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Janet G. Hering Peggy A. O'Day Robert G. Ford Y. Thomas He Azra Bilgin H. James Reisinger David R. Burris 《Ground Water Monitoring & Remediation》2009,29(3):84-92
The potential application of monitored natural attenuation (MNA) as a remedy for ground water contaminated with arsenic (As) is examined for a subset of contaminated sites, specifically those where naturally occurring As has been mobilized due to localized anthropogenic organic carbon (OC) releases. This includes sites subject to petroleum releases, exposure to landfill leachates, and OC additions for biostimulation of reductive dechlorination of chlorinated solvents. The key characteristic of these sites is that, under conditions prevailing before the anthropogenic OC introduction, the naturally occurring As in the subsurface was not mobile and did not adversely affect ground water quality. This suggests that, in the far-field (where background conditions are (re) established), As may be sequestered upon contact of the contaminated ground water with either or both the (uncontaminated) ambient ground water and the background aquifer minerals. The observed extents of elevated concentrations (or "footprints") of As and other chemical species, such as dissolved OC and iron (Fe), and related parameters, such as redox potential ( E h ) and dissolved oxygen, and their evolution over time can be used to assess the mobilization and sequestration of As and the potential feasibility of MNA as a remedial option. Ultimately, the capacity for As sequestration must be assessed in the context of the OC loading to the site, which may require "active" measures for source control. Monitoring is needed to confirm the continuing effectiveness of the MNA remedy or to indicate if contingency measures must be implemented. 相似文献
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Application of Mineral‐Based Amendments for Enhancing Phytostabilization in Lolium perenne L. Cultivation 
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下载免费PDF全文 An experimental investigation is conducted to explore the suitability of Lolium perenne L., diatomite, chalcedonite, dolomite, and limestone for the phytostabilization of Ni and Cu in contaminated soil. A controlled greenhouse study is conducted. The soil is enriched with rising dose of Cu and Ni, that is, (0, 150, 250, and 350 mg kg?1) and (0, 150, 300, and 450 mg kg?1), respectively. The phytostabilization potential of perennial ryegrass is evaluated using a bioaccumulation coefficient and translocation factor. Pseudo‐total and available metal content (0.01 M CaCl2) in soils and bioaccumulated content in plants are defined in laboratory experiments using spectrophotometry experimental technique. L. perenne is adequate in phytostabilization aided programs, simultaneously, diatomite, chalcedonite, dolomite, and limestone used as modifiers are effective in reducing the accessibility and mobility of metals in Cu‐ and Ni‐polluted soils. The finding of the present study suggests that the studied element in the roots and above‐ground parts of L. perenne differs significantly upon applying mineral‐based modifications to the soil, synchronously the effect of increasing Cu and Ni levels. Application of dolomite and limestone to the soil cause the highest percentage of the above‐ground biomass. Diatomite along with limestone cause a significant boost of Cu and Ni absorption in the roots. Limestone causes an increase in the contents of K, Na, and Ca, as well as a reduction in P in the above‐ground parts of L. perenne. Limestone and chalcedonite leads to the highest decrease in available Cu and Ni. 相似文献
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René?LehmannEmail author Jean?Bachmann Bilgin?Karaoglan Jens?Lacker Christian?Polleichtner Hans?Toni?Ratte Monika?Ratte 《Stochastic Environmental Research and Risk Assessment (SERRA)》2018,32(1):213-222
Binary data such as survival, hatching and mortality are assumed to be best described by a binomial distribution. This article provides a simple and straight forward approach for derivation of a no/lowest observed effect level (NOEL/LOEL) in a one-to-many control versus treatments setup. Practically, NOEL and LOEL values can be derived by means of different procedures, e.g. using Fisher’s exact test in coherence with adjusted p values. However, using adjusted p values heavily decreases statistical power. Alternatively, multiple t tests (e.g. Dunnett test procedure) together with arcsin-square-root transformations can be applied in order to account for variance heterogeneity of binomial data. Arcsin-square-root transformation, however, violates normal distribution because transformed data are constrained, while normal distribution provides data in the range \((-\infty ,\infty )\). Furthermore, results of statistical tests relying on an approximate normal distribution are approximate too. When testing for trends in probabilities of success (probs), the step down Cochran–Armitage trend test (CA) can be applied. The test statistic used is approximately normal. However, if probs approach 0 or 1, normal approximation of the null-distribution is suboptimal. Thus, critical values and p values lack statistical accuracy. We propose applying the closure principle (CP) and Fisher–Freeman–Halton test (FISH). The resulting CPFISH can solve the problems mentioned above. CP is used to overcome \(\alpha\)-inflation while FISH is applied to test for differences in probs between the control and any subset of treatment groups. Its applicability is presented by means of real data sets. Additionally, we performed a simulation study of 81 different setups (differing numbers of control replicates, numbers of treatments etc.), and compared the results of CPFISH to CA allowing us to point out the advantages and disadvantages of the CPFISH. 相似文献
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Geochemical and hydrologic controls on the mobilization of arsenic derived from herbicide application 总被引：1，自引：0，他引：1
Arthur G. Fitzmaurice A. Azra Bilgin Peggy A. O&#x;Day Virginia Illera David R. Burris H. James Reisinger Janet G. Hering 《Applied Geochemistry》2009,24(11):2152-2162
The fate and transport of As was examined at an industrial site where soil- and groundwater contamination are derived from the application of As2O3 as a herbicide. Application of arsenical herbicides was discontinued in the 1970s and soils in the source area were partially excavated in 2003. Arsenic contamination (up to 280 mg/kg) remains in the source area soils and a plume of As-contaminated groundwater persists in the surficial aquifer downgradient of the source area with maximum observed As concentrations of 1200 μg/L near the source area. The spatial extent of As contamination as defined by the 10 μg/L contour appears to have remained relatively stable over the period 1996–2006; the boundary of the 1000 μg/L contour has retreated over the same time period indicating a decrease in total As mass in the surficial groundwater.In column experiments conducted with source area soil, the As concentrations in the column effluent were comparable to those observed in groundwater near the source area. A substantial fraction of the As could be leached from the source area soil with ammonium sulfate and ammonium phosphate. Exhaustive extraction with background groundwater removed most of the total As. These results indicate that As in the source area soils is geochemically labile. Source area soils are low in extractable Fe, Mn and Al, and characterization by X-ray absorption spectroscopy and electron microscopy indicated that As is present primarily as arsenate sorbed to (alumino)silicate minerals. Batch sorption experiments showed much less sorption on surficial aquifer sediments than on sediments from the Jackson Bluff Formation (JBF), a presumed confining layer. This limited capacity of the surficial aquifer sediments for As sorption is consistent with the similar As contents observed for these sediments within and upgradient of the As plume. The apparent stability of the As plume cannot be explained by sequestration of As within the surficial aquifer. Sorption to JBF sediments may contribute to As sequestration, but As enrichment in JBF sediments within the plume (i.e., as compared with JBF sediments upgradient) was not observed. These results indicate that neither the persistence of As in the source area soils or the apparent stability of the plume of As-contaminated groundwater at this site can be explained by geochemical controls on As mobility. The absence of demonstrable geochemical bases for such observations suggests that possible hydrologic controls should be further investigated at this site. 相似文献