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401.
祁连山高山草甸土壤CO2通量的时空变化及其影响分析 总被引:1,自引:0,他引:1
采用Li-6400便携式光合作用测量系统连接Li-6400-09土壤呼吸室,在2004年生长季节对祁连山高山草甸土壤CO2通量沿海拔梯度进行了野外定位试验,统计分析了水热因子及根系生物量对高山草甸土壤CO2通量特征的可能影响.结果表明,土壤CO2通量存在明显的空间变化规律, 沿海拔梯度土壤CO2通量随着海拔梯度的增加而逐渐减小,其变异系数逐渐增加;就日变化而言,土壤CO2通量晚间维持在较低水平,02:00~06:00最低,在07:00~08:30开始升高,11:00~16:00达到峰值,16:00~18:30开始下降,整个过程呈单峰曲线.土壤CO2通量的日平均值介于(0.56±0.32) ~ (2.53±0.76) μmol·(m2·s)-1.从季节变化来看,土壤CO2通量均以夏秋季较高,春冬季排放量较低,7~8月份达到最大值[4.736 μmol·(m2·s)-1],6月与9月份次之,5月与10月份基本一致,整个生长过程总的变化趋势呈单峰曲线形式.高山草甸土壤CO2通量在植物生长季与10 cm土壤温度、土壤含水量、根系生物量都存在不同程度的正相关关系,表明高山草甸土壤CO2通量的空间变异主要受温度、水分和植物根系的综合影响. 相似文献
402.
OBJECTIVE: The aim of this study was to investigate head injuries, injury risks, and corresponding tolerance levels of children in car-to--child pedestrian collisions. METHODS: An in-depth accident analysis was carried out based on 23 accident cases involving child pedestrians. These cases were collected with detailed information about pedestrians, cars, and road environments. All 23 accidents were reconstructed using the MADYMO program with mathematical models of passenger cars and child pedestrians developed at Chalmers University of Technology. The contact properties of the car models were derived from the European New Car Assessment Program (EuroNCAP) subsystem tests. RESULTS: The accident analysis demonstrated that the head was the most frequently and severely injured body part of child pedestrians. Most accidents occurred at impact speeds lower than 40 km/h and 98% of the child pedestrians were impacted from the lateral direction. The initial postures of children at the moment of impact were identified. Nearly half (47%) of the children were running, which was remarkable compared with the situation of adult pedestrians. From accident reconstructions it was found that head impact conditions and injury severities were dependent on the shape and stiffness of the car front, impact velocity, and stature of the child pedestrian. Head injury criteria and corresponding tolerance levels were analyzed and discussed by correlating the calculated injury parameters with the injury outcomes in the accidents. CONCLUSIONS: Reducing head injuries should be set as a priority in the protection of child pedestrians. HIC is an important injury criterion for predicting the risks of head injuries in child pedestrian accidents. The tolerance level of head injuries can have a considerable variation due to individual differences of the child pedestrians. By setting a suitable speed limit and improving the design of car front, the head injury severities of child pedestrians can be reduced. 相似文献
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对海底管线穿孔后如何阻止溢油、减少海上.油污染,提出了采用负压保护的可行性方案. 相似文献
406.
统计了洛阳分公司2006年度事故隐患情况,从未遂事件、事故隐患的时间段、后果、性质、直接原因等方面进行了深入细致的分析,找出影响洛阳分公司安全生产的主要隐患,提出了相应对策措施和建议. 相似文献
407.
对几种浮选剂在荆门石化污水处理场的处理效果进行了对比,结果表明岳阳云溪XY-Ⅱ和江苏武进PAFC比现有PAC浮选剂的处理效果佳,且运行成本低. 相似文献
408.
Chunyan Liu Kai Wang Shixie Meng Xunhua Zheng Zaixing Zhou Shenghui Han Deli Chen Zhiping Yang 《Agriculture, ecosystems & environment》2011,140(1-2):226-233
One-year winter wheat–summer maize rotation is the most popular double cropping system in north-central China, and this highly productive system is an important source of nitrous oxide (N2O) and nitric oxide (NO) emissions due to the high fertilizer N and irrigation water inputs. To sustain the high crop production and mitigate the detrimental impacts of N2O and NO emissions, improved management practices are extensively applied. The aim of this study is therefore to evaluate the effects of an improved management practice of irrigation, fertilization and crop straw on grain yield and N2O and NO emissions for a wheat–maize rotation field in northern China. Using automated and manual chamber measuring systems, we monitored N2O and NO fluxes for the conventional (CT, 2007–2008), improved (IT, 2007–2008), straw-amended (WS, 2008–2009), straw-not-amended (NS, 2008–2009), and no N-fertilizer treatments (WS–NN, 2008–2009), respectively, for one rotation-year. The grain yields were determined for CT and IT for three rotation-years (2005–2008) and for WS, NS and WS–NN for one rotation-year (2008–2009). The improved management of irrigation and fertilization reduced the annual N fertilization rate and irrigation amount by 17% and 30%, respectively; increased the maize yield by 7–14%; and significantly decreased the N2O and NO emissions by 7% (p < 0.05) and 29% (p < 0.01), respectively. The incorporation of wheat straw increased the cumulative N2O and NO emissions in the following maize season by 58% (p < 0.01) and 13%, respectively, whereas the effects of maize straw application were not remarkable. The N2O and NO emission factors of applied N were 2.32 ± 2.32% and 0.42 ± 1.69% for wheat straw and 0.67 ± 0.23% and 0.54 ± 0.15% for chemical N-fertilizers, respectively. Compared to conventional management practices using high application rates of irrigation water and chemical N-fertilizer as well as the field burning of crop straw, the improved management strategy presented here has obvious environmentally positive effects on grain yield and mitigation of N2O and NO emissions. 相似文献
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