Accumulation of heavy metals in oil-contaminated peat soils

X-ray fluorescence and X-ray radiometry represent easy and simple methods to determine concentrations of heavy metals in the ash of peat soils contaminated with oil and can be applied for soil monitoring purposes. Oil spills on peat bogs produce two contamination zones differing in the composition of heavy metals. In the zone of primary contamination, the peat surface is covered by a bitumen crust with V, Ni, Sr, Ba, Ce, and La accumulating there. This zone adjoins the zone of secondary peat contamination, where heavy alkaline-earth metals (Sr, Ba) and lanthanides (Ce and La) are accumulated to a lesser extent. Biological preparations recommended for remediation of oil-contaminated peat soils should be tolerant to high concentrations of heavy metals, particularly, V, Ni, and Ba that are present in the oil contaminated soils in relatively high amounts.     

Effectiveness of Plant-Derived Sorbents for the Remediation of Low-Energy Intertidal Wetlands Contaminated by Oil Spills

The use of plant-derived sorbent was investigated as a remediation strategy for low-energy intertidal wetlands contaminated by crude oil spills. Effectiveness of plant-derived sorbent as a wicking agent was evaluated in microcosms simulating intertidal wetlands. Microcosms were designed to impose three different oil penetration depths (0.25, 0.5, and 1.0?cm), two different tidal amplitudes (±5 and ±10?cm above oil-contaminated surface), and two different types of sorbents (raw bagasse and hydrophobic-treated bagasse). We observed that the use of plant-derived sorbent was beneficial not only in removing oil but also in preventing further contamination. Oil penetration depth and tidal amplitude both negatively influenced the effectiveness of the sorbent. Effectiveness of the hydrophobic-treated sorbent was always higher than that of untreated one at any given oil penetration depth and tidal amplitude. Effectiveness of hydrophobic-treated sorbent was relatively low compared to that of raw bagasse. The most plausible explanation is that oil wicking mainly occurred during low tide. From a cost-effectiveness point of view, we suggest the use of raw bagasse immediately after an oil spill for remediation of low-energy intertidal wetlands. The observed results imply that this technique has potential to stimulate biodegradation by wicking oil out of contaminated intertidal wetlands subsurface to the aerobic zone where biodegradation can take place.     

Assessing the biological activity of oil-contaminated soddy-podzolic soils with different textures

The respiratory activity features in oil-contaminated soddy-podzolic soils of different textures have been studied. Unidirectional processes occur in contaminated loamy and loamy sandy soddy-podzolic soils; their intensities depend on the soil parameters. The mineralization rates of the oil products and the activity of the microflora in loamy soils exceed the corresponding parameters for loamy sandy soils. The long-term impact of oil and its transformation products results in more important disturbances of the microbial community in light soils. It has been shown that light soils containing 9% oil require longer time periods or more intensive remediation measures for the restoration of soil microbial cenoses disturbed by the pollutant.     

油污土壤修复微生物的筛选及其影响因素

[目的]探讨微生物原位修复的主要影响因素及水平(正交设计)之间的关系,为石油污染场地生物修复工程的参数设计提供一定理论依据。[方法]选取5因素4水平的正交设计,考察污染强度、营养物、氧化剂、表活剂、接菌量等因素对土壤修复效果的影响。[结果]以原油为唯一碳源经过初步筛选,获得16株石油烃降解优势菌,经过菌群复筛,获得2株偏利共生协同真菌DPF2,DPF4,协同降解率最高,7d达87.77%。选择其进行室内油污土壤的微生物修复模拟试验,60d石油污染强度为10的油污土壤降解率最高,可达94.12%。污染强度为25的油污土壤降解率为90.17%,SPSS数据分析表明生物修复影响的最大影响因素是氧化剂、表活剂和营养物,其次是污染强度、接菌量。[结论]初期添加表活剂、氧化剂、营养剂能对石油生物修复具有重要意义。污染强度仅在35d前有一定影响,在修复后期影响最小。在整个修复过程,接菌量方差均值与其他因素比较都最小,因此其因素水平对石油降解能力的影响不显著。     

生物质炭修复重金属及有机物污染土壤的研究进展

生物质炭是生物质原料在完全或部分缺氧条件下高温热解后的固体产物,它具有丰富的孔隙结构和较高的碳含量。该物质具有巨大的表面积和较强的阳离子交换能力等特殊性质,对受污染土壤中的重金属和有机物都具有很强的吸附能力,有效地降低这些污染物的生物有效性和在环境中的迁移,对改善土壤环境具有重大意义。近年来我国土壤污染严重,利用生物质炭修复受污染土壤的技术得到了广泛的关注。本文简述了生物质炭修复土壤污染的基本原理,探讨了与其他修复方法相比存在的优势,阐述了国内外近年来利用生物质炭修复污染土壤的研究进展,最后展望了今后需要进一步研究的领域。     

Biological and physical resilience of soil amended with heavy metal-contaminated sewage sludge

Stability and resilience of a variety of soil properties and processes are emerging as key components of soil quality. We applied recently developed measures of biological and physical resilience to soils from an experimental site treated with metal‐contaminated sewage sludge. Soils treated with cadmium‐, copper‐ or zinc‐contaminated, digested or undigested sewage sludge were studied. Biological stability and resilience indices were: (i) the time‐dependent effects of either a transient stress (heating to 40°C for 18 hours) or a persistent stress (amendment with CuSO₄) on decomposition, and (ii) the mineralization of dissolved organic carbon (DOC) released by drying–rewetting cycles. Physical stability and resilience measures were: (i) compression and expansion indices of the soils, and (ii) resistance to prolonged wetting and structural regeneration through drying–rewetting cycles. Soil total carbon and DOC levels were greater in the sludge‐amended soils, but there were no differential effects due to metal contamination of the sewage sludge. Effects of metals on physical resilience were greater than effects on soil C, there being marked reductions in the expansion indices with Cd‐ and Cu‐contaminated sludge, and pointed to changes in soil aggregation. The rate of mineralization of DOC released by drying and wetting was reduced by Zn contamination, while biological resilience was increased in the Zn‐contaminated soil and reduced by Cd contamination. We argue that physical and biological resilience are potentially coupled through the microbial community. This needs to be tested in a wider range of soils, but demonstrates the benefits from a combined approach to the biological and physical resilience of soils.     

Contact angles at the water–air interface of hydrocarbon-contaminated soils and clay minerals

Contact angles at the water–air interface have been measured for triturated preparations of clays and soils in order to assess changes in their hydrophobic properties under the effect of oil hydrocarbons. Tasks have been to determine the dynamics of contact angle under soil wetting conditions and to reveal the effect of chemical removal of organic matter from soils on the hydrophilicity of preparations. The potentialities of static and dynamic drop tests for assessing the hydrophilic–hydrophobic properties of soils have been estimated. Clays (kaolinite, gumbrine, and argillite) have been investigated, as well as plow horizons of soils from the Republic of Tatarstan: heavy loamy leached chernozem, medium loamy dark gray forest soil, and light loamy soddy-calcareous soil. The soils have been contaminated with raw oil and kerosene at rates of 0.1–3 wt %. In the uncontaminated and contaminated chernozem, capillary water capacity has been maintained for 250 days. The contact angles have been found to depend on the degree of dispersion of powdered preparation, the main type of clay minerals in the soil, the presence and amount of oxidation-resistant soil organic matter, and the soil–water contact time. Characteristic parameters of mathematical models for drop behavior on triturated preparations have been calculated. Contamination with hydrocarbons has resulted in a reliable increase in the contact angles of soil preparations. The hydrophobization of soil surface in chernozem is more active than in soils poorer in organic matter. The complete restoration of the hydrophilic properties of soils after hydrocarbon contamination is due to the oxidation of easily oxidizable organic matter at the low content of humus, or to wetting during several months in the absence of the mazut fraction.     

黄河三角洲土壤土著菌的石油烃降解潜力

The bioremediation potential of bacteria indigenous to soils of the Yellow River Delta in China was evaluated as a treatment option for soil remediation. Petroleum hydrocarbon degraders were isolated from contaminated soil samples from the Yellow River Delta. Four microbial communities and eight isolates were obtained. The optimal temperature, salinity, pH, and the ratios of C, N, and P （C：N：P） for the maximum biodegradation of diesel oil, crude oil, n-alkanes, and polyaromatic hydrocarbons by indigenous bacteria were determined, and the kinetics changes in microbial communities were monitored. In general, the mixed microbial consortia demonstrated wider catabolic versatility and faster overall rate of hydrocarbon degradation than individual isolates. Our experimental results demonstrated the feasibility of biodegradation of petroleum hydrocarbon by indigenous bacteria for soil remediation in the Yellow River Delta.     

土壤石油污染对植物种子萌发和幼苗生长的影响

为了研究土壤石油污染对植物种子萌发和幼苗生长的影响,选取中原油田地区的原油和潮土,通过盆栽试验研究了不同石油污染水平条件下的植物种子发芽率、株高和鲜重.结果表明,土壤中石油含量不同,对黑麦草(Lolium perenne L.)、高羊茅(Festuca arundinacea)、紫花苜蓿(Medicago sativa L.)、白三叶草(Trifolium repens L.)、红三叶草(Trifolium pratense)的各项生长指标影响不同,当土壤中的石油含量较高时,对植物的生长有抑制作用.向日葵(Helianthus annus L.)、棉花(Gossypium hirsutum L.)、高丹草(Sorghum sudangrass)、狗牙根(Cynodon dactylon)在试验设计石油污染水平范围内发芽率、株高及鲜重受影响较小,能生长在石油污染的土壤上,其中狗牙根,生存能力强,是试验中的最具有修复土壤石油污染研究潜力的植物.     

土壤和土壤悬液中1,2,4-三氯苯的微生物强化降解

Inoculating soil with an adapted microbial community is a more effective bioaugmentation approach than inoculation with pure strains in bioremediation.However,information on the potential of different inocula from sites with varying contamination levels and pollution histories in soil remediation is lacking.The objective of the study was to investigate the potential of adapted microorganisms in soil inocula,with different contamination levels and pollution histories,to degrade 1,2,4-trichlorobenzene (1,2,4-TCB).Three different soils from chlorobenzene-contaminated sites were inoculated into agricultural soils and soil suspension cultures spiked with 1,2,4-TCB.The results showed that 36.52% of the initially applied 1,2,4-TCB was present in the non-inoculated soil,whereas about 19.00% of 1,2,4-TCB was present in the agricultural soils inoculated with contaminated soils after 28 days of incubation.The soils inoculated with adapted microbial biomass (in the soil inocula) showed higher respiration and lower 1,2,4-TCB volatilization than the non-inoculated soils,suggesting the existence of 1,2,4-TCB adapted degraders in the contaminated soils used for inoculation.It was further confirmed in the contaminated soil suspension cultures that the concentration of inorganic chloride ions increased continuously over the entire experimental period.Higher contamination of the inocula led not only to higher degradation potential but also to higher residue formation.However,even inocula of low-level contamination were effective in enhancing the degradation of 1,2,4-TCB.Therefore,applying adapted microorganisms in the form of soil inocula,especially with lower contamination levels,could be an effective and environment-friendly strategy for soil remediation.     

Influence of Water Content and Plants on the Dissipation of Chlorinated Volatile Organic Compounds in Soil

To devise effective procedures for the remediation of soil contaminated by VOCs, an improved understanding of their fate and transport mechanisms in soil is essential. To show the effect of plants on the dissipation of 1,1,1-trichloroethane (TCA), trichloroethylene (TCE) and tetrachloroethylene (PCE), two types of experiments, vial and column, were conducted. The results suggested that keeping the soil moisture content at field capacity is desirable for VOCs dissipation. All VOCs were dissipated quickly in unplanted columns than planted conditions in early periods of the experiment because more volatilization occurred in unplanted conditions. The plants could take up and retard volatile contaminants, and prevent contamination of ambient air. Although the time for acclimation for microbial communities to contaminants for enhanced biodegradation should be considered, phytoremediation is potentially a cost-effective remediation technique for soils contaminated by volatile organic compounds (VOCs).     

Application of bacterial-humus preparations in the remediation of soils contaminated with diesel fuel

The effect of bacterial-humus preparations on the biological activity of soils contaminated with diesel fuel was studied. The influence of the preparations was judged from the intensity of the CO₂ emissions from the soil, the total number of bacteria, and the structure of the saprotrophic bacterial complex. The ability of bacterial-humus preparations to enhance the biological activity of contaminated soils was shown. The possibility of maintaining target populations of bacteria in the soil for at least two months was proved.     

Phytoindication of the water status and nutrient supply of oil-polluted soils in the middle reaches of the Ob’ River

The method of phytoindication of the soil water status and nutrient supply was applied to natural and oil-contaminated soils in the middle reaches of the Ob’ River. These soil characteristics were indirectly assessed using the ecological scales developed by L. G. Ramenskii. On this basis, changes in the soil water status and nutrient supply under the impact of soil contamination with oil and oil products were estimated for the particular soil and landscape conditions     

石油污染土壤中芳烃降解菌及邻苯二酚2,3双加氧酶的克隆

石油污染土壤中的芳烃降解菌是进行土壤修复的主要生物资源,本研究对某炼油厂附近土壤中的芳烃降解菌及邻苯二酚2,3双加氧酶基因进行了研究。结果表明,部分石油烃污染土壤中存在着大量的芳烃降解菌;对其中一个土壤样本中的邻苯二酚2,3双加氧酶基因进行克隆,获得了7个不同的邻苯二酚双加氧酶基因序列,序列分析表明这些基因可能来源于土壤中的假单胞菌,且该基因在土壤中的丰度与污染水平及芳烃降解菌的数量相关。可见,土壤中芳烃降解菌数量及降解基因的丰度和多样性,可以对石油污染土壤的生物修复进行监控并为生物修复提供丰富的微生物资源。     

Application of biological indicators to assess recovery of hydrocarbon impacted soils

Remediation programmes are considered complete when human risk-based criteria are met. These targets are unrelated to the ecological parameters that may be important with regard to future soil uses. As a consequence, there has been a move towards the consideration of biological indicators for hazard assessment in conjunction with the remediation of contaminated soils. This study uses a range of biological assays to assess the ecological health of soils from a former gas works site undergoing various remediation treatments. The indicators that optimally differentiated the extent of soil remediation were biomass-C, respiration, dehydrogenase activity, earthworm toxicity and mustard seed germination. Although they had different end-points, once robust and sensitive biological indicators were incorporated into a quantitative soil quality index, they gave a clearer representation of ecological health than chemical data alone by their integration of contamination effects at a number of trophic levels.     

Surfactant-Enhanced Soil Washing for Removal of Petroleum Hydrocarbons from Contaminated Soils: A Review

An increase in energy demand leads to further exploration, transportation, and utilization of petroleum, which creates severe soil contamination because of recurrent accidents and oil spills. Remediation of these contaminated soils is challenging. Among many treatment methods practiced for remediation of petroleum-contaminated soils, surfactant-enhanced soil washing has been widely practiced as a preferred treatment option, as it is a fast and environmentally accepted method. In this paper, we review research undertaken on various anionic, nonionic, cationic, biological, and mixed surfactants for the remediation of petroleum hydrocarbon-contaminated soils. Upcoming surfactants like gemini and switchable surfactants are summarized. We assess the challenges and opportunities of in-situ and ex-situ soil washing, the mechanisms of surfactant-enhanced soil washing, and the criteria to follow for surfactant selection. Furthermore, we briefly discuss the operational and environmental factors affecting soil washing efficiency and soil and surfactant properties affecting surfactant adsorption. We also describe the advantages of coupling soil washing with effluent treatment and surfactant reuse challenges and opportunities. Moreover, challenges and possible new directions for future research on surfactant-enhanced soil washing are proposed.     

Ecological evaluation of oil-contaminated soils (Sakhalin) using enchytraeidae

The ecological status of oil-contaminated soils of Sakhalin and their background analogues has been evaluated with the use of soil invertebrates. The survival rates of Enchytraeus albidus in soils with different textures and the contents of organic carbon and nutrients have been compared. The indicative role of soil mesofauna (Enchytraeus albidus) for the ecological evaluation of oil-contaminated soils with due account for their properties has been shown. The permissible residual concentration of oil hydrocarbons in some soils of Sakhalin—acid brown forest soils (Umbrisols), high-moor peat soils (Histosols), acid meadow alluvial soils (Fluvisols), cultivated meadow soddy soils (Anthrosols), and mucky-podzolic surface-gleyed soils (Gleysols)— has been determined from data on the response of Enchytraeus albidus to different levels of the soil contamination with oil hydrocarbons.     

Effects of heavy metal contamination and remediation on soil microbial communities in the vicinity of a zinc smelter as indicated by analysis of microbial community phospholipid fatty acid profiles

Heavy metal contamination in an area immediately surrounding a zinc smelter has resulted in destruction of over 485 hectares of forest. The elevated levels of heavy metals in these soils have had significant impacts on the population size and overall activity of the soil microbial communities. Remediation of these soils has resulted in increases in indicators of biological activity and viable population size, which suggest recovery of the microbial populations. Questions remain as to how the metal contamination and subsequent remediation at this site have impacted the population structure of the soil microbial communities. In the current study, microbial communities from this site were analyzed by the phospholipid fatty acid (PLFA) procedure. Principal component analysis of the PLFA profiles indicated that there were differences in the profiles for soils with different levels of metal contamination, and that soils with higher levels of metal contamination showed decreases in indicator PLFAs for mycorrhizal fungi, Gram-positive bacteria, fungi, and actinomycetes. PLFA profiles for remediated sites indicated that remediated soils showed increases in indicator PLFAs for fungi, actinomycetes, and Gram-positive bacteria, compared to unremediated metal contaminated soils. These data suggest a change in the population structure of the soil microbial communities resulting from metal contamination and a recovery of several microbial populations resulting from remediation.     

Assessing the Efficiency of Humic Substances as Washing Agents for Oil–Contaminated Soils and Peats under Model Experimental Conditions

Two humic preparations of different origins have been compared as washing agents for oil-contaminated soils and peat under model experimental conditions using a sample from the plow horizon of soddypodzolic soil artificially contaminated with oil or diesel fuel and a sample of high-moor peat contaminated with crude oil because of a spill occurred 15 years ago. Soil and peat were washed by shaking with solutions of the humic preparations Gumat Sakhalinskii and Lignogumat in a 1: 10 (m/v) ratio. Control samples were washed with distilled water. Washing with a synthetic surfactant (sodium dodecyl sulfate) was also added to the experimental design. After washing, soil and peat samples were air-dried and used for the determination of the total content of petroleum hydrocarbons; the characterization of their hydrocarbon composition; and the assessment of hydrophobicity from the contact angle and the efficiency of colonization by oil-destructing microorganisms Rhodococcus sp. and Candida sp., which are components of the preparation Bioros recommended for oil contaminations. It has been shown that the extraction efficiency of petroleum hydrocarbons by humic preparations did not differ from the extraction efficiency by water and was less than that by sodium dodecyl sulfate in all cases. No appreciable changes in the contact angles of soil and peat have been observed at the use of water and humic preparations as washing agents, while the contact angle decreased to less than 90o after washing with sodium dodecyl sulfate, which indicated the hydrophobicity of the surface of substrate particles. It has been found that humic preparations favor the colonization of soil and peat by oil-destructing microorganisms Rhodococcus sp. and Candida sp. Based on the obtained results, humic preparations have been recommended for further study as preparations favoring the ability of oil-destructing microorganisms to colonize oil-contaminated substrates.     

Assessment of the microbial transformation of nitrogen and carbon compounds under conditions of oil and radioactive contamination

Changes in the parameters of soil biological activity (respiration rate and the intensity of nitrogen fixation and denitrification) and in the structure of soil microbial communities were revealed in a series of field experiments with radioactively contaminated soils of Bryansk region. The microbial transformation of nitrogen and carbon compounds under simultaneous contamination of the soils with oil products and radionuclides was investigated in model experiments.