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J. Kubiak 《洁净——土壤、空气、水》1983,11(4):439-447
The Pomeranian Bay in the south-western part of the Baltic sea has an area of 4300 km2 and a volume of 51.4 km3 and contains a fresh-water inflow of 17.3 km3/a from a catchment area of 137,220 km2. There were evaluated 18 investigations of specific dates at 14 stations in the years 1976 … 1978: 229 … 235 hydrochemical measurements and 75 phytoplankton investigations. It can be demonstrated by multiple regression analyses that the nutrient concentrations are mainly determined by the fresh-water inflow and the mixing ratios, phytoplankton having a secondary effect. Of the nutrients mainly ammonium influences the phytoplankton development and the oxygen production, the full utilization of the nitrogen stock being limited by an N/P ratio of 48 in the surface water and of 41 in the bottom water layers. Obviously, a limitation of the primary production is out of the question due to the high turnover rates of phosphorus. The N/P ratio is also a clear evidence of the great influence of the inflowing nitrate-rich freshwater on the nutrient situation of the bay. 相似文献
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Nitrogen uptake and denitrification in restored and unrestored streams in urban Maryland, USA 总被引：2，自引：0，他引：2
Carolyn A. Klocker Sujay S. Kaushal Peter M. Groffman Paul M. Mayer Raymond P. Morgan 《Aquatic Sciences - Research Across Boundaries》2009,71(4):411-424
There is growing interest in rates of nitrate uptake and denitrification in restored streams to better understand the effects
of restoration on nitrogen processing. This study quantified nitrate uptake in two restored and two unrestored streams in
Baltimore, Maryland, USA using nitrate additions, denitrification enzyme assays, and a 15N isotope tracer addition in one of the urban restored streams, Minebank Run. Restoration included either incorporation of
stormwater ponds below a storm drain and catch basins to attenuate flow or hydrologic “reconnection” of a stream channel to
its floodplain. Stream restoration was conducted for restoring aging sanitary and bridge infrastructure and introducing some
stormwater management in watersheds developed prior to current regulations. Denitrification potential in sediments was variable
across streams, whereas nitrate uptake length appeared to be significantly correlated to surface water velocity, which was
low in the restored streams during summer baseflow conditions. Uptake length of NO3
−–N in Minebank Run estimated by 15N tracer addition was 556 m. Whole stream denitrification rates in Minebank Run were 153 mg NO3
−–N m−2 day−1, and approximately 40% of the daily load of nitrate was estimated to be removed via denitrification over a distance of 220.5 m
in a stream reach designed to be hydrologically “connected” to its floodplain. Increased hydrologic residence time in Minebank
Run during baseflow likely influenced rates of whole stream denitrification, suggesting that hydrologic residence time may
be a key factor influencing N uptake and denitrification. Restoration approaches that increase hydrologic “connectivity” with
hyporheic sediments and increase hydrologic residence time may be useful for stimulating denitrification. More work is necessary,
however, to examine changes in denitrification rates in restored streams across different seasons, variable N loads, and in
response to the “flashy” hydrologic flow conditions during storms common in urban streams. 相似文献
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Samples characterizing the horizontal distribution of bottom deposits of different types in the Upper Volga reservoirs were used to study the statistical relationship between the indicators of the potential and actual trophy of water bodies. These indicators are the amount of biogenic elements (the total nitrogen and phosphorus) and phyto-pigments (in the dry and wet masses of soil and in its organic fraction). The relationship between the above indicators for the channel deposits from the Upper Volga reservoirs and for the deposits in the lake hollows is found to he linear. 相似文献
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Nitrogen concentrations in various tektites and natural glasses have been measured using RNAA and are found to be almost constant at about 15 ppm. A terrestrial origin for tektite formation is favoured. 相似文献
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放养前后鱼塘沉积物中氮、磷、有机质、色素的变化及环境意义 总被引：1，自引：0，他引：1
通过对针塘沉积物中营养盐,有机质及色素在放养前后的测试,对比分析了在人类活动（养殖）的影响下,由于鱼塘水体快速富营养化而引起底质上述指标的变化过程,其中快速沉积环境极有利于沉积色素的保存,具有较好的环境营养状况指示意义,同时有机质,色素和营养盐之间存在着密切的相关关系,这为利用色素方法研究短时间序列环境演变,尤其是在近代人类活动影响下的环境变化提供了一定的依据。 相似文献
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太湖流域望虞河西岸地区氮磷污染来源解析及控制对策 总被引：7，自引：2，他引：5
本文比较全面地调查了太湖流域望虞河西岸地区氮磷污染来源,结果表明:太湖流域望虞河西岸水体氮磷污染严重,氮磷污染物主要来源于生活污染,其氨氮、总氮、总磷排放量分别占总负荷量的60.2%、52.5%和52.9%.工业污染问题突出,纺织印染是污染物排放最大的工业行业.张家港市和江阴市为氮磷污染的主要贡献地.对区域环境容量进行了预测,并提出了氮磷污染削减目标,氨氮、总氮和总磷污染削减率分别达32.4%,51.8%和51.1%.最后,从加大污染综合治理力度、落实河道及生态修复工程、加强环境管理和监控等方面提出了望虞河西岸地区的氮磷污染控制对策. 相似文献
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Linping Xie Baodong Wang Ming Xin Min Wang Xiuping He Qinsheng Wei Xiaoyong Shi Xia Sun 《洁净——土壤、空气、水》2019,47(9)
Variations in carbon (C) and nitrogen (N) of the vegetation in a Tamarix chinensis coastal wetland located in Laizhou Bay, China, are analyzed. It is found that T. chinensis accumulates more C and N than the surrounding herbs, and it allocates more C and N in the aboveground parts but less in the roots. Branches store more C, whereas leaves and flowers accumulate more N than other tissues. The C and N contents in the aboveground parts of T. chinensis are mainly influenced by pH, electrical conductivity (EC), water content, and clay content in the top 100 cm of soil as well as the distance from the sea. For the herbs, their C contents vary little in the supratidal zone, but they are higher than those in the intertidal zone. However, N contents in the herbs are higher in the aboveground parts and varied among different communities. The contents of C and N in the herbs are affected by EC, water content as well as the contents of organic C and total nitrogen (TN) in the top 10 cm of soil. The findings confirm that increasing the biomass of T. chinensis is an effective way to increase C sequestration in temperate coastal wetland. 相似文献
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Nitrogen cycling across the sediment-water interface in an eutrophic,artificially oxygenated lake 总被引：9，自引：0，他引：9
Processes controlling the nitrogen (N) exchange between water and sediment in eutrophic Lake Sempach were studied using three different independent methods: benthic flux chambers, interstitial water data and hypolimnetic mass balances. The sediments released NH
4
+
(1.1–16.1 mmoles m–2 d–1), NO
2
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(0.1–0.4 mmoles m–2 d–1) and dissolved organic N (<0.25 mmoles m–2 d–1). A net NO
3
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consumption (2.4–11.1 mmoles m–2 d–1) related to the NO
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concentrations in the overlying water was observed in all benthic chamber experiments. The flux of the reactive species NO
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and NH
4
+
was found to depend on hydrodynamic conditions in the water overlying the sediment. For this reason, benthic chambers overestimated the fluxes of inorganic N compared to the other methods. Thus, in short-term flux chamber experiments the sediment may either become a sink or a source for inorganic N depending on the O2 concentration in the water overlying the sediment and the stirring rate. As demonstrated with a15NO
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experiment, nitrate-ammonification accounted for less than 12% of the total NO
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consumption. After six years of artificial oxygenation in Lake Sempach, a decrease in hypolimnetic total inorganic nitrogen (TIN) was observed in the last two years. The occurrence of dense mats of H2S-oxidizingBeggiatoa sp. indicated micro-aerobic conditions at the sediment surface. Under these conditions, a shorter distance between the ecological niches of nitrifying and denitrifying bacteria, and therefore a faster NO
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-transport, can possibly explain the lowering of TIN by enhanced net denitrification. 相似文献
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《Ground Water Monitoring & Remediation》1989,9(4):134-140
Prince Edward Island is wholly dependent upon ground water from a highly permeable fractured sandstone aquifer for all industrial, domestic, agricultural, and potable uses. The contamination of this aquifer by agricultural residues, principally aldicarb and nitrate, has caused concern among Islanders. Ground water quality was monitored between 1985 and 1988 beneath two potato fields to which aldicarb (Temik) was applied at planting once or twice between 1983 and 1986. In May of 1988,12 percent of 48 monitoring well samples exceeded the drinking water guideline of 9μg/L for total aldicarb. Furthermore 32 percent of all samples exceeded the nitrate guideline of 10 mg/L. Aldicarb persistence appears related to its application at planting when soil temperatures are low and recharge is high and to the inhibiting pH effect that ammonium (from fertilizers and soil organic nitrogen) oxidation has on its degradation. Therefore, based on the research of others, it is recommended that aldicarb be applied at plant emergence when degradation is more rapid and recharge is lower. 相似文献
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Nitrogen contents range from a few parts per million in ordinary chondrites and achondrites to several hundred parts per million in enstatite chondrites and carbonaceous chondrites. Four major isotopic groups are recognized: (1) C1 and C2 carbonaceous chondrites have δ15N of+30to+50%.; (2) enstatite chondrites have δ15N of?30to?40‰; (3) C3 chondrites have low δ15N with large internal variations; (4) ordinary chondrites have δ15N of?10to+20‰. The major variations are primary, representing isotopic abundances established at the time of condensation and accretion. Secondary processes, such as spallation reactions, solar wind implantation and metamorphic loss may cause small but observable isotopic variations in particular cases. The large isotopic difference between enstatite chondrites and carbonaceous chondrites cannot be accounted for by equilibrium condensation from a homogeneous nebular gas, and requires either unusually large kinetic effects, or a temporal or spatial variation of isotopic composition of the nebula. Nitrogen isotopic heterogeneity in the nebula due to nuclear processes has not been firmly established, but may be required to account for the large variations found within the Allende and Leoville meteorites. The unique carbonaceous chondrite, Renazzo, has δ15N of+170%., which is well beyond the range of all other data, and also requires a special source. It is not yet possible, from the meteoritic data, to establish the mode of accretion of nitrogen onto the primitive Earth. 相似文献
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Elisa Soana Erica Racchetti Alex Laini Marco Bartoli Pierluigi Viaroli 《洁净——土壤、空气、水》2011,39(11):956-965
A nitrogen mass balance, realized for the lower Oglio River basin (Po River Plain, northern Italy), suggested an elevated impact of agricultural activities in this watershed. Livestock manure, synthetic fertilizers, biological fixation, atmospheric deposition, and wastewater sludge contributed 51, 34, 12, 2, and 1% of total N (TN) input, respectively (basin average 450 kg N ha?1 arable land (AL) year?1, overall input 100 115 t N year?1). Crop uptake, ammonia volatilization and denitrification in soils contributed 65, 21, and 14%, respectively, of TN output (basin average 270 kg N ha?1 AL year?1, overall output 60 060 t N year?1). N inputs exceeded outputs by 40 056 t N year?1, resulting in a basin average surplus of about 180 kg N ha?1 AL year?1. About 34% of the N surplus was exported annually from the basin while the remaining amount (about 26 800 t N year?1) underwent other unaccounted for processes within the watershed. The relevance of nitrogen removal via denitrification in aquatic compartments within the watershed was evaluated. Denitrification in the secondary drainage network can represent a relevant nitrogen sink due to great linear extension (over 12 500 km), with estimated nitrogen loss up to 8500 t N year?1. Denitrification in the riverbed and in perifluvial wetlands have the potential to remove only a small fraction of the nitrogen surplus (<3%). Evidence suggests the relevance of groundwater as a site of nitrogen accumulation. 相似文献
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红枫湖、百花湖沉积物全氮、可交换态氮和固定铵的赋存特征 总被引：39，自引：5，他引：34
氮是引起湖泊水体富营养化的关键营养元素之一。本次工作从贵州两个重要水库（红枫湖和百花湖）采集了未受扰动的沉积物样品性,分析了分层沉积物样品中的总氮,无机交换性氮和固定铵的含量及垂直剖面分布,研究表明,红枫湖和百花湖沉积物中具有较高的全氮含量,平均含量约为沉积物干重的0.36%～0.40%,其垂直分布在埋藏过程中受到成岩作用改造,沉积物交换性氮在沉积物中的赋存受到全氮含量和埋藏环境的双重控制,红枫湖和百花湖沉积物具有较强的吸持固定铵的能力,沉积物固定铵的绝对含量的平均值分别为434.05mg/kg和416.94mg/kg,分别占全氮的13.53%和12.53%。 相似文献
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Geomagnetism and Aeronomy - New research methods are being developed to get a broad picture of the temperature changes throughout the World Ocean. A permanent global network of oceanographic... 相似文献