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排序方式: 共有563条查询结果,搜索用时 31 毫秒
501.
Quantification of net carbon flux from plastic greenhouse vegetable cultivation: a full carbon cycle analysis 总被引:1,自引:0,他引:1
Wang Y Xu H Wu X Zhu Y Gu B Niu X Liu A Peng C Ge Y Chang J 《Environmental pollution (Barking, Essex : 1987)》2011,159(5):1427-1434
Plastic greenhouse vegetable cultivation (PGVC) has played a vital role in increasing incomes of farmers and expanded dramatically in last several decades. However, carbon budget after conversion from conventional vegetable cultivation (CVC) to PGVC has been poorly quantified. A full carbon cycle analysis was used to estimate the net carbon flux from PGVC systems based on the combination of data from both field observations and literatures. Carbon fixation was evaluated at two pre-selected locations in China. Results suggest that: (1) the carbon sink of PGVC is 1.21 and 1.23 Mg C ha−1 yr−1 for temperate and subtropical area, respectively; (2) the conversion from CVC to PGVC could substantially enhance carbon sink potential by 8.6 times in the temperate area and by 1.3 times in the subtropical area; (3) the expansion of PGVC usage could enhance the potential carbon sink of arable land in China overall. 相似文献
502.
Jinju Geng Qiang Wang Xiaojun Niu Xiaorong Wang 《Frontiers of Environmental Science & Engineering》2007,1(1):120-124
Effects of pH, temperature, and oxygen on the production and release of phosphine in eutrophic lake sediments were investigated under laboratory tests. Results indicated that the elimination of matrix-bound phosphine was accelerated under initial pH 1 or 12. Phosphine levels could reach maximum under initial pH 10. The contents of phosphine increased with the addition of alkali under pH 4–12. The rates of phosphine production and release from lake sediments varied with temperature. 20°C was the most favorable temperature for the production of matrix-bound phosphine. Oxygen showed little effect on matrix-bound phosphine. Matrix-bound phosphine concentrations in lake sediments were concluded to be dependent on a balance of natural generation and depletion processes. 相似文献
503.
国内焦化废水处理技术探讨 总被引:4,自引:0,他引:4
针对焦化生产环境污染和资源浪费严重的情况,国家自2005年1月1日起实施<焦化行业准入条件>,要求焦化废水经处理后要做到内部循环使用.焦化废水的处理主要采用一级预处理和二级生化处理.目前国内较先进的焦化废水处理技术有A2/O、固定化高效微生物处理技术(3T-AF/BAF)等. 相似文献
504.
Release of polycyclic aromatic hydrocarbons from Yangtze River sediment cores during periods of simulated resuspension 总被引:5,自引:0,他引:5
The role of resuspension duration on release of 16 PAHs was measured experimentally using a particle entrainment simulator (PES). Three sediment cores were resuspended for 12h at 0.2 and 0.5N m(-2). PAHs in water column and total suspended solids (TSS) were monitored at intervals. After 0.25h of resuspension, PAH release was on average 42% of their concentrations after 12h of resuspension, indicating fast release of PAHs from sediments in an initial short time. Moreover, PAHs released faster at 0.5N m(-2) than at 0.2N m(-2); low molecular weight PAHs (2-3-ring) released faster than median molecular weight (4-ring) PAHs. PAH concentrations in TSS showed generally increase with time and differences in magnitudes based on sediment type and energy. Overall, the composition of sediments is the major factor in determining the amount of released PAHs, more so than the level of resuspension energy applied. 相似文献
505.
Nan Bao Yuan Li Xiao-Hong Yu Jun-Jian Niu Guo-Lin Wu Xiao-Hong Xu 《Environmental science and pollution research international》2013,20(2):897-906
Textile dye effluents are typically characterized by strong color and recalcitrance, even at very low concentration. The process of enrichment of anionic azo dye on the surface of TiO2 fibers followed by photosensitization degradation under ambient air conditions was extensively investigated. Adsorption isotherms and zeta potentials were used to describe the “dye/TiO2 surface” interface, taking into account the effects of pH on the nature and population of the surface groups on the TiO2 fibers. The extent of the photocatalytic degradation of dye on TiO2 surface was determined by FTIR. N2 adsorption isotherms and optical spectra were employed to investigate the effect of photosensitization. The adsorption of dyes on the TiO2 surface occurs via electrostatic attraction through the formation of single- or multidentate-coordinated surface complexes. Almost complete photobleaching of the absorption band at 534 nm is achieved in ~4 h. Dye-sensitized TiO2 fiber could absorb part of the visible light spectrum (λ?<?600 nm). Interfacial electron transfer can potentially alter the degradation efficiency. The regenerated TiO2 fiber could be reused for subsequent decolorization without a decline in adsorption efficiency compared with freshly prepared TiO2 samples, which may be attributed to preservation of the hierarchical pore structure and restoration of the original surface properties. In summary, we propose an efficient “adsorption–photoregeneration–reuse” process applying TiO2 fibers for the degradation of dyes in water. 相似文献
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507.
采用共沉淀法合成出一系列镁铝摩尔比不同的碳酸根型水滑石(LDHs),经500℃高温煅烧制备出镁铝复合氧化物CLDH,并用X-射线、红外光谱对它们进行表征。考查了吸附剂投加量、反应时间、初始pH值等因素对LDHs和CLDH处理阴离子染料活性艳红X-3B模拟废水效果的影响,并对吸附机理进行探讨。实验结果表明:以镁铝摩尔比为3∶1时制得的水滑石对活性艳红X-3B溶液的脱色效果最好。水滑石LDHs及其焙烧产物CLDH对活性艳红X-3B染料均具有较好的吸附性能,最佳反应时间分别为60 min和30 min;在较宽的pH范围内二者的脱色性能稳定,且CLDH对该染料的吸附效果要优于LDHs。LDHs及CLDH对活性艳红X-3B的吸附结果符合Langmuir吸附等温式,25℃下饱和吸附量分别为263.77 mg/g和875.23 mg/g。LDHs及CLDH的吸附机理分别为离子交换和层状结构重建。饱和吸附后的CLDH用高温热解法再生,吸附性能良好,随再生次数增多,脱色率下降。 相似文献
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