Characterization of mercury species in contaminated floodplain soils

The chemical form or speciation of mercury (Hg) in the floodplain soils of the East Fork Poplar Creek in Oak Ridge, Tennessee, a site contaminated from past industrial activity, was investigated. The speciation of Hg in the soils is an important factor in controlling the fate and effect of Hg at the site and in assessing human health and ecological risk. Application of three different sequential extraction speciation schemes indicated the Hg at the site was predominantly relatively insoluble mercuric sulfide or metallic Hg, though the relative proportions of each did not agree well between procedures. Application of X-ray and electron beam studies to site soils confirmed the presence of metacinnabar, a form of mercuric sulfide, the first known evidence of authigenic mercuric sulfide formation in soils.     

Effect of biochar on fraction and species of antimony in contaminated soil

Journal of Soils and Sediments - Antimony (Sb) is a highly toxic heavy metal, and its amount in soil is increasing due to anthropogenic activities. Excessive Sb intake could ultimately threat human...     

Biological significance of antimony in contaminated grassland

Highly elevated levels of Sb occurred in grassland soils near the only British Sb smelter. This soil Sb was found largely in immobile forms. Antimony in plant shoots was derived almost exclusively from the atmosphere with little from the soil. Elevated organ concentrations occurred in wild mammalian herbivores but were low compared to their estimated dietary concentrations. In short-term laboratory feeding experiments with Sb₂O₃, this low accumulation rate was confirmed in mice and voles and although elevated organ concentrations occurred they were not obviously harmful. Thus Sb in these smelter grasslands would seem to have low mobility but at present there is insufficient evidence to be confident in this assessment.     

The distribution of heavy metal contaminated soils in Northeast Clwyd,Wales

Water, Air, &; Soil Pollution - Samples of surface soil were collected on a regular grid from an area of 260 km2 in and around the Halkyn Mountain Pb mining district of northeast Clwyd, Wales....     

Biodegradation of hexachlorocyclohexane-isomers in contaminated soils

Several sites that are contaminated with isomers of the chlorinated insecticide hexachlorocyclohexane (HCH) are present across the globe and cause toxicity. For their bioremediation, we studied the degradation of HCH-isomers in contaminated soils by an isolate Pseudomonas aeruginosa ITRC-5. The degradation is optimal at 2 mg technical-HCH (t-HCH)/g soil, 15% water content, pH 8.0, temperature 28 °C and inoculum density 10⁶ colony forming unit/g soil. Under these conditions, from 5 kg soil, >98% α- and γ-HCH, 17% β-HCH and 76% δ-HCH are degraded after 15 days of incubation, which is accompanied with the release of 600 μg chloride/mg t-HCH. Concomitant to the degradation, a four-fold reduction in the toxicity of HCH-isomers to earthworm, Eisenia foetida, is also observed. Addition of ITRC-5 enhanced the degradation of soil-applied HCH-isomers in ‘open field’ conditions as well, and 97%, 43%, 94% and 77% of α-, β-, γ- and δ-HCH, respectively, are degraded after 12 weeks of incubation. Thus, the bacterium causes microbial degradation and detoxification of HCH-isomers, and can be used for the bioremediation of contaminated soils.     

Phytoremediation for soils contaminated by phenanthrene and pyrene with multiple plant species

Purpose  

The remediation of soil polluted by polycyclic aromatic hydrocarbons (PAHs) is of great importance due to the persistence and carcinogenic properties of PAHs. Phytoremediation has been regarded as a promising alternative among suggested approaches. For the establishment of highly effective remediation method and better understanding of the remediation mechanisms by plants, the potentials of three plant species and their planting patterns on the remediation efficacy were studied by pot experiments.     

Vertical distribution of lead and arsenic in soils contaminated with lead arsenate pesticide residues

Many deciduous fruit tree orchard sites throughout the world are contaminated with lead (Pb) and arsenic (As) from past use of lead arsenate insecticides. The vertical distribution of Pb and As was examined in six contaminated orchard soils in the State of Washington, USA. Most of the Pb and As was restricted to the upper 40 cm of soil, with Pb concentration maxima ranging from 2.15 to 10.69 mmol/kg, and As concentration maxima ranging from 0.77 to 4.85 mmol/kg. In all cases, there were lower Pb and As concentrations at the soil surface than deeper in the profile. Arsenic was depleted relative to Pb in the topsoils and was enriched relative to Pb in the subsoils, suggesting that there has been preferential movement of As. Absolute soil enrichment with Pb occurred to depths between 15 and 50 cm. Absolute soil enrichment with As occurred to depths between 45 and > 120 cm. At 120 cm, Pb concentrations were < 0.05 mmol/kg, and As concentrations ranged from 0.07 to 0.63 mmol/kg. The deeper movement of Pb and As in the study soils relative to that reported for lead arsenate-contaminated soils elsewhere is attributed to high loading rates of lead arsenate, coarse soil texture, low organic matter content, and use of irrigation. The results indicate that Pb and As concentrations in lead arsenate-contaminated soils are high enough to be of potential environmental concern. The amount of As redistribution appears to be substantial enough to preclude some methods of remediation and to create potential risk of contamination of underlying shallow groundwater.     

Evaluating soluble toxicants in contaminated soils

Complex mixtures of water soluble materials from contaminated soils can move into groundwater and surface water by leaching, percolation, and runoff. We evaluated the potential toxicity of leachable materials from seven soils. Five soil samples were obtained at designated toxic or hazardous waste sites, and two additional soils samples were obtained from a coal storage area and from an agricultural field. Acidified tap water (pH 4.5) was used to extract toxic materials from elution columns filled with soil samples. Extracts were used as complex mixtures to conduct acute toxicity tests using Daphnia and chronic effects tests using aquatic microcosms. Three classes of effects were observed. Three soil leachates showed acute and chronic toxicity at less than 3% leachate. Two of these soils were contaminated by materials used in wood preserving, and the third soil was contaminated with heavy metals and acid. Two soils showed moderate acute toxicity but no chronic toxicity in microcosm tests. One of these soils was contaminated with low levels of chromium while the other soil was from a coal storage area. The remaining two soil samples showed no toxicity in either acute or chronic toxicity tests. One of these soils was from a reference agricultural field while the other soil was contaminated with solvents. The failure to detect toxicity in the solvent contaminated sample was attributed to the hydrophobicity of the toxicity materials. Results of these toxic screenings are in the same range as leachate toxicities estimated using other methods, although other methods use extraction materials that may interfere with some biological tests. Toxicological evaluations of materials from suspected contaminated soil are recommended for prioritizing clean up efforts at waste sites and for determining if toxic materials and contaminated soils have been effectively removed.     

Potential of Tamarix africana and other halophyte species for phytostabilisation of contaminated salt marsh soils

Purpose

Salt marsh plants are colonising wastes from a steel plant deposited on the Coina River Banks posing a potential contamination risk to the Tagus estuary ecosystem. The objectives of this study were to assess the uptake, accumulation and translocation of hazardous elements/nutrients in three spontaneous halophytic species, to evaluate the capacity of Tamarix africana to stabilise a contaminated salt marsh soil, and to evaluate the ecotoxicity of the pore water and elutriates from phytostabilised soils.

Materials and methods

The work comprises the following: fieldwork collection of soil samples from Coina River (an affluent of Tagus River) bank landfill, estuarine water and spontaneous plants (Aster tripolium, Halimione portulacoides and Sarcocornia sp.), and greenhouse studies (microcosm assay) with T. africana growing in one landfill salt marsh soil, for 97 days, and watered with estuarine water. Soils were analysed for pH, EC, C_organic, NPK, iron and manganese oxides. Soils total (acid digestion) elemental concentrations were determined by ICP/INAA. Estuarine waters, plants roots and shoots (acid digestion), soils available fraction (diluted organic acids extraction-RHIZO or pore water), and salts collected from the T. africana leaves surface were analysed for metals/metalloids (ICP-MS). Ecotoxicity assays were performed in T. africana soil elutriates and pore waters using Artemia franciscana and Brachionus plicatillis.

Results and discussion

Soils were contaminated, containing high total concentrations of arsenic, cadmium, chromium, copper, lead and zinc. However, their concentrations in the available fraction were <4 % of the total. The estuarine waters were contaminated with cadmium, but negligible ecotoxicological effect was observed. The spontaneous plants had significant uptake of the above elements, being mostly stored in the roots. Elemental concentrations in the shoots were within the normal range for plants. These species are not hazardous elements accumulators. Tamarix africana was well adapted to the contaminated saline soils, stored the contaminants in the roots, and had small concentrations of hazardous elements in the shoots. Excretion of hazardous elements by the salt glands was also observed. Elutriates from soils with and without plant did not show ecotoxicity.

Conclusions

The salt marsh species play an important role in the stabilisation of the soils in natural conditions. Tamarix africana showed potential for phytostabilisation of saline-contaminated soils. The low translocation of the elements from roots to shoots and/or active excretion of the elements by the salt glands was a tolerance mechanism in T. africana.

     

Arylesterase activity in trace element contaminated soils

Arylesterase activity was measured along with microbial biomass C (B_C) and respiration, and H₂O‐soluble and NH₄NO₃‐exchangeable trace elements (TE), in contaminated soils (TECS) from three long‐term field trials. The AGIR (AG) soils were contaminated only by inorganic Cd, whereas the Ambarès (AM) and Louis Fargue (LF) soils were contaminated mainly by Mn and Zn, and Cd and Ni, respectively, from past sludge application at different rates. In the AG soils, the arylesterase activity decreased with increasing Cd total concentration and solubility. In the AM soils, the arylesterase activity decreased with increased contamination, whereas in the LF soils the arylesterase activity was increased by sludge additions, with the higher values detected in soils with lower sludge incorporation rates. In the AG and AM soils, arylesterase activity was significantly and negatively correlated with H₂O‐soluble and NH₄NO₃‐exchangeable TE, whereas in the LF soils it showed a ‘hump’‐shaped trend with sludge additions and could not be modelled. Multiple regression analysis showed significant interactions between TE, soil pH value and TOC with this enzyme activity. Respiration values of the AG soils generally increased while the B_C generally decreased with Cd contamination, while different trends were observed in the AM and LF soils. No trends in the enzyme activity‐to‐B_C ratios were found in relation to soil contamination. Information regarding the inhibition of arylesterase activity in TECS can be important for the management of soils co‐contaminated by TE and organic pollutants, in which the detoxification action of arylesterase may be reduced.     

Characterizing the availability of metals in contaminated soils. II

Abstract. Methods that can be used to determine the distribution of metal species in soil solution are critically reviewed and assessed. They are divided into two groups: those that can provide free ion activity, and those that measure labile species in solution. Ion selective electrodes have long been regarded as a promising technique, but there are practical problems in performing accurate measurements and only the Cu electrode has been used routinely. The Donnan membrane technique is capable of measuring the free ion activity of many metals, but adequate sensitivity can be a problem. Although resin competition methods are versatile, care must be exercised to avoid perturbing the solution excessively. Anodic stripping voltammetry (ASV) measures labile species, so the approximation involved in interpretation as simple inorganic species, from which free ion activities can be derived, should be recognized. Diffusive gradients in thin-films also measures labile species, but it is applicable to a much wider range of metals than ASV. It requires larger volumes of solution, but it can be used directly on the whole soil where it also measures the metal that can be rapidly supplied to solution. Other techniques such as permeable liquid membranes have yet to be used for measurements on soil solution. All of these methods have strength and weaknesses, and measure different aspects of speciation. Knowledge of the availability of the metals to biota is likely to be best advanced by the critical use of one or more of these speciation methods with a thorough understanding of exactly what is being measured.     

The abundance of Trichoderma propagules and the distribution of species in forest soils

Propagules of Trichoderma generally formed less than 3 per cent of the total fungal propagules in a variety of forest soils in the southeastern U.S. and Washington State. The largest populations were found in the F and H organic horizons of the forest floor or under conditions of excessive moisture. T. viride Pers. ex S.F. Gray and T. polysporum (Link ex Pers.) Rifai were largely restricted to cool temperate regions; whereas, T. harzianum Rifai was characteristic of warm climates. T. koningii Oud. and T. hamatum (Bon.) Bain, were the most widely distributed species aggregates and were found in all the climatic regions investigated. Under conditions of excessive moisture, strains of T. hamatum and T. pseudokoningii Rifai were the dominant forms.     

Saturated hydrocarbons in the background and contaminated soils of the cisurals

A homologous series of n-alkanes (C₂₀–C₃₅) was identified in peaty-podzolic-gleyic soils. Structures with odd numbers of carbon atoms (C₂₅–C₃₅) were predominant in the soil organic matter. It was found that the major amount of both odd and even n-alkanes was accumulated in the peaty litter. In the mineral horizons, the mass fraction of the odd n-alkanes abruptly decreased to become comparable to that of the even n-alkanes in the soil-forming rock.     

Microelements in anthropogenically contaminated soils in the central part of Petrozavodsk

Urban soils (Urbic Technosols) formed within or near the industrial sites removed of service show a considerable excess over the regional background in the content of Pb, Zn, Cu, Mn, Cr, Ni, as well as over the average content of W, Mo, Pb, Sb, Cr, Cu, Sn, Ni, Zn, and Mn in urban soils. Microelements are concentrated for the most part in the soil fine earth, and above all, in the fraction with particle size <0.1 mm. Surface films (on quartz and feldspar grains) of quartz–feldspar–muscovite (partially with tremolite and chlorite) composition and undifferentiated dispersed mixture of quartz, albite, microcline, muscovite and organomineral soil substance are the strongest concentrators of heavy metals and metalloids. Pb and Sn are partially present in soils as oxides, and a part of Zn and Pb, in the form of substantial admixtures to technogenic chemical compounds. As a whole, distribution of elements in the studied soils is controlled by the specifics and type of contamination, resistance of coarser grains to weathering under the given physicochemical conditions, and by predominantly mineral (quartz–feldspar) composition of the solids in soil layers and the features of elements proper.     

Perchlorate biodegradation in contaminated soils and the deep unsaturated zone

In the United States, perchlorate has been officially recognized as an environmental contaminant. In Israel, widespread perchlorate contamination has been found in the 40-m deep vadose zone near an ammonium perchlorate manufacturing plant north of Tel Aviv, above the central part of Israel's coastal aquifer, with peak concentrations of 1200 mg kg_sediment^?1. In this study, we examined the perchlorate-reduction potential by native microbial communities along this deep contaminated vadose zone profile. We analyzed the effect of various concentrations of nitrate on perchlorate reduction and determined whether perchlorate concentrations in the profile are toxic to the native microbial population. All experiments were performed in soil slurries with sediments taken from the contaminated site. Perchlorate was reduced to chloride in three (1, 15 and 35 m) of the four examined sediment samples taken from different depths (1, 15, 20, and 35 m below surface). No activity was observed in the sediment sample from 20 m below land surface, suggesting low viable microbial communities and water content, and high perchlorate concentrations. In the presence of nitrate, the lag time for perchlorate degradation was inversely correlated to nitrate concentration. We found no perchlorate degradation as long as nitrate was present in the system, and perchlorate degradation initiated only after all the nitrate had been reduced. Nitrate-reduction rates were correlated to the initial concentrations of nitrate and no lag period was observed for nitrate reduction. Viable microbial populations were observed at both high concentrations (10,000 mg l^?1 and 20,000 mg l^?1) and with no addition of perchlorate, at levels of 2.35 × 10⁵, 4.01 × 10⁵, and 3.41 × 10³ CFU ml^?1, respectively; these results were well correlated to those found by PCR amplification analysis of chlorite dismutase. We suggest that the microbial community has adapted to the conditions of high perchlorate concentrations in the unsaturated zone over 30 years of exposure. When no external carbon source was added to the slurry of soil from land surface, all perchlorate was removed after 134 days of incubation. The average perchlorate-reduction rate using natural organic matter as a carbon source was 0.45 mg day^?1, while the average rate using acetate as an external carbon source was 7.2 mg day^?1.     

Remediation of agrosoddy-podzolic soils contaminated with cadmium

Results of a long-term field experiment on the remediation of agrosoddy-podzolic soils (Retisols) contaminated with cadmium have been analyzed. The solidification/stabilization method (S/S technology) has been used for the development of remediation technology. Different rates of ameliorants and fertilizers (limestone and phosphorite meals, superphosphate, sodium sulfide, peat, and zeolite) have been studied as ameliorating additives. It has been shown that the efficiency of ameliorating additives in decreasing the mobility of cadmium in the soil depends on their type (the dissolution of ameliorant in water and solubility products of the resulting Cd compounds), application rate, and the time elapsed since the application. In the first year of the experiment, the highest efficiency has been observed for water-soluble forms of ameliorating additives: sodium sulfide and superphosphate. Limestone meal and zeolite have showed the longest aftereffect. The application of all ameliorating additives under study has increased the yield of agricultural crops and reduced their cadmium content down to below the MPC level in most cases, which makes this agronomic practice promising for the remediation of agricultural lands with an elevated content of cadmium.     

根瘤菌在污染土壤修复中的地位和作用

根瘤菌是一种在环境中广泛存在,常与豆科植物共生结瘤固氮的细菌类群,在农、林、牧业的可持续发展中具有重要作用。近年来研究发现,除了人们熟知的固氮功能,根瘤菌还参与环境中重金属、有机物等污染土壤的修复,在生态环境修复、维持土地生产力以及节能减排方面发挥了重要的作用,尤其是根瘤菌与豆科植物联合修复污染环境效果更为显著。本文综合介绍了根瘤菌在重金属、有机物等污染土壤及滨海盐渍土壤修复中的地位、作用及潜在价值,以期为改善生态环境提供一些可参考的方法和依据。     

Sorption of antimony species by humic acid

The retention of antimony (a potential toxin) in polluted soils or waterway sediments can involve interaction with several component phases. One of these, humic acid, has been found to adsorb antimony (III) from solutions of Sb(OH)₃ or potassium antimonyl tartrate (C₈H₄K₂Sb₂O₁₂) in accordance with Langmuir type isotherms. Using Sb(OH)₃ solutions (initial Sb levels < 10 μM) the bonding constant value (at pH 4) was 6 × 10⁵, with a calculated saturation capacity of 23 μmol g^?1. In the antimonyl tartrate systems (initial Sb levels 0.5 to 75 μM) the bonding constant value for the sorbed species was 1.6 × 10⁵ and the saturation capacity 53 μmol g^?1. Addition of small amounts of HCl or NaOH (to vary the pH between 3.1 and 5.4) had little effect on the amount sorbed from KSbT solutions but with Sb(OH)₃ solutions uptake was reduced (by about 15%). In the presence of NaCl (0.5 or 0.05M) Sb uptake increased (by about 15%). Antimony (V) (introduced as KSb (OH)₆) was not sorbed from solutions < 10 μM in this salt. Using more concentrated solutions, uptake gradually increased, reaching a plateau value of around 8 μmol g^?1 with solutions initially 50 or 75 μM.     

Spectroscopic determination of poly-aromatic compounds in petroleum contaminated soils

The determination of poly-aromatic hydrocarbons (PAHs) in the soil is of interest because of their carcinogenic and mutagenic activity in biological systems. The present study deals with the rapid application of infrared, fluorescence, synchronous luminescence spectrometries and gas chromatography to detect organic pollutants and their quantity in the soil. Sohxlet extraction followed by column separation was used to isolate organic pollutants. Although several solvent mixtures were used as eluents for the column, the solvent mixture, hexane:dichloromethane (50:50) efficiently extracts the aromatic compounds. Total petroleum hydrocarbons (TPH) measured by IR were found at high concentrations (30810.0 ppm) in the contaminated soil compared with the reference soil (30.0 ppm). Furthermore, the fluorescence results reveal that almost one-fourth of the 30810.0 ppm are aromatic hydrocarbons. In addition, the presence of PAHs such as naphthalene, acenaphthene, fluorene, fluoranthene, phenanthrene, pyrene, benzo(a)pyrene, chrysene, and dibenzo(a,h)anthracene in the polluted soil was determined by using synchronous study.     

137Cs在耕作土壤中的均一性分布研究

选择一块面积为35m×30m较为平坦的农耕地作为研究对象,采集68个样点,共计112个样品,对~(137)Cs在土壤中的垂直分布和水平分布进行了探讨.结果表明,~(137)Cs在耕作土壤剖面中分布主要集中在耕层以内,且各个层的质量活度介于2.92～4.01Bq/kg之间,在土壤表层中水平面上质量活度介于28.77～30.98Bq/kg之间,该核素在土壤剖面和地表水平面上都呈现均一性分布特征.