硝基苯与苯胺类废水生物降解协同作用研究

从各种菌源中分离得到硝基苯和苯胺的高效降解菌,研究其对这2类化合物的降解规律,发现C.perfringens在厌氧条件下主要将硝基苯降解为苯胺,而Pseudomonas mendocina和Klebsiella pneumoniae在好氧条件下可将硝基苯分解为无害化物质,但降解速度较厌氧过程慢。好氧条件下,硝基苯对苯胺的降解有明显的抑制作用,而苯胺对硝基苯的抑制作用不明显,导致混合菌对混合基质的降解速度下降。不同微生物对含硝基苯和苯胺类化合物废水的降解机理表现出明显的差异,高效的微生物应该体现在既能分解初始污染物,又能分解次级产物,实现完全无害化的目标。      

Evaluation of biodegradation of nonylphenol ethoxylate and lignin by combining toxicity assessment and chemical characterization

The aerobic biodegradation of commercial nonylphenol ethoxylate (NPE) mixture and alkali lignin was studied using the OECD headspace test accompanied by the simultaneous measurement of ecotoxicity directly from the biodegradation liquors and by the follow-up of the chemical composition of the studied chemicals. NPE degradation was dependent on the inoculum source: approximately 40% of NPE was mineralized into CO₂ during the 4-week experiment when inoculum from Helsinki City wastewater treatment plant (WWTP) was used, and only 12% was mineralized when inoculum from Jyväskylä City WWTP was used. Chemical analyses revealed a shift in the ethoxylate chain length from longer to shorter soon after the beginning of the NPE biodegradation tests. At the same time also toxicity (reverse electron transport assay, RET) and estrogenic activity (human estrogen receptor yeast) measured directly from the biodegradation liquors decreased. In case of alkali lignin, approximately 11% was mineralized in the test and chemical analysis showed in maximum a 30% decrease in lignin concentration. Toxicity of lignin biodegradation liquors started to decrease in the beginning of the test, but became more toxic towards the end of the test again. Especially RET assay proved to be sensitive enough for measuring toxicity changes directly from biodegradation liquors, although a concentrating treatment of the liquors is recommended for a more detailed characterization and identification of toxic metabolites.     

Ageing processes and soil microbial community effects on the biodegradation of soil C-2,4-D nonextractable residues

The biodegradation of nonextractable residues (NER) of pesticides in soil is still poorly understood. The aim of this study was to evaluate the influence of NER ageing and fresh soil addition on the microbial communities responsible for their mineralisation. Soil containing either 15 or 90-day-old NER of ¹³C-2,4-D (NER15 and NER90, respectively) was incubated for 90 days with or without fresh soil. The addition of fresh soil had no effect on the mineralisation of NER90 or of SOM, but increased the extent and rate of NER15 mineralisation. The analyses of ¹³C-enriched FAME (fatty acids methyl esters) profiles showed that the fresh soil amendment only influenced the amount and structure of microbial populations responsible for the biodegradation of NER15. By coupling biological and chemical analyses, we gained some insight into the nature and the biodegradability of pesticide NER.     

Influence of aggregated particles on biodegradation activities for dimethylarsinic acid (DMA) in Lake Kahokugata

Aquatic arsenic cycles mainly depend on microbial activities that change the arsenic chemical forms and influence human health and organism activities. The microbial aggregates degrading organic matter are significantly related to the turnover between inorganic arsenic and organoarsenic compounds. We investigated the effects of microbial aggregates on organoarsenic mineralization in Lake Kahokugata using lake water samples spiked with dimethylarsinic acid (DMA). The lake water samples converted 1 μmol L⁻¹ of DMA to inorganic arsenic for 28 d only under anaerobic and dark conditions in the presence of microbial activities. During the DMA mineralization process, organic aggregates >5.0 μm with bacterial colonization increased the densities. When the organic aggregates >5.0 μm were eliminated from the lake water samples using filters, the degradation activities were reduced. DMA in the lake water would be mineralized by the microbial aggregates under anaerobic and dark conditions. Moreover, DMA amendment enhanced the degradation activities in the lake water samples, which mineralized 50 μmol L⁻¹ of DMA. The DMA-amended aggregates >5.0 μm completely degraded 1 μmol L⁻¹ of DMA with a shorter incubation time of 7 d. The supplement of KNO₃ and NaHCO₃ to lake water samples also shortened the DMA-degradation period. Presumably, the bacterial aggregates involved in the chemical heterotrophic process would contribute to the DMA-biodegradation process in Lake Kahokugata, which is induced by the DMA amendment.     

Effects of biodegradation and sorption by humic acid on the estrogenicity of 17β-estradiol

The removal of 17β-estradiol (E2) by biodegradation and sorption onto humic acid (HA) was examined at various HA concentrations. Subsequently, estrogenicity associated with E2 removal was estimated using E-screen bioassay. Results showed that E2 biodegradation and its subsequent transformation to estrone (E1) were significantly reduced with increasing HA concentration. In addition, the presence of nutrients enhanced the biodegradation of E2. Overall, E2 biodegradation was the dominating contributor to its removal, which demonstrated a significantly negative correlation with E2 sorption at various HA concentrations. The sorption of E2 by HA was significantly enhanced with increasing HA concentration. Estrogenicity associated with residual E2 showed that there existed a significant difference among various HA concentrations, with the lowest value in the absence of HA. The findings suggest that the presence of HA and nutrients in natural waters should be considered in assessing estrogenicity of environmental samples due to complex sorption and biodegradation processes.     

Long Term Monitoring of Hydrocarbon Contamination Using Multi-Level Vapor Phase Piezometers

This study evaluated the feasibility of supplementing groundwater monitoring protocols by assessing the vadose zone for the extent of residual subsurface contamination. The study also characterized the response of the soil gas signatures with respect to different soil types and degrees of contamination. A field study was conducted at a former gasoline vending station located in Ottawa, Canada. The current state of contamination was determined by analysis of soil samples taken from boreholes. A series of 10 nested soil gas wells with monitoring depths of 0.75, 1.5, 2.25 and 3.0 m were then installed. Using these wells, soil gas surveys were performed at regular intervals over an extended period to quantify Gaseous TPH (TPH g ), oxygen and carbon dioxide concentrations in the soil gas. Results indicate that soil gas wells located near the source term exhibited characteristic soil gas signatures and significant fluctuations in TPH g , oxygen, and carbon dioxide concentrations with time. Soil gas wells located beyond the soil contamination demonstrated limited correlation between TPH g , oxygen and carbon dioxide concentrations and decreased seasonal variability.     

Alkytcyclohexanes in Environmental Geochemistry

The n -alkylated cyclohexanes (CHs) are a homologous series of hydrocarbon compounds that are commonly present in crude oil and refinery products such as diesel fuel. These compounds exhibit specific distribution patterns for different fuel types, providing useful fingerprints for characterizing petroleum products, especially after degradation of n -alkanes has occurred. However, there are no published data to show how these compounds are altered in the environment after long-term spillage of petroleum products. This paper presents two case studies of oil spills that demonstrate the changing distribution patterns resulting from long-term anaerobic microbial degradation. These spills are the 1979 crude-oil spill in Bemidji, Minnesota, and a chronic diesel-fuel spillage from 1953-1991 at Mandan, North Dakota. The alkyl CHs in both spilled oil products are affected by similar biodegradative processes in which the compounds undergo a consistent pattern of loss from the high molecular weight end of the homolog distribution. Degradation results in a measurable increase in the concentrations of the homologs in the lower molecular weight range, a gradual lowering in carbon number of the homolog maximum, and a gradual decrease of the total homolog range from the high molecular weight end. This pattern is the opposite of low-end loss expected with weathering and aerobic biodegradation. The enhancement of the low molecular mass alkyl CH homologs, if not recognized as a degradative pathway of diesel fuel in an anaerobic environment, can potentially be misinterpreted in fuel-oil fingerprinting as deriving from lower distillation-range fuels or admixture of diesel with other fuels.     

Kinetics of the biodegradation pathway of endosulfan in the aerobic and anaerobic environments

The enriched mixed culture aerobic and anaerobic bacteria from agricultural soils were used to study the degradation of endosulfan (ES) in aqueous and soil slurry environments. The extent of biodegradation was ∼95% in aqueous and ∼65% in soil slurry during 15 d in aerobic studies and, ∼80% in aqueous and ∼60% in soil slurry during 60 d in anaerobic studies. The pathways of aerobic and anaerobic degradation of ES were modeled using combination of Monod no growth model and first order kinetics. The rate of biodegradation of β-isomer was faster compared to α-isomer. Conversion of ES to endosulfan sulfate (ESS) and endosulfan diol (ESD) were the rate limiting steps in aerobic medium and, the hydrolysis of ES to ESD was the rate limiting step in anaerobic medium. The mass balance indicated further degradation of endosulfan ether (ESE) and endosulfan lactone (ESL), but no end-products were identified. In the soil slurries, the rates of degradation of sorbed contaminants were slower. As a result, net rate of degradation reduced, increasing the persistence of the compounds. The soil phase degradation rate of β-isomer was slowed down more compared with α-isomer, which was attributed to its higher partition coefficient on the soil.     

Enrichment and isolation of endosulfan-degrading microorganism from tropical acid soil

Endosulfan (6,7,8,9,10,10-hexachloro-1,5,5a,6,9,9a-hexahydro-6,9-methano-2,3,4-benzo-dioxathiepin-3-oxide) is a cyclodiene organochlorine currently used as an insecticide all over the world and its residues are posing a serious environmental threat. This study reports the enrichment and isolation of a microbial culture capable of degrading endosulfan with minimal production of endosulfan sulfate, the toxic metabolite of endosulfan, from tropical acid soil. Enrichment was achieved by using the insecticide as sole sulfur source. The enriched microbial culture, SKL-1, later identified as Pseudomonas aeruginosa, degraded up to 50.25 and 69.77 % of α and β endosulfan, respectively in 20 days. Percentage of bioformation of endosulfan sulfate to total formation was 2.12% by the 20th day of incubation. Degradation of the insecticide was concomitant with bacterial growth reaching up to an optical density of 600 nm (OD600) 2.34 and aryl sulfatase activity of the broth reaching up to 23.93 μg pNP/mL/hr. The results of this study suggest that this novel strain is a valuable source of potent endosulfan–degrading enzymes for use in enzymatic bioremediation. Further, the increase in aryl sulfatase activity of the broth with the increase in degradation of endosulfan suggests the probable involvement of the enzyme in the transformation of endosulfan to its metabolites.     

Long-term dynamics of the atrazine mineralization potential in surface and subsurface soil in an agricultural field as a response to atrazine applications

The dynamics of the atrazine mineralization potential in agricultural soil was studied in two soil layers (topsoil and at 35-45 cm depth) in a 3 years field trial to examine the long term response of atrazine mineralizing soil populations to atrazine application and intermittent periods without atrazine and the effect of manure treatment on those processes. In topsoil samples, ¹⁴C-atrazine mineralization lag times decreased after atrazine application and increased with increasing time after atrazine application, suggesting that atrazine application resulted into the proliferation of atrazine mineralizing microbial populations which decayed when atrazine application stopped. Decay rates appeared however much slower than growth rates. Atrazine application also resulted into the increase of the atrazine mineralization potential in deeper layers which was explained by the growth on leached atrazine as measured in soil leachates recovered from that depth. However, no decay was observed during intermittent periods without atrazine application in the deeper soil layer. atzA and trzN gene quantification confirmed partly the growth and decay of the atrazine degrading populations in the soil and suggested that especially trzN bearing populations are the dominant atrazine degrading populations in both topsoil and deeper soil. Manure treatment only improved the atrazine mineralization rate in deeper soil layers. Our results point to the importance of the atrazine application history on a field and suggests that the long term survival of atrazine degrading populations after atrazine application enables them to rapidly proliferate once atrazine is again applied.