类羧酸对棕壤中与氮素转化有关的生物活性的影响

类羧酸是一种带有羧基的化工副产品，其主要成分是二羧酸和三羧酸。具有较强的络合能力，可以用做螯合剂。文章通过室内培养实验，研究了类羧酸对棕壤中与氮素转化有关的生物活性的影响。结果表明类羧酸能显著抑制土壤脲酶活性，有效减少尿素水解产物氨的挥发损失；能促进土壤中含氮有机物的分解，并能抑制土壤中氨态氮向硝态氮的转化。另外施用类羧酸还能改善土壤中氮素的有效性，提高土壤的供氮能力。     

类羧酸对棕壤中与磷素转化有关的生物活性的影响

类羧酸是一种带有羧基的化工副产品，其主要成分是二羧酸和三羧酸，具有较强的络合能力，可以用作鳌合剂。通过室内恒温培养试验，研究了类羧酸对棕壤中与磷素转化有关的生物活性的影响。研究结果表明：土壤中性磷酸酶活性与土壤有机磷转化强度间存在显著直线相关关系。并且，施用类羧酸能增加土壤微生物生物量磷含量，增强土壤中有机磷化合物的水解，增加土壤有效磷的含量，从而改善土壤的供磷能力。     

活性炭多维电极法去除水中腐殖酸过程与宏观动力学研究

采用活性炭多维电极法去除水中溶解态腐殖酸。实验结果表明 ,与活性炭单纯吸附法相比 ,活性炭多维电极法可显著提高对溶解态腐殖酸的去除率 ;在连续运行条件下 ,延长水力停留时间、升高槽电压、溶液偏碱性有利于腐殖酸的去除 ;高效液相色谱分析结果表明 ,电极的氧化还原作用可使有机物分子量变小或矿化 ,因而处理系统有可能延长活性炭的使用寿命     

The occurrence of disinfection by-products in the drinking water of Athens,Greece

Application of chlorination for the disinfection of drinking water results in the formation of a wide range of organic compounds, called disinfection by-products (DBPs), which occur due to the reaction of chlorine with natural organic materials. The occurrence of DBPs was studied in samples from four drinking-water treatment plants (WTPs) and from the distribution network of Athens, Greece. Twenty-four compounds, which belong to different categories of DBPs, were monitored, including trihalomethanes (THMs), haloacetic acids (HAAs), haloacetonitriles (HANs), haloketones (HAKs), chloral hydrate (CH) and chloropicrin (CP). Sampling was performed monthly for a period of two years, from three different points at each WTP and from eight points atthe distribution network. Samples were analyzed by GC-ECD methods, which included pretreatment with liquid-liquid extraction for volatile DBPs and acidic methanol esterification for HAAs. The results of the analyses have shown the presence of disinfection by-products belonging to all categories studied in all water samples collected after prechlorination. The major categories of DBPs detected were THMs and HAAs, while the other volatile DBPs occurred at lower concentrations. The concentrations of DBPs did not in any case exceed the maximum contaminant levels (MCL) set by USEPA and WHO. However, monitoring these compounds needs to be continued, because their levels could increase due to changes in the quality of water entering the water treatment plants. Reduction of the concentrations of DBPs could be achieved by optimization of the chlorination conditions, taking into account the effect of time. Moreover, research on alternative disinfection methods (e.g. ozone, chlorine dioxide, chloramines) and their by-products should be conducted to evaluate their applicability in the case of the drinking water of Greece.     

Distributions, cycling and recovery of amino acids in estuarine waters and sediments

Acid hydrolysis of estuarine water samples for the determination of amino acids (AAs) was tested and found to be effective at high (250 μM) nitrate concentrations when the anti-oxidant, ascorbic acid, was added to the samples. Hydrolysable AA concentrations were then determined in surface sediments collected from low and high salinity regions of the Tamar Estuary (UK) during winter 2003 and 2004, and in overlying water when simulated resuspension of sediment particles was performed. Concentrations of AAs in sediment samples comprised <50% of particulate nitrogen, fitting the paradigm that most sedimentary nitrogen is preserved within an organic matrix. When sediment samples were resuspended in overlying water (salinity 17.5), the rapid, measured increase in dissolved AA concentrations almost equalled the reported nitrate concentration in the lower estuary, with the subsequent decrease in the total dissolved AA levels suggested that bacterial uptake was occurring. Our data concur with previous studies on nitrogen desorption from sediments and suggest that an understanding of organic nitrogen cycling will be an important aspect of future effective estuarine management.     

光(温)敏核不育水稻生态及生理生化研究概述

本文介绍了光、温敏核不育水稻在生态及生理生化方面取得的主要成就.着重概述了光、温敏核不育水稻雄性育性转换的光温生态条件,育性转换过程中蛋白质、氨基酸、酶活性、ATP及内源植物激素持续变化.另外,对光、温敏不育水稻研究存在的问题进行了分析.     

腐殖酸对土壤挥发汞植物有效性的影响研究

土壤挥发汞对植物是非常有效的,并能通过食物链威胁人体健康,因此,本试验设计了“密闭箱的水培试验”定量研究了腐殖酸及其组份对土壤挥发汞生物活性的影响,结果发现：腐殖酸能有效地抑制土壤汞的挥发,降低植株对土壤挥发汞的吸收,其作用机理在于土壤挥发汞的形态转化,通过对转化条件的调节,可以达到控制土壤挥发汞向食物的链转移的目的。     

Study on the action and mechanism of humic acids in Kaschin-Beck disease

Humic acids, especially FA in fractions, contain more oxygen functional groups. In this experiment, on the basis of confirming the action of humic acids on KBD, what was studied is the biological effects of one of main oxygen functional groups, hydroxy group (-OH). The results indicate that inducing pathologic process of KBD, obviously decrease the GSH-Px activity and induce peroxidation membrane injury of tissue. The SOD activity increase in the tissues caused by oxygen functional groups showed that enhancing of free radical reaction should not be neglected.     

SO2污染的次生作用--促进粘虫的生长

将3龄幼虫接种在暴露于低浓度SO_2的小麦植株上自由取食12d,研究SO_2污染对粘虫生长的影响;对照组小麦用经过活性炭过滤的空气处理。结果表明,随着SO_2浓度升高,幼虫历期逐渐缩短,幼虫期的平均相对生长速率依次增大。用人工饲料进行的类似试验结果,排除了SO_2污染直接促进粘虫生长的可能性。根据对食料植物水解氨基酸含量的测定结果,可以假设在非污染条件下生长的麦叶中,蛋氨酸和精氨酸含量偏低使粘虫处于亚最适生长状态,SO_2污染增加了食料中这两种限制性氨基酸的浓度,导致幼虫转入最佳生长状态。