Removal of Cr(VI) by Nanoscale Zero-valent Iron (nZVI) From Soil Contaminated with Tannery Wastes

The illegal disposal of tannery wastes at Rania, Kanpur has resulted in accumulation of hexavalent chromium [Cr(VI)], a toxic heavy metal in soil posing risk to human health and environment. 27 soil samples were collected at various depths from Rania for the assessment of Cr(VI) level in soil. Out of 27 samples, five samples had shown significant level of Cr(VI) with an average concentration of 15.84 mg Kg⁻¹. Varied doses of nanoscale zero-valent iron (nZVI) were applied on Cr(VI) containing soil samples for remediation of Cr(VI). Results showed that 0.10 g L⁻¹ nZVI completely reduces Cr(VI) within 120 min following pseudo first order kinetics. Further, to test the efficacy of nZVI in field, soil windrow experiments were performed at the contaminated site. nZVI showed significant Cr(VI) reduction at field also, indicating it an effective tool for managing sites contaminated with Cr(VI).     

Evaluating the contribution of soil properties to modifying lead phytoavailability and phytotoxicity

Soil properties affect Pb bioavailability to human and ecological receptors and should be considered during ecological risk assessment of contaminated soil. We used path analysis (PA) to determine the relative contribution of soil properties (pH, organic C [OC], amorphous Fe and Al oxides [FEAL], and cation-exchange capacity [CEC]) in modifying Pb bioavailability. The response of biological endpoints (bioaccumulation and dry matter growth [DMG]) of lettuce (Lactuca sativa) grown on 21 Pb-spiked (2,000 mg/kg) soils were determined. Lettuce tissue Pb ranged from 3.22 to 233 mg/kg, and relative DMG ranged from 2.5 to 88.5% of their respective controls. Simple correlation showed strong relationships between CEC and OC (p < 0.01) and weaker relationships between pH and FEAL (p < 0.05) and Pb bioaccumulation. Results of PA suggest that soil pH increased the negative surface charge of organic matter and clay, thereby increasing CEC and decreasing Pb bioaccumulation. Also, the direct effect of OC on tissue Pb can be attributed to formation of surface Pb complexes by organic matter functional group ligands. Increased OC and/or CEC reduced Pb solubility and bioavailability in the 21 soils in the present study. The relative importance of soil properties likely will vary between studies employing different soils. Soil properties should be considered during the ecological risk assessment of metal in contaminated soils. Path analysis is useful for ecological studies involving soils with a wide range of physicochemical properties and can assist in site risk assessment of metals and remediation decisions on contaminated sites.     

Effect of soil properties on lead bioavailability and toxicity to earthworms

Soil properties are important factors modifying metal bioavailability to ecological receptors. Twenty-one soils with a wide range of soil properties (USA; http://soils.usda.gov/technical/classification/taxonomy/) were amended with a single concentration of Pb (2,000 mg/kg) to determine the effects of soil properties on Pb bioavailability and toxicity to earthworms. Earthworm mortality ranged from 0 to 100% acute mortality following exposure to the same total concentration of Pb (2,000 mg/kg) in amended field soils. Internal Pb concentrations in earthworms ranged from 28.7 to 782 mg/kg, with a mean of 271 mg/kg. Path analysis was used to partition correlations in an attempt to discern the relative contribution of each soil property. Results of path analysis indicated that pH was the most important soil property affecting earthworm mortality (p < 0.01) and internal Pb (p < 0.05). Soil pH was related inversely to mortality and internal Pb, soil solution Pb, and Pb bioavailability. The most important soil property modifying reproduction was amorphous iron and aluminum oxides (FEAL). Because FEAL is rich in pH-dependent cation-exchange sites, several soil properties, including pH, FEAL, and cation-exchange capacity, have a causal effect on Pb adsorption and soluble Pb. Path analysis is useful for assessing contaminated soils with a wide range of soil properties and can assist in ecological risk assessment and remediation decisions for contaminated sites. Soil properties are important factors modifying metal bioavailability and toxicity and should be considered during the ecological risk assessment of metals in contaminated soils.     

Demonstrating Ecological Receptor Health at Contaminated Sites with Wild Rodent Sperm Parameters

Consistently at Superfund and other contaminated terrestrial sites, ecological receptors have been chemically exposed for multiple decades by the time risk assessments are conducted. Given that numerous generations of the receptors have lived through the contaminated site condition by the present day, a paradigm shift from risk assessment, where the potential for health effects are forecasted, to a direct, health status assessment scheme for the site-exposed receptor, would seem to be most appropriate. We applied the only such existing direct health status assessment method, Rodent Sperm Analysis (RSA), with small rodents trapped at contaminated sites and at matched noncontaminated reference locations. Reproductive health, ecological risk assessment’s endpoint of greatest concern, is targeted with RSA by comparing the sperm parameters of count, motility, and morphology, for each of which it is known how much of a change from a control condition signifies compromised reproductive capability. Given that sperm parameter thresholds were not exceeded in maximally exposed receptors, the data suggest that in the general case, contaminated terrestrial sites do not need cleanups to afford health protection to ecological species, and particularly the larger, wider-ranging, higher trophic level species. Our findings suggest that RSA has the ability to consistently discriminate between clean and contaminated sites, and that the method can allow for as definitive determinations of terrestrial ecological receptor health as are possible, thereby facilitating early site clean-up decisions. The opinions or assertions contained herein are the views of the author and are not to be construed as official or as reflecting the views of the Department of the Army or the Department of Defense.     

Remediation of Hanford's N-Reactor Liquid Waste Disposal Sites

Hanford's N-Reactor operated from 1963 to 1987 generating approximately 9 x 10 m of radioactive and hazardous liquid effluent as a result of reactor operations. Two liquid waste disposal sites, essentially large trenches designed to filter contaminants from the water as it percolates through the soil column, were established to dispose of the effluent. The discharges to the sites included cooling water from the reactor primary, spent fuel storage, and periphery systems, along with miscellaneous drainage from reactor support facilities. Today, both sites are classified as Treatment Storage and Disposal Facilities under the Resource Conservation and Recovery Act of 1976, which makes them priority sites for remediation. The two sites cover approximately 4,100 m and 9,300 m, respectively. Remediation of the sites requires removing a combined total of approximately 2.6 x 10 kg of contaminated soil and debris. Principal radionuclides contained in the soil/debris are Co, Cs, Pu, and Sr. Remediation of these waste sites requires demolishing concrete structures and excavating, hauling, and disposing of contaminated soils in work areas containing high levels of contamination and whole body dose rates in excess of 1 mSv h. The work presents unique radiological control challenges, such as minimizing external dose to workers in a constantly changing outdoor work environment, maintaining contamination control during removal of a water distribution trough filled with highly contaminated sludge, and minimizing outdoor airborne contamination during size reduction of highly contaminated pipelines. Through innovative approaches to dose reduction and contamination control, Hanford's Environmental Restoration Contractor has met the challenge, completing the first phase on schedule and with a total project exposure below the goal of 0.1 person-Sv.     

Public perceptions of a radioactively contaminated site: concerns, remediation preferences, and desired involvement.

A public attitudes survey was conducted in neighborhoods adjacent to a radioactively contaminated site whose remediation is now under the auspices of the U.S. Department of Energy's Formerly Utilized Sites Remedial Action Program (FUSRAP). The survey's purpose was to ascertain levels of actual and desired public involvement in the remediation process; to identify health, environmental, economic, and future land-use concerns associated with the site; and to solicit remediation strategy preferences. Surface water and groundwater contamination, desire for public involvement, and potential health risks were found to be the most highly ranked site concerns. Preferred remediation strategies included treatment of contaminated soil and excavation with off-site disposal. Among on-site remediation strategies, only institutional controls that leave the site undisturbed and do not require additional excavation of materials were viewed favorably. Cost of remediation appeared to influence remediation strategy preference; however, no strategy was viewed as a panacea. Respondents were also concerned with protecting future generations, better assessment of risks to health and the environment, and avoiding generation of additional contaminated materials.     

Hotspot analysis of spatial environmental pollutants using kernel density estimation and geostatistical techniques

Concentrations of four heavy metals (Cr, Cu, Ni, and Zn) were measured at 1,082 sampling sites in Changhua county of central Taiwan. A hazard zone is defined in the study as a place where the content of each heavy metal exceeds the corresponding control standard. This study examines the use of spatial analysis for identifying multiple soil pollution hotspots in the study area. In a preliminary investigation, kernel density estimation (KDE) was a technique used for hotspot analysis of soil pollution from a set of observed occurrences of hazards. In addition, the study estimates the hazardous probability of each heavy metal using geostatistical techniques such as the sequential indicator simulation (SIS) and indicator kriging (IK). Results show that there are multiple hotspots for these four heavy metals and they are strongly correlated to the locations of industrial plants and irrigation systems in the study area. Moreover, the pollution hotspots detected using the KDE are the almost same to those estimated using IK or SIS. Soil pollution hotspots and polluted sampling densities are clearly defined using the KDE approach based on contaminated point data. Furthermore, the risk of hazards is explored by these techniques such as KDE and geostatistical approaches and the hotspot areas are captured without requiring exhaustive sampling anywhere.     

Soil pollution and soil limit values

One of the tools for preventing soil pollution and thus protection of public health is the application of appropriate limit values. Policies on soil protection in relation to soil pollution include two basic strategies: a preventive approach and a remediation or cleanup approach. Preventive, multifunctional limit values are independent from present or future land use. Remediation limit values are connected with land use--these are functional limit values. Both types of limit values are applied in Hungary. Determination of soil limit values demands long-term field investigations, but to estimate allowable concentration for a given site reverse risk assessment methods are well applicable. A comparison and evaluation of the calculated data and the measurement results obtained at the use of the area is indispensable. Further investigations are needed for establishment of combined limit values when more polluting components are present simultaneously in the soil.     

Application of environmental risk analysis at contaminated sites

Contaminated sites represent a challenge for all European Countries. Clean-up strategies currently focus on a risk-based approach for the definition of remediation goals. Many of the technical standards developed for the application of risk assessment at contaminated sites do not take into account the risk posed to human health by sediment contamination in a common framework. The present paper describes the technical procedure for the application of human health risk assessment at contaminated sites developed and recently updated by the National Environmental Agency and Technical Services (APAT ) of Italy, according to the suggestions of a working group, coordinated by APAT , and composed by members of the main Italian scientific institutes (ISS and ISPESL) and of the Italian Regional Environmental Agencies (ARPA). Furthermore the main issues posed by the application of human health environmental risk analysis to contaminated sediments are discussed.     

Lead concentration in soil from a small 15th-century industrial site: occupational and environmental health implications

Former industrial sites are often reclaimed for new homes and other occupational uses. Such sites may still contain toxic chemicals that could put the health of the community at risk. The persistence of these residual chemicals and their effects on human health must not be underestimated. Hence, there is a need to analyze such sites to ensure that the public health will not be put at risk. It is also essential that the levels of release of heavy metals into the environment be monitored and regulated. In this study the lead (Pb) concentration in soil from a small 15th-century industrial site was determined to assess and evaluate its occupational and environmental health implications. Concentrations of Pb measured by atomic absorption spectroscopy (AAS) and inductively coupled plasma-emission spectroscopy (ICP-AES) techniques were 4,298.755 mg/L (SD 0.316; RSD 0.5%) and 4,300 mg/L (SD 0.3809; RSD 0.8%), respectively, both above the safe limit. It is concluded that reclaiming a disused industrial site without adequate soil analysis and proper remediation would be likely to pose occupational and environmental health risks.     

Lead Concentration in Soil from a Small 15th-century Industrial Site: Occupational and Environmental Health Implications

Abstract

Former industrial sites are often reclaimed for new homes and other occupational uses. Such sites may still contain toxic chemicals that could put the health of the community at risk. The persistence of these residual chemicals and their effects on human health must not be underestimated. Hence, there is a need to analyze such sites to ensure that the public health will not be put at risk. It is also essential that the levels of release of heavy metals into the environment be monitored and regulated. In this study the lead (Pb) concentration in soil from a small 15th-century industrial site was determined to assess and evaluate its occupational and environmental health implications. Concentrations of Pb measured by atomic absorption spectroscopy (AAS) and inductively coupled plasmaemission spectroscopy (ICP-AES) techniques were 4,298.755 mg/L (SD 0.316; RSD 0.5%) and 4,300 mg/L (SD 0.3809; RSD 0.8%), respectively, both above the safe limit. It is concluded that reclaiming a disused industrial site without adequate soil analysis and proper remediation would be likely to pose occupational and environmental health risks.     

A Single Soil Washing with Humic Substance Can Achieve the Risk-Based Remedial Target for Nickel Contaminated Soil

Risk-based soil remediation and management have become a global environmental issue. Here, a nickel (Ni)-contaminated site was selected to conduct the risk-based remediation strategy. The Health and Environment Risk Assessment Software was used to calculate the human health risk and the remedial target value (RTV) of Ni. Soil highly contaminated with Ni (424.30 mg kg^?1) could cause an unacceptable carcinogenic risk (1.41?×?10^?6), which needs further remediation. Hence, a soluble humic substance (HS) was used as the washing agent to remove Ni. After a single wash at pH 4 and 8, the Ni concentrations in soil were reduced to 278.05 and 288.27 mg kg^?1, both below the RTV (300 mg kg^?1). Furthermore, sequential extraction analysis revealed that the residual Ni was maintained stably in the soil after HS washing. These findings suggested that HS is a promising washing agent for Ni-contaminated soil remediation under the guidance of risk control.

     

Nitrogen and Phosphorus Fertilizer Increases the Uptake of Soil Heavy Metal Pollutants by Plant Community

Soil heavy metal pollution is widespread around the world. Compared with hyperaccumulation plants, non-hyperaccumulator plant communities have many advantages in the remediation of heavy metals pollution in soil. The application of nitrogen (N) and phosphorus (P) is inexpensive and convenient, which can promote the growth of plant. N and P fertilizer might increase plant community remediation of heavy metal polluted soils. In our study, the effects of N and P fertilizer on remediation of soil Cd, Cu, Pb pollution by plant community were studied through a greenhouse experiment. Our results indicated that addition of N, P and N?+?P fertilizer increased plant community aboveground biomass. Simultaneously, addition of N and P fertilizer increased the accumulation of heavy metals in aboveground of the plant community and accelerated plants absorption soil heavy metals. Among them, N fertilizer had the best effect. Our results provide an inexpensive method for remediation heavy metal pollution of contaminated farmland, abandoned land and mine tailings, etc.

     

Mutagenic hazards of complex polycyclic aromatic hydrocarbon mixtures in contaminated soil

The objective of the present study was to evaluate hazard/risk assessment methods for complex environmental mixtures that involve a targeted, priority chemical approach based on the cumulative hazard/risk of known mixture components or analyses of sufficiently similar mixtures. Ten polycyclic aromatic hydrocarbon (PAH)-contaminated soils were separated into nonpolar and semipolar fractions, and both fractions elicited positive responses on the Salmonella reverse mutation assay. Targeted and nontargeted methods of hazard prediction routinely overestimated mutagenic activities for the nonpolar soil fractions, suggesting nonadditive interactions of PAHs in complex mixtures. This suggests that current risk assessment methods for complex mixtures may provide conservative estimates regarding soils contaminated with priority PAHs alone. Significant underestimations of total risk, however, will be obtained if the soils also contain unidentified PAHs as well as polycyclic aromatic compounds and related compounds that contribute to the total mutagenic activity. Furthermore, estimates of excess lifetime cancer risk associated with the nondietary ingestion of the PAH-contaminated soils studied here indicate that a traditional risk assessment model based on identified priority PAHs and an assumption of additivity generally underestimates the risk associated with the nonpolar soil fractions (in comparison to bioassay-derived risk estimates). Additional cancer risk may be associated with the more polar compounds that also are found at these contaminated sites and that rarely are included in the standard risk assessment methodology.     

Characterization of Land Contaminated by Past Heavy Metal Mining Using Geostatistical Methods

Aspects of mining operations, including production, processing, transportation, and, finally, abandoned mine workings, can undoubtedly cause varying degrees of environmental pollution and contamination. Characterization of the spatial distribution of pollutants in contaminated soil is important for risk assessment and soil remediation. This study has been carried out using both conventional statistics and geostatistical methods which are useful for site assessment, characterization, and monitoring situations where data are collected spatially. These methods are particularly suited to cases where spatial dependence structure and contour maps of contaminant concentration or other variables are needed. The aims of this paper were to determine the extent and severity of the pollution levels on land contaminated by past mining activity through using geostatistical techniques, assess sampling strategy, and interpret data for potentially contaminated land. In the study, a total of 329 soil samples was collected at 1-, 5-, and 10-m regular grid intervals of 100 × 100-m area of Carsington Pasture in the UK and analyzed using an automatic X-ray fluorescence machine for a large number of elements. Only a few elements (Cu, Pb, Zn, and Ba) were subsequently studied in detail because of their association with the mining operation. Directional and omnidirectional experimental semivariograms of elements Cu, Pb, Zn, and Ba for 10-m grid intervals, pooled data of 10- and 5-m grid intervals (S₁₀₊₅), and pooled data of 10-, 5-, and 1-m grid interval (S₁₀₊₅₊₁) showed that neither geometric nor zonal anisotropy exits in the data. The most evident spatial dependence structure of the continuity for omnidirectional experimental semivariogram, characterized by a spherical model, of each element was obtained for the pooled data set of S₁₀₊₅. Pooling 1-m grid data to S₁₀₊₅ shaded the spatial dependence structure. The spherical model adopted for each element embodied no nugget effect, indicating that mineralization did not occur as nuggets in the study area, but it did show different ranges of influence and sill values. Spherical semivariogram model of each element for the pooled data set of S₁₀₊₅ passed the cross validation tests. Graphs of cross validation test results proved that the isotropic spherical model, with its parameters and kriging search parameters, is representative for the area under study. The values of 10,000 grid nodes established regularly over the study area were estimated by kriging interpolation technique to smooth out the contours. Kriged maps for the Cu, Pb, Zn, and Ba elements were plotted. Anomalies such as bulls-eyes and drift did not observed in the maps generated. Contour maps of estimated element concentrations revealed the extent and severity of contamination. Spatial distribution maps of the elements might be used in the remediation studies and help decision-makers and others involved in the abandoned heavy metal mining site in the UK.     

Phytotoxkit: a critical look at a rapid assessment tool

Terrestrial plant toxicity testing contributes critical information to many site risk assessments, but standardized tests can be labor-intensive, use large amounts of soil, and employ long test durations. The Phytotoxkit (MicroBioTests, Environmental Bio-Detection Products) minimizes the time and cost associated with terrestrial plant testing with a unique test setup, a shorter test duration, and less soil. However, the sensitivity of the test remains an open question. In this research, the Phytotoxkit and the standardized Environment Canada terrestrial plant toxicity test (definitive test) are compared using a parallel testing approach. Three different scenarios were examined: a multiconcentration test, in which an inhibiting concentration (ICp) was derived from chemically amended soils; a soil remediation test, in which plant growth in a remediated soil was compared to the original contaminated soil; and a site soil test, in which plant growth in a contaminated soil was compared to a reference soil. The contaminants tested were boric acid, Cr(VI) with cyclodextrin as a remediation agent, and petroleum hydrocarbons. Trifolium pratense (red clover) was used in the first and second scenarios, and six different plant species were used in the third scenario. In the first scenario, the Phytotoxkit results compared well with the definitive test results after 5 and 7 d of exposure. In the second scenario, the Phytotoxkit results agreed with the definitive test when evaluating the effectiveness of remediation. In the third scenario, the Phytotoxkit results were often not in agreement with the results from the definitive test. The reduced sensitivity of the Phytotoxkit in the third scenario may be driven by test unit design, as plant roots are separated from soil by filter paper.     

蒙脱土对Cs在土壤-大豆系统中迁移的影响及生物有效性研究

目的 放射性Cs是目前土壤放射性污染的主要污染物。本文探讨蒙脱土对Cs在土壤-大豆系统中迁移的影响,为土壤放射性Cs污染修复和生物有效性评价提供一定理论依据。方法 文章以温室盆栽大豆[Glycine max（L.） Merr.]为实验研究对象,在栽培土壤中添加不同比例的蒙脱土,并对3种浸提剂所提取植物根系直接接触土壤、根际土壤和非根际土壤中可交换态Cs的生物有效性含量进行比较分析。结果 土壤中添加0.5%蒙脱土可显著降低Cs向大豆植物体的迁移量,此时,大豆根、茎和叶的富集率（CR）分别下降至对照的51%、76%和66%。浸提实验结果显示提取Cs的含量由多至少所用浸提剂为：NH₄OAc > HAc > MgCl₂,NH₄OAc所提取Cs的可交换态含量是另两种浸提剂的10倍,使用HAc提取土壤可交换态的Cs与大豆器官中Cs含量呈正相关关系。结论 经比较分析土壤中添加0.5%的蒙脱土可作为土壤修复Cs污染的参考量,HAc可作为评价土壤中Cs生物有效性的参考浸提剂。     

Evaluation of the sensitivity of genotoxicity and cytotoxicity endpoints in earthworms exposed in situ to uranium mining wastes

Earthworms were exposed for 56 days to a contaminated soil from an abandoned uranium mine and to the natural reference soil LUFA 2.2. The exposure occurred in situ: the containers with contaminated soil were placed near the mine pit; the containers with reference soil were placed in a reference site. For the assessment of metals bioaccumulation, DNA damages, cell-to-cell variation in DNA content, Median Fluorescence Intensity (MFI), coelomocytes frequency and proliferation, organisms were sampled after 0, 1, 2, 7, 14 and 56 days of exposure. For the assessment of radionuclides bioaccumulation, animals were sampled after 0, 14 and 56 days of exposure. As for growth, organisms were sampled after 0, 14, 28 and 56 days of exposure. The reproduction assay was performed according to the OECD (2004) guideline. DNA damages were assessed by comet assay and flow cytometry was used to determine cell-to-cell variation in DNA content, Median Fluorescence Intensity (MFI), coelomocytes frequency and proliferation. Results have shown a myriad of effects in the organisms exposed to the contaminated soil, namely: the inhibition of reproduction, growth reduction, DNA damages, cytotoxicity, changes in eleocytes fluorescence intensity, coelomocytes proliferation and bioaccumulation of metals and radionuclides. Our results showed that the evaluation of genotoxicity and cytotoxicity endpoints, along with other parameters at an individual level in standard reproduction assays conducted in situ, are important to improve the risk assessment process of areas contaminated with uranium and other radioactive mining wastes.     

Methods to assess the amenability of petroleum hydrocarbons to bioremediation

Bioremediation has achieved acceptance as a cost-effective technique for the remediation of soils and groundwater contaminated with petroleum hydrocarbons (PHC). A range of laboratory techniques to assess the biodegradability and bioavailability of PHCs are presented. Biodegradability and bioavailability are important determinants of the bioremediation performance of PHCs. Novel methods for the assessment of the bioavailability of PHC components are described. The techniques are demonstrated for a hydraulic fluid and a spindle oil from a contaminated site. Biodegradation is measured by oxygen consumption and carbon dioxide production. Bioavailability of the PHCs is estimated based on the PHC-water partitioning of tracer compounds and a novel analysis of gas chromatograms based on Raoult's law. The PHCs tested were only partially biodegradable (< 25% in 78 d) due to the low solubility and likely recalcitrance of some of their components. The combination of techniques outlined is expected to be of use in assessing the likely bioremediation performance of PHCs for which published data are scarce or inadequate.