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621.
A new method of determining the cumulate concentration of hydroxyl radicals in the TiO2/Ti photoelectrocatalytic(PEC)oxidation system was established by o-phenanthroline-Fe(Ⅱ)(Fe(phen)32+) spectrophotometry and using anion exchange membrane. Fe concentration of hydroxyl radicals can be calculated through determining the change of the Fe(phen)33+ absorbency at 509 nm. In addition, the research results showed the production rate of hydroxyl radicals was affected obviously by pH of solution, the cumulate concentration of hydroxyl radicals was the largest at nearby the initial pH 6.3 (isoelectric point), and the change direction of pH after illumination tended to nearby isoelectric point. 相似文献
622.
针对隧道洞口埋深浅且软弱围岩稳定性差这一问题,提出在地表增设混凝土框架梁,设置扩大头锚杆与框架梁连接并深入软弱围岩,运用数值模拟分析“混凝土框架梁-扩大头锚杆”结构加固软弱地层后的力学特性。研究结果表明:采用“混凝土框架梁-扩大头锚杆”加固隧道洞口软弱地层,k=0.4时,相比于没有加固对照模型,隧道最大拱顶沉降值下降68.7%,隧道最大边墙收敛值下降15.1%,初期支护最大等效应力减小12.7%;建立不同加固区围岩松动压力分散系数k下的数值模型,通过拱顶沉降结果与加固区围岩松动压力分散系数的线性拟合,提出采用加固结构后的隧道拱顶沉降规律与围岩松动压力计算方法。 相似文献
623.
提高钠离子交换器工作交换容量浅析 总被引:4,自引:0,他引:4
分析了钠离子交换器影响工作交换容量的因素,研究了交换剂在交换器中工作情况的层状特性,低盐耗条件下再生程度,浓度与工作交换容量关系,再生液流速根据交换剂反应的特性一般控制在4-8 m/h范围时合适,防止交换剂污染也是保证提高钠离子交换器工作交换容量的关键. 相似文献
624.
用人外周血淋巴细胞和大麦根尖细胞做姊妹染色单体交换(SCE)实验,发现丝裂霉素C、放线菌酮D、异烟酰肼及糖精钠能显著提高SCE频率,而且诱发细胞的平均SCE值在两种材料中有极显著的一致性,表明植物细胞SCE在检出环境诱变剂中与人外周血淋巴细胞同样敏感有效。在高浓度介质中植物幼苗生长发育受到抑制,处理的早期可检测到幼苗根尖细胞SCE水平的明显升高。环境中的重金属铬和镉即使浓度较低也能通过大麦SCE实验检测到。结果表明,大麦根尖细胞SCE实验能有效地检测出环境中的有害因素。 相似文献
625.
626.
采用大田开顶式气室熏气实验,研究大气汞浓度升高对水稻叶片气体交换参数、脯氨酸、丙二醛的积累以及超氧化物歧化酶活性的影响。实验结果显示,水稻叶片净光合速率(Pn)和气孔导度(Gs)随大气汞浓度的升高均较对照略微下降,表明大气汞浓度的升高对水稻光合作用和气孔开放程度有一定影响;扬花期水稻胞间CO2浓度(Ci)随大气汞浓度的升高明显降低(P0.05)表明Pn的略微下降属于气孔限制,同时蒸腾速率(Tr)显著增加(P0.01)表明大气汞对水稻的蒸腾生理功能有一定的影响。乳熟期水稻叶片气体交换参数与大气汞浓度无显著差异(P0.05),且各指标均低于扬花期。水稻叶片脯氨酸(Pro)含量在拔节期随大气汞浓度的升高而显著增加(P0.05),扬花期先升高后下降,在45 ng·m-3时达到最大,成熟期无显著差异(P0.05);水稻叶片丙二醛(MDA)含量在拔节期先升高后下降,45 ng·m-3时达到最大,扬花期和成熟期均无显著差异(P0.05);水稻叶片超氧化物歧化酶(SOD)活性在拔节期先升高后下降,15 ng·m-3时达到最大,扬花期无显著差异(P0.05)。以上结果表明大气汞浓度的升高可以引起水稻叶片膜脂过氧化以及脯氨酸和丙二醛含量的积累,且随着体内Pro、MDA和SOD对大气汞胁迫的协同反应,水稻对逆境的适应能力增强,对汞胁迫产生了耐受性。 相似文献
627.
Jörg Rinklebe Anja During Mark Overesch Gijs Du Laing 《Environmental pollution (Barking, Essex : 1987)》2010,158(1):308-318
Environmental pollution by mercury (Hg) is a considerable environmental problem world-wide. Due to the occurrence of Hg volatilization from their soils, floodplains can function as an important source of volatile Hg. Soil temperature and soil water content related to flood dynamics are considered as important factors affecting seasonal dynamics of total gaseous mercury (TGM) fluxes. We quantified seasonal variations of TGM fluxes and conducted a laboratory microcosm experiment to assess the effect of temperature and moisture on TGM fluxes in heavily polluted floodplain soils. Observed TGM emissions ranged from 10 to 850 ng m−2 h−1 and extremely exceeded the emissions of non-polluted sites. TGM emissions increased exponentially with raised air and soil temperatures in both field (R2: 0.49-0.70) and laboratory (R2: 0.99) experiments. Wet soil material showed higher TGM fluxes, whereas the role of soil water content was affected by sampling time during the microcosm experiments. 相似文献
628.
629.
Stankov Jovanovic VP Ilic MD Markovic MS Mitic VD Nikolic Mandic SD Stojanovic GS 《Chemosphere》2011,84(11):1584-1591
Fire has been considered as an improving factor in soil quality, but only if it is controlled. Severe wild fire occurred in the summer 2007 on the Vidlic Mountain (Serbia) overspreading a huge area of meadows and forests.Main soil characteristics and content of heavy metals (Cu, Pb, Cd, Zn) in different fractions obtained after sequential extraction of soil from post-fire areas and from fire non disturbed areas were studied. In four plant species of Lamiaceae family (Ajuga genevensis L., Lamium galeobdolon (L.) L., Teucrium chamaedrys L., Acinos alpinus (L.) Moench.), that grow in typical habitats of the mountain, distribution of heavy metals in aerial parts and roots was investigated too.For all samples from post-fire area cation exchange capacity and soil organic matter content are increased while rH is decreased. Fire caused slightly increased bioavailability of the observed metals but more significant rise happened in metal amounts bound to oxides and organics. The plants showed variable behavior. T. chamaedrys collected on the post-fire area contained elevated concentrations of all analyzed metals. A. alpinus showed higher phytoaccumulation for Zn and Cd, while the other two plant species for Pb and Cd in the post-fire areas. 相似文献
630.
Simultaneous removal of ammonium and phosphate by zeolite synthesized
from coal fly ash as influenced by acid treatment 总被引:5,自引:0,他引:5
ZHANG Bao-hu WU De-yi WANG Chong HE Sheng-bing ZHANG Zhen-ji KONG Hai-nan 《环境科学学报(英文版)》2007,19(5):540-545
Zeolite synthesized from fly ash (ZFA) without modification is not efficient for the purification of NH4+ and phosphate at low concentrations that occur in real effluents, despite the high potential removal capacity. To develop an effective technique to enhance the removal efficiency of ammonium and phosphate at low concentrations, ZFA was modified with acid treatment and the simultaneous removal of ammonium and phosphate in a wide range of concentration was investigated. It was seen that when compared with untreated ZFA, only the treatment by 0.01 mol/L of H2SO4 significantly improved the removal efficiency of ammonium at low initial concentrations. The behavior was well explained by the pH effect. Treatment by more concentrated H2SO4 led to the deterioration of the ZFA structure and a decrease in the cation exchange capacity. Treatment by 0.01 mol/L H2SO4 improved the removal efficiency of phosphate by ZFA at all initial P concentrations, while the treatment by concentrated H2SO4 (≥0.9 mol/L) resulted in a limited maximum phosphate immobilization capacity (PIC). It was concluded that through a previous mild acid treatment (e.g. 0.01 mol/L of H2SO4), ZFA can be used in the simultaneous removal of NH4+ and P at low concentrations simulating real effluent. 相似文献