镉污染土壤的植物修复研究进展

镉会影响植物正常生长,经食物链富集,则会对动物和人体造成危害。植物修复是一种生态友好的修复手段,能有效修复镉污染土壤。因此,开展镉污染土壤植物修复的系统研究非常必要。通过研究发现,目前针对镉污染土壤的植物修复的研究主要集中于两方面:一方面是镉超积累植物和镉富集性植物的筛选,另一方面是植物-微生物联合修复技术的强化。目前已筛选出镉超积累植物11种,镉富集性植物31种,已研究出针对镉污染土壤的植物-微生物匹配组合11个,镉耐性菌16种。     

土壤和植物中镉的污染及防治

阐述了镉在土壤中的含量与形态，镉对植物的毒害效应，各种植物对镉富集能力，以及植物对镉的吸收和在不同器官的积累差异，还综述了镉对植物叶细胞超微结构的影响，提出了防治农业生态系统中镉污染的方法。     

不同镉污染农田土壤上秸秆和炭化秸秆分解动态及其对土壤镉的吸附特征

通过温室土壤培养实验,研究不同镉污染农田土壤上不同的作物秸秆和炭化作物秸秆还田后的分解动态和还田秸秆材料对污染土壤中镉的吸附特征,探讨秸秆和炭化秸秆还田做为重金属镉污染农田土壤修复剂的可行性。实验结果表明,还田的油菜秸秆和玉米秸秆在2种镉污染水稻土壤上6个月分解了43％-65％,秸秆炭化后还田则很稳定,2种镉污染土壤上还田6个月时累计分解量小于5％。2种镉污染土壤上还田的秸秆和炭化秸秆随还田时间延长镉含量逐渐增加。模拟镉污染土壤上,相同时期油菜秸秆中镉含量显著高于玉米秸秆,油菜秸秆炭中镉含量显著高于玉米秸秆炭。在镉污染土壤上,还田的玉米秸秆、油菜秸秆、玉米秸秆炭和油菜秸秆炭对土壤镉的净吸附量相近,均小于1．1μg／g。在模拟镉污染土壤上还田的油菜秸秆和油莱秸秆炭对土壤镉净吸附量最高分别达到2．74μg／g和7．03μg／g,分别是玉米秸秆和玉米秸秆炭的2倍,且显著高于其在镉污染土壤上的净吸附量,具有高的吸附能力。     

中国镉矿的区域分布及土壤镉污染风险分析

系统地分析和评价了中国镉矿的区域分布及长期采选冶活动所带来的土壤镉污染风险。研究结果表明,截至2005年底,中国累计探明镉资源储量约为719.47kt,保有镉资源储量约为587.37kt,且多与铅矿、锌矿等以共、伴生形式存在。中国镉矿主要分布在中部、西南部及华东地区,这些地区的镉资源探明储量占中国累计探明总储量的88.0%,保有储量占中国总保有储量的87.1%。据统计,中国镉采出量约为136.10kt,主要集中在西南地区,其镉采出量占中国总采出量的59.4%。镉污染事件主要发生在镉矿相对丰富及采选冶活动较密集的云南、广东、湖南、贵州等地区,大部分矿冶区及周边土壤呈现重度镉污染,农作物中含镉量超出《食品中污染物限量》(GB 2762—2005)中限值。     

Regional distribution of cadmium minerals and risk assessment for potential cadmium pollution of soil in China

系统地分析和评价了中国镉矿的区域分布及长期采选冶活动所带来的土壤镉污染风险.研究结果表明,截至2005年底,中国累计探明镉资源储量约为719.47kt,保有镉资源储量约为587.37 kt,且多与铅矿、锌矿等以共、伴生形式存在.中国镉矿主要分布在中部、西南部及华东地区,这些地区的镉资源探明储量占中国累计探明总储量的88.0％,保有储量占中国总保有储量的87.1％.据统计,中国镉采出量约为136.10 kt,主要集中在西南地区,其镉采出量占中国总采出量的59.4％.镉污染事件主要发生在镉矿相对丰富及采选冶活动较密集的云南、广东、湖南、贵州等地区,大部分矿冶区及周边土壤呈现重度镉污染,农作物中含镉量超出《食品中污染物限量》(GB2762-2005)中限值.     

土壤作物系统镉污染及其防治研究

选择我国北方主要粮食作物冬小麦和夏谷进行盆栽试验，研究了土壤镉污染对作物生长发育和产量的影响及泥炭、羊粪两种不同类型的有机肥缓减土壤镉污染危害的作用；分析了镉在两种作物不同器官中的迁移效率和累积规律；认为施加有机肥是缓减土壤镉污染危害的有效措施，且施羊粪的效果比施泥炭好。     

海泡石及其复配原位修复镉污染稻田

以天然黏土海泡石作为钝化材料,并分别与磷肥、生物炭和硅肥复配,在湖南某镉污染的酸性水稻田进行原位修复示范实验,考察海泡石及其复配对稻谷产量、糙米镉含量及土壤中镉的有效态含量及形态分布变化用以表征修复效果;研究了海泡石及其复配对土壤pH、土壤碱解氮、有效磷含量以表征其对土壤环境质量的影响,并对各项理化指标之间的相关性进行分析。结果表明,田间示范条件下海泡石及其复配均降低了土壤中镉的生物有效性,明显降低了糙米中镉含量。其中海泡石磷肥复配和海泡石硅肥复配处理后,糙米镉含量最大降幅约为72.7%,分别降低至0.33和0.34 mg/kg。海泡石及其复配处理均能不同程度增加土壤中碱解氮及有效磷含量,对于作物生长有益。综合总体表现,海泡石磷肥复配、海泡石硅肥复配可被推荐作为镉污染酸性稻田的原位钝化修复材料,具有推广应用的潜力。     

可变电荷土壤介入应急混凝处置镉污染的可行性研究

以南方可变电荷土壤作为突发高浓度镉污染水体应急混凝处置的强化混凝药剂,考察了可变电荷土壤介入应急处置对混凝效果的影响。并模拟构建了镉污染应急处置产生沉积物,通过静态释放实验方式,开展了可变电荷土壤介入应急混凝处置对含镉沉积物中Cd释放的影响的研究。结果表明混凝时,在偏碱性条件下,投加可变电荷土壤有利于提高镉的去除率,可以将水体镉浓度由1.892 mg·L-1降到30μg·L-1。在静态释放实验中,不同的溶解氧条件下镉释放量存在差异,但可变电荷土壤介入应急混凝处置都不同程度地促进了沉积物中Cd的释放。在镉污染水体的应急处置中投加可变电荷土壤来强化混凝可以有效降低水体的残余镉浓度,但可变电荷土壤的介入使得沉积物组分发生了变化,使得混合沉积物在应急处置后具有二次污染的风险。     

“镉米”生物能源化过程中Cd的迁移途径

镉属于环境中持久性污染物,毒性大,对环境及人类造成严重危害,"镉米"事件已引起了对环境镉污染尤其是土壤镉污染的高度关注。利用镉米生产酒精不但能为企业能源生产提供新的原料来源,而且可解决有害大米的出路问题。通过摇瓶和UASB厌氧反应器实验,重点研究了Cd2+在厌氧处理过程中的迁移途径。结果表明,90%以上的Cd2+主要以微溶的形式富集于厌氧污泥里。厌氧泥离心分离:泥中镉浓度为0.35~0.40 mg/kg,水中镉浓度低于0.025 mg/kg。厌氧出水镉浓度在0.010~0.015 mg/kg,可以实现达标排放。出水VFA基本维持在300~500 mg/L,COD的去除率达65%~80%。实验结果可为镉米能源化利用提供一定的理论依据和技术支撑。     

一株耐镉细菌的分离及其富集Cd的机理

从重金属镉污染土壤中筛选到一株对镉具有较强抗性和富集能力的细菌RC。经形态学观察和生理生化鉴定以及16SrDNA序列分析,RC为蜡状芽孢杆菌（Bacillus cereus）。在不同镉浓度液体培养条件下研究了菌体的生长曲线,并探讨了RC菌株对Zn、Cu的抗性,结果显示RC对不同重金属的抗性机制存在一定的差异。利用扫描电镜、透射电镜观察了镉在RC胞内外的沉积作用及分布情况,结果表明,在镉浓度为150 mg/L时菌体细胞壁及其内部可见大量的高电子密度颗粒,同时在菌体表面也有沉淀物附着。因此,胞内外沉积作用可能是该菌对高浓度镉的抗性和富集作用的重要途径。通过红外光谱探讨了RC积累镉前后细胞壁表面化学基团的变化情况,结果发现RC的细胞壁上参与积累作用的化学官能团主要有—OH、—NH、—CO和—CO—NH—等。     

Evaluation of trichloroethene recovery processes in heterogeneous aquifer cells flushed with biodegradable surfactants

The ability of two biodegradable surfactants, polyoxyethylene (20) sorbitan monooleate (Tween 80) and sodium dihexyl sulfosuccinate (Aerosol MA), to recover a representative dense non-aqueous-phase liquid (DNAPL), trichloroethene (TCE), from heterogeneous porous media was evaluated through a combination of batch and aquifer cell experiments. An aqueous solution containing 3.3% Aerosol MA, 8% 2-propanol and 6 g/l CaCl(2) yielded a weight solubilization ratio (WSR) of 1.21 g TCE/g surfactant, with a corresponding liquid-liquid interfacial tension (IFT) of 0.19 dyn/cm. Flushing of aquifer cells containing a TCE-DNAPL source zone with approximately two pore volumes of the AMA formulation resulted in substantial (>30%) mobilization of TCE-DNAPL. However, a TCE mass recovery of 81% was achieved when the aqueous-phase flow rate was sufficient to displace the mobile TCE-DNAPL toward the effluent well. Aqueous solutions of Tween 80 exhibited a greater capacity to solubilize TCE (WSR=1.74 g TCE/g surfactant) and exerted markedly less reduction in IFT (10.4 dyn/cm). These data contradict an accepted empirical correlation used to estimate IFT values from solubilization capacity, and indicate a unique capacity of T80 to form concentrated TCE emulsions. Flushing of aquifer cells with less than 2.5 pore volumes of a 4% T80 solution achieved TCE mass recoveries ranging from 66 to 85%, with only slight TCE-DNAPL mobilization (<5%) occurring when the total trapping number exceeded 2 x 10(-5). These findings demonstrate the ability of Tween 80 and Aerosol MA solutions to efficiently recover TCE from a heterogeneous DNAPL source zone, and the utility of the total trapping number as a design parameter for a priori prediction of DNAPL mobilization and bank angle formation when flushing with low-IFT solutions. Given their potential to stimulate microbial reductive dechlorination at low concentrations, these surfactants are well-suited for remedial action plans that couple aggressive mass removal followed by enhanced bioremediation to treat chlorinated solvent source zones.     

The variation of street air levels of PAH and other mutagenic PAC in relation to regulations of traffic emissions and the impact of atmospheric processes

The occurrence of particle associated PAH and other mutagenic PAC was determined in 1996 in the street air of Copenhagen. In addition, particle extracts were tested for mutagenicity. The measurements were compared with previous measurements in 1992/1993. The levels had decreased in this period. The decrease was caused by an implementation of light diesel fuels for buses and the exchange of older petrol-driven passenger cars with catalystequipped new ones. About 65% of the reduction was caused by the application of the light diesel fuels. Under special conditions, chemical processes in the atmosphere produced many more mutagens than the direct emissions. The concentrations of S-PAC and N-PAC were 10 times lower than those of PAH, while the levels of oxy-PAH were in the same order of magnitude as those of PAH. Benzanthrone, an oxy-PAH, is proposed to be formed in the atmosphere in addition to direct emissions. Benzo(a)pyrene, often applied as an air quality criteria indicator, was photochemically degraded in the atmosphere. A strong increase in the mutagenic activities was observed to coincide with a depletion of benzo(a)pyrene.     

Chloroaromatic pollutants in mussels incubated in two finnish watercourses polluted by industry

Concentrations of different chlorinated compounds were measured in mussels incubated in two polluted watercourses, a river (the River Kymijoki) and a lake (Lake Vanaja) for four weeks in summer 1995. The sum concentrations of polychlorinated phenols (PCP) and biphenyls (PCB) were both about 1 μg/g lipid weight (lw) in Lake Vanaja mussels, while in the River Kymijoki mussels PCPs were non-detectable and PCBs were measured 120 ng/g lIw. The concentrations of toxic polychlorinated dibenzo-p-dioxin (PCDD) and dibenzofuran (PCDF) congeners ranged between <17 and 370 pg/g Iw in Lake Vanaja mussels and between <38 and 11,000 pg/g lw in the River Kymijoki mussels. Polychlorinated diphenyl ethers (PCDE) were detected in the mussels incubated in the River Kymijoki (0.4–1.1 ng/g Iw), but not in those incubated in Lake Vanaja. Polychlorinated phenoxyanisoles (PCPA) were measured 33 ng/g lw and polychlorinated phenoxyphenols (PCPP) 300 ng/g lw in the mussels incubated in the River Kymijoki. PCPAs were also detected in reference samples, which were sediment and pike from the River Kymijoki and Baltic salmon, seal and white-tailed sea eagle.     

Teratological effects of pesticides in vertebrates: a review

Abstract

In the last decades, the use and misuse of pesticides in the agriculture have increased, having a severe impact on ecosystems and their fauna. Although the various effects of pesticides on biodiversity have been already documented in several studies, to our knowledge no consistent overview of the impact of pesticides in vertebrates, both terrestrial and aquatic, is available. In this review, we try to present a concise compilation of the teratogenic effects of pesticides on the different classes of vertebrates – mammals, birds, reptiles, amphibians and fish.     

Radionuclides and trace elements in fish collected upstream and downstream of Los Alamos national laboratory and the doses to humans from the consumption of muscle and bone

Abstract

The purpose of this study was to determine radionuclide and trace element concentrations in bottom‐feeding fish (catfish, carp, and suckers) collected from the confluences of some of the major canyons that cross Los Alamos National Laboratory (LANL) lands with the Rio Grande (RG) and the potential radiological doses from the ingestion of these fish. Samples of muscle and bone (and viscera in some cases) were analyzed for ³H, ⁹⁰Sr, ¹³⁷Cs, ^totU, ²³⁸Pu, ^239,240Pu, and ²⁴¹Am and Ag, As, Ba, Be, Cr, Cd, Cu, Hg, Ni, Pb, Sb, Se, and Tl. Most radionuclides, with the exception of ⁹⁰Sr, in the muscle plus bone portions of fish collected from LANL canyons/RG were not significantly (p<0.05) higher from fish collected upstream (San Ildefonso/background) of LANL. Strontium‐90 in fish muscle plus bone tissue significantly (p<0.05) increases in concentration starting from Los Alamos Canyon, the most upstream confluence (fish contained 3.4E‐02 pCi g^‐1 [126E‐02 Bq kg^‐1]), to Frijoles Canyon, the most downstream confluence (fish contained 14E‐02 pCi g^‐1 [518E‐02 Bq kg^‐1]). The differences in ⁹⁰Sr concentrations in fish collected downstream and upstream (background) of LANL, however, were very small. Based on the average concentrations (±2SD) of radionuclides in fish tissue from the four LANL confluences, the committed effective dose equivalent from the ingestion of 46 lb (21 kg) (maximum ingestion rate per person per year) of fish muscle plus bone, after the subtraction of background, was 0.1 ± 0.1 mrem y^‐1 (1.0 ± 1.0 μSv y^‐1), and was far below the International Commission on Radiological Protection (all pathway) permissible dose limit of 100 mrem y^‐1 (1000 μSv y^‐1). Of the trace elements that were found above the limits of detection (Ba, Cu, and Hg) in fish muscle collected from the confluences of canyons that cross LANL and the RG, none were in significantly higher (p<0.05) concentrations than in muscle of fish collected from background locations.     

Book review

The Pesticide Manual ‐ A World Compendium, 8th Edition, C.R. Worthing, Editor and S.B. Walker, Assistant Editor, British Crop Protection Council, BCPC Publications Sales, Bear Farm, Binfield, Bracknell, Berkshire RG12 5QE, England. 1987, 1100 pp., UK £50; Overseas £56. ISBN 0–948404–01–9.     

Patterns of volatile metabolites and nonvolatile trichothecenes produced by isolates of <Emphasis Type="Italic">Stachybotrys,Fusarium, Trichoderma,Trichothecium</Emphasis> and <Emphasis Type="Italic">Memnoniella</Emphasis>

We reported previously that trichodiene, a volatile trichothecene derivative, was produced by a Stachybotrys isolate, also known to produce highly cytotoxic, non-volatile, macrocyclic trichothecenes (satrotoxins). We investigated the relationship between the production of trichodiene and various non-volatile trichothecenes for several molds. Volatile metabolites were concentrated by adsorption on Tenax TA and analyzed by GC/MS, while non-volatile metabolites were separated by HPLC, derivatized and analyzed by GC/MS. Stachybotrys chartarum isolates producing macrocyclic trichothecenes secreted significantly larger amounts of trichodiene and other sesquiterpenes than isolates which only produced simple trichothecenes. The amounts of secreted trichodiene were relatively small in all cases. With the exception of Memnoniella, which excreted small amounts of sesquiterpenes, the other isolates produced varying amounts of sesquiterpenes, including trichodiene, as well as simple tricothecenes, no detectable trichodiene, but large amounts of griseofulvin derivatives. In Stachybotrys there is apparently a correlation between trichodiene and macrocyclic trichothecene production. In the remaining isolates, there was no simple relationship between trichodiene and non-volatile trichothecene synthesis. Trichodiene is produced in larger amounts by Stachybotrys isolates, which also produce satratoxins, but it will be difficult to utilize this metabolite to detect toxic isolates in buildings due to the relatively small amounts excreted.     

Observations on the influence of water and soil pH on the persistence of insecticides

Abstract

The pH‐disappearance rate profiles were determined at ca. 25°C for 24 insecticides at 4 or 5 pH values over the range 4.5 to 8.0 in sterile phosphate buffers prepared in water‐ethanol (99: 1 v/v). Half‐lives measured at pH 8 were generally smaller than at lower pH values. Changes in half lives between pH 8.0 and 4.5 were largest (>1000x) for the aryl carbamates, carbofuran and carbaryl, the oxime carbamate, oxamyl, and the organophosphorus insecticide, trichlorfon. In contrast, half lives of phorate, terbufos, heptachlor, fensulfothion and aldicarb were affected only slightly by pH changes. Under the experimental conditions described half lives at pH8 varied from 1–2 days for trichlorfon and oxamyl to >1 year for fensulfothion and cyper‐methrin. Insecticide persistence on alumina (acid, neutral and basic), mineral soils amended with aluminum sulfate or calcium hydroxide to different pH values and four natural soils of different pH was examined. No correlation was observed between the measured pH of these solids and the rate of disappearance of selected insecticides applied to them. These observations demonstrate the difficulty of extrapolating the pH dependent disappearance behaviour observed in homogeneous solution to partially solid heterogeneous systems such as soil.     

Knowledge transfer initiative between molecular biologists and environmental researchers and regulators

A Natural Environment Research Council (NERC) funded Knowledge Transfer (KT) workshop was held in the United Kingdom (UK) to identify the needs and opportunities in the application of molecular biology and ‘omics’ techniques to environmental monitoring and risk assessment. Attendees highlighted a lack of effective communication between end-users and researchers as well as difficulties with data interpretation as reasons behind the slow uptake of molecular biology and omics techniques. A number of promising areas in which new techniques could be implemented at a practical level in the very near future were identified, thereby raising the profile of these recent technologies and providing vital proof of concept work. Molecular taxonomy, bacterial source tracking and pre-screening of chemicals for potential toxicities were all viewed as areas in which omics and molecular techniques could have immediate value, with the aim of reducing cost, increasing efficiency and providing more comprehensive data of improved quality.     

Sorption and predicted mobility of herbicides in Baltic soils

This study was undertaken to determine sorption coefficients of eight herbicides (alachlor, amitrole, atrazine, simazine, dicamba, imazamox, imazethapyr, and pendimethalin) to seven agricultural soils from sites throughout Lithuania. The measured sorption coefficients were used to predict the susceptibility of these herbicides to leach to groundwater. Soil-water partitioning coefficients were measured in batch equilibrium studies using radiolabeled herbicides. In most soils, sorption followed the general trend pendimethalin > alachlor > atrazine～ amitrole～ simazine > imazethapyr > imazamox > dicamba, consistent with the trends in hydrophobicity (log K_ow) except in the case of amitrole. For several herbicides, sorption coefficients and calculated retardation factors were lowest (predicted to be most susceptible to leaching) in a soil of intermediate organic carbon content and sand content. Calculated herbicide retardation factors were high for soils with high organic carbon contents. Estimated leaching times under saturated conditions, assuming no herbicide degradation and no preferential water flow, were more strongly affected by soil textural effects on predicted water flow than by herbicide sorption effects. All herbicides were predicted to be slowest to leach in soils with high clay and low sand contents, and fastest to leach in soils with high sand content and low organic matter content. Herbicide management is important to the continued increase in agricultural production and profitability in the Baltic region, and these results will be useful in identifying critical areas requiring improved management practices to reduce water contamination by pesticides.