固定化微生物对养殖水体中NH4^＋—N和NO2^——N转化作用

采用聚乙烯醇（PVA）（ρ＝gL^-1)的方法对沼泽红假单胞菌、诺卡氏菌和假丝酵母3种菌株进行固定化，所得的凝胶颗粒机械强度好，经久耐用，运用这3种菌株的固定化细胞对养殖水体中NH4^ -N和NO2^-－N进行转化，其最适作用温度范围为25－30℃，最适pH范围分别为：6．5－8．5，7．0－7．5及5．5－7．0，且对水质初始氮浓度有很强的适应性，3菌株经固定化后，其对养殖水体中NH4^ -NT和NO2^-－N的转化效率明显优于其游离细胞，若将3菌株按2：1：2组合成复合菌株并固定化，其以养殖水体中的NH4^ -N和NO2^-－N论效果将更佳。     

南黄海不同粒度表层沉积物中可转化氮与环境因子的关系

南黄海不同粒度表层沉积物中可转化氮的形成与释放受环境因子的驱动作用各不相同,上覆水体的温度、盐度、pH值、DO的含量以及NH4^ 和NO3^-的含量都对其有一定的影响．其中DO是不同形态的氮形成与释放最显著的影响因素,这是因为上覆水体中DO的含量愈高,扩散进入表层沉积物中的O2就愈多,沉积物处于相对氧化的环境中,有机质的矿化作用较易进行,致使无机形态氮的含量相对较高,而有机形态氮的含量相对较低,所以其与可转化有机形态氮呈负相关,而与可转化无机形态氮呈正相关．温度与中、细粒度沉积物中的SOEF-N的含量呈显著正相关,可能是因为温度的升高加快了海洋底栖生物的生长发育,使生物排泄物和死亡残体增多,尽管温度的升高加快了沉积物中有机质的矿化分解,但由于中、细粒度沉积物堆积紧密,对温度的响应不明显,致使SOEF-N的含量随温度的升高而升高．上覆水体中的NH;和NO3^-分别与中、细粒度沉积物中的SAEF-N和SOEF-N的含量呈正相关,说明上覆水体中的NH4^ 和NO3^-主要来自于沉积物中SAEF-N和SOEF-N的形成与释放．另外,粗粒度沉积物中不同形态的氮对环境的响应较中、细粒度沉积物中的强．     

毛细管离子分析方法测定湖水中主要无机阴离子含量

用毛细管离子分析方法分析阴离子（Br^-,Cl^-,SO4^2-,NO2^-,NO3^-,F^-,HPO4^2-,HCO3^-)的混合标准溶液，并测定了北京颐和园昆明湖表层水样中阴离子的含量，结果表明，用这种方法所做的标准曲线具有良好的线性相关关系，相关系数较好，比较不同季节表层湖水样品中阴离子的含量变化特征表明，在实验期间，表层湖水中阴离子含量在不同季节变化不明显。     

模拟太阳光作用下间甲酚的水相和冰相光转化研究

本文研究了在模拟太阳光作用下间甲酚的水相和冰相光转化规律.考察了不同浓度的H2O2、NO-2和NO3^-对间甲酚光转化的影响,建立了不同条件下间甲酚光转化的动力学方程.结果表明,在模拟太阳光作用下间甲酚在水相和冰相中均可以发生光转化,间甲酚的冰相光转化速率小于水相.在本实验条件下,H2O2和NO2^-促进了间甲酚在水相...     

三种载体上生物膜硝化作用动力学初步研究

通过测定水中COD、：NH4^ —N、NO2^-—N及NO3^-—N的浓度变化，研究了淹没式废水处理装置中沸石、活性炭和沙粒3种载体上硝化作用生物膜的动力学过程和反硝化作用。结果表明，3种载体上生物膜降解有机物(以COD表示)的过程可用一级动力学方程描述，反应速率常数分别为：沙粒0．0848h^-1、活性炭0．1187h^-1、沸石0．1334h^-1。3种载体上生物膜去除氨态氮的过程则可用零级动力学方程描述，反应速率常数分别为：沙粒-0．7743h^-1、活性炭-0．9886h^-1、沸石-1．0714h^-1．附着于沙上的生物膜去除亚硝酸盐氮的过程也可用零级动力学方程描述，反应速率常数为-0．6057h^-1，水中硝酸盐氮浓度较高时，载体沸石和活性炭上可能附着生长反硝化菌。图5表2参15。     

氮在水稻中的行为及其品种间的差别

目前氮肥的利用效率很低，很多研究重点放在氮肥在土壤过程中的损失，对植物本身的氮素损失较少注意。作者利用^15NH4^ 和^15NO3^-双标记，对Indica和Japonica水稻亚种进行水培，在分蘖期、幼穗分化期、开花期施用，将培养液ρ(N)20mg／L的NH4NO3换成相同质量浓度的^15NH4^ NO3或NH^15NO3^；部分水稻在一周后收获，其他分别在分蘖期、幼穗分化期、开花期、成熟期收获。植株分成根系、地上部和穗部，对各自的全氮、^15N进行测定，计算植物的总吸收量。从施用量、植株总吸收量以及三部分总和的植株氮残存量的比较来研究氮素在两种水稻亚种中的行为。研究结果表明，两种植物都近100％吸收了所施用的^15NH4NO3或NH4^15NO3，但^15NH4^ 和^15NO3^-在Japonica的残存量要比Indica多，损失的部分可能往大气中散失了，意味着两种水稻亚种有着明显不同的氮素利用率。比较^15NH4^ 和^15NO3^-的残存量，结果表明^15NH4^ 留在植株体内要比^15NO3^-多，尤其在抽穗期施用的情况下，植物体在后期对^15NO3^-的转化能力大大减弱，但这部分的氮如何损失掉尚不清楚。比较植株体内各部分的氮素含量，发现Japonica的穗部比Indica含有更多的氮素，表明氮在前者的体内转化效率和利用效率高。试验结果表明，不同水稻亚种对氮素的利用以及不同氮素形态在其体内的行为不同。     

Ti02光催化降解乙酰甲胺磷

在TiO2悬浮体系中,利用光催化技术消除乙酰甲胺磷（DMAPT）．探索了催化剂用量和目标物浓度对消除速率的影响．结果表明,催化剂的最佳用量为4g·l^-1DMAPT的光催化降解规律符合L_H模型,吸附常数和反应速率参数分别为2mmol^-1·l和0．6mmol·l^-1·min^-1．反应中主要的活性物种为·OH．反应的主要中间产物和矿化产物有O,S-二甲基硫代磷酰胺酯,O,O＇,S-三甲基硫代磷酸酯和磷酸甲酯等．DMAPT的降解从C-N键的断裂开始,随后经过P—N,P-S,P-C键的氧化分解,生成低毒和无毒的中间产物,并随着反应的继续最终达到彻底矿化,最终产物为SO4^2-,NO3^-,PO4^3-和CO2.     

太湖不同湖区无机氮转化潜力

采集太湖梅梁湾和东太湖的水样和积物,在实验室内模拟研究不同湖区水体中溶解性无机氮(DIN)短期内的转化潜力.研究结果表明,太湖藻型湖区(梅梁湾)和草型湖区(东太湖)水体中存在着强烈的硝化作用,NH 4-N和NO3-N含量之间表现出显著的负相关关系(P＜0.05或P＜0.01),NH 4-N质量浓度下降速率为0.08～0.19 mg·L-1·d-1.在同样的试验条件下,藻型湖区硝化速率高于草型湖区.NH 4-N初始浓度越高则硝化速率也越高,不添加外源氮时硝化速率随着时间的推移而逐渐降低.藻型湖区的反硝化作用强于草型湖区.室内模拟试验20 d后,沉积物中TN含量平均下降了3.7%,东太湖水样中平均下降26.7%,梅梁湾平均下降42.2%.湖泊沉积物是进行反硝化作用的重要场所.短期内DIN的转化潜力反映了不同湖区氮素转化速率,也反映了不同生态类型水体对湖泊氮素转化的影响.     

热活化过硫酸盐降解水体中毒死蜱

本文研究了热活化过硫酸盐降解水体中有机磷农药毒死蜱.考察了温度、过硫酸盐浓度、初始pH值、常见阴离子(CO_3~(2-)、HCO_3~-、Cl-和SO_4~(2-))对毒死蜱降解影响.结果表明,毒死蜱的降解符合准一级动力学,反应速率随过硫酸盐浓度的增加而增大,温度对毒死蜱降解速率的影响符合阿伦尼乌斯模型,pH值的改变对毒死蜱的降解没有显著影响.天然水体4种常见阴离子中,SO_4~(2-)对降解速率无显著影响,Cl~-对毒死蜱降解有促进作用,CO_3~(2-)和HCO_3~-抑制毒死蜱降解,且抑制程度为CO_3~(2-)HCO_3~-.通过自由基淬灭实验验证了体系中·OH和SO_4~-·自由基的存在,且毒死蜱降解过程中·OH起主要作用.     

乌梁素海水体重金属元素赋存形态模拟分析

为探讨重金属元素在湖泊水体中的赋存形态及影响因素,采集乌梁素海水样,对湖水中重金属元素铜(Cu)、铬(Cr)、镉(Cd)含量与赋存形态进行分析,利用PHREEQC软件模拟分析水体温度、氧化还原性、酸碱性的变化对Cu、Cr、Cd赋存形态的影响。结果显示,乌梁素海湖水中Cr、Cd含量都未超出地表水标准和国家渔业用水标准,但部分监测点Cu超标。湖水中Cu主要存在形态为CuCl_2~-、Cu(OH)_2;Cr主要存在形态为Cr(OH)_3;Cd主要存在形态为CdCl~+、Cd~(2+)、CdCl_2。水体中Cu、Cr、Cd赋存形态受水温影响较小,受pH影响较大。水体pH较低时,重金属以配合反应为主,此时水体中Cl~-、SO_4~(2-)等阴离子配位体含量对其影响较为明显,主要赋存形态为CuCl_2~-、Cr(OH)_2~+、CdCl~+、CdSO_4;随着pH的升高,重金属逐渐发生水解反应,主要赋存形态为Cu(OH)_2、Cr(OH)_3、CrO_2~-、CdOHCl、Cd(OH)_2等氢氧化物。水体的氧化还原性对不同重金属有不同影响。当水体处于还原状态时,Cu以CuCl_2~-含量为最大,处于氧化状态时,Cu(OH)_2含量最大。在水体处于中性-弱碱性状态下,水体的氧化还原性对重金属Cr、Cd影响较小。     

Degradation of diuron by the electro-Fenton process

The degradation of the herbicide diuron has been undertaken by electrochemical advanced oxidation in aqueous solution. This process generates catalytically hydroxyl radicals that are strong oxidizing reagents for the oxidation of organic substances. Hydroxyl radicals degrade diuron in less than 10 min. Kinetic results evidence a pseudo-first-order degradation, with a rate constant of reaction between diuron and hydroxyl radicals of 4.8x10⁹ M^–1 s^–1. Several degradation products were identified by chromatography-mass spectrometry (LC-MS). The mineralization degree of a 1.7x10^–4 M diuron solution reached 93% at 1,000 coulombs.     

Degradation of carbendazim by UV/H<Subscript>2</Subscript>O<Subscript>2</Subscript> investigated by kinetic modelling

The transformation of the fungicide carbendazim (methyl-2 benzimidazole carbamate) induced by hydroxyl radical generated by the UV photolysis of H₂O₂ has been studied in dilute aqueous solution. The efficient reaction of hydroxyl radicals with carbendazim led to the rapid degradation of carbendazim. The study of reaction kinetics yielded a second order rate constant of 2.2±0.3 10⁹ M⁻¹ s⁻¹ for HO^· radicals with carbendazim. This value is in agreement with a high reactivity of HO^· radicals with carbendazim. Most degradation products were identified by high performance liquid chromatography mass spectrometry (HPLC-MS). In the presence of hydrogenocarbonate and carbonate ions, hydroxyl radicals were quenched and in turn carbonate radicals CO₃ ^·− were formed. Carbonate radicals are indeed known to react efficiently with compounds containing electron-rich sites such as nitrogen or sulfur atoms. The use of a kinetic modelling software gave evidence for the occurrence of such reactions with carbendazim. The second order rate constant of carbonate radical with carbendazim was equal to 6±2 10⁶ M⁻¹ s⁻¹. Electronic Publication     

HO ‐ initiated oxidation of acridine and aminacrine in aqueous media: Kinetic model

The photodecomposition of diluted aqueous solutions of acridine and aminacrine in the presence of hydrogen peroxide was studied. Irradiation was carried out with a low pressure mercury vapour lamp. The kinetic model describes the photodegradation rate of the organic compound with respect to the technological parameters of the reactor and provides the reaction rate constants of hydroxyl radicals towards these two molecules. This model was extented to high hydrogen peroxide concentrations ([H₂O₂] > 200 μmol/l) by considering the reactivity of hydroxyl radicals towards hydrogen peroxide. This assumption allows us to define an optimal hydrogen peroxide concentration.     

Quantification of singlet oxygen and hydroxyl radicals upon UV irradiation of surface water

We measured the formation rate and the steady-state concentration of hydroxyl radicals and of singlet oxygen upon irradiation of lake water. There is controversy about the importance of singlet oxygen in the environmental photochemistry, but here we show that the steady-state concentration of ¹O₂ under irradiation can be higher by about two orders of magnitude compared to the hydroxyl radical. The higher occurrence of singlet oxygen in surface waters is mainly due to a higher rate of formation, because the transformation rate constants of ¹O₂ (collision with the solvent) and of ^·OH (reaction with dissolved compounds) are comparable.     

Hydroxyl radical generation by redox cycling of some chemotherapeutic antibiotics

The anticancer drugs: adriamycin, farmorubicin and mitomycin C greatly enhance the generation of hydroxyl radicals (HO^.) from H₂O₂ in the presence of Co(II) ions (CoCl2) at pH 7.4 and 8, as measured by the deoxyribose assay. Catalase, hydroxyl radical scavengers (mannitol, cysteine, glutathione, thiourea, lactic dehydrogenase) inhibited the degradation of deoxyribose confirming that HO‐radicals are responsible for the degradation of the carbohydrate.     

Removal of carbamazepine from urban wastewater by sulfate radical oxidation

The occurrence of bioactive trace pollutants such as pharmaceuticals in natural waters is an emerging issue. Numerous pharmaceuticals are not completely removed in conventional wastewater treatment plants. Advanced oxidation processes may represent an interesting alternative to completely mineralize organic trace pollutants. In this article, we show that sulfate radicals generated from peroxymonosulfate/Co^II are more efficient than hydroxyl radicals generated from the Fenton’s reagent (H₂O₂/Fe^II) for the degradation of the pharmaceutical compound, carbamazepine. The second-order rate constant for the reaction of SO₄ ^·− with carbamazepine is 1.92·10⁹ M⁻¹ s⁻¹. In laboratory grade water and in real urban wastewater, SO₄ ^·− yielded a faster degradation of carbamazepine compared to HO^· . Under strongly oxidizing conditions, a nearly complete mineralization of carbamazepine was achieved, while under mildly oxidizing conditions, several intermediates were identified by LC–MS. These results show for the first time in real urban wastewater that sulfate radicals are more selective than hydroxyl radicals for the oxidation of an organic pollutant and may represent an interesting alternative in advanced oxidation processes.     

Degradation of azo dyes in water by Electro-Fenton process

The degradation of the azo dyes azobenzene, p-methyl red and methyl orange in aqueous solution at room temperature has been studied by an advanced electrochemical oxidation process (AEOPs) under potential-controlled electrolysis conditions, using a Pt anode and a carbon felt cathode. The electrochemical production of Fenton's reagent (H₂O₂, Fe²⁺) allows a controlled in situ generation of hydroxyl radicals (^·OH) by simultaneous reduction of dioxygen and ferrous ions on the carbon felt electrode. In turn, hydroxyl radicals react with azo dyes, thus leading to their mineralization into CO₂ and H₂O. The chemical composition of the azo dyes and their degradation products during electrolysis were monitored by high performance liquid chromatography (HPLC). The following degradation products were identified: hydroquinone, 1,4-benzoquinone, pyrocatechol, 4-nitrocatechol, 1,3,5-trihydroxynitrobenzene and p-nitrophenol. Degradation of the initial azo dyes was assessed by the measurement of the chemical oxygen demand (COD). Kinetic analysis of these data showed a pseudo-first order degradation reaction for all azo dyes. A pathway of degradation of azo dyes is proposed. Specifically, the degradation of dyes and intermediates proceeds by oxidation of azo bonds and aromatic ring by hydroxyl radicals. The results display the efficiency of the Electro-Fenton process to degrade organic matter. Electronic Publication     

水热法制备PbMoO4微晶体及其光催化降解灭幼脲

以水热法合成的PbMoO4微晶体为催化剂,考察了反应溶液pH、污染物初始浓度和催化剂用量对光催化降解灭幼脲的影响,研究了光催化降解过程的反应动力学和作用机理.结果表明,最佳反应溶液pH 6.0、污染物初始浓度20 mg.L-1、催化剂用量0.4 g.L-1.反应4 h灭幼脲降解率达99.96%,矿化率达66.4%,降解反应符合一级动力学.通过加入自由基清除剂对比实验发现,PbMoO4微晶体主要通过空穴和.OH的氧化作用使灭幼脲降解,其中空穴起主要作用.     

Comparison of different probe molecules for the quantification of hydroxyl radicals in aqueous solution

We show that the transformation of benzene into phenol is a more selective probe for the hydroxyl radical than the transformation of nitrobenzene or the generation of 4-hydroxybenzoic acid from benzoic acid. The benzene to phenol system showed adequate performance as a probe upon irradiation of lake water samples and humic acids. We show that the use of nitrobenzene and benzoic acid as hydroxyl probes should be avoided because of poor selectivity. Moreover, all the tested probe molecules underwent important interference by irradiated antraquinone-2-sulphonate, and considerably overestimated the formation of the hydroxyl radicals.     

Mechanism of dichloromethane disproportionation over mesoporous TiO2 under low temperature

• Mechanism of DCM disproportionation over mesoporous TiO₂ was studied. • DCM was completely eliminated at 350℃ under 1 vol.% humidity. • Anatase (001) was the key for disproportionation. • A competitive oxidation route co-existed with disproportionation. • Disproportionation was favored at low temperature. Mesoporous TiO₂ was synthesized via nonhydrolytic template-mediated sol-gel route. Catalytic degradation performance upon dichloromethane over as-prepared mesoporous TiO₂, pure anatase and rutile were investigated respectively. Disproportionation took place over as-made mesoporous TiO₂ and pure anatase under the presence of water. The mechanism of disproportionation was studied by in situ FTIR. The interaction between chloromethoxy species and bridge coordinated methylenes was the key step of disproportionation. Formate species and methoxy groups would be formed and further turned into carbon monoxide and methyl chloride. Anatase (001) played an important role for disproportionation in that water could be dissociated into surface hydroxyl groups on such structure. As a result, the consumed hydroxyl groups would be replenished. In addition, there was another competitive oxidation route governed by free hydroxyl radicals. In this route, chloromethoxy groups would be oxidized into formate species by hydroxyl radicals transfering from the surface of TiO₂. The latter route would be more favorable at higher temperature.