Biotransformations of Chlorophenols in River Sediments

Abstract

The accumulation of chlorophenols, including 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TCP) and pentachlorophenol (PCP), from river sediments from southern Taiwan were studied. Through simple or more exhaustive extractions, the results showed that 99% of the samples containing 2,4,6-TCP and PCP could be removed by simple extraction. the concentrations were found to range from non-detectable to 16.60 ngg¹ for 2,4,6-TCP and to 25.02 ngg¹ for PCP. Partition coefficients (K_p) were 0.71, 0.74 mlg¹ for 2,4,6-TCP, 1.35 and 1.41 mlg¹ for PCP. Biodegradation by DCP-adapted or unadapted anaerobes in sediment was carried out. During 21 days' incubation, the complete degradation time for 2,4,6-TCP in DCP-adapted anaerobic, unadapted anaerobic, and unadapted aerobic conditions were found to be 9, 10, 12 days for N3 sediment, and 8, 10, 11 days for N6 sediment, respectively; for PCP it was 19 days, without degradation, 14 days for N3 sediment, and 13, 17, 10 days for N6 sediment, respectively. the biodegradable products were identified as 2,3,4,5-tetrachlorophenol (2,3,4,5-TeCP), 3,4,5-TCP, 3,5-DCP, 3-MCP, phenol, methylphenol, and benzoate for PCP, and 2,4-DCP, 4-MCP, phenol, methylphenol, and benzoate for 2,4,6-TCP.     

Health risk assessment of heavy metal exposure through vegetable consumption around a phosphorus chemical plant in the Kaiyang karst area,southwestern China

The phosphorus chemical industry is an important source of heavy metals in farmland. Vegetables grown on contaminated soil potentially impose adverse effects on human health. In this study, the pollution status and health risks of heavy metals in vegetables around a phosphorus chemical plant in Kaiyang County, Guizhou Province, southwestern China, were assessed, and the low-accumulation vegetables were screened by bioaccumulation factor (BAF) and cluster analysis. Results showed the average concentrations of Hg, As, Cd, Pb, Cr, Mn, Co, and Zn in vegetables were 0.015, 0.728 0.382, 0.227, 0.850, 27.227, 0.525, and 6.438 mg/kg, respectively. The single-factor pollution index showed that Cd was moderately polluted, and Cr, Hg, As, and Pb were slightly polluted. The Nemerow pollution index showed that the overall heavy metal pollution was classified as moderately polluted. The accumulation of heavy metals in different vegetables varied greatly, and chard, crown daisy, chayote, pumpkin, eggplant, white radish, sweet potato, carrot, and potato were selected as the low-accumulator vegetables. The consumption of all vegetables except chayote poses both carcinogenic and noncarcinogenic risks; among them, the consumption of sweet potato leaves has the highest health risks. The local population needs to adjust plantation structure and change dietary habits, and government should strengthen the management of phosphorus chemical plant pollution.

     

Response of activity and community composition of nitrite-oxidizing bacteria to partial substitution of chemical fertilizer by organic fertilizer

Environmental Science and Pollution Research - Nitrite oxidation as the second step of nitrification can become the determining step in disturbed soil systems. As a beneficial fertilization...     

PVA/ZnONPs活细胞固定化载体的构建及喹啉生物降解特性试验研究

利用ZnO纳米颗粒(ZnONPs)修饰聚乙烯醇(PVA)制备活细胞固定化载体,并将喹啉降解菌Ochrobactrum sp.LC-1固定。X射线衍射(XRD)和扫描电镜(SEM)分析结果表明,ZnONPs均匀地分布在PVA内部孔隙表面,强化了对细菌及喹啉的吸附效果,且载体内部有大量孔隙支持细菌生长。喹啉生物降解结果表明,固定化细胞喹啉氧化还原酶(Qor)活性是游离细胞的1.7倍,喹啉降解能力大大增强。固定化细胞经驯化后,在喹啉起始质量浓度500 mg/L的条件下,10 h后,固定化细胞喹啉降解率为99.8%,远高于游离细胞的43.2%。当喹啉质量浓度为600~800 mg/L时,固定化细胞对喹啉的降解率可稳定在95%以上,固定化细胞重复利用30次后,喹啉降解率仍维持在94.9%以上,表现出良好的机械耐受强度,可应用于实际生产。     

Effect of selenium on mercury methylation in facultative lake sediments

The effect of selenium (Na₂SeO₃) on the methylation of mercury (HgCl₂) in facultative sediment was studied. The results showed that small amount of selenium (0.25 μg/g) added to the sediment could significantly reduce the net methylation rate of mercury. The more the selenium was added, the higher the inhibition effect was. These results made the addition of selenium to the aquatic systems more practical and safe as a way to alleviate mercury accumulation in fish. Additionally, higher temperature was favorable to the net methylation of mercury, and high concentration of methylmercury emerged earlier.     

氧化乐果和毒死蜱混剂对大鼠雄性生殖功能的联合毒性

为探讨有机磷农药混合物对生物生殖毒性的影响,以模式动物Sprague- Dawley (SD)大鼠为实验材料,采用亚慢性染毒动物实验,利用3×3析因实验设计方法研究了常见有机磷农药——氧化乐果和毒死蜱的联合雄性生殖毒性效应及机理。结果表明：氧化乐果和毒死蜱联合染毒60 d后,附睾系数增加,精子数量和精子活力降低,联合作用呈现协同效应(p<0.05);混配农药能降低睾丸标志酶乳酸脱氢酶(LDH)、酸性磷酸酶(ACP)、碱性磷酸酶(AKP)、γ-谷氨酰转移酶(γ-GT)的活力,对LDH、ACP、γ-GT的联合作用表现为协同作用(p<0.05);混配农药能增加睾丸中促卵泡生成激素(FSH)含量,降低睾酮(T)含量,联合作用表现为协同作用(p<0.05)。通过组织病理学观察,氧化乐果和毒死蜱混合物能引起曲细精管的萎缩、畸形精子增多、生精细胞坏死、胞浆溶解和线粒体空泡化;支持细胞数量减少,出现坏死,精子从支持细胞上脱落,基底膜脱落等损伤。氧化乐果和毒死蜱对大鼠的联合生殖毒性为协同效应,混合后有明显的增毒作用;对睾丸标志酶(LDH、ACP、γ-GT)活力及睾丸性激素水平(FSH、T)的协同影响,是产生联合生殖毒性的机理之一。以上结果提示,对氧化乐果和毒死蜱进行环境健康风险评价时应考虑这种协同作用。     

Biosorption and biotransformation of crystal violet by Aeromonas hydrophila DN322p

DN322p, an offspring of Aeromonas hydrophila DN322, has the capacity to adsorb and decolorize triphenylmethane dyes in wastewater simultaneously. As a common triphenylmethane dye, crystal violet (CV) was chosen to test the decolorization characteristics of DN322p. Within 0.5 h, the strain DN322p adsorbed a large amount of CV, producing a deep-colored cell pellet and colorless supernatant. The colors of the cell pellet and supernatant lightened over time. The supernatant and dichloromethane extract of the cell pellet both showed conspicuous CV and leuco CV (LCV) characteristic absorbance peaks at 590 nm and 260 nm, respectively, in the UV-vis spectral analysis. This finding indicated that the DN322p cells can adsorb the two dyes. A 99% (w/w) decolorization rate was achieved within 2.5 h with shaking at 30°C for 50 mg CV·L^?1. High Performance Liquid Chromatography (HPLC) analysis of the dichloromethane extract of the supernatant and cell pellet confirmed that CV was mainly converted into its leuco form. Dead cells had a similar adsorption capacity with living cells. About 90% of CV in the dye solution (50 mg·L^?1) was removed by autoclaved cells with an optical delnsity at 600 nm (OD₆₀₀) above 1.0.     

Short-term effects of excessive anaerobic reaction time on anaerobic metabolism of denitrifying polyphosphate-accumulating organisms linked to phosphorus removal and N2O production

The short-term effect of anaerobic reaction time (AnRT) (i.e., 90, 120 and 150 min) on the denitrifying phosphorus (P) removal performance and N₂O production was examined using a denitrifying enhanced biologic phosphorus removal (EBPR) sludge acclimatized with mixed acetate (HAc) and propionate (Pro) (in the molar ratio 3:1) as carbon sources. The results showed that when the AnRT was prolonged from 90 to 150 min, the anaerobic polyhydroxyalkanoate (PHA) synthesis was decreased by 15.3%. Moreover, the ineffective PHA consumption occurred in anaerobic phases and contributed to an increased NO ₂ ^? -N accumulation and higher free nitrous acid (FNA) concentrations (?0.001–0.0011 mg HNO₂-N/L) in the subsequent anoxic phases, causing a severe inhibition on anoxic P-uptake and denitrification. Accordingly, the total nitrogen (TN) and total phosphorus (TP) removal efficiencies dropped by approximately 6.3% and 85.5%, respectively; and the ratio of anoxic N₂O-N production to TN removal increased by approximately 3.8%. The fluorescence in situ hybridization (FISH) analysis revealed that the sludge was mainly dominated by Accumulibacter (62.0% (SE_mean = 1.5%)). In conclusion, the short-term excessive anaerobic reaction time negatively impacted denitrifying P removal performance and stimulated more N₂O production, and its effect on P removal was more obvious than that on nitrogen removal.     

黑麦草在修复铜-芘复合污染水体过程中对污染物的富集效应

采用水培实验的方法,研究了黑麦草对铜和芘复合污染体系的修复能力、黑麦草不同部位对铜和芘的富集效应.结果表明,黑麦草能在96 h内使水体中铜和芘的浓度显著降低,分别由5 mg.L-1和0.1 mg.L-1降低至0.49 mg.L-1和0.009 mg.L-1;黑麦草根部对铜和芘的积累量和富集系数明显大于茎叶,随着铜处理浓度的增加,根和茎叶中铜的积累量随之增加,而根中铜的生物富集系数却随之降低,黑麦草根和茎叶中芘的积累量分别在4.65—5.39 mg.kg-1和0.81—1.08 mg.kg-1之间,铜对水体中芘的去除以及根和茎叶中芘的积累均无显著性影响.     

气象环境要素对北京市消化系统疾病的影响

为探究气象环境条件对消化系统疾病的影响,结合分布滞后非线性模型与广义相加模型,分析了2009~2011年气象环境要素与北京市消化系统疾病急诊人数的暴露-反应关系.结果显示,气温对消化系统疾病的影响主要体现为“高温效应”,高于25℃的气温其危险度RR随气温升高而增加,且滞后效应能达到10d以上.较为极端的湿度(RH<10%或RH>90%)会显著增加消化系统疾病的发病,并有持久的作用,其与高温结合会形成“高温低湿”和“高温高湿”2种让人不适的情况.0～2m/s的风速在短的滞后期(5d)最能增加发病危险性.而3～4m/s的风速对疾病的危险性小,说明适度的风速不影响健康.浓度高于200μg/m³的PM₁₀和浓度高于70μg/m³的 NO₂具有即时的危险性(5d内显著);而较高浓度(>55μg/m³)的SO₂滞后一定时期后效应更加明显.