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291.
Wang Lisha He Zhibin Li Jing 《Environmental science and pollution research international》2020,27(32):40061-40074
Environmental Science and Pollution Research - Identifying the magnitude and seasonal variability of groundwater nitrogen (N) under various land use types and quantifying the contribution of their... 相似文献
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2016年9月利用多波束测深仪调查了张家洲河段河床微地貌的高分辨率形态与分布特征,结合1998年和2013年水下地形资料,分析了三峡截流以来该河段河槽的冲淤变化与演变趋势。结果表明:(1)张家洲河段整体呈冲刷状态,净冲刷量17.2×10.6 m3。其中,张家洲南水道是强冲刷区,最大冲刷深度约9 m;(2)河槽表层沉积物中值粒径为149.1~226.3 μm,与历史资料相比呈粗化趋势;(3)张家洲河段约82.9%的主航道发育了沙波,约14.0%的主航道发育了冲刷坑与冲刷槽,平床地形仅占3.1%。流域来沙量减少是张家洲河段整体冲刷的主要原因,而河流控制工程稳定了河势,迫使水流归槽,加剧了张家洲南水道的冲刷。随着流域来沙量持续减少,张家洲南水道主航道有可能进一步冲刷 相似文献
294.
He Genhe Wang Xiaodong Liu Xu Xiao Xiaoyu Huang Shoucheng Wu Jichun 《Russian Journal of Ecology》2018,49(6):524-533
Russian Journal of Ecology - The present study characterized the nutrients availability of three rare earth tailings deserted in different time stages in Southern Jiangxi of China, and revealed the... 相似文献
295.
Because natural ecosystems and ecosystem services (ES) are both critical to the well-being of humankind, it is important to understand their relationships and congruence for conservation planning. Spatial conservation planning is required to set focused preservation priorities and to assess future ecological implications. This study uses the combined measures of ES models and ES potential to estimate and analyze all four groups of ecosystem services to generate opportunities to maximize ecosystem services. Subsequently, we identify the key areas of conservation priorities as future forestation and conservation hotspot zones to improve the ecological management in Chongqing City, located in the upper reaches of the Three Gorges Reservoir Area, China. Results show that ecosystem services potential is extremely obvious. Compared to ecosystem services from 2000, we determined that soil conservation could be increased by 59.11%, carbon sequestration by 129.51%, water flow regulation by 83.42%, and water purification by 84.42%. According to our prioritization results, approximately 48% of area converted to forests exhibited high improvements in all ecosystem services (categorized as hotspot-1, hotspot-2, and hotspot-3). The hotspots identified in this study can be used as an excellent surrogate for evaluation ecological engineering benefits and can be effectively applied in improving ecological management planning. 相似文献
296.
Qing Zhao Kebin He Kenneth A. Rahn Yongliang Ma Fumo Yang Fengkui Duan 《Atmospheric environment (Oxford, England : 1994)》2010,44(21-22):2615-2624
Depletion of Si in transported dust has been recognized for many years. It can be used to distinguish between transported and local dust in cities, although it rarely has been. Here we use the variations of the Si/Al ratio in 15 months of continuous PM2.5 samples at Beijing (northern China) and Chongqing (southwestern China) to reveal the seasonal patterns of their dust sources. For both cities, peaks of concentration for Si and Al in PM2.5 corresponded with minima of Si/Al, and could often be linked to pulsed air flow from deserts to the northwest. With significant depletion (up to 80%) and homogeneous distribution at urban and rural sites, Si/Al showed a clear seasonal evolution, which decreased from spring to summer, increased from fall to winter, and collapsed during Chinese Spring Festival, indicating the dominance of transported dust, local fugitive dust and firework influence, respectively. The low ratios implied that desert dust is a common source during spring at Chongqing, whereas its presence during cold season at Beijing was also more frequent than expected. Failing to recognize the depletion of Si may lead to an overestimate of desert dust by 15%–65% when using the average abundance of Al in crust (6%–8%), as in previous studies. The difference in Si/Al ratio between local and transported dust implies that >60% of the dust at Beijing came from outside the city during the springs of 2004–2006. This result can help resolve the contradictory findings on this topic that have been presented earlier. 相似文献
297.
Jinzhu Ma Yongchun Liu Hong He 《Atmospheric environment (Oxford, England : 1994)》2010,44(35):4446-4453
To further understand the role of substrates on the heterogeneous reactions of polycyclic aromatic hydrocarbons, the reactions of ozone with anthracene adsorbed on different mineral oxides (SiO2, α-Al2O3 and α-Fe2O3) and on Teflon disc were investigated in dark at 20 °C. No reaction between ozone and anthracene on Teflon disc was observed when the ozone concentration was ~1.18 × 1014 molecules cm?3. The reactions on mineral oxides exhibited pseudo-first-order kinetics for anthracene loss, and the pseudo-first-order rate constant (k1,obs) displayed a Langmuir–Hinshelwood dependence on the gas-phase ozone concentration. The adsorption equilibrium constants for ozone (KO3) on SiO2-1, SiO2-2, α-Al2O3 and α-Fe2O3 were (0.81 ± 0.26) × 10?15 cm3, (2.83 ± 1.17) × 10?15 cm3, (2.48 ± 0.77) × 10?15 cm3 and (1.66 ± 0.45) × 10?15 cm3, respectively; and the maximum pseudo-first-order rate constant (k1,max) on these oxides were (0.385 ± 0.058) s?1, (0.101 ± 0.0138) s?1, (0.0676 ± 0.0086) s?1 and (0.0457 ± 0.004) s?1, respectively. Anthraquinone was identified as the main surface product of anthracene reacted with ozone. Comparison with previous research and the results obtained in this study suggest that the reactivity of anthracene with ozone and the lifetimes of anthracene adsorbed on mineral dust in the atmosphere are determined by the nature of the substrate. 相似文献
298.
石膏浆液旋流器的分离性能实验研究 总被引:1,自引:1,他引:0
通过理论分析及工程经验对石灰石/石膏法烟气脱硫工艺中石膏浆液脱水系统的旋流器进行优化设计,在与工业实际相近的操作条件下,优选出了一根综合性能较好的旋流器。考察了该旋流器的压力、流量与分离效率之间相互关系,与常规石膏浆液旋流器的分级效率进行了比较,确定了最佳操作条件。结果表明,旋流器的进口流量随着进出口压力差的增大而增大,分离效率随着流量增加先上升后下降。在进口硫石膏颗粒平均粒径为24μm,流量为11.8~14.8 m3/h时,分离效率在85%以上,底流出口10μm、15μm以下的颗粒分别占底流出口颗粒总体积的1%、10%左右,起到了很明显的分级浓缩作用,分离性能也优于常规使用的石膏浆液旋流器。 相似文献
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300.