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171.
Huff J 《Chemosphere》2012,89(5):521-525
Carcinogenesis bioassays were conducted by giving 2,4,6-trichlorophenol [2,4,6-TCP] in feed to groups of 50 male and female Fischer rats and male B6C3F1 mice for two years. Dietary concentrations were 0 [20/group], 5000 [0.5%], or 10,000 [1%] ppm. Female mice began with 10,000 and 20,000 ppm but after 38 weeks were lowered due to reduced body weights to 2500 and 5000 ppm for 67 weeks; exposures averaged 5200 and 10,400 ppm. Adverse effects at two years were leukocytosis and monocytosis of peripheral blood and hyperplasia of bone marrow in both sexes of rats. In mice, liver toxicity, including individual liver cell abnormalities, focal areas of cellular alteration, and focal and nodular areas of hyperplasia were commonly present. Regarding carcinogenic activity, TCP caused leukemias/lymphomas in male rats, and possibly in female rats and female mice as well, and induced liver tumors in male and female mice. Using NTP categories of evidence indicates ‘clear evidence of carcinogenicity’ for male rats [hematopoietic system tumors]; ‘equivocal evidence of carcinogenicity’ for female rats [hematopoietic system tumors]; ‘clear evidence of carcinogenicity’ for male and female mice [liver tumors]. 相似文献
172.
M Calabi-Floody G Velásquez L Gianfreda S Saggar N Bolan C Rumpel ML Mora 《Chemosphere》2012,89(6):648-655
The high P retention of acidic Andisols makes necessary to increase our technological approaches in pasture management in the animal system production. Here, we evaluated the clay- or nanoclay-acid phosphatase complexes for improving phosphorus mineralization from degraded cattle dung. We implemented an immobilization mechanism of acid phosphatase (AP) using natural clays (allophanic and montmorillonite) and nanoclays as support materials. Also, we evaluated the mineralization of organic P containing in decomposed cattle dung with clay- and nanoclay-AP complexes by incubation studies. Clays and nanoclays were characterized by microscopy techniques as atomic force and confocal-laser scanning microscopy. We found that these support materials stabilized AP by encapsulation. Our results showed that immobilization on allophanic or montmorillonite materials improved both the specific activity (4-48%) and the Vmax (28-38%) of AP. Moreover, the enzyme had a better performance when immobilized on clay and nanoclay from Andisol than on montmorillonite materials. Phosphorous mineralization of cattle dung was regulated by water-soluble P present in the dung and P re-adsorption on allophanic materials. However, we were able to detect a potential capacity of AP immobilized on allophanic nanoclays as the best alternative for P mineralization. Further research with initially low water-soluble P containing organic materials is required to quantify the P mineralization potential and bioavailability of P from dung. 相似文献
173.
Simone T. T. Bicalho Tomaz Langenbach 《Journal of environmental science and health. Part. B》2013,48(6):505-511
Pesticides applied on sugarcane reach the subsoil of riparian forests and probably contaminate the river water. This work was conducted to learn about the phytoremediation of atrazine and subsoil contamination using the common riparian forest species of Cecropia hololeuca Miq. and Trema micranta (L.) Blum. These plants were grown in soil microcosms where 14C-atrazine at 1/10 of the field-recommended dose was applied at the bottom of the microcosm simulating the movement from contaminated ground water to the upper soil layers and into plants. Residues of 14C-atrazine were detected in all parts of the microcosm including soil, rhizosphere and the roots in different layers of the microcosm, stem and leaves. Atrazine mineralization was higher (10.2%) in the microcosms with plants than the control microcosms without plants (1.2%). The upward movement of this pesticide from deeper to more superficial soil layers occurred in all the microcosms with plants, powered by evapotranspiration process. From the atrazine applied in this study about 45% was taken up by C. hololeuca and 35% by T. micrantha. The highest amount of radioactivity (%) was found in the fine roots and the specific radioactivity (% g?1) showed that thick, fine roots and leaves bioaccumulate atrazine. The enhanced mineralization of atrazine as well the phytostabilization effect of the tree biomass will reduce the bioavailability of these residues and consequently decrease the hazardous effects on the environment. 相似文献
174.
Abstract The metabolism of 14C‐carbaryl and 14C‐1‐naphthol in moist and flooded soils was studied in a continuous flow‐through system over a period of 28 days permitting 14C‐mass balance. The percent distribution of radiocarbon in organic volatiles, carbon dioxide, extractable and non‐extractable (bound) fractions of soils were determined. Organic volatiles could not be detected in both carbaryl and 1‐naphthol treated soils. More of 14CO2 (25.6%) was evolved from moist than flooded soil (15.1%) treated with carbaryl. However, the mineralization of 14C‐1‐naphthol was negligible. The extractable radiocarbon was more in flooded soil (28.9%) than moist soil (5.5%) from carbaryl treatment. Less than one percent was present as parent compound, whereas carbaryl was mainly metabolized to 5‐hydroxy carbaryl in moist soil and to 4‐ and 5‐hydroxy carbaryl in flooded soil. The extractable radiocarbon amounted to 18.2 and 24.3% in moist and flooded soils respectively and the parent compound was less than one percent with 1‐naphthol treatment. Most of the radiocarbon was found as soil bound residues; the formation being more with 1‐naphthol than carbaryl. Humin fraction of the soil organic matter contributed most to soil bound residues of both carbaryl and 1‐naphthol. 相似文献
175.
Simultaneous biodegradation of nitrogen-containing aromatic compounds
in a sequencing batch bioreactor 总被引:1,自引:0,他引:1
LIU Xing-yu WANG Bao-jun JIANG Cheng-ying ZHAO Ke-xin Harold L. Drake LIU Shuang-Jiang 《环境科学学报(英文版)》2007,19(5):530-535
Many nitrogen-containing aromatic compounds (NACs), such as nitrobenzene (NB), 4-nitrophenol (4-NP), aniline (AN), and 2,4-dinitrophenol (2,4-DNP), are environmentally hazardous, and their removal from contaminated water is one of the main challenges facing wastewater treatment plants. In this study, synthetic wastewater containing NB, 4-NP, 2,4-DNP, and AN at concentrations ranging from 50 to 180 mg/L was fed into a sequencing batch reactor (SBR). Analyses of the SBR system indicated that it simultaneously removed more than 99% of the NACs at loading rates of 0.36 kg NB/(m3·d), 0.3 kg 4-NP/(m3·d), 0.25 kg AN/(m3·d), and 0.1 kg 2,4-DNP/(m3·d). Bacterial groups of Bacteriodetes, Candidate division TM7, α-Proteobacteria, and β-Proteobacteria were dominant in the clone libraries of 16S rRNA genes retrieved from the microbial communities in the SBR system. "Cycle tests" designed to alter feeding and aeration parameters of the SBR system demonstrated that the resident microbial biome of the SBR system responded rapidly to changing conditions. Consumption of O2 was concomitant with the apparent mineralization of NACs. Aromatic ring-cleaving dioxygenase activities suggested that (1) AN and NB were degraded via catechol 2,3-dioxygenase; (2) 4-NP was degraded via 1,2,4-benzentriol 1,2-dioxygenase; and (3) 2,4-DNP was degraded via an unresolved pathway. 相似文献
176.
Anoxic biodegradation of dimethyl phthalate (DMP) by activated sludge cultures under nitrate-reducing conditions 总被引:3,自引:0,他引:3
Worldwide extensive use of plasticized plastics has resulted in phthalates pollution in different environment. Nitrates from industry and agriculture are also widely disseminated in the soils, natural waters and wastewaters. Dimethyl phthalate (DMP) biodegradation by activated sludge cultures under nitrate-reducing conditions was investigated. Under one optimized condition, DMP was biodegraded from 102.20 mg/L to undetectable level in 56 h under anoxic conditions and its reaction fitted well with the first-order kinetics. Using the high-performance liquid chromatography (HPLC) and liquid chromatography mass spectrometry (LC-MS) analysis, mono-methyl phthalate (MMP) and phthalic acid (PA) were detected as the major intermediates of DMP biodegradation. When combined with the determination of chemical oxygen demand (CODCr) removal capacity and pH, DMP was found to be mineralized completely under anoxic conditions. The biodegradation pathway was proposed as DMP → MMP → PA → … → CO2 H2O.The molar ratio of DMP to nitrate consumed was found to be 9.0:1, which agrees well with the theoretical stoichiometric values of DMP biodegradation by nitrate-reducing bacteria. The results of the non-linear simulation showed that the optimum pH and temperature for the degradation were 7.56 and 31.4℃, respectively. 相似文献
177.
Xianwei Wang Xiuzhen Li Yuanman Hu Jiujun Lv Ju Sun Zongmei Li Zhifeng Wu 《环境科学学报(英文版)》2010,22(7):1057-1066
Boreal peatlands represent a large global carbon pool.The relationships between carbon mineralization,soil temperature and moisture in the permafrost peatlands of the Great Hing'an Mountains,China,were examined.The CO2 emissions were measured during laboratory incubations of samples from four sites under different temperatures(5,10,15,and 20°C) and moisture contents(0%,30%,60%,100% water holding capacity(WHC) and completely water saturated).Total carbon mineralization ranged from 15.51 to 112.92 mg C under the treatments for all sites.Carbon mineralization rates decreased with soil depth,increased with temperature,and reached the highest at 60% WHC at the same temperature.The calculated temperature coefficient(Q10) values ranged from 1.84 to 2.51 with the soil depths and moisture.However,the values were not significantly affected by soil moisture and depth for all sites due to the different peat properties(P 0.05).We found that the carbon mineralization could be successfully predicted as a two-compartment function with temperature and moisture(R2 0.96) and total carbon mineralization was significantly affected by temperature and moisture(P 0.05).Thus,temperature and moisture would play important roles in carbon mineralization of permafrost peatlands in the Great Hing'an Mountains,indicating that the permafrost peatlands would be sensitive to the environment change,and the permafrost peatlands would be potentially mineralized under future climate change. 相似文献
178.
稻田土壤常处于频繁的干湿交替过程中,水分条件的改变不仅影响土壤理化性质,而且使土壤微生物群落结构和多样性发生改变,进而影响土壤有机碳矿化速率.然而,不同水分条件和土壤微生物生物量水平对土壤有机碳矿化过程的影响及其机制尚不明确.因此,本研究选取典型亚热带水稻土为研究对象,采用室内模拟培养试验,设置干湿交替和持续淹水这2个水分条件,并通过氯仿熏蒸方法减少土壤微生物生物量,从而获得微生物生物量碳含量高低两个水平的土壤,探讨水分条件和微生物生物量对水稻土有机碳矿化的影响机制.结果表明在培养前30 d,干湿交替处理处在不淹水状态,其CO2累积排放量显著低于持续淹水处理;30 d后干湿交替处理进入淹水状态,在高微生物生物量碳含量土壤中,其CO2累积排放量和持续淹水处理的差距逐渐减小,直至78 d无显著差异;在低微生物生物量碳含量土壤中,78 d时干湿交替处理的CO2累积排放量仍显著低于持续淹水处理.低微生物生物量碳含量土壤在培养初期(前20 d)受其高可溶性有机碳(DOC)含量影响,CO2排放速率可达高微生物生物量碳土壤的1.1~6.1倍;在培养后期(第45~78 d)土壤有机碳矿化速率达到稳定,高微生物生物量碳土壤的稳定矿化速率比低微生物生物量碳土壤高20%~30%.多元回归分析结果表明,土壤DOC含量的减少(ΔDOC)和Fe2+含量的增加(ΔFe2+)显著影响持续淹水条件下的CO2累积排放量的变化值(ΔCO2),但对干湿交替处理淹水阶段的CO2累积排放量却无影响.相关分析结果表明,高微生物生物量碳土壤的CO2日排放速率在干湿交替处理下与葡萄糖苷酶(BG)活性呈显著正相关,在持续淹水处理下与乙酰葡糖氨糖苷酶(NAG)和过氧化酶(PER)活性呈显著负相关;在低微生物生物量碳土壤中,CO2日排放速率在持续淹水处理下与NAG活性呈负相关,在干湿交替处理下与酶活性无关.综上,干湿交替处理的CO2累积排放量低于持续淹水处理,且该差异在低微生物生物量碳的土壤中显著;土壤微生物生物量大小会决定土壤有机碳稳定矿化速率水平;可溶性有机碳量和铁元素的还原量影响持续淹水条件下土壤的CO2排放量;土壤水分条件会影响CO2日排放速率及其关键生物酶因子.本研究为深入研究水稻土碳循环和固碳潜力提供数据和理论支持. 相似文献
179.
180.
康滇地轴东缘不同时代碳酸盐地层中铅锌矿床的铅同位素研究表明 ,其2 0 7Pb/2 0 4 Pb与2 0 6 Pb/ 2 0 4 Pb呈良好线性关系 ,2 0 7Pb/ 2 0 6 Pb和2 0 8Pb/ 2 0 6 Pb为一常数。结合对本区矿床的稀土元素及成矿流体地球化学的研究 ,判定不同层位铅锌矿床是在同一个成矿体系同时形成的 ,一次成矿 ,其成矿年龄为 2 4 5Ma(峨眉运动 ) ;同时说明不同矿床成矿金属有相同的来源 ,主要来自上地幔。成矿硫以来自地层中的硫酸盐还原硫为主 ,幔源硫次之。本区铅锌矿床的成矿作用与峨眉山玄武岩的喷流关系密切 ,这是与著名的MVT型铅锌矿床的显著区别。 相似文献