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931.
在全球变化背景下,青藏高原降水格局发生改变,并影响高寒草地温室气体排放.为了更好地认识降水变化与高寒草地温室气体排放的关系,在2015年7月24日,通过人工降水6.7 mm,研究了单次降水对高寒草地温室气体昼夜变化的影响.表明:(1)单次降水没有改变土壤温度,但显著增加了土壤湿度;(2)单次降水后24小时内,高寒草地CH4吸收量降低了2.46倍,CO2和N2 O排放量分别提高15.3%和98.9%;(3)单次降水弱化了高寒草地CH4和N2 O排放量与土壤温度的关系. 相似文献
932.
933.
杭州市PM2.5中水溶性离子的污染特征及其消光贡献 总被引:4,自引:3,他引:1
对杭州市2013年大气PM_(2.5)进行采样分析,探讨了其中水溶性离子的污染特征和消光贡献.杭州市PM_(2.5)中总水溶性离子的质量浓度为37.5μg·m~(-3),占PM_(2.5)质量浓度的44.4%,二次离子SNA(SO_4~(2-)、NO_3~-和NH_4~+)是水溶性离子的主要成分,共占到水溶性离子的83.4%.PM_(2.5)和主要水溶性离子的质量浓度都在冬季最大,夏季最低,夏秋季水溶性离子占PM_(2.5)的比值明显高于冬春季,而SNA在总水溶性离子中的比例4个季节非常接近.燃料燃烧和汽车尾气排放导致的二次离子生成,对杭州市PM_(2.5)贡献最大.SOR和NOR的年平均值分别为0.27和0.15,SO_2在大气中的转化率大于NO_x,SOR和NOR与相对湿度都呈现出明显正相关,非均相氧化过程对SO_4~(2-)和NO_3~-的生成具有重要贡献.气溶胶中[NO_3~-]/[SO_4~(2-)]的年平均值为0.63,主要受到燃煤排放的影响.霾天随着霾污染等级的逐渐加重,PM_(2.5)、水溶性离子和SNA的浓度都逐渐增大,SOR和NOR值也不断升高,霾天稳定的天气条件,能有效促进污染物的积累和二次转化.PM_(2.5)和SNA的质量浓度与大气消光系数都呈现出明显正相关,使用IMPROVE公式对不同化学组分消光系数的计算结果能够基本反映出气溶胶对大气散射的变化趋势,其结果显示SNA对大气总消光系数的贡献达60.8%.SNA的消光系数冬季最高,夏季最低,随着霾污染等级的加重,SNA的消光系数和对总消光的贡献比例也逐步增加. 相似文献
934.
935.
混凝和活性炭吸附去除微污染水源水中DON的研究 总被引:8,自引:4,他引:4
溶解性有机氮(dissolved organic nitrogen,DON)作为饮用水中新兴氮消毒副产物(nitrogenous disinfection by-products,N-DBPs)的前体物逐渐受到国内外学者的关注.为探讨混凝和活性炭吸附对微污染水源水中DON的去除机制,首先测定原水中DON、溶解性有机炭(dissolved organic carbon,DOC)、NH4+-N、UV254、pH和溶解氧(dissolved oxygen,DO)等指标和DON、DOC分子量分布;接着通过混凝和活性炭吸附试验来考察原水中DON、DOC和UV254变化,并应用三维荧光光谱对原水中DON变化进行表征.结果表明,微污染水源水中DON、DOC和UV254分别为1.28 mg.L-1、8.56 mg.L-1和0.16 cm-1,DOC与DON比值(DOC/DON)为6.69 mg.mg-1,SUVA为1.87 m-1.(mg.L-1)-1;小分子量(<6 000)DON占较高比例约为68%,大分子量(>20 000)DON占的比例为22%;当混凝剂投加量为10 mg.L-1,DON的去除率大约为20%,DOC和UV254去除率约26%、70%;当活性炭投加量为1.0 g,DON、DOC和UV254的去除率大约为60%、35%、100%;混凝和活性炭吸附组合试验时,对DON、DOC的去除率大约为82%和64%;三维荧光光谱证实,原水中DON变化与3个主要峰有关,分别代表物质为色氨酸类蛋白质、芳香族类蛋白质和富里酸类物质. 相似文献
936.
The production, use, and disposal of nanomaterials may inevitably lead to their appearance in water. With the development of new industries around nanomaterials, it seems necessary to be concerned about the transport of nanomaterials in the environment. In this paper, the transport of acid-treated carbon nanotubes (CNTs) in porous media was investigated. Before the mobility investigation, the stability of acid-treated CNT dispersions was studied using ultraviolet-visible spectra and it was indicated that, under the chemical conditions employed in this work, there was no apparent aggregation. The mobility investigation showed that transport of acid-treated CNTs increased with treatment time due to increase in particle zeta potential. Carbon nanotubes treated with nitric acid for 2, 6, and 12 h possessed measured zeta potentials of -30.0, -43.0, and -48.5 mV, respectively. Utilizing clean-bed filtration theory, we showed that acid-treated CNTs have the potential to migrate 3.28, 5.67, and 7.69 m in saturated glass beads, respectively. We showed that solution ionic strength and pH have important effects on the mobility of acid-treated CNTs. Increasing the pH from 6.0 to 7.9 resulted in an increase in migration potential from 2.96 to 10.86 m. Increasing the ionic strength from 0.005 to 0.020 M resulted in a decrease in CNT migration potential from 5.67 to 1.42 m. 相似文献
937.
Tracking the implementation of green credit policy in China: top-down perspective and bottom-up reform 总被引:1,自引:0,他引:1
The Chinese government has introduced the green credit policy to mitigate the environmental impact of industrialization by reining in credit loans to companies and projects with poor environmental performance. This research investigated the implementation of the green credit policy both at the national and provincial levels. Our results show that the green credit policy is not fully implemented. The wide-ranging impact on high-polluting and high energy-consuming industries, vague policy details unclear implementing standards, and lack of environmental information are the main problems in the implementation of the green credit policy in China. On the other hand, the practice at local level (Jiangsu Province) is more practical by integrating green credit policy with the environmental performance rating system. Finally, suggestions are outlined to improve China's green credit policy. 相似文献
938.
The Jianghan Plain and the Dongting lake area, located in the middle reaches of the Yangtze River are famous for their abundant freshwater lakes. The lakes have undergone changes in size and number over thousands of years due to natural causes and human activities. The 20th century particularly, witnessed dramatic changes in the freshwater resources of this region. This paper traces and analyzes lake evolution in the middle reaches of the Yangtze River over the past century. Lakes greater than 0.1 km(2) in size are mapped using Geographic Information System. Data is acquired and integrated from drainage network maps, relief maps, historical maps and remotely sensed images for different time periods. The results indicate that while there has been little change in the number of lakes over the past century, the lake area has experienced a dramatic decrease of 58.06%. The paper also examines the natural processes and human activities that may have contributed to the decrease in lake area. The results show that the decrease in total lake area appears to coincide with periods of rapid land reclamation in the middle reaches of the Yangtze River. Moreover, uncontrolled land reclamation activities can create an increase in sediment deposition in lakes thereby further reducing the lake size. Reduction of the lake area directly affects flood-control and has a negative ecological impact on the environment and on human life and property. 相似文献
939.
940.
植物激素对平菇茵丝生长及酶活性的影响 总被引:2,自引:0,他引:2
采用固体平板和液体摇瓶培养方法,研究了赤霉素、2,4-D、吲哚乙酸和萘乙酸4种激素对平菇- 126菌丝生长及酶活性的影响.结果表明,吲哚乙酸虽然能提高发酵液胞外蛋白的含量和过氧化物酶活性,但对菌丝的生长起抑制作用,这与吲哚乙酸能引起平菇菌丝裂解和细胞膜渗漏有关;萘乙酸、低浓度2,4-D能促进菌丝的伸长;萘乙酸、赤霉素在低浓度下也能促进菌丝的分枝,对菌丝的生长整体上起促进作用.除吲哚乙酸外,其他3种激素对平菇菌丝生长影响都有两重性:低浓度下能促进菌丝的生长,浓度过高则会对菌丝生长产生毒害作用. 相似文献