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871.
火花放电条件下CS_2转化为COS的反应 总被引:3,自引:1,他引:2
利用火花放电技术模拟研究了自然界闪电作用下CS2转化为COS的反应. 结果表明, 放电条件(电压3000 V)下CS2(初始分压为1.33×103 Pa)能与空气(25 ℃, 103 Pa)中的氧气、水蒸气作用, 转化为COS以及其他含硫含碳产物(CO、CO2、SO2等); CS2初始分压、水蒸气和放电时间等因素对COS生成量有明显的影响. 并在实验基础上结合多种理论, 探讨了相关过程的大气闪电反应机理. 这些结果可为自然界闪电条件下的硫循环、碳循环过程的研究提供重要依据. 相似文献
872.
多壁碳纳米管对土壤微生物的生态毒理效应 总被引:2,自引:0,他引:2
以多壁碳纳米管为研究对象,从生化作用、酶活性、微生物数量和群落结构4个方面系统评估其对土壤微生物的影响。设置两组实验,分别为碳纳米管组和对照组。对于碳纳米管组,按1mg碳纳米管·g-1土的浓度将多壁碳纳米管与土样均匀混合,对照组中不加入多壁碳纳米管。定期(每28d)取样测定两组土壤中的各项生态毒理指标。近5个月的实验结果显示,不同指标对多壁碳纳米管的响应不同。土壤呼吸作用初期受抑制但后期恢复,氨化作用初期被促进但后期被抑制,脱氢酶活性发生增强和抑制两次波动,荧光素二乙酸酯酶活性在整个实验期间一直被抑制,微生物量出现先减少后增加再减少的规律,群落结构在实验初期和后期均有较大变化。总体上,多壁碳纳米管对土壤微生物表现了一定的生态毒性,但除荧光素二乙酸酯酶活性外,各毒理效应在统计意义上并不显著(0.05水平)。 相似文献
873.
Using the tomato variety 'Qin Feng Bao Guan' as experimental material, and by the hydroponics nutrient solution method, we investigated the effects of single and compound applications of nitric oxide (NO) donor sodium nitroprusside (SNP) and salicylic acid (SA) on the gas exchange and chlorophyll fluorescence parameters, RuBisCO activation, CO2 response curve, photosynthetic pigment content, and xanthophyll cycle in seedling leaves under an NaCl stress of 100 mmol/L. The main findings were as follows: (1) Single or combined applications of SNP and SA could increase the net photosynthetic rate (Pn), stomatal conductance (Gs), PS II maximal photochemistry efficiency (Fv/Fm), antenna conversion efficiency (Fv'/Fm'), practical photochemical efficiency (φPS?), photochemical fluorescence quenching coefficient (qP), and chlorophyll fluorescence decay rate (Rfd) of tomato seedling leaves at different rates, and significantly reduce the intercellular CO2 concentration (Ci), original fluorescence (Fo), and PS II non-photochemical fluorescence quenching coefficient (NPQ), after NaCl stress treatment. The strongest effect was observed after applying a combination of SNP and SA. (2) Under NaCl stress, the decrease of CO2 carboxylation efficiency (CE), RuBP maximum regeneration rate (Jmax), RuBisCO and its activation enzyme activity, and the maximum carboxylation rate (Vc max) in tomato seedling leaves could be effectively relieved by SNP, SA, or SNP + SA applications; however, SNP + SA treatment had the strongest effect. (3) Single or combined applications of SNP and SA could effectively inhibit the decrease of the contents of photosynthetic pigments (chlorophyll a, chlorophyll b, and carotenoids), the ratio of chlorophyll a and chlorophyll b, xanthophyll cycle pool size (V + A + Z), and the increase of the de-epoxidation extent of the xanthophyll cycle (A + Z)/(V + A + Z). The combined application of SNP and SA had the most prominent effect. In conclusion, the heat dissipation of the antenna, which is dependent on the xanthophyll cycle, is not the physiological mechanism for the protection of the photosynthetic apparatus by exogenous NO, SA alone, or compound treatment in tomato seedling leaves under NaCl stress. It is the main reason for the increase of photosynthetic function and enhanced salt tolerance of leaves tomato seedlings that the protection of PS II and its primary electron acceptor quinone (QA) downstream electron transfer patency, and the improvement of CO2 assimilation activity by application of exogenous NO, SA alone, or a combination of the two; synergistic effects were observed after using a combination of SNP and SA. © 2018 Science Press. All rights reserved. 相似文献
874.
There is a rapidly emerging and potentially huge market for the remediation of contaminated groundwater in China. The Chinese government published a Water Action Plan in April 2015, a Soil Action Plan in May 2016, and a draft Soil Pollution Prevention and Control Law in June 2017. All of these new policies and regulations put pressures on local governments and contaminated site owners, obliging them to conduct site investigation and to cleanup contaminated groundwater. The Chinese population in northern regions heavily depend on groundwater, with nearly 70% of water supply coming from aquifer sources in the Beijing-Tianjin-Hebei region. However, poor groundwater quality due to natural geochemical background and anthropogeic pollution is a serious concern, with poor or very poor quality water observed in nearly 80% of groundwater monitoring wells in 17 northern provinces. Shallow groundwater in many areas has been contaminated by toxic pollutants such as heavy metals and chlorinated organic compounds. There is an urgent need to better understand the situation and to conduct groundwater remediation at contaminated sites. The Chinese government is investing heavily in the research and development for groundwater remediation, which is expected to greatly add to the quality and quantity of groundwater remediation projects in the near future. 相似文献
875.
Lirong Z Linglong H Yunyan H Jingguo S Wenqing C 《Journal of environmental biology / Academy of Environmental Biology, India》2010,31(6):1023-1030
In recent years, there has been an apparent increase in the occurrence of harmful algalblooms in fresh waters. The value of applying the novel wattle extract (Acacia mimosa) to inhibitalgal growth was assessed. Our results showed that the growth of Microcystis aeruginosa was successfully repressed by the plant extract and resulted in decreased extracellular microcystin-LR production. In the experiments, it showed a very effective inhibition in the stage of exponential growth (the largest decrease in level is 47.3% of the control) especially in nonsterile conditions, and the extract can reduce 14.5-24.7% cell density of the control in the stationary stage. In outdoor experiments, the extract reduced dissolved oxygen and pH, and selectively cut down cyanobacterial cell density to one-third of the control after 36 d of treatment. Accordingly due to competitive inhibition in interspecies, other nanoalgae and small-sized aquatic animals declined, while macrozooplankton increased. Finally more large algae were eliminated and thereby the water treated was clarified and the recovery of the freshwater ecosystem was promoted. Hence, the present study suggested a new and more effective and very low ecological risk approach to reduce nuisance blooms cyanobacteria in eutrophic water 相似文献
876.
Forest succession is the base of establishing restoration reference which plays an important role in forest restoration and restoration estimation. The study presented the establishment of a Markov successional model (MSM) and its application to restoration reference in lower subtropical forest in China. The compositions of successional system in MSM were divided into three species types: pioneering pine trees, heliophytic trees and mesophytic trees. The successional system was divided into three subsystems: early successional stage, mid-successional stage and late-successional stage. Based on the site survey on the changes in the species and their individuals in 25 years, the transition matrices in various subsystems were determined. The predicted results were used to establish the restoration reference of the vegetation restoration in lower subtropical China. According to the ecological restoration reference established in this study, it would take 150 years for the forest to change from pioneer to mature communities in the region. Successional change of tree composition was forecast by the model, and the scenario forecast by the model reflects the actual conditions observed through 52 years of long-term permanent site research. The restoration experience in the region matches the forecast results. The application of a restoration reference model indicates that forest restoration can be accelerated by taking measures which change forest structure. The above results imply that a restoration reference established on the rule of regional forest succession could be very useful not only in directing, but also in assessing and managing regional forest restoration. Previously, one “ideal reference ecosystem” was used as a restoration reference in all correlative studies. In this study, the restoration “process” was used as the restoration reference. 相似文献
877.
曝气复氧对滇池重污染支流底泥污染物迁移转化的影响 总被引:5,自引:3,他引:2
利用模拟试验方法,研究和探讨了河道曝气复氧对滇池重污染支流底泥污染物迁移转化的影响,结果表明:(1)曝气复氧会导致上覆水体pH值上升0.6~1.0;(2)曝气复氧对上覆水体中TN、TP的质量浓度影响相似,在好氧处理条件下呈下降趋势,而在不曝气的对照处理中呈持续上升趋势,两种状况上覆水体TN、TP的平均变化速率分别为:-0.156 mg·L-1·d-1、-0.060mg·L-1·d-1和0.414mg·L-1·d-1、0.036mg·L-1·d-1;(3)上覆水体中COD的质量浓度在好氧和对照两种处珲条件下,表现出两种不同的变化趋势,前者先上升后下降,而后者先下降后上升,平均变化速率分别为-0.361 mg·L-1·d-1和0.314 mg·L-1·d-1;(4)曝气复氧可抑制河道底泥向上覆水释放污染物质,适合于重污染河道水体修复. 相似文献
878.
采用包埋曝气流化床与陶粒曝气生物滤池对相同微污染源水进行处理,比较二者在出水氨氮、亚硝酸氮、CODMn、浊度的差异。结果表明,虽然陶粒曝气生物滤池的去除效果要好于包埋曝气流化床,但是包埋的出水效果较好,而且不需要反冲洗,一旦激活后便运行稳定。包埋菌固化技术应用在微污染水处理方面具有较大潜力。 相似文献
879.
Xiaojing Ren Changwei Zhao Songshan Du Tao Wang Zhaokun Luan Jun Wang Deyin Hou 《环境科学学报(英文版)》2010,22(9):1335-1341
The feasibility of employing nanofiltration for the removal of chromium(VI) from wastewater was investigated. Poly (m-phenylene
isophthalamide) (PMIA) was used to fabricate asymmetric nanofiltration membrane through the phase-inversion technique. Scanning
electron microscopy (SEM) and atomic force microscopy (AFM) were used to characterize the obtained membrane, and the both
confirmed a much smoother surface which could reduce membrane fouling. The PMIA membrane showed di erent rejections to
electrolytes in a sequence of Na2SO4 > MgSO4 > NaCl > MgCl2, which was similar to the sequence of the negatively charged
nanofiltration membranes. Separation experiments on chromium(VI) solution were conducted at various operating conditions, such
as feed concentration, applied pressure and pH. It is concluded that chromium(VI) could be e ectively removed from chromiumcontaining
wastewater by the PMIA nanofiltration membranes while maintaining their pollution resistance under alkaline condition. 相似文献
880.
Deyin Hou Jun Wang Changwei Zhao Baoqiang Wang Zhaokun Luan Xiangcheng Sun 《环境科学学报(英文版)》2010,22(12):1860-1867
The direct contact membrane distillation applied for fluoride removal from brackish groundwater was investigated.The self-prepared polyvinylidene fluoride membrane exhibited high rejection of inorganic salt solutes.The maximum permeate flux 35.6 kg/(m2 ·hr) was obtained with the feed solution at 80°C and the cold distillate water at 20°C.The feed concentration had no significant impact on the permeate flux and the rejection in fluoride.The precipitation of CaCO3 would clog the hollow fiber inlets and foul the membrane surface with increasing concentration factor when natural groundwater was used directly as the feed,which resulted in a rapid decline in the module efficiency.This phenomenon was diminished by acidification of the feed.The experimental results showed that the permeate flux and the quality of obtained distillate kept stable before concentration factor reached 5.0 with the acidified groundwater as feed.The membrane module efficiency began to decline gradually when the feed continued to be concentrated,which can be mainly attributed to the formation of CaF2 deposits on the membrane surface.In addition,a 300 hr continuous fluoride removal experiment of acidified groundwater was carried out with concentration factor at 4.0,the permeate flux kept stable and the permeate fluoride was not detected. 相似文献