Influence of environmental factors on the biological treatment of organic compounds in contaminated lagoon sediments

Background and Scope  Many technologies available to remediate soils are not cost-effective when applied to marine and lagoon sediments, due to the physico-chemical characteristics of these matrices (high percentages of small particle size material, high moisture and organic matter content, many different types of inorganic and organic contamination). For these types of waste, slurry phase bioreactors can provide versatile processes, with very high removal efficiencies of recalcitrant organic compounds. The biodegradation of these contaminants strictly depends on the specific structure of the molecules and on environmental factors, such as the dissolved oxygen concentration, salinity, pH, and macronutrient availability. This paper presents the results of lab-scale tests performed to investigate the effect of the above-mentioned factors on the removal efficiency of saturated hydrocarbons, polycyclic aromatic hydrocarbons (PAHs) and polychlorobiphenyls (PCBs) in slurry phase biological treatment of lagoon sediments. Methods  Sediments were contaminated by saturated hydrocarbons (958 mg/kg d.w.), polyaromatic hydrocarbons (PAHs) (29 mg/kg d.w.) and polychlorobiphenyls (PCBs) (236 μg/kg d.w.). Carbon to nitrogen to phosphorous ratios in the matrix were not properly balanced for biological treatment. High concentrations of metals were also present (Cu: 200 mg/kg d.w.; Zn: 1710 mg/kg d.w.; As: 33 mg/kg d.w.; Cd: 13 mg/kg d.w.; Pb: 244 mg/kg d.w.). Biodegradation studies were carried out at 21 ± 1°C, in completely mixed slurry phase aerobic, anaerobic and sequential anaerobic/aerobic batch systems (3.5 1), with a solid to liquid ratio of 10% w/w. Where required, anaerobic conditions occurred naturally within three days of not aerated treatment. The aerated reactors were also equipped with traps for the waste vapors. Twelve tests were performed, over a period between ten and twenty-two days, mixing water, sediments and different amounts of various additives (macronutrients to balance C:N:P to 100:10:1 w/w, sodium chloride from 0 to 20 g/1, pH buffer solution) in the reactors, depending on the test being performed. Results and Discussion  No significant differences among the removal efficiencies of saturated hydrocarbons in tests could be observed. Abatements between 63% and 93% were obtained. The dissolved oxygen concentration was the most critical factor affecting the treatment of PAHs. Removal efficiencies below 20% were obtained for two and three-ring PAHs in the non-aerated tests. Higher values, between 45% and 61%, were obtained for these compounds in the aerated treatments; however, large (16% to 21%) abiotic losses (volatilization) were observed in these cases. Four-ring PAH removal efficiency was below 5% in all the non-aerated treatments, except for test performed without additions (30%); in the aerobic processes, removal efficiencies between 40% and 50% were obtained, except for test performed with nutrient addition and 10 g NaCl/1 (16%). Abatements of five and six-ring PAHs were between 43% and 69% in the aerated tests, and between 17% and 51% in the non-aerated treatments. Concerning PCBs, tests evidenced that reductive dehalogenation mechanisms have occurred in the anaerobic reactors with the most stable pH values, resulting in an increase of 2,4,4′-CB and 2,2′,5,5′-CB concentrations; the aerobic treatments did not modify the PCB mixture. In both types of systems, no variation of the total PCB concentration could be observed. Conclusions  This study showed that saturated hydrocarbon removal efficiency was nearly insensitive to the environmental factors investigated. The molecule structure and the dissolved oxygen concentration were the most affecting factors the removal efficiency of PAHs. PCB degradation under anaerobic conditions could be related to the pH values measured during the tests. Evaluation of results suggested that the abatement of pollutants investigated was not limited by a high salinity. High concentrations of dissolved metals and macronutrient addition did not influence the removal efficiency. Recommendations and Outlook. The slurry phase biological treatment of contaminated sediments could be applied whenever moderate removal efficiencies were required for remediation from saturated hydrocarbons and PAHs within a few days; further studies should be performed to improve the PCB abatement. Aerobic conditions should be maintained for the biodegradation of polyaromatic compounds; seawater or lagoon water could be used in the system.     

蚯蚓和发酵牛粪促进南瓜苗修复PAHs污染农田土壤

为了寻求高效修复土壤中持久性有机污染物多环芳烃(PAHs,polycyclic aromatic hydrocarbon),在温室盆栽试验条件下,研究接种蚯蚓和施用发酵牛粪对南瓜苗修复3环以上PAHs污染土壤的影响。试验设置施用牛粪(D)、单接蚯蚓(E)、接种蚯蚓和施用牛粪(ED)、不接种蚯蚓和不施用牛粪的对照(CK)共4个处理,播种10周后收获。研究结果表明,接种蚯蚓和施用牛粪的共同作用下能有效提高南瓜苗生物量,有利于南瓜苗在PAHs污染的土壤生长,特别是地上部分的生长;接种蚯蚓或/和施用牛粪有效地提高了南瓜苗从土壤中吸收3～5环PAHs化合物的效率,且南瓜苗地上部吸收的PAHs量最低是地下部的6倍。因此,结合蚯蚓和发酵牛粪的辅助作用,南瓜苗地上部生物量较大,能从土壤中吸收多种PAHs化合物,与仅依赖于土壤自身的作用相比,三者的共同作用使得土壤中3环以上PAHs化合物的去除率提高23%以上,可组合应用于PAHs污染土壤的强化修复。该研究为土壤多环芳烃污染修复提供参考。     

亚油酸钠刺激多环芳烃污染土壤微生物修复的机理研究

根系分泌物在多环芳烃(PAHs)污染土壤的植物根际修复过程中发挥关键作用,但是向土壤中单独施入根系分泌物化学物质对PAHs去除的影响还少有研究。本试验通过土壤微宇宙培养试验和高通量测序技术研究了根系分泌物亚油酸钠对土壤微生物群落及PAHs降解的影响。结果发现,60 d后,添加肥料与亚油酸钠处理对土壤中PAHs的去除率为40.6%,显著高于仅施肥处理的17.4%。主坐标分析(PCo A)表明添加亚油酸钠显著改变了土壤微生物群落,土壤细菌和真菌群落组成与仅施肥处理明显分异。此外,亚油酸钠的添加还促进了PAHs降解菌如Marmoricola、Streptomyces、unclassified_Intrasporangiaceae和Kribbella等细菌,以及unclassified_Chaetomiaceae、Mortierella和Humicola等真菌的富集。LEFSe分析表明,Streptomyces、Kribbella和Humicola是添加亚油酸钠处理的主要微生物标记物,且Streptomyces和Kribbella相对丰度与土壤中PAHs...     

Enhanced bioremediation of PAH-contaminated soil by immobilized bacteria with plant residue and biochar as carriers

Purpose

Polycyclic aromatic hydrocarbons (PAHs) are largely accumulated in soils in China. The immobilized-microorganism technique (IMT) is a potential approach for abating soil contamination with PAHs. However, few studies about the application of IMT to contaminated soil remediation were reported. Due to recalcitrance to decomposition, biochar application to soil may enhance soil carbon sequestration, but few studies on the application of biochars to remediation of contaminated soil were reported. In this study, we illustrated enhanced bioremediation of soil having a long history of PAH contamination by IMT using plant residues and biochars as carriers.

Materials and methods

Two PAH-degrading bacteria, Pseudomonas putida and an unidentified indigenous bacterium, were selected for IMT. The extractability and biodegradation of 15 PAHs in solution and an actual PAH-contaminated soil amended with immobilized-bacteria materials were investigated under different incubation periods. The effects of carriers and the molecular weight of PAHs on bioremediation efficiency were determined to illustrate their different bio-dissipation mechanisms of PAHs in soil.

Results and discussion

The IMT can considerably enhance the removal of PAHs. Carriers impose different effects on PAH bio-dissipation by amended soil with immobilized-bacteria, which can directly degrade the carrier-associated PAHs. The removal of PAHs from soil depended on PAH molecular weight and carrier types. Enhanced bio-dissipation by IMT was much stronger for 4- and 5-ring PAHs than for 3- and 6-ring ones in soil. Only P400 biochar-immobilized bacteria enhanced bio-dissipation of all PAHs in contaminated soil after a 90-day incubation.

Conclusions

Biochar can promote bioremediation of contaminated soil as microbial carriers of IMT. It is vital to select an appropriate biochar as an immobilized carrier to stimulate biodegradation. It is feasible to use adsorption carriers with high sorptive capabilities to concentrate PAHs as well as microorganisms and thereby enhance dissipation of PAHs and mitigate soil pollution.     

Removal of polycyclic aromatic hydrocarbons from soil amended with biosolid or vermicompost in the presence of earthworms (Eisenia fetida)

Earthworms burrow through the soil thereby accumulating many lipophilic organic pollutants from the surrounding environment, so they could be used to remove polycyclic aromatic hydrocarbons (PAHs) from soil. Sterilized and unsterilized soil was contaminated with phenanthrene (Phen), anthracene (Anth) and benzo[a]pyrene (BaP), with or without added Eisenia fetida and biosolid or vermicompost. Concentrations of PAHs were monitored in soil and earthworms for 70 days. Removal of PAHs increased in soil with earthworms added as 91% of Anth, 16% BaP and 99% Phen was dissipated compared to 42%, 3% and 95% in unamended soil. The microorganisms in the gut of the earthworm contributed to PAHs removal and 100% of Phen, 63% of Anth and 58% of BaP was removed from sterilized soil with E. fetida added. Biosolid and to lesser extent vermicompost accelerated removal of PAHs from soil. Applying earthworms to a contaminated site might be an environmentally friendly way to remove hydrocarbons from soil. However, a limitation might be the cost of the large amounts of earthworms required to remove PAHs from soil and the necessity to supply them with sufficient substrate while maintaining the water content of the soil high enough for their normal functioning.     

Effect of soil bacteria on the ability of polycyclic aromatic hydrocarbons (PAHs) removal by Trametes versicolor and Irpex lacteus from contaminated soil

The effect of bacteria represented by indigenous soil microflora or a mixture of soil bacteria Pseudomonas aeruginosa and Rhodococcus erythropolis on fungal growth, extracellular enzyme production and polycyclic aromatic hydrocarbons (PAHs) biodegradation efficiency in soil of white-rot fungi Trametes versicolor and Irpex lacteus was investigated. Both fungi were able to colonize soil. The growth yields measured by ergosterol were about two-fold in I. lacteus after 10 weeks. Laccase was produced in T. versicolor cultures in the presence or absence of bacteria but live bacteria reduced the laccase levels in soil about 5 times. Manganese-dependent peroxidase (MnP) was not detected in T. versicolor cultures. The amounts of MnP and laccase in I. lacteus cultures were not affected by the presence of bacteria. T. versicolor was more efficient in PAH removal for all PAHs tested although its capacity to colonize soil was lower. The removal rates of PAHs by T. versicolor in sterile soil were 1.5-fold, 5.8-fold and 1.8-fold for 2-3-ring, 4-ring and 5-6-ring PAHs, compared to I. lacteus, respectively. I. lacteus showed a low efficiency of removal of pyrene, benzo[a]anthracene and benzo[k]fluoranthene, compared to T. versicolor, whereas chrysene and benzo[b]fluoranthene were degraded by neither fungus. The main effect of the presence of the indigenous microflora or R. erythropolis and P. aeruginosa was a significant decrease of degradation of total PAHs by both T. versicolor and I. lacteus. Weak fungal/bacterial synergistic effects were observed in the case of removal of acenapthylene, benzo[a]pyrene, dibenzo[a,h]anthracene and benzo[g,h,i]perylene by I. lacteus and acenapthylene by T. versicolor. However, the bacterial effects were different in the two fungi. PAH abiotic losses represented 15 and 21% of the total PAHs after 5 and 10 weeks, respectively; naphthalene and acenaphthene were removed from the soil due to volatilization.     

Earthworms,a means to accelerate removal of hydrocarbons (PAHs) from soil? A mini-review

Contamination of soil with hydrocarbons occurs frequently. Restoring contaminated soils is costly and time consuming. Earthworms accelerate the removal of hydrocarbons as they burrow through soil by rendering contaminants available for microbial degradation, by feeding on the organic matter that harbour contaminants, and by improving soil structure and aeration. Polycyclic aromatic hydrocarbons (PAHs) are recalcitrant hydrocarbons that can contaminate the environment and can thus serve as models to study the factors that control the removal of petroleum from soil. The effect of earthworms on the removal of PAHs was reviewed. It was found that earthworms have the capacity to accelerate the removal of PAHs and their degradation products from soil. However, large numbers of earthworms are required, which might be expensive. Moreover, it may be difficult to provide sufficient organic material as feed while simultaneously maintaining high soil water content to allow burrowing.     

茶叶皂角用于提高大豆油-水体系洗脱修复焦化厂土壤中多环芳烃、Cd、Ni的可行性研究

Mixed contaminated brownfield sites have brought serious risks to human health and environmental safety. With the purpose of removing polycyclic aromatic hydrocarbons(PAHs) and heavy metals from a coking plant site, an innovative technology for ex-situ washing was developed in the present work. The combination of 15.0 mL L~(-1) soybean oil and 7.5 g L~(-1) tea saponin proved an effective method to extract co-pollutants from soil. After two consecutive washing cycles, the efficiency rates of removal for 3-, 4-,5(+6)-ring, and total PAHs, Cd, and Ni were approximately 98.2%, 96.4%, 92.3%, 96.3%, 94.1%, and 89.4%, respectively. Meanwhile,as evaluated by Tenax extraction method and metal stability indices, the residual PAHs and heavy metals after consecutive washing mainly existed in the form with extremely low bioaccessibility in the soil. Thus, in the soil after two washing cycles, there appeared limited environmental transfer risk of co-pollutants. Moreover, a subsequent precipitation method with alkaline solution and PAHdegrading strain Sphingobium sp. PHE9 inoculation effectively removed 84.6%–100% of Cd, 82.5%–91.7% of Ni, and 92.6%–98.4% of PAHs from the first and second washing solvents. The recovered solvents also exhibited a high recycling effectiveness. Therefore, the combined cleanup strategy proposed in this study proved environmentally friendly, which also played a major role in risk assessment and management in mixed polluted sites.     

Contamination of soils in the urbanized areas of Belarus with polycyclic aromatic hydrocarbons

The content of polycyclic aromatic hydrocarbons (PAHs) in the soils of urbanized areas, including the impact zones of Belarus, were studied. The concentrations of 16 PAHs in the soils were determined for individual and high-rise building zones, forests, and forest parks of Belarus. The levels of the PAH accumulation in the soils of different industrial enterprises and boiler stations were analyzed. Possible sources of soil contamination with PAHs were considered, and the structure of the PAHs in the soils was shown. The levels of the soil contamination were determined from the regulated parameters for individual compounds and the sum of 16 PAHs.     

酸碱调控对泥浆反应去除土壤中多环芳烃的影响研究

采用摇瓶试验模拟研究了酸碱调控对泥浆反应去除污染土壤中多环芳烃的影响,结果表明,泥浆反应对污染土壤中的多环芳烃具有一定的去除效果,长期污染土壤中多环芳烃的去除率为10.6% ~ 20.7%,模拟污染土壤中的去除率为37.4% ~ 42.1%;酸碱调控对不同性质的多环芳烃的去除影响不同,整体上看,酸性条件有利于高环（五环和六环）多环芳烃的去除,而中性条件有利于低环（三环和四环）多环芳烃的去除。在实际修复中,根据污染土壤中多环芳烃的组成进行适当的酸碱调控,可以促进污染土壤的快速修复。     

A highly effective polycyclic aromatic hydrocarbon-degrading bacterium, Paracoccus sp. HPD-2, shows opposite remediation potential in two soil types

Bioaugmentation is an efficient and eco-friendly strategy for the bioremediation of polycyclic aromatic hydrocarbons(PAHs). Since the degrading abilities of soils can greatly alter the abilities of PAH-degrading bacteria, illustrating the potential and mechanism of highly efficient degrading bacteria in different soil environments is of great importance for bioremediation. A PAH-degrading bacterium, Paracoccus aminovorans HPD-2, and two soil types,red and paddy soils, with distinct PAH-degrading...     

Influence of different bulking agents on the disappearance of polycyclic aromatic hydrocarbons (PAHs) during sewage sludge composting

In order to improve properties of compost produced from sewage sludge, a wide range of additives is used. The aim of the present study has been to determine the influence of fly ash and sawdust on the range of losses of 16 PAHs (US EPA). Composting was carried out in containers in which there was sewage sludge (100%), sewage sludge with fly ash added (20 or 30% w/w) and sewage sludge with sawdust added (30% w/w). Composting was carried out for 353 days. Then the compost obtained was stored for another 300 days. The content of 16 PAHs was determined using the HPLC-UV method. After composting, in all the experimental treatments, ie, with sludge alone, and with the additions of 20% and 30% fly ash, and sawdust, decreases in the total PAH load of 87.5, 83.4, 82.9 and 88.1% respectively, were found. The content of the total PAH load was mainly determined by 3-ring compounds. In the case of these last PAHs the highest level of their disappearance (> 90%) was noted after composting. In all composts obtained, the content of PAHs was within allowable limits for biosolids that can be used for agricultural purposes. A significant lowering of total concentration of the 16 PAHs after storage period was noted only in the experimental variant with 20% of fly ash. However, the process of composts storage influenced individual PAHs.     

Distribution of Polynuclear Aromatic Hydrocarbons (PAHs) in the Soil of Tokushima,Japan

The distribution of polynuclear aromatic hydrocarbons (PAHs) inthe soil samples of rural, suburban and urban areas of TokushimaCity was studied, HPMC with UV and fluorescence detection wasused for the determination of PAHs. The separation was acquiredby an ODS column and acetonitrile-water as the mobile phase.Results showed that the distribution of PAHs in the samplingsites were similar but differed from that in river sediment. Amodel test suggested that the burning of rice straw and otherplants was not the main source of PAHs in the soil of this citybut could be one of the important sources of PAHs in the river ecosystem.     

Enhanced Mobilization of Field Contaminated Soil-bound PAHs to the Aqueous Phase under Anaerobic Conditions

Although microbially-mediated redox environments can alter the characteristics of soil/sediment organic matter (SOM) and its interactions with persistent hydrophobic organic contaminants (HOCs) bound to soils and sediments, the nature of their effects has not been adequately addressed. In this study, a field soil collected from a manufacturer gas plant site and contaminated historically with creosotes was incubated under aerobic and anoxic/anaerobic conditions along with various amendments (extra carbon and enrichment minerals) for stimulating microbial activities. Anaerobic conditions stimulated significant fractions of bound polycyclic aromatic hydrocarbons (PAHs) encompassing naphthalene through benzo[g,h,i]perylene to be mobilized to the aqueous phase, leaving their aqueous phase concentrations far in excess of solubility (increases in their apparent aqueous phase concentrations by factors as high as 62.8 relative to their initial aqueous phase concentrations). Such effects became more evident for high molecular weight PAHs. Dissolved organic matter exhibiting a high affinity for PAHs was liberated from soils during the anaerobic soil incubations. Feasibility of this concept for field applications was evaluated with a lab-scale continuous flow system composed of an anaerobic soil column followed by an aerobic bioreactor inoculated with PAH-degrading microbes. High quantities of PAHs exceeding their aqueous solubilities were eluted from the anaerobic soil column and those mobilized PAHs were readily bioavailable in the secondary aerobic bioreactor. This study may offer a potential method for cost-effective and performance-efficient ex situ remediation technologies (or in situ if appropriate hydrological control available in the contaminated field site) and risk assessment for the HOC-contaminated soils/sediments.     

外源添加作物秸秆对PAHs污染土壤有机碳矿化和污染物降解的影响

本文通过土壤腐解试验研究外源添加水稻或玉米秸秆对多环芳烃（PAHs）污染土壤CO2-C释放和污染物去除率的影响，同时清晰秸秆腐解中间产物溶解性有机碳（DOC）与土壤PAHs降解的关系。结果表明：秸秆添加处理促进了PAHs污染土壤CO2-C的释放，以玉米秸秆提升效果较好。外源添加秸秆显著增加了土壤DOC含量，且增加幅度随秸秆添加量的增加而增大；水稻秸秆对土壤DOC含量的提升幅度较大。与对照相比，秸秆添加处理下土壤菲、芘残留量均显著降低，菲、芘去除率显著增加，去除效果：玉米＞水稻，高量＞低量，菲＞芘；与对照相比，添加高量玉米秸秆处理（PY15）对土壤菲、芘去除率的增加幅度分别为91.7%和182%。此外，在一定范围内土壤DOC含量与PAHs去除率呈正相关关系。可见，农作物秸秆，尤其是玉米秸秆添加可提升PAHs污染土壤有机碳矿化，亦可在提升土壤DOC含量的同时促进污染土壤PAHs的降解。     

海洋细菌生物膜用于生物修复陆地生态系统中土壤多环芳烃污染

Polycyclic aromatic hydrocarbons(PAHs) in soil retain for a quite long period due to their hydrophobicity and aggregation properties. Biofilm-forming marine bacterial consortium(named as NCPR), composed of Stenotrophomonas acidaminiphila NCW702,Alcaligenes faecalis NCW402, Pseudomonas mendocina NR802, Pseudomonas aeruginosa N6P6, and Pseudomonas pseudoalcaligenes NP103, was used for the bioremediation of PAHs in a soil microcosm. Phenanthrene and pyrene were used as reference PAHs. Parameters that can affect PAH degradation, such as chemotaxis, solubility of PAHs in extracellular polymeric substances(EPS), and catechol2,3-dioxygenase(C23O) activity, were evaluated. P. aeruginosa N6P6 and P. pseudoalcaligenes NP103 showed chemotactic movement towards both the reference PAHs. The solubility of both the PAHs was increased with an increase in EPS concentration(extracted from all the 5 selected isolates). Significantly(P 0.001) high phenanthrene(70.29%) and pyrene(55.54%) degradation was observed in the bioaugmented soil microcosm. The C23O enzyme activity was significantly(P 0.05) higher in the bioaugmented soil microcosm with phenanthrene added at 173.26 ± 2.06 nmol min~(-1) mg~(-1) protein than with pyrene added at 61.80 ± 2.20 nmol min~(-1) mg~(-1) protein. The C23O activity and gas chromatography-mass spectrometer analyses indicated catechol pathway of phenanthrene metabolism. However, the metabolites obtained from the soil microcosm added with pyrene revealed both the catechol and phthalate pathways for pyrene degradation.     

蚯蚓和丛枝菌根真菌对南瓜修复多环芳烃污染土壤的影响

在温室盆栽实验条件下,研究接种AM(arbuscular mycorrhiza)真菌、蚯蚓(Eisenia fetida)对南瓜(Cucurbita moschata)修复3环以上多环芳烃(PAHs)污染农田土壤的影响,试验设置单接AM真菌、单接蚯蚓、双接AM真菌和蚯蚓、不接种的对照共4个处理,播种10周后收获。结果表明,接种AM真菌和蚯蚓促进AM真菌侵染南瓜,增加南瓜生物量;显著提高南瓜修复土壤中Phe(菲)、An(t蒽)、Py(r芘)、BkF(苯并(k)荧蒽)、BaP(苯并(a)芘)、BPe(r苯并(g,h,i)苝)等PAHs污染物的效率,促进南瓜高效地吸收3~5环PAHs,尤其是AM真菌和蚯蚓共同接种条件下对南瓜修复土壤效果最优;AM真菌利于南瓜转移根系吸收的高浓度PAHs化合物至地上部,降低PAHs对根系的胁迫,增强南瓜在高浓度PAHs污染土壤中存活,有利于南瓜应用于高浓度PAHs污染土壤的高效修复;蚯蚓对南瓜地下部吸持3~5环高分子量的PAHs化合物有积极作用。因此,选用的AM真菌和蚯蚓在土壤中具有协同作用,促进南瓜高效修复PAHs污染土壤。     

多环芳烃污染土壤的植物-微生物联合修复初探

在温室盆栽条件下,通过种植紫花苜蓿单独或联合接种菌根真菌(Glomus caledonium L.)(AM)和多环芳烃专性降解菌(DB),研究了利用植物-微生物强化修复多环芳烃(PAHs)长期污染土壤的效果。试验结果表明,接种菌根真菌和PAHs专性降解菌能促进紫花苜蓿的生长和土壤中PAHs的降解。经过90天修复试验,种植紫花苜蓿接种AM、DB和DB+AM处理的PAHs的降解率分别为47.9%、49.6%、60.1%,均高于只种植紫花苜蓿的对照处理(CK)(21.7%)。另外,随着PAHs苯环数的增加,其平均降解率逐渐降低,但是接种PAHs专性降解菌能够提高4环和5环PAHs的降解率。同时也发现土壤中脱氢酶活性和PAHs降解菌数量越高的处理,土壤PAHs的降解率也越高,这也是种植紫花苜蓿接种微生物能够有效促进土壤PAHs降解的原因。     

蚯蚓在植物修复菲污染土壤中的作用

采用盆栽试验法,研究了蚯蚓（Pheretima sp.）在植物修复菲污染土壤中的作用。结果显示,试验浓度（20.05-322.06 mg.kg-1）范围内,蚯蚓活动促进了菲污染土壤中修复植物黑麦草（Lolium multiforum）的生长,其根冠比明显增大。添加蚯蚓72 d后,种植黑麦草的土壤中菲的去除率高达64.35%-93.40%,其平均去除率（80.92%）比无蚯蚓活动的土壤-植物系统（71.57%）提高9.35%,比无植物对照组（22.58%）提高57.34%。各种生物、非生物修复因子中,植物-微生物交互作用对菲去除的平均贡献率（53.56%）最为突出,比无蚯蚓活动时（47.48%）提高6.08%。说明蚯蚓活动可强化土壤-植物系统对土壤菲污染的修复作用。     

农药企业搬迁土地多环芳烃的风险评价

以常州市某农药厂搬迁土地为研究对象,在监测分析土壤中16种多环芳烃（PAHs）的基础上,对该区域土壤进行健康风险和生态风险评价。结果表明,研究区域土壤中∑PAHs的含量范围为0～1.546mg·kg-1,优势化合物中萘、菲等低环化合物含量大于高环的荧蒽、苯并[k]荧蒽和芘等化合物,且土壤中PAHs可能来源于石油源。健康风险评价结果在可接受的10-6～10-4范围内,而生态风险评价表明,尽管研究区域土壤中的多环芳烃不存在严重的生态风险,但是化合物苊和芴含量超出了风险评价低值（ER-L和ISQV-L）,存在着对生物的潜在危害。