Preliminary study of groundwater denitrification using a composite membrane bioreactor

A composite membrane bioreactor (CMBR) integrating the immobilized cell technique and the membrane separation technology was developed for groundwater denitrification. The CMBR had two well mixed compartments with one filled with the nitrate- containing influent and the other with a dilute ethanol solution; the compartments were separated by the composite membrane consisting of a microporous membrane facing the influent and an immobilized cell membrane facing the ethanol solution. Nitrate and ethanol molecules diffused from the respective compartments into the immobilized cell membrane where nitrate was reduced to gaseous nitrogen by the denitrifying bacteria present there with ethanol as the carbon source. The microporous membrane was attached to one side of the immobilized cell membrane for retention of the disaggregated bacteria. Relative to the single dose of external ethanol, the two-dose supplementation produced better treatment results as evidenced by the lower concentrations of NO3--N and ethanol (as measured by total organic carbon) of the effluent. The batch treatment in CMBR removed most of the nitrate in the influent and attained a stable denitrification rate of 0.1 g·m^-2·h^-1 for most of the 96-h cycles during the 30-cycle study. The effluent was essentially free of ethanol and nitrite nitrogen.     

In vitro cytotoxicity of multi-wall carbon nanotubes on human cell lines

The aim of this study was to evaluate the in vitro toxicity of two multi-wall carbon nanotubes on four different cell lines: human alveolar epithelial (A549) cells, hepatocytes (Hep 3B cells), human embryonic kidney cells, and intestinal (P407 cells) cells. The adverse effects of carbon nanoparticles were analyzed after 24 h incubation with different cell lines using the trypan blue dye exclusion method. Incubation of carbon nanotubes with different cells produced a concentration-dependent inhibition of growth of the cells. The TC₅₀ or IC₅₀ values (toxic concentration 50, i.e., concentration of particles inducing 50% cell mortality) of two nanoparticles were (1) found to be in the range 23.5–30.5 µg mL^?1, and (2) less than that of quartz (known toxic agent, 28.8–66.9 µg mL^?1), indicating the greater cytotoxic effect of carbon nanoparticles than quartz particles.     

Mutagenicity of polyaromatic hydrocarbons by chemical models for cytochrome P450 in Ames assay

DNA damage is an important step in carcinogenesis. The Ames assay is a short-term screening of carcinogens that induce DNA damage. Most carcinogens require enzymatic activation through oxidation by cytochrome P450 (CYP450) in the presence of S9 mix. A combination of iron (Fe)(III) porphyrin and an oxidant is also able to oxidize compounds as an alternative metabolic pathway to CYP450. Previously it was reported that a chemical model containing a water-soluble 5,10,15,20-tetrakis(1-methylpyridinium4-yl)porphyrinatoiron(III) chloride (4-MPy) and tert-butyl hydroperoxide (t-BuOOH) activated aromatic amines and amides. In this study, a chemical model composed of an Fe porphyrin, water-insoluble 5,10,15,20-tetrakis(pentafluorophenyl)porphyrinatoiron(III) chloride (F₅P) or water-soluble 4-MPy was optimized with an oxidant – t-BuOOH, magnesium monoperoxyphthalate (MPPT), or iodosylbenzene (PhIO). Subsequently the mutagenicity of benzo[a]pyrene (B[a]P) and chrysene in Salmonella typhimurium TA strains was compared. B[a]P was activated by a combination of F₅P or 4-MPy plus MPPT or PhIO in S. typhimurium TA1538. The B[a]P-induced mutagenicity with F₅P plus oxidant was higher than 4-MPy plus oxidant. Mutagenicity of chrysene, a tetracyclic aromatic hydrocarbon, was not detected in the presence of F₅P/PhIO in S. typhimurium TA98, but was activated in the presence of F₅P/MPPT. The F₅P/MPPT activated other polyaromatic hydrocarbons (PAH) in the S. typhimurium TA98 assay including dibenz[a,c]anthracene, dibenz[a,h]anthracene, 3-methylcholanthrene, and benzo[a]anthracene. The results indicated that the F₅P/MPPT was the most efficient model for detecting PAH-induced mutagenicity in the Ames assay.     

Phosphorous cycling and biogeochemistry in a Venezuelan-flooded savanna

In 1970, a programme of land recuperation started in Venezuelan savannas, strongly affected by the seasonality of precipitation; therefore, a network of dykes has been built to alleviate the floods and retain water throughout the dry period. Under the dyked system, the environment has been altered, allowing a change in the herbaceous vegetation towards aquatic species and an increase in primary production. It is assumed that a considerable quantity of nutrients is lost from the ecosystem through the floodgates, a situation that could be worsened with the climate change. This contribution describes the atmospheric input and total output in stream run-off of phosphorous (P) in a flooded savanna. Internal pools of the biogeochemical cycle of P associated with terrestrial compartments are described. In the flooded savanna, a large amount of P is immobilised (29.6?kg?ha^?1) in their above ground biomass by grasses, and in soil microbial biomass. The P budget was nearly balanced, as measured losses were cancelled out by the inputs in rainfall. Soils act as a sink, retaining P coming either from precipitation or from desorption/mineralisation processes. That interruption can be maximised, and losses of P and other nutrients can be minimised with an adequate management of the floodgate.     

Natural and Anthropogenic Effects On Phytoplankton Primary Productivity in Mangroves

Abstract

Spatial and temporal variations and the factors influencing primary production have been studied in three different mangrove waters (Pichavaram, Ennore Creek and Adyar Estuary) of South India characterised by different anthropogenic impacts. the gross primary productivity in the unpolluted Pichavaram mangrove was 113 g Cm^?2yr^?1 exhibiting natural variability with the environmental forcing factors. Human activities have elevated primary productivity in the Ennore Creek mangrove (157g Cm^?2yr^?1) primarily through the direct discharge of fertilizer effluents. By contrast, a combination of domestic and industrial effluent discharges into the Adyar Estuary mangrove has considerably reduced phytoplankton primary productivity 83g Cm^?2yr^?1 the Redfield N: P ratio varies from 0.96 N: 1P at Ennore Creek, 1.75N: 1P at Adyar Estuary to 15.2 N: 1P at Pichavaram mangroves. This suggests that the Pichavaram mangroves represent a well equilibrated ecosystem with N: P ratio close to steady-state values in contrast to the anthropogenically altered mangrove ecosystems studied. Results show a significant temporal variability in nutrient concentration in the three mangrove areas. Distinct differences in nutrient concentrations between the dry and the wet seasons have been observed.     

亚磷酸盐降解微生物的筛选、鉴定和降解特性

从太湖底泥中筛选出一株能够利用亚磷酸盐(+3价)的细菌P1.通过生理生化实验及16S rDNA基因序列分析鉴定,P1菌与所有已知菌的同源性都很低,属于未知的新菌株.P1菌的最适培养条件为:pH6.5~7.0、温度30℃.P1菌能以亚磷酸盐为唯一磷源生长,在60~100mg P/L的初始亚磷酸盐培养条件下,100mgP/L的亚磷酸盐培养基中亚磷酸盐减少量最大(11%),培养基中生成正磷酸盐的比例最高1.6%.初始亚磷酸盐浓度越低,碱性磷酸酶(BAP)活性越高,60mgP/L的亚磷酸盐培养基中BAP的最高活性为1.86mol PNP/(L菌液·h).P1菌可能通过BAP将亚磷酸盐转化成生物体内所需的磷源.     

Research progress in microbial cytochrome P450 and xenobiotic metabolism北大核心CSCD

Cytochrome P450 (CYP450s) is a type of heme-mercaptide protein superfamily, which is distributed widely in animals, plants, and microorganisms. CYP450s can oxidize and degrade many exogenous compounds such as drugs, herbicides, pesticides, some persistent organic pollutants, and so on. Based on recent researches, this paper reviews the nomenclature, classification, structure, and catalytic mechanism of P450 enzymes, and summarizes the research progresses in the metabolism and biodegradation of xenobiotics using P450 enzymes from microorganisms. The nomenclature and classification of the P450 gene superfamily mainly rely on the similarities of amino acid sequences. Although the structures of P450 are conserved, their recognition sites towards to the substrates are variable. This is also the structural basis for the catalytic diversities of P450 enzymes. Few P450 enzymes from bacteria and fungi can metabolize and degrade xenobiotics such as polycyclic aromatic hydrocarbons, herbicides, and so on. However, these P450 enzymes are less likely be used in practical applications because of their low catalytic activities. In the future, more P450 enzymes with high degradable efficiencies towards xenobiotics are needed to be obtained using multiple omics tools or modifying the existing P450 enzymes, to achieve the bioremediation of the environment. © 2018 Science Press. All rights reserved.     

P2P防污染机制的研究

文件污染是当前P2P文件共享系统普遍存在的问题,其中用户行为是导致污染的重要因素.在考察用户行为的基础上,建立了一个污染文件传播模型,描述了用户的污染意识、共享倾向等因素对污染传播的影响,并据此提出了相应的反污染机制.仿真实验表明,该机制能够有效地控制P2P文件共享系统中污染文件的传播.图6,表12.     

硅和磷配合施入对镉污染土壤的修复改良

为了研究两种改良剂配合施入对重金属污染土壤的改良效果,以棕壤为供试土壤,以玉米（OryzasativaL.）作为供试作物,采用二元二次正交回归组合设计方法,通过室外盆栽试验,研究了硅和磷配合施入对镉污染土壤中玉米生物量以及玉米茎叶中镉吸收量的影响。结果表明：硅、磷施入都能增加镉污染条件下玉米的生物量,其中磷的增产作用大于硅;硅、磷施入都能降低镉污染条件下玉米茎叶中的镉含量,硅降低玉米茎叶中镉含量的效应大于磷;硅、磷配合施入降低玉米茎叶中镉含量的效果大于上述两种改良剂单独施入。在本实验条件范围内,当硅为6.60g·kg-1,磷施入量范围在2.29～2.39g·kg-1时,玉米茎叶中镉含量为最低。因此可以由硅磷配合施入改良重金属污染的土壤。     

淹水对酸性红壤磷吸附解吸特性的影响——以江西省旱地红壤和水稻土为例

采用室内培养法研究了淹水对2种酸性红壤（旱地红壤、水稻土）磷吸附解吸特性及草酸可提取态P的影响。淹水培养实验中,2种土壤分别淹水0（对照）,1、2、3、4、8周,淹水培养结束后进行P吸附解吸实验,解吸实验结束后测定土样中草酸可提取态P。结果表明：与氧化状态相比,淹水后旱地红壤P吸附量减少,水稻土淹水1、2、3周P吸附量高于氧化状态,继续淹水4和8周后P吸附量减少。淹水前后旱地红壤P吸附量均大于水稻土。用简单Langmuir方程拟合P等温吸附曲线,除淹水4周外,P最大缓冲容量（MBC）随淹水时间延长而降低。结合能常数（K）淹水前后的变化规律性差。2种土壤P解吸量随加入P量增加而增加。氧化、还原状态下,2种土壤酸性草酸铵可提取P均远远大于CaCl2解吸P,虽然水稻土吸附P量低于旱地红壤,但P解吸量无论是CaCl2解吸P还是酸性草酸铵可提取P均大于旱地红壤,主要原因在于水稻土全P及速效P含量大于旱地红壤。淹水后草酸可提取态P增加,吸附P的释放和被新近形成的铁氧化物再吸附是淹水后草酸可提取态P增加的主要原因。