高铁酸盐氧化絮凝去除水中腐殖质的研究

研究了高铁酸盐对饮用水中富里酸（ＦＡ）的去除性能与作用条件，考察了高铁酸盐单独氧化、氧化絮凝和与聚合氯化铝联合应用的除ＦＡ效果。结果表明，当高铁酸钾与ＦＡ的质量比为１２时，高铁酸盐氧化可以去除水中９０％以上的ＦＡ，在浑浊水中高铁酸盐具有氧化和絮凝的双重作用效能，同样高铁酸盐投加量下，可将９５％以上的ＦＡ去除。采取高铁酸盐与聚合铝联用可显提高对ＦＡ的去除效果。     

高铁酸盐氧化絮凝去除藻类的机制

 研究了高铁酸盐氧化絮凝去除水中藻类的机制.结果表明,高铁酸盐的强氧化性对藻类呼吸作用和生长方式有影响,同时其还原产物Fe(OH)3对藻类有絮凝作用,因此高铁酸盐对水中藻类的去除是氧化和絮凝协同作用的结果.采用聚合氯化铝(PAC)作絮凝剂,投加少量高铁酸盐可以明显地影响藻类细胞表面的电动电势,强化PAC的电位和絮凝效果.     

高铁酸盐溶液的制备与去除氨氮的实验研究

根据现场制备要求,优化传统高铁制备工艺,得出工业化现场制备液体高铁的最佳工艺条件,进而用于水库水氨氮的去除研究。实验结果表明,通过优化工艺所制得高铁浓度为24 g/L左右,铁转化率为80%左右。高铁对氨氮的去除效果随高铁与氨氮的摩尔比增大而增大,当摩尔比为0.45时,高铁对水源水中氨氮的去除率可达75%;在保证高去除率的基础上,通过延长絮凝反应时间,可降低高铁投加量;如果采用高铁预氧化,聚合铝或三氯化铁作絮凝剂,可提高对氨氮的去除率,还能大幅度降低高铁投加量,缩短反应时间。     

氧化絮凝复合剂(XOF)去除源水氨氮的实验研究

研究了复合药剂（XOF）对饮用源水中氨氮的去除效果，并考察了投加量、反应时间、pH等因素对去除效率的影响。结果表明，XOF在浑浊水中充分利用氧化絮凝协同作用对氨氮有较高的 作效果，在pH值为7－8、投加量为药剂与氨氮质量比10：1、反应时间20min的条件下，复合药剂（XOF）以氨氮去除率最高。     

高铁氧化去除饮用水中邻氯苯酚的研究

采用自制的固体高铁酸钾作为氧化剂，研究高铁对水中微量邻氯苯酚的去除效果及主要影响因素。结果表明，当水中邻氯苯酚的含量为4mg/L时，加入60mg/L的K2FeO4氧化处理10min，对邻氯苯酚的去除率可达99．3％。取得高铁酸钾对邻氯苯酚的最佳氧化去除效果的pH范围为9－10，高铁氧化邻氯苯酚近似的二级动力学反应。     

高铁酸盐预氧化对颤藻去除效果及机理的研究

以深圳市铁岗水库水源为主要研究对象，通过与单纯投加聚合氯化铝（PAC）相比，研究了高铁酸盐预氧化对铁岗水中颤藻（Oscillatoria)的去除效能，藻类去除率高达97．85％。证明在处理较难去除的颤藻时，高铁酸盐与PAC联用，可显著提高对藻类的去除效能，初步研究了预氧化方法对水中颤藻去除的机理。     

电絮凝法同步去除氨氮和磷的模拟试验

采用电絮凝法去除废水中的氨氮和磷,电极板采用铝板或不锈钢板,研究了电絮凝除磷热力学与动力学过程,考察了不同工艺参数对氨氮和磷去除效果的影响.结果表明:相对于铝电极而言,不锈钢电极更适宜于电絮凝去除氨氮和磷;RedlichPeterson方程能较好地描述电絮凝产生的絮凝体对磷的吸附行为,得到的Gibbs自由能变都在-20～0 kJ/mol范围内,并且吸附是自发进行的吸热过程,升高温度有利于吸附;由于假二级动力学方程拟合时其相关系数(R2)均大于0.98,故假二级动力学方程更适宜描述电絮凝产生的絮凝体对磷的吸附动力学过程;随着电流密度的增加,氨氮和磷的去除率呈逐渐上升趋势;在强碱性条件下,氨氮的去除率相对降低,酸性条件下水中磷的去除率较高,随着溶液pH的增高,磷的去除率呈逐渐降低趋势.去除氨氮和磷的能耗分别为0.15 ～0.50和0.02～0.04 kW·h/g.     

电絮凝-过滤法去除源水中微量有机物

利用电絮凝-过滤法进行了源水中有机物去除的实验研究,探讨了电流密度、电解时间和pH值等因素对源水中TOC去除效果的影响。结果表明,在电极间距1.0cm,电流密度47.2 A/m2,初始TOC浓度为12.4mg/L时,反应12min后,出水浓度为3.60mg/L,TOC去除率可达71%。表明电絮凝法可有效去除源水中微量有机物。其去除机理包括电絮凝、电化学氧化和还原以及电气浮等。     

高铁酸盐对2种水源水中藻类的去除效果

研究了高铁酸盐对深圳2种原水水中藻类的去除效能.实验结果表明,在处理以小球藻为主的东湖水时,单纯PAC混凝就可有效地去除水中的藻类,藻类去除率均在95%左右.在处理含藻量多,以颤藻为主的铁岗原水时,单纯PAC混凝除藻效果不理想,投加少量高铁酸盐进行预氧化,再投加PAC混凝,可使水中藻的去除率提高10%～20%,去除率高达97.85%.而且用高铁预氧化除藻法明显优于传统预氯化方法.     

包埋固定化菌去除絮凝余水中氨氮的研究

研究采用聚乙烯醇（PVA）为载体的包埋固定化微生物处理低浓度氨氮絮凝余水,较短的水力停留时间（HRT）成功实现了氨氮的去除,在HRT为3h之内从地表水环境质量V类水标准以外达到了I类水标准,同时该菌对CODCr也有一定的去除能力,并系统的研究了HRT、颗粒填充率对絮凝余水处理效果的影响。     

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.     

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.     

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.     

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.