填埋场渗漏风险评估的三级PRA模型及案例研究

在对填埋场渗滤液渗漏的环境风险进行系统分析的基础上,基于层次化风险评价,构建了填埋场渗漏风险评估的三级PRA模型,其中第1级概率风险评价模型(PRA)评价填埋场渗漏风险,第2级PRA评价地下水污染风险,第3级PRA评价人体健康风险.为定量研究不确定性因素对风险评价结果的影响,采用Monte Carlo方法研究三级PRA模型中参数的不确定性;采用事故树方法研究防渗层破损事故的不确定性.应用三级PRA模型评价了西南地区某危险废物填埋场渗滤液渗漏的环境风险,通过与实测数据和EPACMTP模型的比较,验证了该模型模拟结果的准确性. 第1级PRA评价结果显示,该填埋场渗漏量大于可接受渗漏量的概率为0.85,表明渗漏风险较大;第2级PRA评价结果指出,自第28年起渗滤液污染地下水的概率逐渐增大,在第47年污染概率等于1.00,主要污染物为Ni和Pb;第3级PRA评价结果表明,被污染的地下水将对填埋场周边居民构成健康危害,主要危害物为Pb,正常情况下其非致癌危害商为1.05;在不利条件下(降水量大、漏洞多、水文地质条件利于污染物扩散),非致癌危害商为1.34.      

基于Landsim的填埋场长期渗漏的污染风险评价

介绍了Landsim模型的基本理论及其填埋场防渗系统、导排系统长期性能变化的表征方式,在此基础上提出了填埋场长期渗漏风险的表征方式..通过Landsim和HELP模型的耦合,弥补了Landsim模型中堆体入渗计算过于简单的缺陷.运用耦合的Landsim-HELP模型评价了西南地区某危险废物填埋场的长期渗漏的地下水污染风险.结果表明,该耦合模型可以准确的评价填埋场性能变化条件下的渗漏量及其对应概率;该填埋场在短期内(1~3a)地下水被污染的概率风险较小(￡0.33),而在长期内(34a)被污染的风险较大(30.68).建议在制定填埋场的设计和运行标准时需考虑防渗膜、导排管等重要单元长期性能的变化,从而减小其长期渗漏造成的地下水污染风险.     

填埋场长期渗漏的环境风险评价方法与案例研究

填埋场的长期渗漏是由于防渗膜老化、导排层淤堵等原因,导致填埋场封场后渗滤液渗漏量增加的现象. 为分析渗滤液长期渗漏对填埋场环境风险的影响,采用Landsim-HELP耦合模型进行渗漏源强计算和污染组分迁移转化计算. 在此基础上,以致癌风险和非致癌风险为渗滤液渗漏的环境风险表征,采用剂量-效应模型对风险值进行计算. 最终构建了基于Landsim-HELP耦合的填埋场长期渗漏的环境风险评价模型,并将其用于山西省某工业固体废物填埋场渗漏风险研究. 结果表明:①短期(0~100 a)内,在CLTP(考虑长期性能衰减)和NCLTP(不考虑长期性能衰减)情景下,渗滤液渗漏的环境风险无明显差异, 并且二者的风险值均低于可接受风险水平;而长期(>100~1 000 a)状态下,2种情景的风险值差别较大,其中CLTP情景下的风险为NCLTP情景下的7倍左右,并且主要体现为Cr(Ⅵ)的致癌风险(10-4). 采用Monte Carlo方法分析风险结果的不确定性,其中Cr(Ⅵ)致癌风险值的不确定性为6.7,Cr(Ⅵ)和TCr的非致癌风险评价结果的不确定性分别为2.3、2.1.      

填埋场环境下HDPE膜老化特性及其对周边地下水污染风险的影响

为研究危险废物填埋场环境下防渗系统HDPE膜（高密度聚乙烯膜）材料老化规律及其对渗滤液产生、渗漏和区域地下水环境的影响,通过HDPE膜缺陷现场检测及室内老化性能测试,获取了HDPE膜初始缺陷特征参数（漏洞密度）和缺陷演化特征参数（老化起始时间和半衰期）,并以上述参数作为输入,综合运用HELP模型（填埋场水文过程评估模型）与Landsim模型（填埋场地下水污染风险模拟模型）对HDPE膜老化条件下的渗滤液产生、渗漏和地下水污染过程进行模拟预测.结果表明:①现场条件下HDPE膜在第2年开始老化,第8年达到半衰期.②HDPE膜老化导致漏洞数量和渗透系数增加,进而导致渗滤液渗漏量增加,地下水污染风险逐渐增加.短期（0~5 a）内,地下水超标概率为0,污染风险较小;中期（5~10 a）内,距离填埋场200 m内污染超标概率污染≥ 80%,污染风险较大,但400 m外的污染概率为0,污染风险较小;就长期（>10 a）而言,距离填埋场1 000 m处,污染超标概率达100%,地下水污染风险极大.填埋场现场条件下,防渗材料劣化及老化过程较实验室条件更为迅速,导致渗滤液长期渗漏、地下水污染风险加剧,因此建议加强填埋场设计和运行中HDPE膜抗老化研究,保障危险废物填埋场长期安全运行.      

简易垃圾填埋场地下水污染风险评价

对简易垃圾填埋场污染地下水的风险进行评价是开展地下水保护的重要手段. 基于对简易垃圾填埋场污染地下水的系统结构分析,构建了包括填埋场危险性、评价对象暴露性、包气带抗污性、含水层脆弱性以及地下水危害性等影响因素的地下水污染风险评价指标体系,确定了各评价指标的取值依据和取值范围(为1~10),采用层次分析(AHP)法确定了各评价指标的权重,并建立了综合指数风险评价模型. 以北天堂简易垃圾填埋场对北京市水源四厂地下水污染的风险评价为例,对该风险评价模型进行了验证. 结果表明,北天堂简易垃圾填埋场对北京市水源四厂地下水污染风险指数为7.455 6,污染风险等级较高,与有关研究结果相符,证实所建立的地下水污染的综合指数风险评价模型与指标体系合理.      

贵阳市比例坝垃圾填埋场渗滤液中重金属污染现状调查

为了解贵阳市比例坝生活垃圾填埋场渗滤液中重金属污染现状,对该填埋场产生的渗滤原液及周边水样中的重金属Fe、Mn、Zn、Pb、Cr、Cd、Ni、Cu、As、Hg等的含量进行了调查分析。结果表明,渗滤原液中除Fe、Mn含量较高外,其余重金属含量较低或未检出,经过现场渗滤液处理站的处理,重金属含量均远低于相关排放标准或未检出;渗滤液对周边地下水的重金属污染主要表现为Fe和Mn,对周边地表水的重金属影响不大。     

城镇生活垃圾填埋场开采的可行性评估体系

近年来,填埋场开采成为填埋场生态治理的重要技术之一。然而,填埋场开采的可行性评估一直是制约填埋场开采项目的关键决策因素。以绍兴市越城区简易垃圾堆放场为例,基于该填埋场建设、运营概况及场地调查结果,从填埋场稳定化程度、环境风险等级和经济效益3个维度筛选并建立评估指标体系,采用层次分析法和综合评价法,构建了适用于城镇生活垃圾填埋场开采的可行性评估体系,为填埋场开采提供决策依据。结果表明:一期堆放场为中度稳定,低环境风险,低经济效益;二期堆放场为中度稳定,低环境风险,高经济效益。2期堆放场均具有填埋场开采的可行性,适合采用填埋场开采技术进行生态治理。     

基于环境风险的危险废物填埋场安全寿命周期评价

通过系统分析危险填埋场的设计功能,结合安全寿命周期的定义,对危险废物填埋场的安全寿命周期进行了定义.在此基础上,通过文献查阅和理论推导确定了描述危险废物填埋场主要单元性能衰减的老化模型,并结合课题组开发的渗漏环境风险分析模型,建立了危险废物填埋场的安全寿命评估模型,并选择中部某危险废物填埋场进行了案例研究.结果表明:随着防渗材料老化以及导排层淤堵,渗滤液渗漏量将逐渐增加,其安全贮存功能将逐渐丧失,并逐渐达到其安全寿命周期.仅就本案例而言,该填埋场的安全寿命周期为385a;对安全寿命周期相关参数的敏感性分析表明,浸出浓度与填埋场安全寿命周期呈负相关,包气带厚度和含水层厚度与安全寿命周期呈正相关,相关系数分别为-0.79、0.99和0.72,这说明包气带厚度对安全寿命周期影响更大,其次为浸出浓度,最后为含水层厚度;应加强填埋场相关单元老化模型研究,开展其他因素对填埋场安全寿命周期的影响,进一步完善危险废物填埋场安全寿命周期评价理论和方法.     

基于改进的水质标识指数法垃圾填埋场地下水评价

非正规生活垃圾填埋场产生的渗滤液易对地下水环境造成严重污染,为了精准评价劣Ⅴ类水质和同类水质间的差异,引入水质标识指数法对典型非正规垃圾填埋场地下水水质进行评价。结果表明：由于浅层地下水与生活垃圾渗滤液直接接触,导致各监测点地下水中氨氮、高锰酸盐指数、氯化物指标单因子水质评价结果分别为66.362～255.3251、13.89～40.036、15.111～21.417;各监测点地下水综合水质评价结果为9.645～25.9521,均为劣Ⅴ类;最小值出现在2005年以前垃圾填埋区。受隔水层对污染物的有效阻隔作用,微承压水水质较潜水层水质显著好转,各监测点地下水综合水质评价结果为3.100～3.700。从空间分布特征看,不同填埋区潜水或微承压水单因子水质评价结果均存在显著差异;不同填埋区潜水水质综合评价结果存在显著差异,而微承压水综合水质评价结果差异不显著。研究成果对于今后我国垃圾填埋场地下水水质评价和环境管理具有借鉴作用。     

垃圾填埋场填埋气回收处理与利用

简单介绍了阿苏卫垃圾卫生填埋场的建设和运行情况,并对填埋场的垃圾成分和垃圾量进行了分析,得到该填埋场填埋气的实测组分.依据经典EPA产气模型对填埋场潜在填埋气产量进行了预测.结果表明,在2005-2039年的运行期间,预计该填埋场填埋气的平均产量约为33.7×106 m3/a.比较研究了填埋场填埋气的回收利用技术,指出并网发电是该填埋场填埋气的最佳利用方式.通过对填埋场填埋气发电项目进行的技术经济分析表明,该工程总投资为3 394×104元,项目年直接经济效益达230×104元.      

Toxic effects of acetochlor, methamidophos and their combination on nifH gene in soil

Toxic effects of two agrochemicals on nifH gene in agricultural black soil were investigated using denaturing gradient gel electrophoresis （DGGE） and sequencing approaches in a microcosm experiment. Changes of soil nifH gene diversity and composition were examined following the application of acetochlor, methamidophos and their combination. Acetochlor reduced the nifH gene diversity （both in gene richness and diversity index values） and caused changes in the nifH gene composition. The effects of acetochlor on nifH gene were strengthened as the concentration of acetochlor increased. Cluster analysis of DGGE banding patterns showed that nifH gene composition which had been affected by low concentration of acetochlor （50 mg/kg） recovered firstly. Methamidophos reduced nifH gene richness that except at 4 weeks. The medium concentration of methamidophos （150 mg/kg） caused the most apparent changes in nifH gene diversity at the first week while the high concentration of methamidophos （250 mg/kg） produced prominent effects on nifH gene diversity in the following weeks. Cluster analysis showed that minimal changes of nifH gene composition were found at 1 week and maximal changes at 4 weeks. Toxic effects of acetochlor and methamidophos combination on nifH gene were also apparent. Different nifH genes （bands） responded differently to the impact of agrochemicals： four individual bands were eliminated by the application of the agrochemicals, five bands became predominant by the stimulation of the agrochemicals, and four bands showed strong resistance to the influence of the agrochemicals. Fifteen prominent bands were partially sequenced, yielding 15 different nifH sequences, which were used for phylogenetic reconstructions. All sequences were affiliated with the alpha- and beta-proteobacteria, showing higher similarity to eight different diazotrophic genera.     

Arsenic uptake by arbuscular mycorrhizal maize （Zea mays L.） grown in an arsenic-contaminated soil with added phosphorus

The effects of arbuscular mycorrhizal (AM) fungus (Glomus mosseae) and phosphorus (P) addition (100 mg/kg soil) on arsenic (As) uptake by maize plants (Zea mays L.) from an As-contaminated soil were examined in a glasshouse experiment.Non-mycorrhizal and zero-P addition controls were included.Plant biomass and concentrations and uptake of As,P,and other nutrients,AM colonization,root lengths,and hyphal length densities were determined.The results indicated that addition of P significantly inhibited root colonization and development of extraradical mycelium.Root length and dry weight both increased markedly with mycorrhizal colonization under the zero-P treatments,but shoot and root biomass of AM plants was depressed by P application.AM fungal inoculation decreased shoot As concentrations when no P was added,and shoot and root As concentrations of AM plants increased 2.6 and 1.4 times with P addition,respectively.Shoot and root uptake of P,Mn,Cu,and Zn increased,but shoot Fe uptake decreased by 44.6%,with inoculation, when P was added.P addition reduced shoot P,Fe,Mn,Cu,and Zn uptake of AM plants,but increased root Fe and Mn uptake of the nonmycorrhizal ones.AM colonization therefore appeared to enhance plant tolerance to As in low P soil,and have some potential for the phytostabilization of As-contaminated soil,however,P application may introduce additional environmental risk by increasing soil As mobility.     

Degradation of metabolites accumulated of benzo[a]pyrene by coupling Penicillium Chrysogenum with KMnO4

Several main metabolites of benzo[a]pyrene （BaP） formed by Penicillium chrysogenum, Benzo[a]pyrene-1,6-quinone （BP 1,6- quinone）, trans-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene （BP 7,8-diol）, 3-hydroxybenzo[a]pyrene （3-OHBP）, were identified by high-performance liquid chromatography （HPLC）. The three metabolites were liable to be accumulated and were hardly further metabolized because of their toxicity to microorganisms. However, their further degradation was essential for the complete degradation of BaP. To enhance their degradation, two methods, degradation by coupling Penicillium chrysogenum with KMnO4 and degradation only by Penicillium chrysogenum, were compared; Meanwhile, the parameters of degradation in the superior method were optimized. The results showed that （1） the method of coupling Penicillium chrysogenum with KMnO4 was better and was the first method to be used in the degradation of BaP and its metabolites; （2） the metabolite, BP 1,6-quinone was the most liable to be accumulated in pure cultures; （3） the effect of degradation was the best when the concentration of KMnO4 in the cultures was 0.01% （w/v）, concentration of the three compounds was 5 mg/L and pH was 6.2. Based on the experimental results, a novel concept with regard to the bioremediation of BaP-contaminated environment was discussed, considering the influence on environmental toxicity of the accumulated metabolites.     

Impact of atrazine and nitrogen fertilizers on the sorption of chlorotoluron in soil and model sorbents

Sorption of chlorotoluron in ammonium sulfate, urea and atrazine multi-solutes system was investigated by batch experiments. The results showed application of nitrogen fertilizers to the soil could affect the behavior of chlorotoluron. At the same concentration of N, sorption of chlorotoluron decreased as the concentration of atrazine increased on the day 0 and 6 in soil, respectively. The sorption of chlorotoluron increased from 0 to 6 d when soils were preincubated with deionized water, ammonium sulfate and urea solution for 6 d. That indicated incubation time was one of the most important factors for the sorption of chlorotoluron in nitrogen fertilizers treatments. The individual sorption isotherms of chlorotoluron in rubbery polymer and silica were strictly linear in single solute system, but there were competition sorption between pesticides or between pesticides and nitrogen fertilizers. That indicated the sorption taken place by concurrent solid-phase dissolution mechanism and sorption on the interface of water-organic matter or water-mineral matter.     

Potential of plant polyphenol oxidases in the decolorization and removal of textile and non-textile dyes

In this study an effort has been made to use plant polyphenol oxidases; potato （Solanum tuberosum） and brinjal （Solanum melongena）, for the treatment of various important dyes used in textile and other industries. The ammonium sulphate fractionated enzyme preparations were used to treat a number of dyes under various experimental conditions. Majority of the treated dyes were maximally decolorized at pH 3.0. Some of the dyes were quickly decolorized whereas others were marginally decolorized. The initial first hour was sufficient for the maximum decolorization of dyes. The rate of decolorization was quite slow on long treatment of dyes. Enhancement in the dye decolorization was noticed on increasing the concentration of enzymes. The complex mixtures of dyes were treated with both preparations of polyphenol oxidases in the buffers of varying pH values. Potato polyphenol oxidase was significantly more effective in decolorizing the dyes to higher extent as compared to the enzyme obtained from brinjal polyphenol oxidase. Decolorization of dyes and their mixtures, followed by the formation of an insoluble precipitate, which could be easily removed simply by centrifugation.     

Removal of heavy metals from sewage sludge by low costing chemical method and recycling in agriculture

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Isolation and preliminary characterization of a 3-chlorobenzoate degrading bacteria

A study was conducted to compare the diversity of 2-, 3-, and 4-chlorobenzoate degraders in two pristine soils and one contaminated sewage sludge. These samples contained strikingly different populations of mono-chlorobenzoate degraders. Although fewer cultures were isolated in the uncontaminated soils than contaminated one, the ability of microbial populations to mineralize chlorobenzoate was widespread. The 3- and 4-chlorobenzoate degraders were more diverse than the 2-chlorobenzoate degraders. One of the strains isolated from the sewage sludge was obtained. Based on its phenotype, chemotaxonomic properties and 16S rRNA gene, the organism S-7 was classified as Rhodococcus erythropolis. The strain can grow at temperature from 4 to 37℃. It can utilize several （halo）aromatic compounds. Moreover, strain S-7 can grow and use 3-chlorobenzoate as sole carbon source in a temperatures range of 10-30℃ with stoichiometric release of chloride ions. The psychrotolerant ability was significant for bioremediation in low temperature regions. Catechol and chlorocatechol 1,2-dioxygenase activities were present in cell free extracts of the strain, but no （chloro）catechol 2,3- dioxygenase activities was detected. Spectral conversion assays with extracts from R. erythropolis S-7 showed accumulation of a compound with a similar UV spectrum as chloro-cis,cis-muconate from 3-chlorobenzoate. On the basis of these results, we proposed that S-7 degraded 3-chlorobenzoate through the modified ortho-cleave pathway.     

Single and joint effects of pesticides and mercury on soil urease

The influence of two pesticides including chlorimuron-ethyl and furadan and mercury （Hg） on urease activity in 4 soils （meadow burozem and phaeozem） was investigated. The soils were exposed to various concentrations of the two pesticides and Hg individually and simultaneously. Results showed that there was a close relationship between urease activity and organic matter content in soil. Chlorimuron-ethyl and furadan could both activate urease in the 4 soils. The maximum increment of urease activity by chlorimuronethyl was up to 14%-18%. There was almost an equal increase （up to 13%-21%） in the urease activity by furadan. On the contrary, Hg markedly inhibited soil urease activity. A logarithmic equation was used to describe the relationship （P〈0.05） between the concentration of Hg and the activity of soil urease in the 4 tested soils. Semi-effect dose （ED50） values by the stress of Hg based on the inhibition of soil urease in the 4 soils were 88, 5.5, 24 and 20 mg/kg, respectively, according to the calculation of the corresponding equations. The interactive effect of chlorimuron-ethyl or furadan with metal Hg on soil urease was mainly synergic at the highest tested concentrations.     

Organochlorine pesticides in soils under different land usage in the Taihu Lake region, China

A field study was conducted in the Taihu Lake region, China in 2004 to reveal the organochlorine pesticide concentrations in soils after the ban of these substances in the year 1983. Thirteen organochlorine pesticides (OCPs) were analyzed in soils from paddy field, tree land and fallow land. Total organochlorine pesticide residues were higher in agricultural soils than in uncultivated fallow land soils. Among all the pesticides, ΣDDX (DDD, DDE and DDT) had the highest concentration for all the soil samples, ranging from 3.10 ng/g to 166.55 ng/g with a mean value of 57.04 ng/g and followed by ΣHCH, ranging from 0.73 ng/g to 60.97 ng/g with a mean value of 24.06 ng/g. Dieldrin, endrin, HCB and α-endosulfan were also found in soils with less than 15 ng/g. Ratios of p,p'-(DDD DDE)/DDT in soils under three land usages were: paddy field ＞ tree land ＞ fallow land, indicating that land usage inlfuenced the degradation of DDT in soils. Ratios of p,p'-(DDD DDE)/DDT ＞1, showing aged residues of DDTs in soils of the Taihu Lake region. The results were discussed with data from a former study that showed very low actual concentrations of HCH and DDT in soils in the Taihu Lake region, but according to the chemical half-lives and their concentrations in soils in 1980s, the concentration of DDT in soils seemed to be underestimated. In any case our data show that the ban on the use of HCH and DDT resulted in a tremendous reduction of these pesticide residues in soils, but there are still high amounts of pesticide residues in soils, which need more remediation processes.     

Alterations of organ histopathology and metallolhionein mRNA expression in silver barb, Puntius gonionotus during subchronic cadmium exposure

Common silver barb,Puntius gonionotus,exposed to the nominal concentration of 0.06 mg/L Cd for 60 d,were assessed for histopathological alterations(gills,liver and kidney),metal accumulation,and metallothionein(MT)mRNA expression.Fish exhibited pathological symptoms such as hypertrophy and hyperplasia of primary and secondary gill lamellae,vacuolization in hepatocytes,and prominent tubular and glomerular damage in the kidney.In addition,kidney accumulated the highest content of cadmium,more than gills and liver.Expression of MT mRNA was increased in both liver and kidney of treated fish.Hepatic MT levels remained high after fish were removed to Cd-free water.In contrast,MT expression in kidney was peaked after 28 d of treatment and drastically dropped when fish were removed to Cd-free water.The high concentrations of Cd in hepatic tissues indicated an accumulation site or permanent damage on this tissue.