Selective removal of 2,4-dichlorophenoxyacetic acid from water by molecularly-imprinted amino-functionalized silica gel sorbent

A molecularly-imprinted amino-functionalized sorbent for selective removal of 2,4-dichlorophenoxyacetic acid(2,4-D) was prepared by a surface imprinting technique in combination with a sol-gel process.The 2,4-D-imprinted amino-functionalized silica sorbent was characterized by FT-IR,nitrogen adsorption and static adsorption experiments.The selectivity of the sorbent was investigated by a batch competitive binding experiment using an aqueous 2,4-D and 2,4-dichlorophenol(2,4-DCP) mixture or using an aqueous 2...     

洱海流域农田土壤氮素的矿化及其影响因素

采用好氧间歇淋洗培养法,对洱海流域内的农田、菜地土壤样品培养2周,研究土壤氮的矿化及其影响因素.结果表明,表层土壤2周氮矿化量平均为65.54mg/kg.不同农田利用方式下,表层土壤氮矿化量的平均值为露地菜田粮田大蒜田.土壤氮素矿化以硝态氮为主,且随着土壤深度的增加而降低.土壤氮矿化同全氮、有机质含量呈明显的正相关关系,与pH值呈负相关;氮矿化与无机氮含量、C/N之间无显著关系.全氮、有机质和pH值是影响该流域农田土壤矿化的主要因子.     

四川盆地紫色丘陵区不同种植模式下氮流失特征

氮素流失是农业面源污染的重要来源.为了解四川盆地紫色丘陵区不同种植模式下氮的流失特征,以四川盆地紫色丘陵区4种典型耕作模式紫云英-水稻(M1)、空地-大豆-空地(M2)、空地-生姜(M3)、空地-玉米+红薯(M4)等为研究对象,研究了4种模式从2008年12月到2009年8月共8次有效降雨中氮通过地表径流和渗透水的流失特征.研究期间,4种模式下氮流失量随着降雨量的增加而增加,总氮流失量表现为:M3((30.388±2.86)kg·hm-2)M4((17.118±1.677)kg·hm-2)M2((10.987±1.108)kg·hm-2)M1((6.090±1.051)kg·hm-2).相对于其它模式,M4模式下地表径流量和渗透水量在研究期间均最大,但M3模式下氮通过地表径流和渗透水的流失量最大.另外,非生长季节4个模式下氮流失量相对较低且各模式间差别较小,生长季节4个模式间可溶性氮和总氮通过地表径流和渗透水流失量均表现为M3M4M2M1.4种种植模式下氮通过地表径流和渗透水的流失形态均以硝态氮为主.渗透水中铵态氮和可溶性总氮占总氮的比例高于地表径流.这些结果为该区区域合理选择耕作模式、优化耕作方式、加强管理以控制区域农业面源污染提供了一定的基础数据.     

A comparative investigation of NdSrCu_(1-x) Co_x O_(4-δ) and Sm_(1.8) Ce_(0.2) Cu_(1-x) Co_x O_(4-δ) (x:0–0.4) for NO decomposition

A series of single-phase T-structured NdSrCu 1-x Co x O 4-δ with oxygen vacancies and T -structured Sm 1.8 Ce 0.2 Cu 1-x Co x O 4-δ (x: 0–0.4) with oxygen excess were prepared using ultrasound-assisted citric acid complexing method, and characterized by means of techniques such as thermogravimetric analysis and NO temperature-programmed desorption (NO-TPD). The catalytic activities of these materials were evaluated for the decomposition of NO. It was found that the NdSrCu 1-x Co x O 4-δ catalysts were of oxygen vacancies whereas the Sm 1.8 Ce 0.2 Cu 1-x Co x O 4-δ ones possessed excessive oxygen (i.e., over-stoichiometric oxygen); with a rise in Co doping level, the oxygen vacancy density of NdSrCu 1-x Co x O 4-δ decreased while the over-stoichiometric oxygen amount of Sm 1.8 Ce 0.2 Cu 1-x Co x O 4-δ increased. The NO-TPD results revealed that NO could be activated much easier over the oxygen-deficient perovskite-like oxides than over the oxygen-excessive perovskite-like oxides, with the NdSrCuO 3.702 catalyst showing the best efficiency in activating NO molecules. Under the conditions of 1.0% NO/helium, 2800 hr -1 , and 600–900°C, the catalytic activity of NO decomposition followed the order of NdSrCuO 3.702 NdSrCu 0.8 Co 0.2 O 3.736 NdSrCu 0.6 Co 0.4 O 3.789 Sm 1.8 Ce 0.2 Cu 0.6 Co 0.4 O 4.187 Sm 1.8 Ce 0.2 Cu 0.8 Co 0.2 O 4.104 Sm 1.8 Ce 0.2 CuO 4.045 , in concord with the sequence of decreasing oxygen vacancy or oxygen excess density. Based on the results, we concluded that the higher oxygen vacancy density and the stronger Cu 3+ /Cu 2+ redox ability of NdSrCu 1-x Co x O 4-δ account for the easier activation of NO and consequently improve the catalytic activity of NO decomposition over the catalysts.     

Catalytic performance of Fe3O4-CoO/Al2O3 catalyst in ozonation of 2-(2,4-dichlorophenoxy)propionic acid, nitrobenzene and oxalic acid in water

Fe3O4-CoO/Al2O3 catalyst was prepared by incipient wetness impregnation using Fe(NO3) 3·9H2O and Co(NO3) 2·6H2O as the precursors,and its catalytic performance was investigated in ozonation of 2-(2,4-dichlorophenoxy) propionic acid(2,4-DP) ,nitrobenzene and oxalic acid.The experimental results indicated that Fe3O4-CoO/Al2O3 catalyst enabled an interesting improvement of ozonation eciency during the degradation of each organic pollutant,and the Fe3O4-CoO/Al2O3 catalytic ozonation system followed a radical-type mechanism.The kinetics of ozonation alone and Fe3O4-CoO/Al2O3 catalytic ozonation of three organic pollutants in aqueous solution were discussed under the mere consideration of direct ozone reaction and OH radical reaction to well investigate its performance.In the catalytic ozonation of 2,4-DP,the apparent reaction rate constants(k) were determined to be 1.456×10-2 min-1 for ozonation alone and 4.740×10-2 min-1 for O3/Fe3O4-CoO/Al2O3.And O3/Fe3O4-CoO/Al2O3 had a larger Rct(6.614×10-9) calculated by the relative method than O3 did(1.800×10-9) ,showing O3/Fe3O4-CoO/Al2O3 generated more hydroxyl radical.Similar results were also obtained in the catalytic ozonation of nitrobenzene and oxalic acid.The above results demonstrated that the catalytic performance of Fe3O4-CoO/Al2O3 in ozonation of studied organic substance was universal to a certain degree.     

Cover crop effects on nitrous oxide emission from a manure-treated Mollisol

Agriculture contributes 40–60% of the total annual N₂O emissions to the atmosphere. Development of management practices to reduce these emissions would have a significant impact on greenhouse gas levels. Non-leguminous cover crops are efficient scavengers of residual soil NO₃, thereby reducing leaching losses. However, the effect of a grass cover crop on N₂O emissions from soil receiving liquid swine manure has not been evaluated. This study investigated: (i) the temporal patterns of N₂O emissions following addition of swine manure slurry in a laboratory setting under fluctuating soil moisture regimes; (ii) assessed the potential of a rye (Secale cereale L.) cover crop to decrease N₂O emissions under these conditions; and (iii) quantified field N₂O emissions in response to either spring applied urea ammonium nitrate (UAN) or different rates of fall-applied liquid swine manure, in the presence or absence of a rye/oat winter cover crop. Laboratory experiments investigating cover crop effects N₂O emissions were performed in a controlled environment chamber programmed for a 14 h light period, 18 °C day temperature, and 15 °C night temperature. Treatments with or without a living rye cover crop were treated with either: (i) no manure; (ii) a phosphorus-based manure application rate (low manure): or (iii) a nitrogen-based manure application rate (high manure). We observed a significant reduction in N₂O emissions in the presence of the rye cover crop. Field experiments were performed on a fine-loamy soil in Central Iowa from October 12, 2005 to October 2, 2006. We observed no significant effect of the cover crop on cumulative N₂O emissions in the field. The primary factor influencing N₂O emission was N application rate, regardless of form or timing. The response of N₂O emission to N additions was non-linear, with progressively more N₂O emitted with increasing N application. These results indicate that while cover crops have the potential to reduce N₂O emissions, N application rate may be the overriding factor.     

基于不同土壤数据单元法的DNDC模型对太湖地区水稻土CH4排放模拟研究

利用农业土壤痕量气体排放模型DNDC(DeNitrification-DeComposition),以整个太湖地区37个县234万hm2水稻土为例,分析了3种不同土壤数据单元法对CH4排放模拟的影响.其中,1∶5万图斑单元法土壤属性来自1∶5万土壤数据库,图斑为最小模拟单元;1∶5万"县级"单元法土壤属性也取自1∶5万土壤数据库,"县"为最小模拟单元;1∶1 400万"县级"单元法土壤属性取自国内同类研究使用最多的1∶1 400万土壤图和《中国土种志》,"县"为最小模拟单元.结果表明,虽然1∶5万图斑单元法大多数县的CH4排放量都在1∶5万"县级"单元法最大与最小值范围之间,但整个地区总排放量(以C计,下同)相差达到1 680 Gg;而1∶1 400万"县级"单元法CH4排放量与1∶5万图斑单元法相比,尽管整个地区总排放量只相差180 Gg,但各"县级"单元之间的估算差异却很大,这一方面说明了土壤数据的详细程度是保证地球生物化学模型模拟精度的重要因子,另一方面也说明在区域CH4排放量估算模拟中使用更详细的土壤资料是非常必要的.     

利用3S技术评价凌河口湿地生态环境质量

基于3S技术,利用中巴地球资源卫星解译数据,于2008年秋季对辽宁省锦州市凌河口湿地自然保护区的土地利用／土地覆盖现状进行野外核查,并结合对湿地进行的鸟类、鱼类、植被状况、空气、水体、土壤状况等调查,采用多样性、代表性、稀有性、自然性、稳定性和人类威胁等6项指标组成的湿地生态环境评价指标体系,对凌河口湿地生态环境质量进行了评价。结果表明,凌河口湿地生态环境处于较好水平。     

黄海鳀鱼中痕量金属浓度与体长的关系

测定了在黄海采集的各种体长的鳀鱼(Engraulis japonicus)中6种痕量金属(Zn、Cu、Fe、Al、Mn和Sr)和3种主要元素(C、N和P)的浓度.除Zn浓度在4～5倍内变动外,其余5种痕量金属浓度的变动范围均接近或超过一个数量级;并且,这6种金属均显示出了浓度随体长增长而下降的趋势.对于3种主要元素,N和P的含量也与体长存在负相关关系,而C却显示出了强烈的正相关关系.聚类分析表明,Zn和Cu在鳀鱼内的浓度变化较为接近,可能验证了这两种金属与生物体内新陈代谢活动较为密切的性质;而其余4种金属的浓度变化规律更为接近,可能反映了陆源输入的影响.     

低碳氮比猪场废水短程硝化反硝化-厌氧氨氧化脱氮

针对低碳氮比猪场废水传统脱氮法碳源不足的问题,采用SBBR反应器进行短程硝化反硝化-厌氧氨氧化联合脱氮.实验表明,短程硝化反硝化预处理可为厌氧氨氧化创造良好的进水条件;经预处理的猪场废水厌氧氨氧化脱氮效果显著,氨氮、亚硝态氮和总氮的平均去除率分别为91.8%、 99.3%、 84.1%,废水中残留有机物未对厌氧氨氧化效果产生明显影响,氨氮、亚硝态氮、硝态氮平均变化量之比为 1∶1.21∶0.24.色质联用分析结果显示,猪场废水中有机物成分在厌氧氨氧化反应前后未发生明显变化,主要化合物为酯类和烷烃类物质;特殊功能菌种检测结果表明,实验条件下的微生物系统是一个厌氧氨氧化菌与硝化菌、亚硝化菌和反硝化菌共存的系统,厌氧氨氧化菌是该系统主要脱氮功能菌.