Effects of polycyclic aromatic hydrocarbons on germination and subsequent growth of grasses and legumes in freshly contaminated soil and soil with aged PAHs residues

The relevance of germination trials for screening plants that may have potential for use in the phytoremediation of PAH contaminated land was evaluated. The germination and subsequent growth of 7 grass and legume species were evaluated in soil spiked with a pure PAH mixture or coal tar and soil from a former coking plant heavily contaminated with aged PAHs. None of these treatments adversely affected germination of the plants. However, apart from Lolium perenne all species exhibited reduced growth in the coking plant soil after 12 weeks growth when compared to the untreated soil. In the coal tar spiked soil 4 out of the 7 species showed reduced growth, as did 3 out of the 7 in the soil spiked with a mixture of 7 PAHs. Therefore, germination studies alone would not predict the success of subsequent growth of the species tested in the ranges of soil PAH levels studied.     

Degradation of polycyclic aromatic hydrocarbons (PAHs) in an aged coal tar contaminated soil under in-vessel composting conditions

In-vessel composting of polycyclic aromatic hydrocarbons (PAHs) present in contaminated soil from a manufactured gas plant site was investigated over 98 days using laboratory-scale in-vessel composting reactors. The composting reactors were operated at 18 different operational conditions using a 3-factor factorial design with three temperatures (T, 38 degrees C, 55 degrees C and 70 degrees C), four soil to green waste ratios (S:GW, 0.6:1, 0.7:1, 0.8:1 and 0.9:1 on a dry weight basis) and three moisture contents (MC, 40%, 60% and 80%). PAH losses followed first order kinetics reaching 0.015 day(-1) at optimal operational conditions. A factor analysis of the 18 different operational conditions under investigation indicated that the optimal operational conditions for degradation of PAHs occurred at MC 60%, S:GW 0.8:1 and T 38 degrees C. Thus, it is recommended to maintain operational conditions during in-vessel composting of PAH-solid waste close to these values.     

Phytotoxicity of nitroaromatic energetic compounds freshly amended or weathered and aged in sandy loam soil

The toxicities of 2,4,6-trinitrotoluene (TNT), 1,3,5-trinitrobenzene (TNB), 2,4-dinitrotoluene (2,4-DNT), and 2,6-dinitrotoluene (2,6-DNT) to terrestrial plants alfalfa (Medicago sativa L.), Japanese millet (Echinochloa crusgalli L.), and perennial ryegrass (Lolium perenne L.) were determined in Sassafras sandy loam soil using seedling emergence, fresh shoot, and dry mass measurement endpoints. A 13-week weathering and aging of energetic materials in soils, which included wetting and drying cycles, and exposure to sunlight of individual soil treatments, was incorporated into the study design to better reflect the soil exposure conditions in the field than toxicity determinations in freshly amended soils. Definitive toxicity tests showed that dinitrotoluenes were more phytotoxic for all plant species in freshly amended treatments based on EC20 values for dry shoot ranging from 3 to 24mgkg(-1) compared with values for TNB or TNT ranging from 43 to 62mgkg(-1). Weathering and aging of energetic materials (EMs) in soil significantly decreased the toxicity of TNT, TNB or 2,6-DNT to Japanese millet or ryegrass based on seedling emergence, but significantly increased the toxicity of all four EMs to all three plant species based on shoot growth. Exposure of the three plant species to relatively low concentrations of the four compounds initially stimulated plant growth before the onset of inhibition at greater concentrations (hormesis).     

Degradation of toxaphene in water during anaerobic and aerobic conditions

The degradation of technical toxaphene in water with two kinds of bioreactors operating in sequence was studied. One packed bed reactor was filled with Poraver (foam glass particles) running at anaerobic conditions and one suspended carrier biofilm reactor working aerobically. Chemical oxygen demand (COD), chloride, sulphate, pH, dissolved oxygen, total toxaphene and specific toxaphene isomers were measured. After 6 weeks approx. 87% of the total toxaphene was degraded reaching 98% by week 39. The majority of the conversion took place in the anaerobic reactor. The concentrations of toxaphene isomers with more chlorine substituents decreased more rapidly than for isomers with less chlorine substituents.     

Phytoremediation of an aged petroleum contaminated soil using endophyte infected and non-infected grasses

Phytoremediation is a promising technique for cleaning petroleum contaminated soils. In this study, the effects of two grass species (Festuca arundinacea Schreb. and Festuca pratensis Huds.), infected (E(+)) and non-infected (E(-)) by endophytic fungi (Neotyphodium coenophialum and Neotyphodium uncinatum, respectively) on the degradation of petroleum hydrocarbons in an aged petroleum contaminated soil was investigated. Plants were grown in the soil for 7 months and unplanted soil considered as control. At the end of the experiment, total and oil-degrading bacteria, dehydrogenase activity, water-soluble phenols, total petroleum hydrocarbons (TPH) and polycyclic aromatic hydrocarbons (PAHs) contents were measured in the soil. The results demonstrated that E(+) plants contained more root and shoot biomass than E(-) plants and created higher levels of water-soluble phenols and dehydrogenase activity in the soil, while there was no significant difference in bacterial counts of planted soils. Planting stimulated total and oil-degrading bacterial numbers, dehydrogenase activity and the soil content of water-soluble phenols. Regardless of endophyte infection, PAH and TPH removal in the rhizosphere of plants were 80-84 and 64-72% respectively, whereas the removals in controls were 56 and 31%, respectively. It was revealed that TPHs in retention time range of n-alkanes with C(10)-C(25) chain lengths and TPH were more degraded in the rhizosphere of E(+) plants compared to E(-) ones. Thus, grasses infected with endophytic fungi could be more efficient for removal of TPH from oil-contaminated soils.     

零价铁活化过硫酸钠体系降解污染土壤中的多环芳烃

采用Fe0活化Na2S2O8体系降解污染土壤中的PAHs,其代表化学物为NAP、PHE、FLA和BAP。分别研究了Na2S2O8的添加量、Na2S2O8与Fe0的物质的量比、水土比和温度对降解效果的影响,同时探讨了PAHs的降解动力学;并利用电子顺磁共振法(EPR)验证了Fe0活化Na2S2O8的自由基产生情况。结果表明,当1 mol·L-1的Na2S2O8添加量为10 mL、Na2S2O8与Fe0物质量之比为200∶1、水土比为2∶1、温度为60 ℃时反应36 h后,NAP、PHE、FLA、BAP的降解率分别为98.15%、78.41%、93.47%和97.64%。PAHs的降解符合一级反应动力学,且BAP的反应速率常数最大为0.030 5 h-1。EPR谱图表明,Fe0活化Na2S2O8降解PAHs污染的土壤是SO4-·和·OH共存的反应体系。该研究可为Fe0活化Na2S2O8体系降解PAHs污染土壤的机理提供一定的依据。     

Toxicity of emerging energetic soil contaminant CL-20 to potworm Enchytraeus crypticus in freshly amended or weathered and aged treatments

We investigated the toxicity of an emerging polynitramine energetic material hexanitrohexaazaisowurtzitane (CL-20) to the soil invertebrate species Enchytraeus crypticus by adapting then using the Enchytraeid Reproduction Test (ISO/16387:2003). Studies were designed to develop ecotoxicological benchmark values for ecological risk assessment of the potential impacts of accidental release of this compound into the environment. Tests were conducted in Sassafras Sandy Loam soil, which supports relatively high bioavailability of CL-20. Weathering and aging procedures for CL-20 amended into test soil were incorporated into the study design to produce toxicity data that better reflect soil exposure conditions in the field compared with the toxicity in freshly amended soils. Concentration-response relationships for measurement endpoints were determined using nonlinear regressions. Definitive tests showed that toxicities for E. crypticus adult survival and juvenile production were significantly increased in weathered and aged soil treatments compared with toxicity in freshly amended soil, based on 95% confidence intervals. The median effect concentration (EC50) and EC20 values for juvenile production were 0.3 and 0.1 mg kg-1, respectively, for CL-20 freshly amended into soil, and 0.1 and 0.035 mg kg-1, respectively, for weathered and aged CL-20 soil treatments. These findings of increased toxicity to E. crypticus in weathered and aged CL-20 soil treatments compared with exposures in freshly amended soils show that future investigations should include a weathering and aging component to generate toxicity data that provide more complete information on ecotoxicological effects of emerging energetic contaminants in soil.     

Electro-migration of heavy metals in an aged electroplating contaminated soil affected by the coexisting hexavalent chromium

Cr(VI) was often reported to oxidize soil organic matter at acidic environments due to its high ORP, probably thus changing cationic metal species bound to soil organic matter, and influencing their electro-migration patterns. However, such an effect on the electro-migration was not confirmed in most previous studies. Therefore, this study applied a fixed voltage direct current field on an aged electroplating contaminated clayed soil, with a special interest in the direct or indirect influence of Cr(VI) on the electro-migration of other coexisting metals. After 353 h electrokinetic process, 81% of Zn, 53% of Ni and 22% of Cu in the original soil were electro-migrated into the electrolyte, and most of the remaining concentrated near the cathode. The Cr(VI) oxidized some soil organic matter along its migration pathway, with a pronounced reaction occurred near the anode at low pHs. The resulting Cr(III) reversed its original movement, and migrated towards the cathode, leading to the occurrence of a second Cr concentration peak in the soil. Metal species analyses showed that the amount of metals bound to soil organic matter significantly decreased, while a substantial increase in the Cr species bound to Fe/Mn (hydro-)oxides was observed, suggesting an enhancement of cationic metal electro-migration by the reduction of Cr(VI) into Cr(III). However, the Cr(VI) may form some stable lead chromate precipitates, and in turn demobilize Pb in the soil, as the results showed a low Pb removal and an increase in its acid-extractable and residual fractions after electrokinetic remediation.     

Degradation of telone II in contaminated and noncontaminated soils

Abstract

Degradation of the nematicide Telone II (cis‐ and trans‐1,3‐dichloropropene comprise the active ingredients) in soil was studied using ¹⁴C‐l,3‐dichloropropene (DCP) along with soil samples collected from a field test site near Quincy, Florida. A mixed bacterial culture isolated from the soil in the presence of a second carbon source, glucose or yeast extract, completely degraded ¹⁴C‐DCP to ¹⁴CO₂, water‐soluble products, and microbial mass. ¹⁴C‐DCP in soil was also degraded to ¹⁴CO₂. After 28 days of incubation, the labeled chemical was completely degraded to ¹⁴CO₂, water‐soluble metabolites, bound‐residues, and possibly some microbial mass. Little or no difference was observed in the degradation of ¹⁴C‐DCP in soil samples collected one week prior to field application of Telone II, or two weeks and two years after application.     

A column method for determination of leaching of polycyclic aromatic hydrocarbons from aged contaminated soil

In this study a column leaching method for investigation of hydrophobic organic contaminants (HOCs) leaching from soil was developed. The method set-up is based on a recycled flow of sterile water through a soil column with a sedimentation chamber mounted on top of the column, in connection with on-line filtration. The combination of a sedimentation chamber and an on-line filtration enables the measurement of leaching concentrations from contaminated materials consisting of very fine particle fractions. In addition, by using on-line solid phase extraction, minute amounts of leaching HOCs may be captured and quantified with high accuracy and reproducibility. The method was applied successfully on a contaminated aged soil sample and the leaching behavior of seven PAHs, with three to six aromatic rings, was monitored for more than 1600 h under saturated conditions. The tested PAHs were fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo(a)pyrene and benzo(ghi)perylene. The method proved to be reliable and capable of providing data on leachable amounts of the PAHs under field-like conditions and over a longer period of time. The results indicated low availability of the studied contaminants since only a minor fraction (0.3%) of the initial amount of PAHs in the soil was removed during the experiment (liquid/solid-ratio of 700 l/kg). Thus PAHs in aged contaminated soil are not to be expected to be released to any great extent only by leaching with water.     

Effects of alfalfa and organic fertilizer on benzo[a]pyrene dissipation in an aged contaminated soil

BACKGROUND: A climate-controlled pot experiment was conducted to investigate the effects of planting alfalfa and applying organic fertilizer on the dissipation of benzo[a]pyrene from an aged contaminated agricultural soil. RESULTS: Short-term planting of alfalfa inhibited the dissipation of benzo[a]pyrene from the soil by 8.9%, and organic fertilizer enhanced benzo[a]pyrene removal from the soil by 11.6% compared with the unplanted and unfertilized treatments, respectively. No significant interaction was observed between alfalfa and organic fertilizer on benzo[a]pyrene dissipation. Sterilization completely inhibited the removal of benzo[a]pyrene from the soil indicating that its degradation by indigenous microorganisms may have been the main mechanism of dissipation. Furthermore, significant positive relationships were observed between benzo[a]pyrene removal and the contents of soil ammonium nitrogen, nitrate nitrogen, and total mineral nitrogen at the end of the experiment, suggesting that competition between plants and microorganisms for nitrogen may have inhibited benzo[a]pyrene dissipation in the rhizosphere of alfalfa and the addition of organic fertilizer may facilitate microbial degradation of benzo[a]pyrene in the soil.     

对二氯苯污染土壤的植物修复研究

采用种植物的方法.对以对二氯苯(PDCB)为代表的多氯代有机污染物(PCOPs)污染土壤的植物修复进行了研究.以黑麦草、紫花苜蓿和大蒜作为供试植物.在PDCB为1 856μg/kg的污染土壤中种植90 d,研究了不同植物条件下土壤中PDCB的降解情况.结果表明,与空白对照相比.种植物大大提高了土壤中微生物的数量和酶的活性.试验结束后,种植黑麦草、紫花苜蓿和大蒜后,PDCB分别降低82.44%、62.82%和59.59%.种植黑麦草时PDCB降解最快,对PDCB污染土壤修复的效果最好.     

Release of hexachlorocyclohexanes from historically and freshly contaminated soils in China: implications for fate and regulation

Hexachlorocyclohexanes (HCHs) were produced and used in large quantity worldwide and are common soil pollutants. In this study, desorption of α-HCH and γ-HCH from two soil samples collected from a historical pesticide plant in Tianjin, China, was examined. As a comparison, desorption of freshly sorbed γ-HCH was examined, using five typical Chinese soils. Strong resistant desorption was observed for both historically contaminated and freshly contaminated soils, and desorption results were well modeled with a biphasic desorption isotherm. The unique thermodynamic characteristics associated with the desorption-resistant fraction indicated that physical constraint within soil organic matrices was likely the predominant mechanism controlling resistant desorption. Resistant desorption could have significant effects on fate and exposure of HCHs in soil environment. More accurate biphasic desorption models that take into account of the resistant desorption can be used to facilitate regulating, management and remediation of HCH-contaminated sites.     

污染土壤的淋洗法修复研究进展

污染土壤淋洗技术是修复污染土壤的一种新方法 ,是对污染土壤生物修复的一种补充 ,使污染土壤修复的系统化成为可能。淋洗法主要使用淋洗剂清洗土壤 ,使土壤中污染物随淋洗剂流出 ,然后对淋洗剂及土壤进行后续处理 ,从而达到修复污染土壤的目的。因为淋洗剂的种类和淋洗方式的不同 ,土壤淋洗法可分为许多种类。土壤淋洗法主要受土壤条件、污染物类型、淋洗剂的种类和运行方式等因素影响。综合考虑多方面因素 ,就有潜力设计出经济高效的土壤淋洗系统。土壤淋洗法有很多优点 ,尽管也存在一些问题 ,但其技术上的优势也是其他方法难以取代的 ,所以有良好的应用前景。     

Level of oxidative stress for the land snail Cepaea nemoralis from aged and bioremediated soil contaminated with petroleum products

Environmental Science and Pollution Research - Here, we investigated whether the widely distributed snail Cepaea nemoralis could be used as a suitable sentinel animal for assessing the effects of...     

Investigation of organic matter dynamics during in-vessel composting of an aged coal-tar contaminated soil using fluorescence excitation-emission spectroscopy

In-vessel composting of an aged coal-tar contaminated soil from a manufactured gas plant site was investigated over 98days using laboratory-scale in-vessel composting reactors. The composting reactors were operated at 18 different operational conditions using a logistic three-factor factorial design with three temperatures (T=38, 55 and 70 degrees C), four soil to green waste ratios (S:GW; 0.6:1, 0.7:1, 0.8:1 and 0.9:1 on a dry weight basis) and three moisture contents (MC; 40%, 60% and 80%). Excitation-emission matrix (EEM) fluorescence spectroscopy was used to investigate organic matter dynamics in the composting mixture. The results of this investigation indicated that formation of humic substances can be monitored by fluorescence excitation-emission matrix, and provided evidence of progressive mineralization or humification of the composting mixture. Peak excitation wavelength shifts and peak fluorescence intensity can both be used as indicators to monitor the humification or maturation of compost. Finally, the fluorescence index can be applied to investigate the origin of humic substances and fulvic acids, and the humification or maturation of compost.     

Biochar- and phosphate-induced immobilization of heavy metals in contaminated soil and water: implication on simultaneous remediation of contaminated soil and groundwater

Long-term wastewater irrigation or solid waste disposal has resulted in the heavy metal contamination in both soil and groundwater. It is often separately implemented for remediation of contaminated soil or groundwater at a specific site. The main objective of this study was to demonstrate the hypothesis of simultaneous remediation of both heavy metal contaminated soil and groundwater by integrating the chemical immobilization and pump-and-treat methods. To accomplish the objective, three experiments were conducted, i.e., an incubation experiment was first conducted to determine how dairy-manure-derived biochar and phosphate rock tailing induced immobilization of Cd in the Cd-contaminated soils; second, a batch sorption experiment was carried out to determine whether the pre-amended contaminated soil still had the ability to retain Pb, Zn and Cd from aqueous solution. BCR sequential extraction as well as XRD and SEM analysis were conducted to explore the possible retention mechanism; and last, a laboratory-scale model test was undertaken by leaching the Pb, Zn, and Cd contaminated groundwater through the pre-amended contaminated soils to demonstrate how the heavy metals in both contaminated soil and groundwater were simultaneously retained and immobilized. The incubation experiment showed that the phosphate biochar were effective in immobilizing soil Cd with Cd concentration in TCLP (toxicity characteristics leaching procedure) extract reduced by 19.6 % and 13.7 %, respectively. The batch sorption experiment revealed that the pre-amended soil still had ability to retain Pb, Zn, and Cd from aqueous solution. The phosphate-induced metal retention was mainly due to the metal–phosphate precipitation, while both sorption and precipitation were responsible for the metal stabilization in the biochar amendment. The laboratory-scale test demonstrated that the soil amended with phosphate removed groundwater Pb, Zn, and Cd by 96.4 %, 44.6 %, and 49.2 %, respectively, and the soil amended with biochar removed groundwater Pb, Zn, and Cd by 97.4 %, 53.4 %, and 54.5 %, respectively. Meanwhile, the metals from both groundwater and soil itself were immobilized with the amendments, with the leachability of the three metals in the CaCl₂ and TCLP extracts being reduced by up to 98.1 % and 62.7 %, respectively. Our results indicate that the integrated chemical immobilization and pump-and-treat method developed in this study provides a novel way for simultaneous remediation of both metal-contaminated soil and groundwater.     

生物强化修复石油污染土壤

筛选高效石油降解菌,考察菌株的降解性能及降解机理,进行花盆模拟高效外源菌强化修复石油污染土壤实验,在降解后期添加激活剂H2O2以及木屑来试图改善微生物的修复环境,减缓微生物的衰亡,并考察修复效果。结果表明,菌株L-1的降解效果较好,其对pH和温度有较大范围的适应性,能分泌较多的表面活性物质,细胞疏水性较强。将其应用于土壤修复中,经过50 d的修复,石油残留率达到50.6%左右,生物强化比自然修复残留率降低了8%左右。在第45天添加激活剂能有效改善修复效果,70 d时添加外源菌的土样最小石油残留率达到37.9%。     

Arsenic and chromium speciation in an urban contaminated soil

The distribution and speciation of As and Cr in a contaminated soil were studied by synchrotron-based X-ray microfluorescence (μ-XRF), microfocused X-ray absorption spectroscopy (μ-XAS), and bulk extended X-ray absorption fine structure spectroscopy (EXAFS). The soil was taken from a park in Wilmington, DE, which had been an important center for the leather tanning industry along the Atlantic seaboard of the United States, until the early 20th century. Soil concentrations of As, Cr, and Pb measured at certain locations in the park greatly exceeded the background levels of these heavy metals in the State of Delaware. Results show that Cr(III) and As(V) species are mainly present in the soil, with insignificant amounts of Cr(VI) and As(III). Micro-XRF maps show that Cr and Fe are distributed together in regions where their concentrations are diffuse, and at local spots where their concentrations are high. Iron oxides, which can reduce Cr(VI) to Cr(III), are present at some of these hot spots where Cr and Fe are highly concentrated. Arsenic is mainly associated with Al in the soil, and to a minor extent with Fe. Arsenate may be sorbed to aluminum oxides, which might have transformed after a long period of time into an As-Al precipitate phase, having a structure and chemical composition similar to mansfieldite (AlAsO(4)?2H(2)O). The latter hypothesis is supported by the fact that only a small amount of As present in the soil was desorbed using the characteristic toxicity leaching procedure tests. This suggests that As is immobilized in the soil.     

石油污染土壤的植物与微生物修复技术

石油污染土壤的生物修复技术具有成本低、简便高效、对环境影响小等优点,正逐步成为石油污染治理研究的热点领域,具有广阔的发展前景.介绍了我国的石油污染概况及生物修复技术在石油污染治理中的应用,重点对石油污染土壤的微生物修复、植物修复、植物一微生物联合修复技术的研究进展及各自的优点、局限性进行了综述,并提出了石油污染土壤生物修复技术研究的重点领域.