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701.
The amount of struvite (MgNH4PO4·6H2O) produced by Myxococcus xanthus as well as the culture parameter values (pH, total phosphorus, total Kjeldahl nitrogen) were dependent on the culture medium used. Struvite formation started during the exponential phase and the maximum concentration was observed at the beginning of stationary growth phase. The addition of each medium component to the liquid culture influenced the amount of crystal produced. This amount did not depend on the pH increase during the culture period. The moment of the bacterial growth phase, at which each medium component was added, influenced the struvite formation. 相似文献
702.
703.
以2020年1月—2021年9月对流层观测仪(TROPOMI)卫星观测资料反演获取的对流层甲醛(HCHO)、二氧化氮(NO2)柱浓度数据为依据,采用统计方法分析了扬州市HCHO和NO2柱浓度的时空分布特征。结果表明,扬州市对流层HCHO、NO2平均柱浓度分别为903.01×1013, 633.77×1013mole/cm2;受太阳紫外辐射影响,HCHO柱浓度变化特征表现为6月最高、1月最低;受气象条件和人为排放强度影响,NO2则表现为1月最高、8月最低。2021年1—9月扬州市对流层HCHO、NO2柱浓度月均值同比2020年分别增长4.0%,40.6%。空间分布特征显示,扬州市对流层HCHO和NO2浓度高值区主要分布在扬州市南部,且浓度高值区域与重点排污企业分布情况较为一致,多为电力供热、工业锅炉、冶金、石化与化工、表面涂层等行业。相关性分析显示,对流层HCHO与气温、臭氧浓度呈显著正相关,而NO2与气温、臭氧浓度呈显著负相关。 相似文献
704.
Elofsson K 《Environmental management》2006,37(1):54-68
Excess nutrient loads to coastal waters lead to increased production of algae, which when decaying cause oxygen depletion
in bottom sediments, which in turn leads to major changes in marine ecosystems. A cost-minimization model was investigated
in which nitrogen and phosphorus were assumed to interact with respect to algae production. It was investigated under what
conditions only a single nutrient should be decreased and when it is cost-effective to decrease both nutrients. The model
was applied to the Baltic Proper, which is the largest of the seven major basins in the Baltic Sea. Results showed that the
stringency of the environmental target, as well as assumptions regarding substitutability between nutrients, are important
factors to determine the nutrient on which to focus. Uniform decrease rates for emissions are often used in international
agreements, and the results of this model showed that the costs of making such proportional decreases could be substantial. 相似文献
705.
Assessing the Effects of Nutrient Management in an Estuary Experiencing Climatic Change: The Neuse River Estuary, North Carolina 总被引:1,自引:0,他引:1
Eutrophication is a serious water quality problem in estuaries receiving increasing anthropogenic nutrient loads. Managers
undertaking nutrient-reduction strategies aimed at controlling estuarine eutrophication are faced with the challenge that
upstream freshwater segments often are phosphorus (P)-limited, whereas more saline downstream segments are nitrogen (N)-limited.
Management also must consider climatic (hydrologic) variability, which affects nutrient delivery and processing. The interactive
effects of selective nutrient input reductions and climatic perturbations were examined in the Neuse River Estuary (NRE),
North Carolina, a shallow estuary with more than a 30-year history of accelerated nutrient loading and water quality decline.
The NRE also has experienced a recent increase in Atlantic hurricanes and record flooding, which has affected hydrology and
nutrient loadings. The authors examined the water quality consequences of selective nutrient (P but not N) reductions in the
1980s, followed by N reductions in the 1990s and an increase in hurricane frequency since the mid-1990s. Selective P reductions
decreased upstream phytoplankton blooms, but increased downstream phytoplankton biomass. Storms modified these trends. In
particular, upstream annual N and P concentrations have decreased during the elevated hurricane period. Increased flushing
and scouring from storms and flooding appear to have enhanced nutrient retention capabilities of the NRE watershed. From a
management perspective, one cannot rely on largely unpredictable changes in storm frequency and intensity to negate anthropogenic
nutrient enrichment and eutrophication. To control eutrophication along the hydrologically variable freshwater–marine continuum,
N and P reductions should be applied adaptively to reflect point-source–dominated drought and non–point-source–dominated flood
conditions. 相似文献
706.
高浓度氨氮废水处理技术及其发展趋势 总被引:9,自引:0,他引:9
介绍了高浓度氨氮废水的主要来源及其危害性,对国内外主要的高浓度氨氮废水处理工艺进行了分析和对比,并阐述了其发展趋势,为处理高浓度氨氮废水工艺技术的选择提供了参考。 相似文献
707.
708.
采用缺氧/好氧一体式膜生物反应器(A/O-MBR)处理城市污水,试验结果表明:系统处理效果稳定,出水COD、NH3-N、TN的平均去除率分别达到92%、95%和80%以上,各项出水水质优于《城市杂用水水质》(GB/T18920-2002)标准。当水力停留时间在6~18 h、曝气强度(气水比)在20∶1~60∶1之间变化时,水力停留时间和曝气强度对MBR运行效果的影响不甚显著;温度对COD去除的影响不大,但温度对NH3-N、TN有显著的影响,温度由9.5℃升至30℃时,NH3-N、TN去除率分别由6.2%、7.9%提高到99.0%、83.3%。 相似文献
709.
To study the pH preference of epiphytic lichens, the bark pH of Fraxinus, Tilia, Quercus and Ulmus trees in an urban environment was measured using a flat surface electrode. The total number of trees was 253. A survey was made of the lichens in a 40 × 40 cm quadrat surrounding the pH measurement point. Our data analysis using multivariate and univariate statistical techniques indicates that the tree species is the most important factor influencing lichen colonisation, and that bark pH alone is of less importance. We hypothesize that the changed pollution climate, with strong decreases in both sulphur dioxide and ammonia concentrations over the past two decades and a concomitant general increase in bark pH, has made epiphytes less sensitive to pH. 相似文献
710.
Cecilia Akselsson Salim Belyazid Gunilla Pihl-Karlsson 《Environmental pollution (Barking, Essex : 1987)》2010,158(12):3588-3595
Nitrogen leaching from boreal and temporal forests, where normally most of the nitrogen is retained, has the potential to increase acidification of soil and water and eutrophication of the Baltic Sea. In parts of Sweden, where the nitrogen deposition has been intermediate to high during recent decades, there are indications that the soils are close to nitrogen saturation. In this study, four different approaches were used to assess the risk of nitrogen leaching from forest soils in different parts of Sweden. Nitrate concentrations in soil water and C:N ratios in the humus layer where interpreted, together with model results from mass balance calculations and detailed dynamic modelling. All four approaches pointed at a risk of nitrogen leaching from forest soils in southern Sweden. However, there was a substantial variation on a local scale. Basing the assessment on four different approaches makes the assessment robust. 相似文献