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排序方式: 共有170条查询结果,搜索用时 15 毫秒
1.
研究对比了邻苯二甲酸二丁酯(DBP)在不同降解过程(水解、UV/H2O2光解、直接光解、过硫酸钾光氧化)中的碳、氢同位素组成变化、分馏特征及二维同位素(Δδ2H-Δδ13C)的相关性.水解反应中DBP分子产生了显著的碳同位素分馏,未发现氢同位素分馏,而且碳同位素富集因子εC为(-2.7±0.4)‰,表明DBP水解时发生C-O键断裂,氢原子不参与反应.而UV/H2O2光解和直接光解反应(pH值分别为2、7和10)中,DBP分子呈现了相似的二维同位素相关性Λ值[(9±2)~(11±2)],推测经历了相同的反应过程.过硫酸钾光氧化降解时,明显偏大的Λ值(31±3)说明反应可能发生C-H键断裂.结果表明:二维单体同位素分析(2D-CSIA)技术可以有效区分DBP的水解、光解、光氧化3种不同类型的降解过程,有助于分析其降解路径. 相似文献
2.
从如下几方面研究了三氟羧草醚在土壤-水环境中的化学行为:一是土壤对该药的吸附,结果表明,吸附强度与土壤理化特性密切相关,Freundlich常数kf=0.94Wom+0.65Wclay-9.59pH(r^2=0.94);二是吸附机理研究,发现三氟羧草醚能与碱金属以外的许多金属离子形成配合物,并证实了与CU^2+形成的双核桥联合物的可能性;三是实验指出它在水中避光有一定的稳定性,不易水解;四是它在〈 相似文献
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采用紫外可见光谱(UV-Vis)、傅立叶变换红外光谱(FTIR)及离子色谱(IC)技术对HNO3在α-Fe2O3表面暗反应和308nm下光解反应进行了研究.考察了时间、HNO3浓度、相对湿度(RH)等条件对反应的影响.结果表明,随着HNO3浓度、光照时间的增加,HNO3在气相与α-Fe2O3表面光解产物浓度均呈指数增加;HNO3在α-Fe2O3表面光解产生的NO2、NO分别为气相产生的3.27及3.87倍,而无论气相还是表面光解的NO2浓度均约为NO的2倍.随着RH的增加,HNO3光解产生的HONO的浓度随之呈指数增大,其产率从RH 20%时的0.023增加到90%时的0.087.α-Fe2O3的表面效应在HNO3的表面光解反应中起主导作用. 相似文献
5.
Ling R. Zeng Li H. Shi Xin G. Meng J. Xu Gui F. Jia T. Gui 《Journal of environmental science and health. Part. B》2019,54(4):317-325
This study evaluated the hydrolysis and photolysis kinetics of pyraclostrobin in an aqueous solution using ultra-high-performance liquid chromatography–photodiode array detection and identified the resulting metabolites of pyraclostrobin by hydrolysis and photolysis in paddy water using high-resolution mass spectrometry coupled with liquid chromatography. The effect of solution pH, metal ions and surfactants on the hydrolysis of pyraclostrobin was explored. The hydrolysis half-lives of pyraclostrobin were 23.1–115.5?days and were stable in buffer solution at pH 5.0. The degradation rate of pyraclostrobin in an aqueous solution under sunlight was slower than that under UV photolysis reaction. The half-lives of pyraclostrobin in a buffer solution at pH 5.0, 7.0, 9.0 and in paddy water were less than 12?h under the two light irradiation types. The metabolites of the two processes were identified and compared to further understand the mechanisms underlying hydrolysis and photolysis of pyraclostrobin in natural water. The extracted ions obtained from paddy water were automatically annotated by Compound Discoverer software with manual confirmation of their fragments. Two metabolites were detected and identified in the pyraclostrobin hydrolysis, whereas three metabolites were detected and identified in the photolysis in paddy water. 相似文献
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利用UVC去除低浓度苯的实验研究 总被引:3,自引:1,他引:2
探讨了不同实验参数对苯的UVC去除效果的影响,获得了苯的去除率与苯的初始浓度、气体流量、相对湿度和氧气含量等参数之间的关系。数据表明,在实验条件范围内,苯的去除率的倒数与苯初始浓度、气体流量之间为线性关系;苯的去除率随相对湿度的增加呈现先升高后缓慢降低的关系,最佳相对湿度值在30%~50%之间;苯的去除率随氧气量的增加而缓慢增加;波长为185+254 nm的UV与254 nm的UV相比净化效果更为理想。还分析了苯降解产生的中间产物,探讨了苯的降解机理。 相似文献
8.
Minero C Maurino V Bono F Pelizzetti E Marinoni A Mailhot G Carlotti ME Vione D 《Chemosphere》2007,68(11):2111-2117
The effect of selected organic and inorganic compounds, present in snow and cloudwater was studied. Photolysis of solutions of nitrate to nitrite was carried out in the laboratory using a UVB light source. The photolysis and other reactions were then modelled. It is shown that formate, formaldehyde, methanesulphonate, and chloride to a lesser extent, can increase the initial formation rate of nitrite. The effect, particularly significant for formate and formaldehyde, is unlikely to be caused by scavenging of hydroxyl radicals. The experimental data obtained in this work suggest that possible causes are the reduction of nitrogen dioxide and nitrate by radical species formed on photooxidation of the organic compounds. Hydroxyl scavenging by organic and inorganic compounds would not affect the initial formation rate of nitrite, but would protect it from oxidation, therefore, increasing the concentration values reached at long irradiation times. The described processes can be relevant to cloudwater and the quasi-liquid layer on the surface of ice and snow, considering that in the polar regions irradiated snow layers are important sources of nitrous acid to the atmosphere. Formate and (at a lesser extent) formaldehyde are the compounds that play the major role in the described processes of nitrite/nitrous acid photoformation by initial rate enhancement and hydroxyl scavenging. 相似文献
9.
Richeng Xuan Lestley Arisi Qiquan Wang Scott R. Yates Keka C. Biswas 《Journal of environmental science and health. Part. B》2013,48(1):73-81
Oxytetracycline ((2Z,4S,4aR,5S,5aR,6S,12aS)-2-(amino-hydroxy-methylidene)-4-dimethylamino-5,6,10,11,12a-pentahydroxy-6-methyl-4,4a,5,5a-tetrahydrotetracene-1,3,12-trione) is a member of tetracycline antibiotics family and is widely administered to farm animals for the purpose of therapeutical treatment and health protection. Increasing attention has been paid to the environmental fate of oxytetracycline and other veterinary antibiotics with the occurrence of these antibiotics in the environment. The hydrolysis and photolysis degradation of oxytetracycline was investigated in this study. Oxytetracycline hydrolysis was found to obey the first-order model and similar rate constant values ranging from 0.094 ± 0.001 to 0.106 ± 0.003 day? 1 were obtained at different initial concentration ranging from 10 to 230 μ M. Solution pH and temperature were shown to have remarked effects on oxytetracycline hydrolysis. The hydrolysis in pH neutral solution appeared to be much faster than in both acidic and alkaline solutions. Oxytetracycline half-life decreased from 1.2 × 102 to 0.15 day with the increasing temperature from 4 ± 0.8 to 60 ± 1°C. The presence of Ca2 + made oxytetracycline hydrolytic degradation kinetics deviate from the simple first-order model to the availability-adjusted first-order model and greatly slowed down the hydrolysis. Oxytetracycline photolysis was found to be very fast with a degradation rate constant at 3.61 ± 0.06 day? 1, which is comparable to that of hydrolysis at 60°C. The presence of Ca2 + accelerated oxytetracycline photolysis, implying that oxytetracycline become more vulnerable to sunlight irradiation after chelating with Ca2 +. The photolysis may be the dominant degradation pathway of oxytetracycline in shallow transparent water environment. 相似文献
10.
利用紫外及红外吸收光谱等分析手段对365 nm光照下HNO3在气相与SiO2表面的光解反应进行了研究.考察了HNO3浓度、光照时间、相对湿度等条件对反应的影响.结果表明:随着HNO3浓度及光照时间的增加,光解产生的NO2和NO浓度均呈指数增加;无水汽情况下,400 Pa的HNO3光解45 min后,产生NO2及NO浓度比气相光解产生的分别高约3及1.7倍.HNO3光解产生的HONO的浓度随相对湿度的增加而呈线性增加,在SiO2颗粒物表面光解产生的NO2浓度随着相对湿度的增加而减少,而NO浓度则随之增大.400 Pa的HNO3光照45 min后,SiO2表面光解产生的HONO浓度是气相光解的3倍、SiO2表面暗反应的约30倍. 相似文献