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961.
南京市臭氧、VOCs和PANs污染特征及变化趋势 总被引:1,自引:0,他引:1
对2013—2016年基于国家环境空气质量监测站以及省建大气多参数站所获取的南京市O_3、NO_2、CO、VOCs、PANs观测结果进行综合评价,结果表明:2016年南京市O_3第90百分位日最大8 h平均质量浓度比2013年上升33.3%,超标天数中O_3引起的超标占比增至32.0%。南京市区大气中非甲烷总烃冬季浓度高于夏季,含氧挥发性有机物则与之相反;在5—9月,含氧挥发性有机物组分在日变化过程中出现峰值的时间先后顺序依次为醚、醛、酮类,且O_3和过氧乙酰硝酸酯(PANs)生成存在有一定的线性关系。VOCs/NOx比值表明南京市处于VOCs控制区,因此对NO_2浓度下降不敏感,植物源挥发性有机物连续3年上升,夏季大气光化学反应活性未显著下降,这些现象是城市O_3浓度维持在较高水平的重要因素。 相似文献
962.
TiO2光催化-微滤膜分离深度净化亚甲基蓝印染废水 总被引:1,自引:1,他引:0
采用悬浮式TiO2光催化膜反应器深度净化纺织工业园区含亚甲基蓝印染废水经生物处理二级出水,利用中空纤维微滤膜进行催化剂截留分离,研究催化剂投加量、运行时间、溶解氧、搅拌方式对出水水质及膜通量的影响。结果表明:光催化会消耗体系溶解氧,鼓风曝气搅拌可同时为系统供氧,优于机械搅拌;该耦合体系的催化剂最佳投加量为1 g/L,经光催化氧化-膜组合工艺处理后水质优于GB 4287-1992《纺织染整工业污染物排放标准》的I级标准,符合建设部颁布的《生活杂用水水质标准》(CJ/T 48-1999)。 相似文献
963.
城市污水厂污泥化学调理深度脱水机理 总被引:3,自引:0,他引:3
城市污水厂剩余污泥脱水是当前实际生产中亟待解决的问题。考察了厦门市集美污水厂剩余污泥经FeCl3和CaO,投加量分别为污泥质量分数的0.5%~0.7%和1.0%~1.5%化学调理前后污泥粒度、形态及胞外聚合物(extracellular polymeric substances,EPS)的变化。结果表明,调理后污泥比阻降低86%,污泥颗粒之间细碎紧密,细菌表面变得粗糙,经板框压滤后含水率低于60%。由三维荧光光谱(three-dimensional emission and excitation matrixs,EEM)光谱分析可知,LB-EPS(loosely bound-EPS)同TB-EPS(Tightly bound-EPS)的荧光峰整体发生红移,出现位于IV区域的色氨酸类蛋白质荧光峰Ex/Em=313/380 nm。FeCl3和CaO的加入一方面破坏了污泥颗粒的细胞结构,使EPS大量溶出,细胞结合水变成表面吸附水;另一方面Fe3+和CaO水解,中和污泥负电荷,通过压缩双电层作用破坏污泥胶体颗粒的稳定,去除表面吸附水,大幅提高了污泥的脱水性能,利于进一步板框压滤脱水。 相似文献
964.
建于城市远郊区的污水处理厂由于长距离管道输送污水中通常含有一定浓度的硫化物。通过郊区和城区污水处理厂硝化菌最大比增长速率常数(μA)的测定和硫化物抑制实验研究了硫化物对硝化菌活性的影响。经测定,位于郊区的白龙港污水处理厂15、20和25℃下μA值分别为0.19 d-1、0.50 d-1和0.72 d-1,而15℃和20℃下位于市区的曲阳厂μA值分别为0.41 d-1和0.80 d-1。通过向曲阳厂污泥中加入硫化钠和氯化钠的实验发现,低浓度钠离子对硝化菌活性没有明显的抑制作用;而硫化物在曝气条件下直接与污泥接触对硝化菌活性几乎没有影响,但不曝气混合接触后再曝气则硝化菌μA值将下降50%左右。硫化物的抑制作用很可能是白龙港厂硝化菌μA值明显低于曲阳厂实测值和文献报道值的原因。 相似文献
965.
曝气对生物促生剂修复城市黑臭河道水体的影响 总被引:3,自引:0,他引:3
在实验室条件下研究了曝气对生物促生剂修复城市黑臭河道水体效果的影响,并通过控制曝气时间及强度考察处理效果以确定曝气方式和曝气量。结果表明:在生物促生剂修复城市河道黑臭水体过程中使用曝气协同作用可大大增强生物促生剂的修复作用,加快修复速度。使用间歇曝气协同生物促生剂作用时效果与连续曝气相近,且可以降低运行成本。实验60d后,上覆水COD、NH3-N和TP去除率分别达46.8%、98.7%和73.3%,上覆水pH由7.61提高至7.92;底泥削减达5.49cm,底泥有机质削减率达10.5%。 相似文献
966.
Control strategies of atmospheric mercury emissions from coal-fired power plants in China 总被引:1,自引:0,他引:1
Tian H Wang Y Cheng K Qu Y Hao J Xue Z Chai F 《Journal of the Air & Waste Management Association (1995)》2012,62(5):576-586
Atmospheric mercury (Hg) emission from coal is one of the primary sources of anthropogenic discharge and pollution. China is one of the few countries in the world whose coal consumption constitutes about 70% of total primary energy, and over half of coals are burned directly for electricity generation. Atmospheric emissions of Hg and its speciation from coal-fired power plants are of great concern owing to their negative impacts on regional human health and ecosystem risks, as well as long-distance transport. In this paper, recent trends of atmospheric Hg emissions and its species split from coal-fired power plants in China during the period of 2000-2007 are evaluated, by integrating each plant's coal consumption and emission factors, which are classified by different subcategories of boilers, particulate matter (PM) and sulfur dioxide (SO2) control devices. Our results show that the total Hg emissions from coal-fired power plants have begun to decrease from the peak value of 139.19 t in 2005 to 134.55 t in 2007, though coal consumption growing steadily from 1213.8 to 1532.4 Mt, which can be mainly attributed to the co-benefit Hg reduction by electrostatic precipitators/fabric filters (ESPs/FFs) and wet flue gas desulfurization (WFGD), especially the sharp growth in installation of WFGD both in the new and existing power plants since 2005. In the coming 12th five-year-plan, more and more plants will be mandated to install De-NO(x) (nitrogen oxides) systems (mainly selective catalytic reduction [SCR] and selective noncatalytic reduction [SNCR]) for minimizing NO(x) emission, thus the specific Hg emission rate per ton of coal will decline further owing to the much higher co-benefit removal efficiency by the combination of SCR + ESPs/FFs + WFGD systems. Consequently, SCR + ESPs/FFs + WFGD configuration will be the main path to abate Hg discharge from coal-fired power plants in China in the near future. However advanced specific Hg removal technologies are necessary for further reduction of elemental Hg discharge in the long-term. 相似文献
967.
Yi He Christopher E. Pedigo Billion Lam Zhongqi Cheng Yan Zheng 《Journal of environmental science and health. Part. B》2013,48(2):74-80
Rice can be a major contributor to dietary arsenic exposure because of the relatively high total arsenic concentration compared to other grains, especially for people whose main staple is rice. This study employed in vitro gastrointestinal fluid digestion to determine bioaccessible or gastrointestinal fluid extractable arsenic concentration in rice. Thirty-one rice samples, of which 60 % were grown in the United States, were purchased from food stores in New York City. Total arsenic concentrations in these samples ranged from 0.090 ± 0.004 to 0.85 ± 0.03 mg/kg with a mean value of 0.275 ± 0.161 mg/kg (n = 31). Rice samples with relatively high total arsenic (>0.20 mg/kg, n = 18) were treated by in vitro artificial gastrointestinal fluid digestion, and the extractable arsenic ranged from 53 % to 102 %. The bioaccessibility of arsenic in rice decreases in the general order of extra long grain, long grain, long grain parboiled, to brown rices. 相似文献
968.
Yong-Jun Zhao Pu Cheng Xi Pei Hui Zhang Cheng Yan Shou-Bing Wang 《Environmental science and pollution research international》2013,20(7):4886-4894
The performance and temporal variation of hybrid vertical-subsurface flow constructed wetlands (VFCWs) in response to two-stage combinations of vertical upflow (VUF) and vertical downflow (VDF) were analyzed in this research. The results of high carbon (C) treatment and high nitrogen (N) treatment were similar. The Lythrum salicaria treatment showed higher removal efficiency than CWs planted with Acorus calamus. Under high C- and N-loading treatments, the optimum two-stage combination was VDF-VUF VFCWs planted with A. calamus. Furthermore, the highest nutrient removal efficiencies were achieved in late summer (July and August) and early autumn (September). The chemical oxygen demand and total nitrogen removal efficiencies were significantly affected (P?<?0.05) by season, system, and wetland plant. 相似文献
969.
Danqing Liu Chunhua Zhang Xue Chen Yazhou Yang Shu Wang Yujiao Li Hao Hu Ying Ge Wangda Cheng 《Environmental science and pollution research international》2013,20(12):8947-8954
The rhizosphere plays an important role in altering cadmium (Cd) solubility in paddy soils and Cd accumulation in rice. However, more studies are needed to elucidate the mechanism controlling rice Cd solubility and bioavailability under different rhizosphere conditions to explain the discrepancy of previous studies. A rice culture with nutrient solution and vermiculite was conducted to assess the effects of pH, Eh, and iron (Fe) concentration on Cd, Fe fractions on the vermiculite/root surface and their uptake by rice. The solution pH was set from 4.5 to 7.5, with additions of Fe (30 and 50 mg L?1) and Cd (0.5 and 0.9 mg L?1). At pH 5.5, the Eh in the rice rhizosphere was higher whereas transpiration, Cd2+, and Fe2+ adsorption on the vermiculite/root surface and accumulation in rice were lower than the other pH treatments. Cadmium addition had no impact on pH and Eh in rice rhizosphere while Fe addition decreased pH and increased Eh significantly. Compared with control, Fe addition resulted in the decrease of rhizosphere Cd, Fe solubility and bioavailability. Higher redox potential in the rice rhizosphere resulted in the decline of transpiration, Cd, and Fe accumulation in the rice tissues, suggesting that the transfer of two elements from soil to rice was depressed when the rhizosphere was more oxidized. 相似文献
970.
Aquatic plant debris improve phosphorus sorption into sediment under anoxic condition 总被引:1,自引:0,他引:1
Chong-Wei Jin Shao-Ting Du Wu-Yuan Dong Jue-Hua Wang Cheng Shen Yong-Song Zhang 《Environmental science and pollution research international》2013,20(11):8237-8244
The effects of plant debris on phosphorus sorption by anoxic sediment were investigated. Addition of plant debris significantly enhanced the decrease of soluble relative phosphorus (SRP) in overlying water at both 10 and 30 °C during the 30-day investigation. Both cellulose and glucose, two typical plant components, also clearly enhanced the SRP decrease in anoxic overlying water. The measurement of phosphorus (P) fractions in sediment revealed that the levels of unstable P forms were decreased by plant debris addition, whereas the opposites were true for stable P forms. However, under sterilized condition, plant debris/glucose addition has no effect on the SRP decrease in overlying water. Overall, our results suggested that plant debris improve P sorption into sediment under anoxic condition through a microorganism-mediated mechanism. 相似文献