我国低纬度、亚热带地区的降水化学及其雨水酸化趋势分析

在世界上酸沉降研究尚为空白的低纬度、亚热带地区建立了酸沉降监测网，通过两年的监测，结果表明降水中酸度和离子总浓度季节变化明显，ＳＯ４＾２－，Ｃａ＾２＋和ＮＨ４＾＋在降水离子构成中占百分率较高，阳离子总和略大于阴离子总和，两广地区降水酸度是水中多种阴、阳离子综合作用的结果，降水中ＳＯ４＾２－浓度高的地区是ＳＯ２排放量高的地区，控制雨水逐年酸化趋势的唯一途径是限制ＳＯ２排放。     

黄海西部大气湿沉降(降水)的离子平衡及离子组成研究

对黄海西部的千里岩、青岛的麦岛两个降水采样点１９９７、１９９８两年收集的１１３个降水样品进行了分析,测定了Ｈ＾＋、ＮＨ４＾＋、Ｋ＾＋、Ｎａ＾＋、Ｃａ＾２＋、Ｍｇ＾２＋、Ｆ＾－、Ｃ１＾－、ＮＯ３＾－、ＳＯ４＾２－共１０种离子成分的含量。计算了阴离子和阳离子的浓度总量,考察了∑－／∑＋值,对所８测１０种离子的含量顺序进行了探讨。结果表明：１１０个样品离子平衡（∑－／∑＋在０．７５～１．２５之间）,３个     

瓦里关山降水化学特征的初步分析

报告了１９９７年在中国大气本底基准观象台（观测站点位于青海省瓦里关山）的降水化学观测结果，该站点位于我国北方高原的半干旱地区，周围较少有局地污染排放源影响，对获的５９个降水样品进行了ｐＨ值、电导率和可溶性离子成分的分析，其结果显示，该地降水的年平均ｐＨ值为６．４，呈中性；年平均电导率为１４．８μＳ／ｃｍ，降水较为洁净；降水中的主要离子成分依次为ＮＨ＾＋４，Ｃａ＾２＋，ＳＯ＾２－４，Ｍｇ＾２＋，Ｎａ     

南京市降水化学成分特征及变化趋势

通过对１９９２－１９９８年南京市降水化学成分特征及其变化趋势的分析，表明南京市降以化明显，但无恶化迹象，降水化学成分中ＳＯ＾２－４对酸化起主要作用，但其作用呈下降趋势，而ＮＯ＾－３，Ｃｌ＾－的作用呈上升趋势。Ｃａ＾２＋，ＮＨ＾４＋在中和降水的酸性方面起十分重要的作用，Ｃａ＾２＋的作用逐渐减弱，而ＮＨ＾＋４的作用则逐渐增大。     

黄海西部大气湿沉降(降水)的pH与主要酸碱离子的关系

对黄海西部的千里岩、青岛的麦岛两个降消要样点１９９７、１９９８丙年所收集的１１３个降 Ｈ＾＋、ＮＨ４＾＋、Ｋ＾＋、Ｎａ＾＋、Ｃａ＾２＋、Ｍｇ＾２＋、Ｆ＾－、Ｃｌ＾－、ＮＯ３＾－、ＳＯ４＾２－共１０种离子成分的含量，分别用ＮＡ＾＋、Ｍｇ＾２＋、Ｃａ＾２＋＋ＮＨ４＾＋）／（ＮＯ３＋ｎｓａＳＯ４＾２－、ｃｍｓｓＳＯ４＾２－（ｎｓｓＳＯ４＾２－）的相关分析。结果表明：（１）以Ｍｇ＾２＋作为参考元素计算得到     

青岛市酸雨污染的状况及发展趋势

本文研究青岛市酸雨污染的状况及其发展趋势。研究结果表明，近年来青岛市酸雨污染相当严重，并有逐年加重的趋势。近年来，青岛市降水酸度ｐＨ峰值的平均值为３．４８，降水酸度ｐＨ的平均值为４．４７，酸雨的频率大于６３％。研究还表明，ＳＯ４＾２－和ＮＯ３＾－是降水的主要污染物，其浓度平均值为１９４μｅｑ／ｌ；而ＳＯ４＾２－是降水的最主要的污染物，平均浓度为１８１μｅｑ／ｌ。青岛市酸雨污染属于硫酸型污染。预测表     

二氧化氮气体氧化亚硫酸根的反应机理

在有氧和无氧条件下，利用罗曼光谱测定反应生成物的方法，研究了ＮＯ２和含ＳＯ＾２－３溶液的反应机理，反应的生成物中含有ＮＯ－３，ＳＯ２－４和Ｓ２Ｏ２－５，反应的初始产物是ＮＯ－２离子和ＳＯ－３，基团：ＮＯ２＋ＳＯ＾２－３→ＮＯ＾－２＋ＳＯ＾－３。ＳＯ＾－３基团可以进行重组，或与氧反应生成ＳＯ－３基团。在无氧条件下，（ＳＯ＾２－４）／（Ｓ２Ｏ＾２－３）＝１．８±０．３，反映ＳＯ＾－３基团重组的反应如下     

我国部分城市降水中离子浓度与pH值的关系研究

为了对酸雨的危害进行有效地控制，有必要研究降水中某些离子的浓度与降水ｐＨ值的关系．应用投影寻踪回归新技术，建立了以某些离子作因子的我国部分城市降水ｐＨ值的投影寻踪预测模型，并计算了各离子对降水ｐＨ值的权重贡献率．结果表明这些城市降水ｐＨ值不但受酸性离子［ＳＯ４２－］和［ＮＯ３－］的影响，而且也强烈地受碱性离子［Ｃａ２＋］和［ＮＨ４＋］的影响．     

地下水中硒存在形态的分析方法

本文采用含高浓度Ｍｇ＾２＋和ＳＯ４＾２－的三种地下水样，在ＰＨ〈５条件下，地下水样中的ＳｅＯ３＾２－和ＳｅＯ４＾２－选择性地吸附于ＣｕＯ颗粒物上，然后在ＰＨ＝１２．５时解吸。接着用ＨＧＡＡＳ和ＩＣ法分别测出ＳｅＯ３＾２－，ＳｅＯ４＾２－浓度。并对二阶阳离子影响水中ＳｅＯ４＾２－的测定作了估算。     

胶东半岛可吸入尘酸碱特性的季节变化研究

胶东半岛大气可吸入尘酸碱特性呈现出明显的季节变化，青岛市区ＩＰ中离子浓度冬夏两季均高于平度和薜家岛特别是夏季。冬季ＳＯ４＾２－，ＮＨ４＾＋要明显高于夏季，大致是夏季的２－３倍，其它离子变化不大。ＳＯ４＾２－为ＩＰ中的主要阴离子，占总阴离子的７０％以上，ＮＨ４＾＋为ＩＰ中的主要阳离子，约占总量的４０－５０％。     

Evaluation of phytoextracting cadmium and lead by sunflower, ricinus, alfalfa and mustard in hydroponic culture

Soil contaminated with heavy metals cadmium(Cd)and lead(Pb)is hard to be remediated.Phytoremediation may be a feasible method to remove toxic metals from soil,but there are few suitable plants which can hyperaccumulate metals.In this study,Cd and Pb accumulation by four plants including sunflower(Helianthus annuus L.),mustard(Brassica juncea L.),alfalfa(Medicago sativa L.), ricinus(Ricinus communis L.)in hydroponic cultures was compared.Results showed that these plants could phytocxtract heavy metals, the ability of accumulation differed with species,concentrations and categories of heavy metals.Values of BCF(bioconcentration factor)and TF(translocation factor)indicated that four species had dissimilar abilities of phytoextraction and transportation of heavy metals.Changes on the biomass of plants,pH and Eh at different treatments revealed that these four plants had distinct responses to Cd and Pb in cultures.Measurements should be taken to improve the phytoremediation of sites contaminated with heavy metals,such as pH and Eh regulations,and so forth.     

Oxidation of As(Ⅲ) by potassium permanganate

The oxidation of As(Ⅲ) with potassium permanganate was studied under conditions including pH, initial As(Ⅲ) concentration and dosage of Mn(Ⅶ). The results have shown that potassium permanganate was an effective agent for oxidizing of As(Ⅲ) in a wide pH range. The pH value of tested water was not a significant factor affecting the oxidation of As(Ⅲ) by Mn(Ⅶ). Although theoretical redox analyses suggest that Mn(Ⅶ) should have better performance in oxidization of As(Ⅲ) within lower pH ranges, the experimental results show that the oxidation efficiencies of As(Ⅲ) under basic and acidic conditions were similar, which may be due to the adsorption of As(Ⅲ) on the Mn(OH)2 and MnO2 resulting from the oxidation of As(Ⅲ).     

Chlorobenzenes in waterweeds from the Xijiang River （Guangdong section） of the Pearl River

The Xijiang River is the major source of water for about 4.5 millions of urban population and 28.7 millions of rural population. The water quality is very important for the health of the rural population. The concentration and distribution of chlorobenzenes (CBs) in both water and waterweeds collected from 4 stations in the Xijiang River (Gangdong section) of the Pearl River in April and November were determined. The result showed that nearly every congener of CBs was detected. The total contents of CBs (∑CBs) in the river water ranged from 111.1 to 360.0 ng/L in April and from 151.9 to 481.7 ng/L in November, respectively. The pollution level of CBs in the water in April was higher than that in November. The contents of ∑ CBs in waterweeds ranged from 13.53×102 μg/g to 38.27×102μg/g dry weight (dw). There was no significant difference between April and November in waterweeds. The distribution of CBs in roots, caulis, and leaves of Vallisneria spiralis L. showed different patterns. The leaves mainly contained low-molecular-weight CBs(DCBs), whereas the roots accumulated more PCBs and HCBs. The average lgBCFlip (bioconcentration factor) of CBs ranged from 0.64 to 3.57 in the waterweeds. The spatial distribution character of CBs in the Xijiang River was: Fengkai County ＜ Yunan County ＜Yun'an County ＜ Gaoyao County according to the ∑CBs, and the pollution deteriorated from the upstream to the downstream of the Xijiang River. Further analysis demonstrated that the discharge of waste containing CBs may be the main source of CBs pollution in the Xijiang River.     

Degradation of 2,4-dichlorophenol with a novel TiO2/Ti-Fe-graphite felt photoelectrocatalytic oxidation process

Degradation of 2,4-dichlorophenol(2,4-DCP)was studied in a novel three-electrode photoelectrocatalytic(PEC)integrative oxidation process,and the factors influencing the degradation rate,such as applied current,flow speed of O_2,pH,adscititious voltage and initial 2,4-DCP concentration were investigated and optimized.H_2O_2 was produced nearby cathode and Fe~(2 )continuously generated from Fe anode in solution when current and O_2 were applied,so,main reactions,H_2O_2-assisted TiO_2 PEC oxidation and E-Fenton reaction,occurred during degradation of 2,4-DCP in this integrative system.The degradation ratio of 2,4-DCP was 93% in this integrative oxidation process,while it was only 31% in E-Fenton process and 46% in H_2O_2-assisted TiO_2 PEC process.So,it revealed that the degradation of 2,4-DCP was improved greatly by photoelectrical cooperation effect.By the investigation of pH,it showed that this integrative process could work well in a wide pH range from pH 3 to pH 9.     

Effect of copper on the degradation of pesticides cypermethrin and cyhalothrin

The influence of coexisting copper (Cu) ion on the degradation of pesticides pyrethroid cypermethrin and cyhalothrin in soil and photodegradation in water system were studied.Serial concentrations of the pesticides with the addition of copper ion were spiked in the soil and incubated for a regular period of time,the analysis of the extracts from the soil was carried out using gas chromatography (GC).The photodegradation of pyrethroids in water system was conducted under UV irradiation.The effect of Cu~(2 ) on the pesticides degradation was measured with half life (t_(0.5)) of degradation.It was found that a negative correlation between the degradation of the pyrethroid pesticides in soil and Cu addition was observed.But Cu~(2 ) could accelerate photodegradation of the pyrethroids in water.The t_(0.5) for cyhalothrin extended from 6.7 to 6.8 d while for cypermethrin extended from 8.1 to 10.9 d with the presence of copper ion in soil.As for photodegradation,t_(0.5) for cyhalothrin reduced from 173.3 to 115.5 rain and for cypermethrin from 115.5 to 99.0 min.The results suggested that copper influenced the degradation of the pesticides in soil by affecting the activity of microorganisms.However, it had catalyst tendency for photodegradation in water system.The difference for the degradation efficiency of pyrethroid isomers in soil was also observed.Copper could obviously accelerate the degradation of some special isomers.     

Effects of arsenic on seed germination and physiological activities in wheat seedlings

The effects of arsenic(As)were investigated on seed germination,root and shoot length and their biomass and some other factors to elucidate the toxicity of As.The results showed low concentrations of As(O-1 mg/kg)stimulated seed germination and the growth of root and shoot,however,these factors all decreased gradually at high concentrations of As(5-20 mg/kg).The contents Of O2-,MDA,soluble protein and peroxidase(POD)activity all increased with increasing As concentrations.Soluble sugar content,ascorbate peroxidase(APX),and superoxide dismutase(SOD)activities decreased at low concentrations of As,and increased at high concentrations of As.While acetylsalicylic acid(ASA)and chlorophyll contents,catalase(CAT)activity displayed increasing trend when the concentrations of As was lower than 1 mg/kg,and then decreasing trend.By polyacrylamide gel electrophoresis(PAGE).As induced the expression of POD isozymes of wheat seedlings.As induced the expression of CAT isozymes but inhibited the expression of SOD isozymes of wheat seedlings at concentrations lower than 1 mg/kg.However,As inhibited the expression of CAT isozymes but induced the expression of SOD isozymes at concentrations higher than 5 mg/kg.The results indicated As could exert harmfulness in the early development stage of wheat at inappropriate concentrations.     

Sustainability： A view from the wind-eroded field

This article explores the assessment of sustainability in fields subject to wind erosion. In the first part, simple sustainability audits are examined, as of soil depth and nutrients. Direct measurement of these characteristics has many problems, largely because of huge variability in space and time at all scales. Modelling still has its problems, but it may be possible to overcome many of them soon. It is true that wind erosion preferentially removes soil nutrients, but there are imponderables even here. The nutrient balance in many of these soils includes considerable input from dust. In West Africa, it has been shown that the amounts of calcium and potassium that are added in dust are sufficient to fertilize dispersed crops. In mildly acidic sandy soils, such as those found on the widespread palaeo- aeolian deposits, much of the phosphorus is fixed and unavailable to plants by the time it is removed by wind erosion, so that erosion has no added downside. Most of the nutrients carried by dust have been shown to travel close to the ground （even when they are attached to dust-sized particles）, and so are trapped in nearby fallow strips, and are thus not lost to the farming system. Second, the sustalnabillty of a whole semi-arid farming system is explored. Wind erosion in semi-arid areas （like China, the Sahel and Norflawestern Europe） generally takes place on aeolian deposits of the recent geological past. Most of these soils are deep enough to withstand centuries of wind erosion before they are totally lost to production, and some of these soils have greater fertility at greater depth （so that wind erosion may even improve the soil）. Finally some remarks are made about environmental change in relation to sustainability.     

Bioconcentration kinetics of PCBs in various parts of the lifecycle of the tadpoles Xenopus laevis

Polychlorinated biphenyls （PCBs） in Xenopus laevis have been reported only for a few congeners. Additionally, there is very little information on the ability of Xenopus laevis to bioconcentrate PCBs. To address these issues, the tadpole Xenopus laevis was exposed to Aroclor 1254 mixtures in water at room temperature for 110 d followed by an additional 110 d of nonspiked PCBs in the water for the control group. During the whole process, bioconcentration factors （BCFs） of PCBs ranged from 1180 to 15670. For most PCB congeners, the highest and lowest bioconcentrations of the kinetic curves were found to be remarkably simultaneous, respectively. All 141 PCB congeners under the same experimental conditions had no linear correlation on the lgBCF versus lgKow relationship. The relationship between lgBCFs and lgKow followed a parabolic pattern indicative of selective bioconcentration, suggesting that the kinetic curves of the PCB congeners observed in the lifecycle of the tadpoles may be concentrated due to the amphibian special species and internal metabolism. In contrast, lgBCFs for PCBs were inversely related to lgKow, suggesting that a metabolism of the higher Kow PCB congeners occurred. These results support the author＇s conclusion that the tadpole Xenopus laevis plays major roles in the bioconcentration of PCB congeners, and demonstrated that the exposure kinetic curves of PCB congeners are complex. Besides the amphibian metamorphous development, the lifecycle of the tadpole Xenopus laevis also may be of importance in determining the bioconcentration of PCB congeners.     

Amplification of plasmid DNA bound on soil colloidal particles and clay minerals by the polymerase chain reaction

Polymerase chain reaction(PCR)was used to amplify a 600-base pair(bp)sequence of plasmid pGEX-2T DNA bound on soil colloidal particles from Brown soil(Alfisol)and Red soil(Ultisol),and three different minerals(goethite,kaolinite,montmorillonite). DNA bound on soil colloids,kaolinite,and montmorillonite was not amplified when the complexes were used directly but amplification occurred when the soil colloid or kaolinite-DNA complex was diluted,10- and 20-fold.The montmorillonite-DNA complex required at least 100-fold dilution before amplification could be detected.DNA bound on goethile was amplified irrespective of whether the complex was used directly,or diluted 10- and 20-fold.The amplification of mineral-bound plasmid DNA by PCR is,therefore,markedly influenced by the type and concentration of minerals used.This information is of fundamental importance to soil molecular microbial ecology with particular reference to monitoring the fate of genetically engineered microorganisms and their recombinant DNA in soil environments.     

Arsenic uptake and transport of Pteris vittata L. as influenced by phosphate and inorganic arsenic species under sand cu｜ture

In order to understand the similarity or difference of inorganic As species uptake and transport related to phosphorus in As-hyperaccumulator, uptake and transport of arsenate (As(Ⅴ)) and arsenite (As(Ⅲ)) were studied using Pteris vittata L. under sand culture. Higher concentrations of phosphate were found to inhibit accumulation of arsenate and arsenite in the fronds of P. vittata. The reduction in As accumulation was greater in old fronds than in young fronds, and relatively weak in root and rhizome. Moderate increases, from 0.05 to 0.3 mmol/L, in phosphate reduced uptake of As(Ⅲ) more than As(Ⅴ), while the reverse was observed at high concentrations of phosphate (≥ 1.0 mmol/L). Phosphate apparently reduced As transport and the proportion of As accumulated in fronds of P. vittata when As was supplied as As(Ⅴ). It may in part be due to competition between phosphorus and As(Ⅴ) during transport. In contrast, phosphate had a much smaller effect on As transport when the As was supplied as As(Ⅲ). Therefore, the results from present experiments indicates that a higher concentration of phosphate suppressed As accumulation and transport in P. vittata, especially in the fronds, when exposure to As(Ⅴ); but the suppression of phosphate to As transport in the root or rhizome may be insignificant when P. vittata when exposure to As(Ⅲ) under sand culture conditions. The finding will help to understand the interaction of P and As during their uptake process in P. vittata.