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971.
972.
Concurrent ground-level ozone(O3) pollution and anthropogenic nitrogen(N) deposition can markedly influence dynamics and productivity in forests.Most studies evaluating the functional traits responses of rapid-turnover organs to O3 have specifically examined leaves,despite fine roots are another major source of soil carbon and nutrient input in forest ecosystems.How elevated O3 levels impact fine root biomass and biochemistry remains to be resolved.This study was... 相似文献
973.
土地细碎化是与土地规模经营理念相背离的一种土地形态,细碎化的土地经营模式会造成土地利用效率下降、粮食减产以及景观美观度降低等一系列问题。目前,土地细碎化程度的衡量多通过细碎度表征,但尚无统一标准,且主要针对农用地。以江苏东海县为例,首先结合景观指数与主成分分析,分别计算耕地、基础设施用地、居民点用地以及生态用地的细碎度,再通过系统聚类,分析不同地类细碎度组合的地域分异特征。结果显示:不同用地类型的细碎度是自然、社会经济的综合影响结果,耕地细碎度与居民点细碎度有着较显著的正相关关系,与生态用地细碎度有着较显著的负相关关系,基础设施用地细碎度和居民点细碎度存在一定的正相关关系,与生态用地细碎度存在一定的负相关关系,土地细碎度基于不同自然、社会经济条件,其分区也有着特定的区位特征。探讨不同用地类型细碎度间的关联性及空间分异特征可以为土地利用、经济发展以及景观改善等提供科学的引导 相似文献
974.
Abstract Public willingness to pay (WTP) for urban rivers restoration was investigated in Shanghai, Nanjing and Hangzhou in China with a sample of 1,285. The factors influencing positive WTP against zero WTP are analyzed using a binary logit model. The results indicate that income, Huji (residential registration) status, household size, home property ownership, riverfront access, and attitudes toward current water quality are statistically significant in the likelihood of positive WTP. It is also found that respondents without local Huji are less willingness to pay positively in pooled sample and Shanghai sample. In the group holding property right of house but without local Huji is less willingness to pay positively in Hangzhou. Respondents in Nanjing are more willingness to pay positively than those in Hangzhou. Most common arguments against to pay for the restoration are “government’s duty”, “low income”, “non-local-Huji” and “lack of trust in the government in how it spends money”. The results are generally consistent with the hypothesis and specific situations in China. The findings make some contributions to the non-market valuation studies as well as provide useful information for public policy making in China. 相似文献
975.
The Bashang area is a water-source area and ecological barrier zone for Beijing and Tianjin. The area is located at 200 km from Beijing and Tianjin and is a typical agriculture-pasture-interlacing zone, in which theis vulnerable and hence it is sensitive to anvironmental change. The area is relatively lagged in social and economic development, where the traditional cultivation mode is predominatedin agriculture and animal husbandry, but the disturbance by human activity is relatively small. Therefore, in order to reveal the interrelation between eco-environmental change in the area and environmental change in Beijing and Tianjin area, it is fairly necessary to study the effect of land-use and land-cover change on nutrients in soil in this area. According to the actual situation of changed land use for the limited time period, five series of changed land plots were selected and 4 samples were collected from each series for the study. The samples were collected from different soil-forming levels at the same site in different time. Analysis of the collected samples indicates that in the process of change of land use and land cover, the nutrients in soil, such as organic matter, total N, total P, total K, and available N, P, K, and B, Mo, Mn,Zn, Cu, and Fe, have regularly changed. When the land had changed from grassland and non-irrigated farmland into woodland, and from non-irrigated farmland into irrigated field, the nutrients in soil totally increased. But there exists some exception, i.e. quick-acting N, P, K, and some micreelements have appeared to be inconsistent with the mentioned above regularity in some cases. 相似文献
976.
大亚湾红海束毛藻赤潮生消过程研究 总被引:1,自引:0,他引:1
2004年6月15~18日广东省大亚湾海域发生了一次红海束毛藻(Trichodesmium erythraeum)赤潮,面积达100 km2,本文在现场监测与室内模拟实验的基础上,探讨了赤潮过程中红海束毛藻数量的时空分布特点及其与营养盐的关系.结果表明,赤潮高峰期(18日),表层红海束毛藻密度与叶绿素a浓度的平面分布趋势相同,呈现中心区>过渡区>边缘区的特点,且与水体营养盐含量(尤其是N、P)正相关;密度的垂直分布趋势是随水深的增加而迅速递减;表层藻细胞数量和叶绿素a浓度的最大值分别为4.71×107 /L和51.6 mg/m3.室内模拟实验结果显示,稀释对红海束毛藻的生长有促进作用,N: P比为16时对其生长的促进作用最大.本文还初步探讨了此次赤潮的来源和消亡的原因. 相似文献
977.
Peili Zhang Yang Du Yi Zhou Sheng Qi Songlin Wu Jiafeng Xu 《Journal of Loss Prevention in the Process Industries》2013,26(6):1279-1284
In order to investigate the effects of branch tunnels on explosion propagation, experiments were performed in five different configuration tunnels (straight configuration and configurations with 1 branch, 2 branches, 3 branches and 4 branches). Pressure and flame transducers were used to record the history of the pressure development and track the velocity of the flame front. It was shown that the branch tunnels had ability to enhance the maximum overpressure, rate of overpressure rise, and deflagration index (KG) of the gasoline–air mixture explosion due to the turbulence induced by the branch tunnels. The overpressure rise rate and KG of the explosion increased as a function of the number of branch tunnels. Experiments also showed that the maximum flame speed increased as the branch number increasing from 0 to 3 due to the enlargement of turbulence induced by the branch tunnels. However, an increase of branch number did not always lead to an enhancement of flame speed because the heat loss was intensified resulting from the increase of flame surface caused by the branch tunnels. When the number of branch tunnels exceeded 3, the maximum flame speed dropped. 相似文献
978.
Jun Dong He Sheng Chunyu Wen Mei Hong Huizhong Jiang 《Process Safety and Environmental Protection》2013,91(6):483-488
Anaerobic bioreactor attracted more attention in recent years because of its environmental and financial benefits. Nutrients and moisture could exert profound influences on the degradation of the pollutants and stabilization of solid waste in anaerobic landfill. The objective of this work was to investigate the effects of the activated sludge and phosphorous addition on the stabilization of solid waste. The experimental results indicated that phosphorous is the limiting nutrients in the landfill leachate; phosphorous and activated sludge simultaneously could stimulate the growth of the bacteria, enhance the attenuation of pollutants in landfill leachate and accelerate the stabilization of solid waste; the final removal efficiency of COD and NH4+-N in R-C (phosphorous and activated sludge added simultaneously) was up to 95.13% and 73.4%, respectively. Therefore, phosphorous addition is an effective way to enhance the stabilization of solid waste in anaerobic landfill. 相似文献
979.
Burning of crop residues is a common agricultural practice that incorporates the resulting particulate matter (ash) of high adsorptivity into soils. To investigate the effect of ash on the biodegradation of pesticides in soils, we measured the sorption, desorption, and biodegradation of benzonitrile in a silt loam in the presence and absence of an ash resulting from burning of wheat (Triticum aestivum L.) residue. Biodegradation experiments were conducted by inoculating sorbent slurries with a pure culture of benzonitrile-degrading bacteria (Nocardia sp.). Both liquid- and sorbed-phase benzonitrile concentrations were quantified over time. The ash was approximately 2000 times more effective per unit mass than the soil in sorbing benzonitrile. Amendment of the soil with 1% ash (by weight) resulted in a 10-fold increase in sorption. Sorption of benzonitrile by the ash significantly decreased the solution-phase concentration in the slurries of ash and ash-amended soil. Desorption of benzonitrile from the ash required approximately 60 min to complete, whereas approximately 20 min were required for desorption from the soil. Benzonitrile in the extracts of various sorbents and soil slurry was completely degraded within 500 min. However, the degradation was substantially reduced in the presence of the ash. At 2000 min, only 20% of benzonitrile in ash slurry and only 44% in ash-amended soil slurry were degraded. An acclimation period of approximately 100 min was observed in extracts and slurries containing the ash. Substantial reduction in the biodegradation of benzonitrile in the presence of wheat ash was apparently due to sorption of benzonitrile by the ash, slow desorption from the ash, and the increased acclimation period. Our results suggest that the presence of crop-residue-derived ash may increase the persistence of pesticides in agricultural soils. 相似文献
980.
呼吸防护用品符合人的形态与生理特征,才能保证其防护效果和舒适性。笔者从人体的面部形态与生理机能角度,分析了呼吸防护用品与人体的适配性,系统提出密合性、呼吸阻力、死腔、视野等呼吸防护用品的人机工效学问题。该论文取得的成果,对进一步丰富呼吸防护用品人机工效学研究内容,指导呼吸防护用品的设计与生产,提升我国呼吸防护用品的防护效果与核心竞争力,以期发挥积极的推动作用。 相似文献