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71.
Steven G. McNulty Johnny L. Boggs 《Environmental pollution (Barking, Essex : 1987)》2010,158(6):2053-2058
Federal agencies of several nations have or are currently developing guidelines for critical forest soil acid loads. These guidelines are used to establish regulations designed to maintain atmospheric acid inputs below levels shown to damage forests and streams. Traditionally, when the critical soil acid load exceeds the amount of acid that the ecosystem can absorb, it is believed to potentially impair forest health. The excess over the critical soil acid load is termed the exceedance, and the larger the exceedance, the greater the risk of ecosystem damage. This definition of critical soil acid load applies to exposure of the soil to a single, long-term pollutant (i.e., acidic deposition). However, ecosystems can be simultaneously under multiple ecosystem stresses and a single critical soil acid load level may not accurately reflect ecosystem health risk when subjected to multiple, episodic environmental stress. For example, the Appalachian Mountains of western North Carolina receive some of the highest rates of acidic deposition in the eastern United States, but these levels are considered to be below the critical acid load (CAL) that would cause forest damage. However, the area experienced a moderate three-year drought from 1999 to 2002, and in 2001 red spruce (Picea rubens Sarg.) trees in the area began to die in large numbers. The initial survey indicated that the affected trees were killed by the southern pine beetle (Dendroctonus frontalis Zimm.). This insect is not normally successful at colonizing these tree species because the trees produce large amounts of oleoresin that exclude the boring beetles. Subsequent investigations revealed that long-term acid deposition may have altered red spruce forest structure and function. There is some evidence that elevated acid deposition (particularly nitrogen) reduced tree water uptake potential, oleoresin production, and caused the trees to become more susceptible to insect colonization during the drought period. While the ecosystem was not in exceedance of the CAL, long-term nitrogen deposition pre-disposed the forest to other ecological stress. In combination, insects, drought, and nitrogen ultimately combined to cause the observed forest mortality. If any one of these factors were not present, the trees would likely not have died. This paper presents a conceptual framework of the ecosystem consequences of these interactions as well as limited plot level data to support this concept. Future assessments of the use of CAL studies need to account for multiple stress impacts to better understand ecosystem response. 相似文献
72.
The United States’ legal strategy for addressing climate change in recent years has relied on authority from existing legislation. This has led to measures on a number of different greenhouse gases, notably carbon dioxide, methane and hydrofluorocarbons. However, one greenhouse gas has been largely forgotten: nitrous oxide. Nitrous oxide is the third most abundantly emitted greenhouse gas in the U.S. and worldwide, as well as the largest remaining threat to the stratospheric ozone layer. In addition, the nitrogen atoms in nitrous oxide are part of the highly fluid nitrogen cycle where nitrogen atoms transform readily among different chemical forms, each with a unique environmental and human health impact – a process known as the nitrogen cascade. While the science of the nitrogen cascade has been explored for over a decade, there has been little work on the legal implications of this phenomenon. And yet the nitrogen cascade expands the legal options available for controlling nitrous oxide. This paper studies these options in a U.S. context and explores the environmental and economic impacts of enacting them. We determine that the Clean Air Act, and in particular its broad authority for controlling ozone depleting substances, is the most promising legal pathway for regulating nitrous oxide across all major sources. Invoking such authority could generate significant climate and stratospheric ozone benefits over 2015–2030, equivalent to taking 12 million cars permanently off the road, and 100 million chlorofluorocarbon-laden refrigerators out of service. The economic benefits could sum to over $700 billion over 2015–2030, with every $1.00 spent on abating emissions leading to $4.10 in societal benefits. The bulk of these benefits would come from reductions in other forms of nitrogen pollution such as ammonia and nitrate, highlighting the important and multiple co-benefits that could be achieved by abating nitrous oxide emissions. With the Paris Climate Agreement calling for limiting global temperature increases to “well below” two degrees Celsius, all mitigation opportunities across all sectors need to be considered. This paper suggests that nitrous oxide warrants more attention from policy-makers in the U.S. and around the world. 相似文献
73.
Tianlong Zheng Peng Li Xiaoyu M Xiaohong Sun Chuanfu Wu Qunhui Wang Ming Gao 《环境科学学报(英文版)》2019,31(3):336-345
A pilot-scale multilevel contact oxidation reactors system, coupled with saran lock carriers,was applied for the treatment of poultry farm wastewater. The removal efficiencies of CODcr, ammonia, and the total nitrogen as well as the elimination performance of CODcr and total nitrogen along the three-level contact oxidation tanks under six designed operational models were investigated. Based on the performance of the nitrogen removal of the saran lock carriers and the distribution of anoxic–aerobic interspace under the suitable operation model, the mechanism of nitrogen removal of the system was also explored. The results revealed that the intermittent aeration under parallel model is the most suitable operation model, while the removal efficiencies of CODcr, ammonia, and the total nitrogen were 86.86%, 84.04%, and 80.96%, respectively. The effluent concentration of CODcr,ammonia, and the total nitrogen were 55.6 mg/L, 8.3 mg/L, and 12.0 mg/L, which satisfy both the discharge standard of pollutants for livestock and poultry breeding industry(GB18596–2001) and the first grade of the integrated wastewater discharge standard(GB 8978–1996). Moreover, the mechanism for the nitrogen removal should be attributed to the plenty of anoxic–aerobic interspaces of the biofilm and the three-dimensional spiral structure of the saran lock carriers, where the oxygen-deficient distribution was suitable for the happening of the simultaneous nitrification and denitrification process. Therefore, the multilevel contact oxidation tanks system is an effective pathway for the treatment of the poultry farm wastewater on the strength of a suitable operation model and novel carriers. 相似文献
74.
Sesbania rostrata in pure and amended Pb/Zn tailings. About 90% of seeds of S. rostrata germinated in pure Pb/Zn tailings, which contained high concentrations of Pb, Zn, Cu, and Cd. Although seedling growth suffered
from the adverse environment of Pb/Zn tailings, they became established on tailings stands, in the greenhouse, as well as
on the actual tailings dam, and completed their life cycle in 4 months. Dry matter production and nitrogen accumulation was
3200 kg/ha and 69.4 kg/ha, respectively in the actual tailings dam. Applying inorganic fertilizer to Pb/Zn tailings led to
no obvious improvement in growth and nodulation of S. rostrata, while tailings amended by river sediment or domestic refuse rich in organic matter improved the growth and nodulation of
the species. Azorhizobium caulinodans survived and formed N-fixing stem and root nodules in S. rostrata grown in pure Pb/Zn tailings with a nodule biomass exceeding 300 mg fresh matter per plant. 相似文献
75.
Xiaoya Liu Yu Hong Peirui Liu Jingjing Zhan Ran Yan 《Frontiers of Environmental Science & Engineering》2019,13(5):78
76.
Zhiqiang Chen Lizhi Zhao Ye Ji Qinxue Wen Long Huang 《Frontiers of Environmental Science & Engineering》2019,13(4):54
77.
《Ecological modelling》2003,170(2-3):245
With the increasing importance and awareness of water quality in the small basins, the modelling system is developed for monitoring and predictions of surface water pollution. The compartment model deals with basin characteristics extended by land cover attributes. The parameters of the model are estimated by experimental data of water quality together with land cover types that serve as nutrient detention media or transformers. The study examines methodology to determine the potential areas of nitrate pollution from point and non-point sources by remote sensing techniques. Classification of water, agricultural, forest and urban areas is processed with satellite images (LANDSAT 7). Whereas the agricultural and urban areas act as sources of pollution, forest zones operate as sinks. The nitrate levels are decreased downstream, if the proportion of the forest inside contribution zones increases. The modelling system is used to simulate amounts of nitrates in each compartment of the stream during the monitored period of one year. The number of compartments and their lengths are estimated on the basis of morphology of the basin. Simulation of the dynamic model is carried out with the TabSim. Geographic information system (GIS) and remote sensing tools are used to manage and estimate nitrate inflows from point and non-point sources of pollution. The article presents the spatial and time variation of the nitrate (NO3−) within the basin of the stream Rakovnický (the west part of Bohemia, the whole area of 368 km2). It is shown that the model approach extended by the GIS and remote sensing can support decision-making process for better management practices in the basins. 相似文献
78.
饮用水生物预处理除氮技术 总被引:4,自引:0,他引:4
依据饮用水中氮元素各种污染形式间的转化机量,介绍了国内外利用生物预处理技术除氮的工艺和经验,讨论了运行控制中的各种影响因素,对生物预处理技术的除氮发展进行了展望。 相似文献
79.
F.?L.?Toma G.?Bertrand D.?KleinEmail author C.?Coddet 《Environmental Chemistry Letters》2004,2(3):117-121
We studied the removal of nitrogen oxides pollutants via TiO2 Degussa P25 powder by photocatalysis. Parameters such as mass of catalyst, geometric irradiated surface, catalyst morphology, and thermal treatment were tested to explain the photocatalytic concentration decrease of nitrogen oxides. According to our working conditions, the conversion rates increased until an optimal value of the TiO2 weight, 35% of NO concentration and around 20% of NOx, was decomposed by the photocatalysis. The NOx removal increased proportionally with the irradiated geometric surface. The structural transformation of anatase to rutile performed by thermal treatment involved the decrease of the photocatalytic activity. 相似文献
80.
M. A. C. Veer 《Journal of Coastal Conservation》1997,3(1):41-48
The encroachment of some tall grass species in open dune vegetation, as observed in a Dutch dry dune area, is considered unfavourable
from a conservation viewpoint. This paper investigates differences in vegetation and soil properties between grass-dominated
and still existing open dune grassland plots at four locations along the coast. Soil properties studied include nitrogen and
phosphorus pools and nitrogen availability by mineralization. Vegetation properties included are above and below-ground biomass
and nitrogen and phosphorus concentrations in above-ground biomass.
Systematic differences in N-pools between grass-dominated and open dune grassland plots were not observed. However, N-availability
by mineralization and its turnover rates are higher in grass-dominated plots than in open dune grassland plots, as well as
above and below-ground biomass. In open dune grassland plots, atmospheric N-input is an important source of N, whereas in
grass-dominated plots mineralization largely exceeds atmospheric N-input. However, these observations do not explain the mosaic-like
vegetation pattern. Grazing intensity is most likely the determinant factor in the dry dune system. It is concluded, that
grass encroachment is probably triggered by atmospheric deposition and is enhanced by positive feedbacks in the N-cycle. The
relevance of these results for restoration management is briefly discussed. 相似文献