Fenton's Reagent-Based In Situ Chemical Oxidation Treatment of Saturated and Unsaturated Soils at a Historic Railroad Site

A targeted treatment program utilizing in situ chemical oxidation was used to remediate diesel fuel-derived petroleum compounds in unsaturated and saturated soils at a historic railroad facility. This program consisted of multiple injections at varying depths within temporary Geoprobe® injection points. The actual treatment time was less than 3 months. Overall concentrations of volatile and semivolatile organic petroleum compounds were reduced by approximately 70%, while the total petroleum hydrocarbon concentration was reduced by nearly 50%. Treatment efficiency in unsaturated soil was similar to that in saturated soil. The results of the remedial program indicate that the effect of grain size of the subsurface materials on treatment efficacy is significant. The project has shown that the use of this technology can be as effective as other in situ treatment technologies used for treating subsurface diesel fuel contamination.     

The Use of Conocarpus lancifolius Trees for the Remediation of Oil-Contaminated Soils

The role of the Conocarpus lancifolius tree in remediaitng oil-contaminated soil, which was bioremediated using conventional methods, was investigated. The selected tree was used to phytoremediate bioremediated oil-contaminated soil for three successive growing seasons. At the end of the phytoremediation experiment, 85.7% of measurable total petroleum hydrocarbon (TPH) was degraded in Conocarpus lancifolius rhizosphere, and the detectable concentrations of some poly aromatic hydrocarbons (PAHs) were less than 0.02 ppm. A number of hydrocarbon degrading microorganisms (HDMs) were isolated at 35°C under aerobic conditions, and were identified using 16S rRNA gene sequencing and fatty acid methyl ester (FAME) analysis. The efficiency of the isolated HDMs in degrading a mixture of hydrocarbon compounds (HC) was assessed. Among the bacterial isolates, Rhodococcus equi was distinguished from the other isolates because of its efficient degradation of some compounds in the HC mixture.

Samples were also collected from Conocarpus lancifolius vegetative parts and were analyzed for heavy metal and mineral accumulation. The results demonstrated that the Conocarpus lancifolius tree was able to uptake high levels of chromium (Cr), vanadium (V), and nickel (Ni) and accumulate them in the tree's roots. Additionally, Conocarpus trees tolerated high concentration and accumulated several metals in all plant tissues. These metals included aluminum (Al), calcium (Ca) and iron (Fe).     

菲污染土壤的微生物修复机制

菲(Phenanthrene)是存在于煤焦油中,含三个苯环的稠环芳烃。除了具有"三致"作用外,菲稳定的化学结构和高辛醇-水分配系数等特性,使其具备较强的抗降解能力,易在环境中富集,破坏土壤微生态结构,降低农作物品质,威胁人类健康。而且随着化石燃料的长期大量使用,受菲污染的土地面积也急速增加,给人类的健康及生产活动带来极大的威胁。因此,有效清除土壤中菲及其他多环芳烃污染物,净化环境,具有重要的现实意义。微生物降解作为治理菲污染的方法之一,具有高效、低成本、环境友好的特点,受到研究者的高度重视。本文从菲降解菌的种类、降解机理、分子机制、影响修复等因素及微生物与植物联合修复五个方面进行综述,为进一步利用环境微生物,开发高效菲降解菌,治理菲污染提供参考。     

Bioremediation of Diesel-contaminated Soil by Composting with Locally Generated Bulking Agents

Herein, we conducted a study toward understanding the impact of composting of the diesel-contaminated soil with some locally available bulking agents (rice husks (RHs), sawdust (SD), and wood chips (WCs)). In order to ascertain the effectiveness of petroleum degradation by the process assayed, we compared the protocols with monitored natural attenuation (MNA). The overall degradation pattern was modeled with non-linear regression by comparing the experimental data with first and second-order kinetic equations. At the end of the six-week study, the amount of total petroleum hydrocarbon removed from contaminated soil was 98.26 ± 1.33% (amendment with SD + RHs + WCs), 96.89 ± 1.20 (RHs amendment), 96.55 ± 1.29% (amendment with SD), 90.01 ± 0.22% (WCs amendment), and 85.02 ± 0.21% (MNA). The degradation of TPH trends followed a second-order kinetic model for all the four compost treatments while the MNA was found to follow a first-order (slower) degradation pattern. In general, the results of the parameter estimate showed that amendment with mixture of the three bulking agents was 1.08 (8%) slower (k₂ = (1.289 ± 0.16) × 10^?5 (g mg^?1 d^?1), r² = 0.991) than SD amendment alone (k₂ = (1.392 ± 0.14) × 10^?5 (g mg^?1 d^?1), r² = 0.995). However, the mixture of the bulking agents was found to be 1.67, 1.41, and 2.4 times faster than amendments with WCs, rice, and MNA, respectively. The phytotoxicity test revealed that all the compost treatments except WCs resulted in germination index of ≥80% after six weeks of bioremediation tests. The outcome of the current investigation confirms the effectiveness of bulking agents (especially when combined) in the supply of nutrients for the bioremediation of diesel-impacted soil.     

The Detoxification of Heavy Metals in the Phosphate Tailing-contaminated Soil through Sequential Microbial Pretreatment and Electrokinetic Remediation

In this paper, the heavy metals (HMs) in the phosphate tailing-contaminated soil were detoxified using the microbial pretreatment in combination with electrokinetic remediation (EKR).. This study provides compelling evidence that the sequential usage of the bioleaching and electrokinetics is superior to the individual method for the detoxification of Pb, Cu, Zn, Cd, and As from the contaminated soil. In the sequential system, the detoxification efficiency of Zn was the highest and that of As was the lowest. Except the element As, the detoxification efficiencies of HMs in the sequential system were generally higher than that using the single biological treatment and EKR technique. Bioleaching, generation of the passivation, and migration direction of the ions are concluded as the factors attributable to the final results; and, the initial increase in the inoculation doping of Thiobacillus ferrooxidans considered has no obvious impact on improving the final detoxification efficiency rates.     

1,2,3-三氯丙烷降解机制与污染场地修复技术研究进展

1,2,3-三氯丙烷(1,2,3-trichloropropane,1,2,3-TCP)是一种人工合成的脂肪族氯代烃,在工、农业生产中得到广泛应用。1,2,3-TCP作为环氧氯丙烷工业生产的中间产物,可作为前体物质用于生产土壤熏蒸剂、有机溶剂等。因其环境持久性、迁移性和生态毒性,国内外机构逐渐开始关注该有机氯污染物的环境归趋、生态健康风险和环境管控。当前,1,2,3-TCP污染物的降解与场地修复仍然是研究热点,但是对于1,2,3-TCP降解转化机制尚缺乏深入研究与总结。鉴于此,文中在讨论1,2,3-TCP的来源、环境污染、生态效应及物理化学降解方法与技术等的基础上,进一步综述了1,2,3-TCP的微生物降解与修复机制(如好氧共代谢降解、厌氧降解等);重点讨论了地下水等厌氧环境中1,2,3-TCP的厌氧微生物降解转化途径与机制,并从热力学角度论证了厌氧条件下1,2,3-TCP作为电子受体被有机卤呼吸微生物利用并降解的可行性;最后,对1,2,3-TCP污染场地原位生物修复进行了总结并对未来研究发展方向进行了展望。     

Stability of Prussian Blue in Soils of a Former Manufactured Gas Plant Site

Soil contamination with iron-cyanide complexes is a common problem at former manufactured gas plant (MGP) sites. Dissolution of the cyanide, from Prussian Blue (ferric ferrocyanide), creates an environmental hazard, whereas the risk of groundwater contamination depends on the stability of dissolved iron–cyanide complexes. Lack of a standard leaching method to determine the water-soluble (plant-available) cyanide fraction generates potential limitations for implementing remediation strategies like phytoremediation. Applicability of neutral solution extraction to determine the water-soluble cyanide fraction and the stability of Prussian Blue in surface and near-surface soils of an MGP site in Cottbus, undersaturated and unsaturated water conditions, was studied in column leaching and batch extraction experiments. MGP soils used in the long-term tests varied according to the pH (5.0–7.7) and the total cyanide content (40–1718 mg kg^?1). Column leaching, after four months of percolation, still yielded effluent concentrations exceeding the German drinking water limit (> 50 μg L^?1) and the solubility of Prussian Blue reported in the literature (< 1 mg L^?1) from both alkaline and acidic soils. Long-term (1344 h) extraction of MGP soils with distilled water was sufficient to dissolve 97% of the total cyanide from the slightly alkaline soils and up to 78% from the acidic soils. Both experiments revealed that dissolution of ferric ferrocyanide under circum-neutral pH and oxic water conditions is a function of time, where the released amount is dependent on the soil pH and total cyanide content. Unexpectedly high and continuous solubility of Prussian Blue, both in acidic and slightly alkaline MGP soils, implies the need to introduce an additional cyanide fraction (“readily soluble fraction”) to improve and specify cyanide leaching methods. Long-term extraction of cyanide-contaminated soil in neutral solution seems to be a promising approach to evaluate the potential hazard of groundwater pollution at the MGP sites.     

Biodegradation of Petroleum Hydrocarbons in a Soil Polluted Sample by Oil-Based Drilling Cuttings

Microbial degradation of hydrocarbons in soils polluted by oil-based drilling mud and cuttings has been investigated by static methods such as composting or biopiling. Bioremediation of polluted soils by oil-based drilling cuttings through a slurry bioreactor has not previously been reported. The main aim of this work is to monitor hydrocarbon biodegradation in slurry of drilling cuttings and unpolluted soils and the effects of nutrients on it. Indigenous, bacterial-mixed culture isolated from a polluted soil by drilling cuttings adapted to drilling mud concentrations up to 15% (v/v) was done during a 15-month program. The total petroleum hydrocarbons’ (TPHs) removal efficiency in C/N/P 100/5/1 ratio was 90.5 and 79.85% under experimental and control conditions, respectively. The microbial count on the first day, 15 × 10⁷ CFUg^?1, reached 20 × 10⁹ CFUg^?1on the twenty-first day at experimental conditions. The TPH removal efficiency in C/N/P 100/10/2 was 92.5 and 82.25% at experiment and control, respectively. Increasing nitrogen and phosphorous amount couldn't increase microbial count in comparison with C/N/P ratio 100/5/1. The measured biomass contents and microbial counts in experiments were significantly higher than the control and confirmed hydrocarbons’ biodegradation during the time. Results showed that slurry bioreactors could accelerate the biodegradation of TPHs and reduce remediation time in soil polluted by oil-based drilling cuttings.     

沈阳某冶炼厂废弃厂区的人类健康风险评价

以沈阳某冶炼厂废弃厂区重金属污染监测为依据,采用美国环保局最新的人类健康风险评价标准方法对沈阳某冶炼厂废弃地块污染土壤进行了评价,并且假设未来该土地利用类型为工业用地(Ⅰ)或休闲用地(Ⅱ).评价结果显示:工业用地(Ⅰ)和休闲用地(Ⅱ)的累积非致癌风险指数分别为2.65×10-2和3.67×10-2;工业用地(Ⅰ)和休闲用地(Ⅱ)由呼吸摄入Cd造成的潜在致癌风险指数分别为4.48×10-9和7.30×10-10,不会对在该地区工作和休闲的人们造成身体健康上的伤害;无论是工业用地假设还是休闲用地假设,由无机铜造成的人类健康风险在整个风险中所占的比例最大;由美国环保局的人类健康风险评价方法反推得出的冶炼厂地块未来为工业用地的土壤修复目标值均小于我国工业企业土壤环境质量风险评价基准值.