Effects of organic acids on Cd adsorption and desorption by two anthropic soils

The objective of this experiment was to study the effects of malic, tartaric, oxalic, and citric acid on the adsorption and desorption characteristics of Cd by two typical anthropic soils (lou soil and irrigation-silted soil) in North-west China. Cadmium adsorption and desorption were studied under a range of temperatures (25°C, 30°C, 35°C, 40°C), organic acid concentrations (0.5–5.0 mmol·L^-1), and pH values (2–8). The results showed that the Cd adsorption capacity of the lou soil was significantly greater than that of the irrigation-silted soil. Generally, Cd adsorption increased as the temperature increased. In the presence of NaNO₃, the adsorption of Cd was endothermic with ΔH values of 31.365 kJ·mol^-1 for lou soil and 28.278?kJ·mol^-1 for irrigation-silted soil. The endothermic reaction indicated that H bonds were the main driving force for Cd adsorption in both soils. However, different concentrations of organic acids showed various influences on the two soils. In the presence of citric acid, chemical adsorption and van der Waals interactions were the main driving forces for Cd adsorption rather than H bonds. Although the types of organic acids and soil properties were different, the effects of the organic acids on the adsorption and desorption of Cd were similar in the two soils. The adsorption percentage of Cd generally decreased as organic acid concentrations increased. In contrast, the adsorption percentage increased as the pH of the initial solution increased. The exception was that adsorption percentage of Cd increased slightly as oxalic acid concentrations increased. In contrast, the desorption percentage of Cd increased with increasing concentrations of organic acids but decreased as the initial solution pH increased.     

The abatement of major pollutants in air and water by environmental catalysis

This review reports the research progress in the abatement of major pollutants in air and water by environmental catalysis. For air pollution control, the selective catalytic reduction of NO _x (SCR) by ammonia and hydrocarbons on metal oxide and zeolite catalysts are reviewed and discussed, as is the removal of Hg from flue gas by catalysis. The oxidation of Volatile organic compounds (VOCs) by photo- and thermal-catalysis for indoor air quality improvement is reviewed. For wastewater treatment, the catalytic elimination of inorganic and organic pollutants in wastewater is presented. In addition, the mechanism for the procedure of abatement of air and water pollutants by catalysis is discussed in this review. Finally, a research orientation on environment catalysis for the treatment of air pollutants and wastewater is proposed.     

厌氧氨氧化工艺的抑制现象

厌氧氨氧化(Anammox)工艺因其高效低耗优势,在废水生物脱氮领域中具有广阔的应用前景.然而,基质、有机物、盐度、重金属、磷酸盐及硫化物等物质对Anammox工艺产生的抑制作用制约了工艺的推广应用.基质主要通过游离氨和游离亚硝酸对Anammox产生抑制,而温度和pH是基质抑制的重要调控参数.非致毒性有机物对Anammox的作用因其种类跟浓度而异.在较低的浓度条件下对Anammox的抑制作用不显著,而高于抑制阈值将严重抑制Anammox.其抑制机制尚无定论.部分研究证明致毒性有机物(醇、醛、酚及抗生素等)对Anammox具有抑制作用,但研究有待拓展深化.超过抑制阈值的盐度会抑制Anammox活性,但合适的盐度(3~15 g L-1NaCl)却能够促进Anammox生物颗粒的形成.重金属对Anammox的抑制报道较少.因试验条件及菌种等的差异使得磷酸盐及硫化物对Anammox的抑制在不同试验中存在很大差异.Anammox抑制是可控的,通过pH和温度调节、基质浓度及负荷控制、污泥驯化以及添加辅助剂等方法可解除或缓解抑制.建议今后在特种废水的Anammox脱氮、复合抑制以及Anammox抑制的分子生态学机理等方面开展深入研究.     

两相分配生物反应器治理高浓度有机污染研究进展

高浓度有机污染物难以进行生物降解的主要原因之一是其会对微生物产生较大毒害作用而抑制微生物生长以及降解过程,而两相分配生物反应器(Two-phase partitioning bioreactor,TPPB)可以有效解决污染物毒性的问题,因而在高浓度有机污染治理中具有较大的应用潜力.本文系统介绍了TPPB类型以及各自的工作原理,即TPPB通过非水相的引入可以溶解系统内大部分有机污染物,减少水相中污染物的浓度,降低其对微生物的毒性,并通过微生物的代谢活动实现污染物的降解,随着降解过程的进行污染物在两相间的分配平衡不断被打破,污染物又不断从非水相进入到水相之中,使得微生物的降解过程持续进行.同时分析了反应过程中的各种影响因素,如传质速率、微生物影响等,进而阐述了该技术在水体、土壤、大气污染治理中的应用,最后根据目前的研究进展,对TPPB技术的工程应用前景进行了展望.     

降水变化、氮添加对鼎湖山主要森林土壤有机碳矿化和土壤微生物碳的影响

全球变化对土壤有机碳(SOC)存贮与分解的影响在全球碳(C)循环中具有重要地位.分别通过室内土壤培养法和氯仿熏蒸法,研究了降水变化和氮(N)添加处理对鼎湖山3种不同演替阶段的季风常绿阔叶林、针阔混交林和马尾松针叶林SOC矿化和土壤微生物量碳(SMBC)的影响.结果表明:1)降水量增加能够提高森林演替晚期SOC累积矿化量和矿化速率,而对森林演替早期SOC累积矿化量和矿化速率没有显著影响(P>0.05).2)干旱条件(降水量减少)降低森林SMBC含量,且在鼎湖山季风林表层土壤(0～10 cm)中SMBC的减少达到显著水平(P<0.05).3)N添加处理对鼎湖山3种森林类型SOC累积矿化量、矿化速率以及SMBC都没有显著影响(P>0.05).未来关于SOC矿化对全球变化响应的研究,要综合考虑土壤有机质质量、C/N比例、外源性氮输入等因素的作用.图4表2参37     

硝基化合物的高效液相色谱(HPLC)分析

硝基化合物是炸药废水的主要成分,大部分硝基化合物具有较高的毒性.本文对奥克托今、黑索今、1,3,5-三硝基苯、1,3-二硝基苯、硝基苯、2,4,6-三硝基甲苯、2-氨基-4,6-二硝基甲苯、2,4-二硝基甲苯共8种硝基化合物的紫外光谱和液相色谱分离条件进行了研究,其最佳检测波长分别为228 nm、227 nm、227 nm、237 nm、272 nm、230 nm、226 nm、244 nm.本文建立了8种硝基化合物的高效液相色谱测定方法,色谱条件为:色谱柱为ZORBAX SB-C18(3.0 mm×250 mm,5μm),检测器为紫外检测器,流动相为甲醇-水(50∶50),流速为0.5 mL.min-1.水中8种硝基化合物可以在13 min内得到较好的分离,检出限均≤0.8 ng,回收率大于95%.     

土壤和沉积物中有机质对双酚A和17α-乙炔基雌二醇的吸附行为

研究了土壤和沉积物原始样品bulk及其有机质组分(非水解性有机质NHC、碳黑BC和腐殖酸HA)对17α-乙炔基雌二醇(EE2)和双酚A(BPA)的吸附行为.所有的吸附等温线都很好地拟合了Freundlich模型,除HA和bulk外,所有的吸附等温线都为显著的非线性(n值为0.46—0.76).对于EE2和BPA的吸附非线性因子n值都存在这样的关系:HA>NHC>BC.EE2以有机碳归一化的Freundlich吸附能力(lgKOC)有BC>NHC>bulk>HA的关系,说明有机质成熟度越高,对EE2或者BPA的吸附能力越高.在土壤和沉积物有机质SOM(NHC、BC和HA)对吸附BPA和EE2的贡献上,NHC、BC和HA对沉积物和土壤对BPA总吸附贡献上要明显弱于它们对EE2的贡献.除了内分泌干扰物(EDCs)的疏水性影响EE2和BPA的吸附能力的差异外,分子大小和带电子苯环数也影响它们的吸附能力差异.     

超高效液相色谱串联质谱法检测鱼体中的全氟化合物

采用超高效液相色谱-串联质谱联用法(UPLC-ESI-MS/MS),建立了检测1种贝类和2种鱼类的肌肉组织中11种全氟化合物(PFCs)的分析方法.采用碱液消解做为样品前处理法,选Carbon/NH2双层SPE小柱做为净化小柱,并以ACQUITY UPLC BEH C18为分析柱,甲醇和2 mmol.L-15%甲醇乙酸铵溶液为梯度淋洗液.所选定的11种全氟化合物在6 min内就可以达到良好分离,外标法定量.平均回收率在72.1%—93.6%之间,相对标准偏差在0.6%—9.5%之间,实际检出限在3.4—26.7 pg.g-1.     

Effects of a diesel oxidation catalyst on gaseous pollutants and fine particles from an engine operating on diesel and biodiesel

The effects of a diesel oxidation catalytic (DOC) converter on diesel engine emissions were investigated on a diesel bench at various loads for two steady-state speeds using diesel fuel and B20. The DOC was very effective in hydrocarbon (HC) and CO oxidation. Approximately 90%–95% reduction in CO and 36%–70% reduction in HC were realized using the DOC. Special attention was focused on the effects of the DOC on elemental carbon (EC) and organic carbon (OC) fractions in fine particles (PM_2.5) emitted from the diesel engine. The carbonaceous compositions of PM_2.5 were analyzed by the method of thermal/optical reflectance (TOR). The results showed that total carbon (TC), OC and EC emissions for PM_2.5 from diesel fuel were generally reduced by the DOC. For diesel fuel, TC emissions decreased 22%–32% after the DOC depending on operating modes. The decrease in TC was attributed to 35%–97% decrease in OC and 3%–65% decrease in EC emissions. At low load, a significant increase in the OC/EC ratio of PM_2.5 was observed after the DOC. The effect of the DOC on the carbonaceous compositions in PM_2.5 from B20 showed different trends compared to diesel fuel. At low load, a slight increase in EC emissions and a significant decrease in OC/EC ratio of PM_2.5 after DOC were observed for B20.     

Characterization of soil low-molecular-weight organic acids in the Karst rocky desertification region of Guizhou Province, China

Soil low-molecular-weight (LMW) organic acids play important roles in the soil-forming process and the cycling of nutrients in Karst regions. In this study, we quantified the contents of LMW organic acids (including lactate, acetate, formate, malate, and oxalate) in soil solution over the Karst region of Guizhou Province, China using ion chromatography. The concentration of total LMW organic acids in topsoil solution ranged from 0.358 to 1.823 μmol·g^-1, with an average of 0.912 μmol·g^-1. The mean concentrations of lactate, acetate, formate, malate, and oxalate were 0.212±0.089, 0.302±0.228, 0.301±0.214, 0.014±0.018 and 0.086±0.118 μmol·g^-1, respectively. There were also significant difference in the contents of these acids among four phases of rocky desertification, and their concentrations decreased with the aggravation of rocky desertification. The concentrations of the LMW organic acids were significantly positive correlated each other. Significant positive correlations were also observed among individual LMW organic acids in soil solution, and between them and soil available P, available K, exchangeable Ca, respectively. Furthermore, the concentrations of LMW organic acids were significantly positively correlated with inorganic anions (chlorides, nitrates, and sulfates) in Karst topsoil solution. Therefore, the concentrations of soil LMW organic acids might be one of driving force in the Karst rock desertification process in Guizhou Province.