Effects of Nitrate Nitrogen Additions on Physical, Chemical and Biological Parameters in Lake Enclosures

The effects of nitrate additions on the physics, chemistry and biology of lake water were studied in 5 × 10 m polyethylene enclosures installed in Lake Kastoria, a shallow eutrophic lake in Northern Greece. The water physics, chemistry, chlorophyll a and nitrogenase activity were monitored from July 10 till October 17 1985 at 2 week intervals. The experiment included a control enclosure.

Water confinement in the control enclosure resulted in ammonia accumulation, a slight decrease in chlorophyll a, a significant reduction of nitrogenase activity and an increase in phosphorus release from the sediments at the end of the experimental period.

The addition of KNO₃ resulted in higher than the control accumulation of NH₃, chlorophyll reduction, increase in water transparency and reduction of nitrogenase activity. Large losses of nitrogen added were measured which were attributed to denitrification, organic matter sedimentation and ammonia volatilization. Anaerobic but not aerobic phosphorus release from sediments was inhibited at the end of the period. The reduction of nitrogenase activity and of chlorophyll a concentration are attributed to changes in phytoplankton composition from blue-greens to small-sized species grazed by zooplankters.     

环境条件和化学物质对叶类蔬菜硝酸盐的效应研究

在人工气候室和常温栽培条件下，研究了不同生长期化学物质赤霉素和钼酸铵对莴笋，小白菜硝酸盐含量和营养品质的效应。结果表明，两种环境下外源化学物质明显提高莴笋株高和小白菜根重，但却使莴笋叶绿素含量降低。两种环境Ｇ２和Ｍ２均明显提高两种叶类蔬菜ＡＡ的Ｖｃ含量，因而是Ｇ和Ｍ的最适施用时期。     

离子色谱法测定硝酸盐氮研究

文章探讨了一处测定地表水和饮用水中硝酸盐氮的直接方法－离子色谱法，与常用的酚二磺酸比色法相比，该方法具有简便，安全的优点，干扰少，准确度高。     

消化污泥上清液碳源生物反硝化

挥发性脂肪酸（ＶＦＡ）是消化污泥上清液（ＤＳＳ）中主要的组分。ＤＳＳ是反硝化很好的碳源。在本试验条件下，ＤＳＳ碳源完全反硝化的临界值为１．７４ｍｇ ＤＳＳ－Ｃ／ｍｇＮＯ３－Ｎ。但是，ＤＳＳ中的ＴＫＮ除了很小一部分被用于同化合成外，其大部分进入反硝化系统后不发生任何变化并出水排放。     

Vulnerability and risk evaluation of agricultural nitrogen pollution for Hungary's main aquifer using DRASTIC and GLEAMS models

In recent years, the significant improvement in point source depuration technologies has highlighted problems regarding, in particular, phosphorus and nitrogen pollution of surface and groundwater caused by agricultural non-point (diffuse) sources (NPS). Therefore, there is an urgent need to determine the relationship between agriculture and chemical and ecological water quality.This is a worldwide problem, but it is particularly relevant in countries, such as Hungary, that have recently become members of the European Community. The Italian Foreign Ministry has financed the PECO (Eastern Europe Countries Project) projects, amongst which is the project that led to the present paper, aimed at agricultural sustainability in Hungary, from the point of view of NPS. Specifically, the aim of the present work has been to study nitrates in Hungary's main aquifer. This study compares a model showing aquifer intrinsic vulnerability to pollution (using the DRASTIC parameter method; Aller et al. [Aller, L., Truman, B., Leher, J.H., Petty, R.J., 1986. DRASTIC: A Standardized System for Evaluating Ground Water Pollution Potential Using Hydrogeologic Settings. US NTIS, Springfield, VA.]) with a field-scale model (GLEAMS; Knisel [Knisel, W.G. (Ed.), 1993. GLEAMS—Groudwater Leaching Effects of Agricultural Management Systems, Version 3.10. University of Georgia, Coastal Plain Experimental Station, Tifton, GA.]) developed to evaluate the effects of agricultural management systems within and through the plant root zone. Specifically, GLEAMS calculates nitrate nitrogen lost by runoff, sediment and leachate.Groundwater monitoring probes were constructed for the project to measure: (i) nitrate content in monitored wells; (ii) tritium (³H) hydrogen radioisotope, as a tool to estimate the recharge conditions of the shallow groundwater; (iii) nitrogen isotope ratio δ¹⁵N, since nitrogen of organic and inorganic origin can easily be distinguished.The results obtained are satisfactory, above all regarding the DRASTIC evaluation method, which is shown to satisfactorily explain both low and high aquifer vulnerability, and furthermore proves to be a good tool for zoning hydrogeological regions in terms of natural system susceptibility to pollution. The GLEAMS model, however, proves not to be immediately usable for predictions, above all due to the difficulty in finding sufficient data for the input parameters. It remains a good tool, but only after an accurate validation, for decision support systems, in the specific case to integrate intrinsic vulnerability, from DRASTIC (or similar methods), with land use nitrate loads from GLEAMS, or similar methods.The PECO project has proved a positive experience to highlight the fundamental points of a decision support system, aimed to mitigate the nitrate risk for groundwater coming from Hungarian agricultural areas.     

Microbial characterization of nitrification in a shallow, nitrogen-contaminated aquifer, Cape Cod, Massachusetts and detection of a novel cluster associated with nitrifying Betaproteobacteria

Groundwater nitrification is a poorly characterized process affecting the speciation and transport of nitrogen. Cores from two sites in a plume of contamination were examined using culture-based and molecular techniques targeting nitrification processes. The first site, located beneath a sewage effluent infiltration bed, received treated effluent containing O₂ (> 300 µM) and NH₄⁺ (51–800 µM). The second site was 2.5 km down-gradient near the leading edge of the ammonium zone within the contaminant plume and featured vertical gradients of O₂, NH₄⁺, and NO₃⁻ (0–300, 0–500, and 100–200 µM with depth, respectively). Ammonia- and nitrite-oxidizers enumerated by the culture-based MPN method were low in abundance at both sites (1.8 to 350 g^− 1 and 33 to 35,000 g^− 1, respectively). Potential nitrifying activity measured in core material in the laboratory was also very low, requiring several weeks for products to accumulate. Molecular analysis of aquifer DNA (nested PCR followed by cloning and 16S rDNA sequencing) detected primarily sequences associated with the Nitrosospira genus throughout the cores at the down-gradient site and a smaller proportion from the Nitrosomonas genus in the deeper anoxic, NH₄⁺ zone at the down-gradient site. Only a single Nitrosospira sequence was detected beneath the infiltration bed. Furthermore, the majority of Nitrosospira-associated sequences represent an unrecognized cluster. We conclude that an uncharacterized group associated with Nitrosospira dominate at the geochemically stable, down-gradient site, but found little evidence for Betaproteobacteria nitrifiers beneath the infiltration beds where geochemical conditions were more variable.     

Rapid and long-effective removal of broad-spectrum pollutants from aqueous system by ZVI/oxidants

• The coupling of oxidants with ZVI overcome the impedance of ZVI passive layer. • ZVI/oxidants system achieved fast and long-effective removal of contaminants. • Multiple mechanisms are involved in contaminants removal by ZVI/oxidant system. • ZVI/Oxidants did not change the reducing property of ORP in the fixed-bed system. Zero-valent iron (ZVI) technology has recently gained significant interest in the efficient sequestration of a wide variety of contaminants. However, surface passivation of ZVI because of its intrinsic passive layer would lead to the inferior reactivity of ZVI and its lower efficacy in contaminant removal. Therefore, to activate the ZVI surface cheaply, continuously, and efficiently is an important challenge that ZVI technology must overcome before its wide-scale application. To date, several physical and chemical approaches have been extensively applied to increase the reactivity of the ZVI surface toward the elimination of broad-spectrum pollutants. Nevertheless, these techniques have several limitations such as low efficacy, narrow working pH, eco-toxicity, and high installation cost. The objective of this mini-review paper is to identify the critical role of oxygen in determining the reactivity of ZVI toward contaminant removal. Subsequently, the effect of three typical oxidants (H₂O₂, KMnO₄, and NaClO) on broad-spectrum contaminants removal by ZVI has been documented and discussed. The reaction mechanism and sequestration efficacies of the ZVI/oxidant system were evaluated and reviewed. The technical basis of the ZVI/oxidant approach is based on the half-reaction of the cathodic reduction of the oxidants. The oxidants commonly used in the water treatment industry, i.e., NaClO, O₃, and H₂O₂, can be served as an ideal coupling electron receptor. With the combination of these oxidants, the surface corrosion of ZVI can be continuously driven. The ZVI/oxidants technology has been compared with other conventional technologies and conclusions have been drawn.     

镉柱还原法测定海水中硝酸盐氮有关问题的探讨

对GB 17378.4—2007中镉柱还原法测定海水中硝酸盐氮的有关问题进行了分析与探讨。结果表明,GB 17378.4—2007中硝酸盐氮的测定方法和计算公式存在一定缺陷,针对这些问题,提出了相应的改进措施和修正方法,改进后的方法操作步骤更加便捷,计算结果更加准确。     

Farmyard point discharges and their influence on nutrient and labile carbon dynamics in a second order stream draining through a dairy unit

Two small piped sources deriving from a single farmyard together with the receiving second order stream above and below the farmyard region were sampled over a two-year period. Although not measured directly, observations at the time of sampling suggested that maximum drain flow was about 2% of downstream base flow. Both point sources were flowing on each sampling occasion (~62) and usually had concentrations of phosphorus (P), nitrate (NO(3)-N) and biological oxygen demand (BOD) well above those from the upstream site. Individual sample concentrations ranged over more than two orders of magnitude for most determinants and a large proportion of the total P was present as soluble (inorganic and organic) and therefore labile forms. More than 70% of samples collected at the downstream site had concentrations that were >1.2 times those of the corresponding upstream site. On certain sampling occasions >80% of total dissolved phosphorus (TDP) and >90% of the BOD and NO(3) instantaneous load appeared to originate from the farmyard region with the composition of downstream samples being completely overwhelmed after the passage through the farmyard. Extrapolations using instantaneous loads suggest that the farmyard and adjacent areas contributed on average 25-30% of the total and dissolved annual downstream P load of 3 kg P ha(-1) and 1.7 kg P ha(-1), respectively. There was no clear relationship between the relative proportion of the contaminant loading originating from the farmyard region and hydrological events. This emphasises the potential localised significance that small, highly concentrated, continuous or semi-continuous farmyard sources can impact headwater streams during periods of low stream flow.     

Identification and quantification of a novel nitrate-reducing community in sediments of Suquía River basin along a nitrate gradient

We evaluated the molecular diversity of narG gene from Suquía River sediments to assess the impact of the nitrate concentration and water quality on the composition and structure of the nitrate-reducing bacterial community. To this aim, a library of one of the six monitoring stations corresponding to the highest nitrate concentration was constructed and 118 narG clones were screened. Nucleotide sequences were associated to narG gene from alpha-, beta-, delta-, gammaproteobacteria and Thermus thermophilus. Remarkably, 18% of clones contained narG genes with less than 69% similarity to narG sequences available in databases. Thus, indicating the presence of nitrate-reducing bacteria with novel narG genes, which were quantified by real-time PCR. Results show a variable number of narG copies, ranging from less than 1.0 × 10² to 5.0 × 10⁴ copies per ng of DNA, which were associated with a decreased water quality index monitored along the basin at different times.