典型岩溶地下河流域水体中硝酸盐源解析

地下河是岩溶地区地下水赋存运动的主要场所和重要水源,近年来,硝酸盐污染严重.为解析典型岩溶地下河流域水体中硝酸盐的来源,利用δ~(15)N-NO~-_3、δ~(18)O-NO~-_3和δ~(18)O-H_2O稳定同位素示踪技术开展研究,并通过SIAR稳定同位素模型,对不同污染源的贡献率进行了定量识别,同时阐明了土地利用类型对流域水体硝酸盐分布及来源的影响.结果表明:①降雨/化肥中的氨盐、土壤有机氮和粪肥污水是流域内水体硝酸盐的主要来源;②流域内水体硝酸盐的转化过程主要以硝化作用为主导,水体硝酸盐氮氧同位素初始值未受分馏影响;③基于SIAR模型,不同端元对流域内水体硝酸盐的贡献比例呈季节性差异,化肥、土壤有机氮和粪便污水对丰水期流域内水体硝酸盐的贡献比例分别为57.07%、 34.06%和8.87%;对流域内枯水期水体硝酸盐的贡献比例分别为34.14%、 33.02%和32.84%.     

叶菜类蔬菜硝酸盐含量及其与土壤肥力因素的关系

对长沙市蔬菜生产基地春夏季节3种叶菜类蔬菜硝酸盐含量进行测定并与对应的菜园土壤8个肥力因素进行相关分析。结果表明,叶菜类蔬菜中,以小白菜硝酸盐含量最高,平均含量为3336±1359mg/kg,污染最严重;所调查的14个样本中超过四级标准达到严重污染水平的占64%以上。叶菜类蔬菜硝酸盐含量与土壤硝酸盐含量呈正相关,其中小白菜和苋菜相应的相关系数和通径分析系数均达5%以上显著水平。土壤硝酸盐含量是影响叶菜类蔬菜硝酸盐含量的主要土壤肥力因素。     

大肠杆菌JM105中硝酸盐还原酶的制备及其性质

近年来,硝酸盐和亚硝酸盐的污染已引起普遍关注。目前,蔬菜和粮食的NO3-含量过高主要由于农药和化肥的使用、工业废水或生活污水灌溉等,食品类主要来自腌制食品和食品添加剂或防腐剂等。另外,向乳制品或食品中参碱、食盐、化肥、脏水、碱性水等也是硝酸盐污染的来源之一。因此,迫切需要快速、简便、可用于现场的硝酸盐检测方法。这就需仰赖生物酶方法,而生物酶方法的关键是酶制剂的制备和检测方法的建立。本研究通过筛选、厌氧和硝酸盐诱导培养、超声波细胞破碎和差速离心提取等方法,从大肠杆菌(Escherichia coli)JM105细胞膜中制备了硝酸盐还原酶并对其性质进行了研究。结果表明:从大肠杆菌JM105中制得的酶制剂活力很高,且在酶过量的情况下可将NO3-完全转化为NO2-,在用磷酸缓冲液清洗并冷冻保藏过夜后不含有亚硝酸盐还原酶。在加入黄素单核苷酸辅酶(FMN)后,该酶的活力可提高64%,比活力达0.42U·mg-1蛋白。该酶十分稳定,在40℃下24h活力无影响,在浓度为1mmol·L-1的Cu2 、Fe3 、Ca2 、Zn2 、Mg2 和Mo6 存在下,其活力亦不改变。因此,该酶可用于测定食品、蔬菜和环境中硝酸盐的含量。     

东莞市蔬菜硝酸盐污染现状研究

通过对东莞市11种蔬菜48个样品中硝酸盐质量分数的分析，初步摸清了东莞市蔬菜硝酸盐的污染状况。分析结果表明，硝酸盐检出率为100％，其中21个样品的硝酸盐质量分数超标，超标率为46．5％；叶菜类最高检出值为国家标准的2．6倍；瓜果类最高检出值为国家标准的2．98倍。     

Application of a water quality model in the White Cart water catchment,Glasgow, UK

Water quality models of urban systems have previously focused on point source (sewerage system) inputs. Little attention has been given to diffuse inputs and research into diffuse pollution has been largely confined to agriculture sources. This paper reports on new research that is aimed at integrating diffuse inputs into an urban water quality model. An integrated model is introduced that is made up of four modules: hydrology, contaminant point sources, nutrient cycling and leaching. The hydrology module, T & T consists of a TOPMODEL (a TOPography-based hydrological MODEL), which simulates runoff from pervious areas and a two-tank model, which simulates runoff from impervious urban areas. Linked into the two-tank model, the contaminant point source module simulates the overflow from the sewerage system in heavy rain. The widely known SOILN (SOIL Nitrate model) is the basis of nitrogen cycle module. Finally, the leaching module consists of two functions: the production function and the transfer function. The production function is based on SLIM (Solute Leaching Intermediate Model) while the transfer function is based on the flushing hypothesis which postulates a relationship between contaminant concentrations in the receiving water course and the extent to which the catchment is saturated. This paper outlines the modelling methodology and the model structures that have been developed. An application of this model in the White Cart catchment (Glasgow) is also included.     

黄潮土的土壤水渗漏及硝态氮淋溶研究

在黄淮海平原 1hm2 小麦 -玉米轮作田块上 ,利用水量平衡模型对黄潮土的土壤水渗漏和硝态氮淋溶状况进行了定量研究。结果表明 ,黄潮土的土壤水渗漏和硝态氮淋溶状况非常严重 ,全耕作年土壤水渗漏量达到2 73 .9mm ,为灌溉水量的 60 .6% ;硝态氮淋溶达到 81.8kg·hm-2 ,为氮输入总量的 15 .7%。     

脱除地下水中硝酸盐氮的研究进展

地下水中硝酸盐氮的脱除可以采用传统脱除法和催化反硝化脱除法。介绍了地下水脱氮技术的发展历史,着重介绍了最新发展提出的催化反硝化脱氮法。具体阐述了催化反硝化脱氮的原理、处理效果、主要影响因素、优势和局限性,对目前存在的问题和今后的发展方向,指明催化活性和催化选择性的提高,是催化反硝化法实用化过程中需要解决的关键问题。     

Groundwater quality: Responsible agriculture and public perceptions

The chief sources of groundwater contamination on farms come from point sources and diffuse sources. Possible point sources are feedlots, poorly-sited manure piles, septic sewage-treatment systems—all of which can release nitrate, phosphates and bacteria— and sites of chemical spills. Diffuse sources are typified by excess fertilizer leaching from a number of arable fields. The basis of quality standards for drinking-water is discussed in relation to common contaminants present on farms. Samples of drinking-water were collected in 1991–1992 from wells on about 1,200 farms in order to study the quality of rural groundwater in Ontario. Analysis showed that approximately one third of wells were contaminated with bacteria, 14% were contaminated with nitrate, two wells were contaminated with pesticide, but 40% were considered unsafe because of the presence of at least one contaminant. These values were similar to those reported for similar regions in the U.S. There was no significant effect of agricultural practice on the proportion of contaminated samples. One response of Ontario's farmers to information on water quality has been to initiate their own program, the Environmental Farm Plan, which has 23 modules by which the risk of environmental contamination can be assessed. Government policies for agriculture can be expected to influence farming practices. However, the literature suggests that the consequences of policies aimed at reducing environmental contamination are poorly understood, not least because the instruments used for implementation can have widely differing impacts. The need for discussions on the ethics surrounding the relationship between food producers and consumers with regard to environmental contamination is identified.     

High-performance size exclusion chromatography with a multi-wavelength absorbance detector study on dissolved organic matter characterisation along a water distribution system

This study examined the associations between dissolved organic matter(DOM) characteristics and potential nitrification occurrence in the presence of chloramine along a drinking water distribution system. High-performance size exclusion chromatography(HPSEC) coupled with a multiple wavelength detector(200–280 nm) was employed to characterise DOM by molecular weight distribution, bacterial activity was analysed using flow cytometry, and a package of simple analytical tools, such as dissolved organic carbon, absorbance at 254 nm, nitrate,nitrite, ammonia and total disinfectant residual were also applied and their applicability to indicate water quality changes in distribution systems were also evaluated. Results showed that multi-wavelength HPSEC analysis was useful to provide information about DOM character while changes in molecule weight profiles at wavelengths less than 230 nm were also able to be related to other water quality parameters. Correct selection of the UV wavelengths can be an important factor for providing appropriate indicators associated with different DOM compositions. DOM molecular weight in the range of 0.2–0.5 k Da measured at210 nm correlated positively with oxidised nitrogen concentration(r = 0.99), and the concentrations of active bacterial cells in the distribution system(r = 0.85). Our study also showed that the changes of DOM character and bacterial cells were significant in those sampling points that had decreases in total disinfectant residual. HPSEC-UV measured at210 nm and flow cytometry can detect the changes of low molecular weight of DOM and bacterial levels, respectively, when nitrification occurred within the chloraminated distribution system.     

有机碳源葡萄糖对钝顶螺旋藻生长和硝态氮去除效果的影响研究

利用Zarrouk培养基,通过改变葡萄糖的初始加入量,研究钝顶螺旋藻的生长情况及其对硝态氮的去除效果,探讨其在废水处理中的可行性.结果表明,添加葡萄糖碳源能够促进钝顶螺旋藻的生长,影响其叶绿素和粗蛋白含量,当葡萄糖投加量≥1 g/L时,生长对数期提前,藻液OD560在培养4天时达到稳定,叶绿素和粗蛋白含量培养7天后急剧下降.研究结果还表明,添加葡萄糖碳源有助于提高水中硝态氮的去除率,当硝态钠、葡萄糖投加量均为2.5 g/L,培养5天时,氮素去除率最高,达99.96％,但硝态氮浓度过高时会产生单盐毒害作用.