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51.
为了解华东某市老城区潜层地下水硝酸盐分布特征,对老城区地下水现场采样,运用统计学软件spss中的Pearson相关系数和sufer软件Kriging插值方法分析数据,研究了无机氮与地球化学因素间的相关性,同时绘制了p H值、总硬度、硝酸盐、亚硝酸盐的空间分布图。结果表明,硝酸盐是该地区地下水中无机氮的主要存在形态,其所占总氮含量为45.5%~74.8%,封口井的硝酸盐的含量明显低于敞口井的含量,其硝酸盐所占比例最低达到2.2%,且敞口井均受到污染;从相关性的角度来看,氮的转化受到Fe影响较弱。同时氮的形态与p H值、矿化度(TDS)、电导率(EC)等地球化学因素相关水平显著;从分布特征来看,地下水环境中硝酸盐和亚硝酸盐含量东北部高于西南部;不同形态氮的相互转化影响地下水p H值和总硬度,致使p H值的高值区为西南部,而总硬度高值区为东北部。 相似文献
52.
Trends of nitrogen in air and precipitation: model results and observations at EMEP sites in Europe, 1980--2003 总被引:1,自引:0,他引:1
We analyze trends of some nitrogen compounds using long-term measurements and results from the EMEP (co-operative programme for monitoring and evaluation of the long-range transmissions of air pollutants in Europe) chemical transport model at EMEP sites. We find statistically significant declines at the majority of sites for NH(x) (sum of ammonia and ammonium) in air and for nitrate and ammonium in precipitation, but only at a few sites for xNO3 (sum of nitrate and nitric acid) in air. Model calculations and measurements give similar results. We demonstrate that the lack of trends for xNO3 in air at least partly can be attributed to a shift in the equilibrium between nitric acid and ammonium nitrate towards particulate phase, caused by reductions in the sulfur dioxide emissions. 相似文献
53.
A field study was established to investigate the chemical composition of atmospheric aerosols in Chicago, IL. One goal of
this study was to determine the influence of precursor trace gases and local meteorology on concentrations of secondary aerosol
ionic species. This paper describes the method details, shows the method is analytically valid, and reports overall as well
as some specific results found during the field study. Two particulate air samples were collected per day onto quartz fiber
filters at the Loyola University Chicago Air Station during the summer months in 2002–2004. In parallel, mixing ratios of
ozone and nitrogen oxides were monitored and weather parameters were recorded. Particulates were extracted from the filter
substrates and the subsequent solutions were analyzed by ion chromatography for anions, including low molecular weight organic
acids, and cations. A washing procedure was implemented to reduce the high background values of the quartz fiber filters.
Method validation showed that the collection method was efficient for all ions with exception of nitrate, whose efficiency
of 70% indicated losses caused by volatilization. The extraction method also proved efficient for both field and laboratory
samples, and the repeatability of the method was high with relative standard deviations less than 10% for all ions. Reproducibility
of the results was determined by comparison of sulfate to sulfur analyzed by total reflection X-ray fluorescence spectrometry
and proved to be high as well. Concentrations differed significantly between the three summer studies due to varying levels
of precursor species as a consequence of distinct temperatures and wind direction profiles. 相似文献
54.
Vesna Zupanc Martina ŠturmSonja Lojen Nina Marši?-KacjanJoseph Adu-Gyamfi Branka Bra?i?-?eleznikJanko Urbanc Marina Pintar 《Agriculture, ecosystems & environment》2011,144(1):167-174
In the search for new technologies that would ensure optimum yield and environmental sustainability, various irrigation, nitrogen and cropping system management strategies for the production of vegetables with a shorter growing period were assessed at a benchmark site in Slovenia for the years 2006 and 2007. In the studied years four irrigation and fertilization treatments were applied: (1) 50% drip irrigation of plants water requirements ETcrop and the farmer's practice of fertilisation (broadcasting), (2) fertilisation and 100% drip irrigation (fertigation), (3) the farmer's practice of irrigation (sprinkler irrigation using water stored in plastic tanks) and fertilisation, and (4) control (the farmer's practice of irrigation but no fertilisation). An equivalent of 80, 80 and 200 kg ha−1 of nitrogen (N), 50, 50 and 80 kg ha−1 of phosphorous (P) and 120, 120 and 300 kg ha−1 of potassium (K) was added for iceberg lettuce, endive and cabbage, respectively. Nitrogen (N) labelled fertilizer (15N) was applied to trace the movement of the applied N fertiliser. The tested irrigation and fertilisation techniques for the production of vegetables with a shorter growing period in the Slovenian climate showed that environmentally sustainable practices (split application of nutrients compared to broadcast incorporating fertilisation) should be a practice of choice in water protection zones. The results confirm that fertigation and improved irrigation scheduling can be an effective way of minimizing nitrate leaching, and should be considered for vegetable production in or close to groundwater protection zones. 相似文献
55.
56.
Krywult M Smykla J Kinnunen H Martz F Sutinen ML Lakkala K Turunen M 《Environmental pollution (Barking, Essex : 1987)》2008,156(3):1105-1111
Needles of 20-year-old Scots pine (Pinus sylvestris L.) saplings were studied in an ultraviolet (UV) exclusion field experiment (from 2000 to 2002) in northern Finland (67 °N). The chambers held filters that excluded both UV-B and UV-A, excluded UV-B only, transmitted all UV (control), or lacked filters (ambient). UV-B/UV-A exclusion decreased nitrate reductase (NR) activity of 1-year-old needles of Scots pines compared to the controls. The proportion of free amino acids varied in the range 1.08-1.94% of total proteins, and was significantly higher in needles of saplings grown under UV-B/UV-A exclusion compared to the controls or UV-B exclusion. NR activity correlated with air temperature, indicating a “chamber effect”. The study showed that both UV irradiance and increasing temperature are significant modulators of nitrogen (N) metabolism in Scots pine needles. 相似文献
57.
Ling Sun Hui Wang Yuanqing Kan Shiliang Wang 《Frontiers of Environmental Science & Engineering》2018,12(6):13
To reveal the distribution characteristics of phytoplankton and the main influence factors under different conditions in the urban rivers, the investigations were conducted during autumn and winter 2014 in Changzhou City, East China. 178 taxa of phytoplankton belonging to 28 functional assemblages were identified. In autumn, the phytoplankton community compositions have high similarity for enhanced hydrological connectivity. The chlorophytes and diatoms (prevailing functional groups C, F, J, P), together with euglenoids (W1), showed high proportions of biomass in the main rivers and connected rivers. It was related to the well mixed eutrophic conditions. The phytoplankton community exhibited spatiotemporal heterogeneity in winter. Affected by the low water level and temperature, the free-living phytoflagellates (X2) replaced groups F and J in the main rivers. Phytoplankton productivity was the highest in the Tongji River. Chlorophytes Dictyosphaerium ehrenbergianum and Chlamydobotrys stellata had an overwhelming superiority during the winter bloom. They were significantly correlated with ammonium, total phosphorus and biochemical oxygen demand. Affected by tail water supply, the diatoms (MP) and euglenoids (W1) dominated in a beheaded river. The multivariate analyses based on the phytoplankton functional groups helped to evaluate the relationships and variations between the urban rivers. The redundancy analysis (RDA) results showed that nitrate nitrogen, water temperature, total nitrogen and total suspended solids were the main influence factors on the phytoplankton community. Except MP, the prevailing groups all showed significant negative correlations with nitrate nitrogen. Availability and utilization of dissolved inorganic nitrogen and hydrodynamic conditions affected the phytoplankton distribution.
相似文献
58.
Wilbur H. Campbell Pengfei Song Guillaume G. Barbier 《Environmental Chemistry Letters》2006,4(2):69-73
Nitrate analysis in water is one of the most frequently applied methods in environmental chemistry. Current methods for nitrate are generally based on toxic substances. Here, we show that a viable alternative method is to use the enzyme nitrate reductase. The key to applying this Green Chemistry solution for nitrate analysis is plentiful, inexpensive, analytical grade enzyme. We demonstrate that recombinant Arabidopsis nitrate reductase, expressed in the methylotrophic yeast Pichia pastoris, is a highly effective catalyst for nitrate analysis at 37°C. Recombinant production of enzyme ensures consistent quality and provides means to meet the needs of environmental chemistry. 相似文献
59.
硝酸盐浓度及投加方式对反硝化除磷的影响 总被引:29,自引:0,他引:29
采用SBR反应器,详细研究了硝酸盐浓度及其投加方式对反硝化除磷过程的影响。结果表明,缺氧环境下的反硝化吸磷速率与作为电子受体的硝酸盐浓度有很大的关系,硝酸盐浓度越高.吸磷速率越快。当硝酸盐浓度较低.不足以氧化反硝化聚磷菌细胞内的PHB从而导致体系反硝化除磷效率的下降。相同浓度的硝酸盐,采用流加的方式可以获得比一次性投加更高的反硝化吸磷速率。缺氧环境下,反硝化脱氮量与磷的吸收量成良好的线性关系.借助于反硝化聚磷菌,反硝化脱氮与除磷可在一种环境中完成,有效解决了废水中COD不足的问题.同时达到了节省能源和降低污泥产量的目的。 相似文献
60.
同分异构体喹啉和异喹啉的缺氧降解性能比较 总被引:3,自引:0,他引:3
研究了同分异构体的含氮杂环化合物喹啉和异喹啉在缺氧条件下的降解情况,发现两者表现出不同的缺氧降解特性。喹啉可以在缺氧条件下得到有效降解,其缺氧降解的最佳碳氮比为8。在最佳碳氮比条件下,喹啉的缺氧降解过程符合一级动力学规律,在其降解过程中首先以硝酸盐为电子受体,当硝酸盐氮浓度为零时,亚硝酸盐氮浓度达到最高,此后喹啉的降解主要以亚硝酸盐为电子受体,并和亚硝酸盐氮同时达到最低浓度。异喹啉对硝酸盐的利用甚微,其降解主要表现为厌氧降解特征,降解过程符合零级动力学规律。 相似文献