage piles, tailings piles, and mine haul roads that Tier II: Establish Source Signatures are near sites that have high lead concentration should for Receptor Model Input also be considered.
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. mass and chemical composition of lead and other geo
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Model Reconciliation FIGURE 4-12 Expansion of the committee's Tier III strategy for estimating emission potential and particle-size distribution to provide inputs to modeling for source attribution. FIGURE 4-13 Comparison of size distribution of particles from Fresno (CA)
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2012. Lead contamination of tions in the natural isotopic composition of mercury.
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Chen, X Wang, and of Lead Contamination at or Near Superfund Sites.
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1996a. Meth Sensitivity of fluvial sediment source apportionment to od 1669: Sampling Ambient Water for Trace Metals at mixing model assumptions: A Bayesian model compari- EPA Water Quality Criteria Levels.
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2015. Use of lead isotopes to identify sources um Method IO-3.5: Determination of Metals in Ambient of metal and metalloid contaminants in atmospheric aero Particulate Matter Using Inductively Coupled Plasma/ sol from mining operations.
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:2279-2290. lead isotopes and element concentrations in epiphytic li- Hudson-Edwards, K.A., M
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23. Quantifica- variations in Pb concentrations and isotopic composition tion of Mass Loading from Mined and Unmined Areas in road dust, farmland soil and vegetation in proximity to along the Red River, New Mexico.
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2000. Lead isotopic signatures of wine and vineyard soils - Reservoir sediments -- A witness of mining and industrial Tracers of lead origin.
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2012. Stable lead isotopes Prapaipong, P., C.W.
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Source attribution of elevated residential soil from a lead mining waste superfund site.
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Kimball, and R.L. Run- Enrichment factors, fluxes, isotopic composition, and kel.
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1993. Quantitative sediment source mining-impacted Superfund site.
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