Increases in Nitrate Concentrations in the River Frome (Dorset) Catchment Related to Changes in Land Use, Fertiliser Applications and Sewage Input

Nitrate concentrations and nitrate loads throughout the River Frome catchment (Dorset) are compared for the periods 1970-71 and 1984-86. Nitrate concentrations and loads have increased at every site, the increase in mean nitrate concentrations varying from 31% to 123%. These increases in nitrate concentrations are related to changes in land use and fertiliser applications and also to an increase in sewage effluent entering the river.     

硝酸盐污染饮用水的去除技术研究进展

近年来,世界上许多地区的饮用水硝酸盐污染日益严重,因为饮用水中的硝酸盐易导致"蓝婴综合症"而使其倍受关注。本文阐述了地下水硝酸盐氮的化学、物理及生物去除技术的最新研究进展,探讨了其今后的研究方向。     

Environmental cross-compliance mitigates nitrogen and phosphorus pollution from Swiss agriculture

In 1993 the Swiss agricultural policy was revised with – amongst other goals – the objective of improving the environmental performance of agriculture. A voluntary agri-environmental scheme to promote integrated production (IP) was introduced. In 1999 the IP standards were integrated in cross compliance requirements and termed Proof of Ecological Performance (PEP). We evaluated the effectiveness of this policy in terms of reducing diffuse nitrogen (N) and phosphorus (P) pollution of ground and surface water. We combined monitoring schemes covering the reference period from before the introduction of IP/PEP (1990–1992) with the evaluation of cause/effect relationships in selected case-study areas. The evaluation showed an overall reduction of diffuse N and P pollution from agriculture even though some goals were not reached. Nitrate leaching declined, but only a 3–4 mg L⁻¹ reduction was observed rather than the intended decrease of 5 mg L⁻¹. The P pollution of surface waters from agriculture decreased by only 10–30% instead of 50%. The intended reduction of the nitrogen surplus of Swiss agriculture by 33% was not attained, but the P surplus of Swiss agriculture was more than halved. IP/PEP practices that improved N and P management included reduced N and P fertiliser inputs and pig and poultry feedstuffs with reduced N and P contents, both of which are a consequence of the requirement of equilibrated farm nutrient balances, as well as increased use of cover cropping and of conservation tillage systems.     

碳源强化对人工湿地反硝化过程的影响研究

反硝化是人工湿地去除硝酸盐氮的主要机制,高含氮污水中低碳氮比是导致脱氮效果低的主要原因.研究了添加碳源对人工湿地反硝化过程的强化效果,结果表明,外界温度对湿地内的反硝化影响不大,而碳源则是重要的影响因素,对湿地投加碳源可以显著提高湿地的硝氮去除能力,在进水硝氮浓度25～45mg.L-1,24h水力停留时间的条件下,投加...     

Early responses of soil ammonium and nitrate nitrogen to forest gap harvesting of a Pinus massoniana plantation in the upper reaches of Yangtze River北大核心CSCD

To understand the short-term effects of forest gap by human harvesting on soil available nutrient in Pinus massoniana plantations, the variations of soil ammonium nitrogen (NH4+-N) and nitrate nitrogen (NO3-N) concentrations in the gap center and gap edge during growing season were observed in seven gaps of different size (Gl: 100 m2; G2:225 m2; G3:400 m2; G4:625 m2; G5:900 m2; G6:1225 m2; G7:1600 m2) and pure understory of a 39-year-old masson pine plantation in a hilly area of the upper reaches of Yangtze River. The results showed that in the early stage of gap formation, the gap size had significant effect on NH4+-N, the season changes on NP3--N, and the interaction effect of gap size and seasonal variation on NH4+-N and NO3--N. The difference of NH4+-N and NO3--N between the gap center and gap edge was not significant. (I) The NH4+-N content was 4.30-11.99 mg kg-1, and NO3--N content was 2.57-10.81 mg kg-1. There was no obvious difference in NH4+-N and N03--N among gaps of different size in early or late growing seasons, when both increased first and decreased afterwards in the middle of growing season. The gaps of 100∼400 m2 area had a higher content of available nitrogen. (2) The seasonal dynamic differed between NH4+-N and NO3--N, with the former lower in middle growing season whereas the latter higher in the middle growing season but lower in the end of growing season. The soil NH4+-N was higher than NO3- -N in the early and late periods, but lower in the middle period. (3) The soil NH4+-N and NO3--N in parts of gaps were lower than understory in the early and late growing season. (4) Correlation analyses showed that NH4+-N had significant positive correlation with microbial biomass nitrogen (MBN), and NO3--N with soil temperature, MBN and organic matter. But the impact of soil water content on available nitrogen was not significant. These results suggested that soil temperature and microbial activity variation caused by gap harvesting are the main factors affecting soil available nitrogen content of Pinus massoniana plantations.     

Electrochemical removal of nitrate in industrial wastewater

A number of recent studies have demonstrated that electrochemical technologies, including electroreduction (ER), electrocoagulation (EC), and electrodialysis (ED), are effective in nitrate elimination in wastewater due to their high reactivity. To obtain the maximal elimination efficiency and current efficiency, many researchers have conducted experiments to investigate the optimal conditions (i.e., potential, current density, pH value, plate distance, initial nitrate concentration, electrolyte, and other factors) for nitrate elimination. The mechanism of ER, EC and ED for nitrate removal has been fully elucidated. The ER mechanism of nitrate undergoes electron transfer and hydrogenation reduction. The EC pathways of nitrate removal include reduction, coagulation and flotation. The ED pathways of nitrate include redox reaction and dialysis. Although the electrochemical technology can remove nitrate from wastewater efficiently, many problems (such as relatively low selectivity toward nitrogen, sludge production and brine generation) still hinder electrochemical treatment implementation. This paper critically presents an overview of the current state-of-the-art of electrochemical denitrification to enhance the removal efficiency and overcome the shortages, and will significantly improve the understanding of the detailed processes and mechanisms of nitrate removal by electrochemical treatment and provide useful information to scientific research and actual practice.

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紫色土地区水文特征对硝态氮流失的影响研究

采用人工降雨模拟的方法,研究水文传输途径对紫色土中NO3--N流失的影响.研究结果表明,在所有雨强中均观察到壤中流的存在.在小雨强长历时的降雨中壤中流的径流量大于大雨强短历时降雨;随着雨强的增大,壤中流的径流系数下降.在紫色土地区,氮素的流失途径不仅包括地表径流而且包括壤中流,并且壤中流是NO3--N的主要水文传输途径.无论是否受到施肥措施的影响,壤中流中NO2--N浓度均高于地表径流.在对照小区,壤中流中NO3--N平均浓度是地表径流的7倍以上;施肥后壤中流NO3--N平均浓度为26.07mg·L-1,是地表径流的20倍以上.在对照小区,壤中流NO3--N的流失量占流失总量的30%以上;在施肥小区,壤中流NO3--N流失量占总流失量的90%以上.在紫色土地区,土壤特征和降雨特征决定了该地区壤中流形式的普遍存在,而NO3--N以壤中流流失的特点与当地施肥习惯的耦合效应增大了该地区的NO3--N流失风险.     

五大连池水体中氮素分布及规律的初步研究

分析了2009年9月至2010年10月五大连池水体的总氮、氨氮、硝氮3项指标.得出水体氮素的年度变化规律及相关性,即总氮和氨氮、氨态氮与硝态氮两组指标的相关性很高,总氮与硝态氮之间相关性较弱.3种指标都是冬季明显高于其他季节,总氮在春季最低随后升高,氨态氮和硝态氮在春夏秋季均维持较低水平,且结合3者变化规律,夏季和秋季...     

Chemical characteristics of haze particles in Xi'an during Chinese Spring Festival: Impact of fireworks burning

Fireworks burning releases massive fine particles and gaseous pollutants, significantly deteriorating air quality during Chinese Lunar New Year(LNY) period. To investigate the impact of the fireworks burning on the atmospheric aerosol chemistry, 1-hr time resolution of PM_(2.5) samples in Xi'an during the winter of 2016 including the LNY were collected and detected for inorganic ions, acidity and liquid water content(LWC) of the fine aerosols. PM_(2.5) during the LNY was 167 ± 87 μg/m~3, two times higher than the China National Ambient Air Quality Standard(75 μg/m~3). K~+(28 wt.% of the total ion mass) was the most abundant ion in the LNY period, followed by SO_4~(2-)(25 wt.%) and Cl-(18 wt.%). In contrast, NO_3~-(34 wt.%) was the most abundant species in the haze periods(hourly PM32-2.5 75 μg/m), followed by SO_4(29.2 wt.%) and NH_4~+(16.3 wt.%), while SO_4~(2-)(35 wt.%) was the most abundant species in the clean periods(hourly PM_(2.5) 75 μg/m~3), followed by NO_3~-(23.1 wt.%) and NH_4~+(11 wt.%). Being different from the acidic nature in the non-LNY periods, aerosol in the LNY period presented an alkaline nature with a pH value of 7.8 ± 1.3. LWC during the LNY period showed a robust linear correlation with K_2SO_4 and KCl, suggesting that aerosol hygroscopicity was dominated by inorganic salts derived from fireworks burning. Analysis of correlations between the ratios of NO--3/SO_4~(2-) and NH_4~+/SO_4~(2-) indicated that heterogeneous reaction of HNO_3 with NH_3 was an important formation pathway of particulate nitrate and ammonium during the LNY period.     

氮同位素方法在地下水氮污染源识别中的应用

地下水硝酸盐来源复杂多样.介绍了用15N/14N的方法(N同位素方法)分析辨明污染物来源.氮污染源不同,氮同位素值(δ15N值)也就不同.例如:雨水的δ15N值偏低,为-1.08%～0.21%;生活排水的δ15N值偏高,为1.0%～1.7%.污染源不同,受污染的地下水的δ15N值也不同,据此能有效地判断地下水硝酸盐的来源.