Photocatalytic mineralization of glyphosate in a small-scale plug flow simulation reactor by UV/TiO2

The present work involves the photocatalytic mineralization of glyphosate on a plug flow reactor by UV/TiO₂. The effect of catalyst loading shows an optimal value (0.4 g L^?1) which is necessary to mineralize glyphosate. The kinetic rate of glyphosate mineralization decreases with the increasing initial concentration of glyphosate, and the data can be described using the first-order model. An alkaline environment is conducive to glyphosate mineralization. The mineralization efficiency increases with elevated flow rate to 114 mL min^?1, which is followed by a decrease with a further increase in flow rate due to the reduction of the residence time. The presence of external oxidants (K₂S₂O₈, H₂O₂ and KBrO₃) and photosencitizer (humic acid) can significantly enhance glyphosate mineralization. Photocatalysis oxidation ability of the three studied oxidants decrease in the order of: S₂O₈ ^2? > BrO₃ ^? > H₂O₂. Finally, the Langmuir–Hinshelwood (L-H) model was used to rationalize the mechanisms of reactions occurring on TiO₂ surfaces and L-H model constants were also determined.     

Metabolic fate of the 14C-labeled herbicide clodinafop-propargyl in a sediment–water system

The metabolic fate of ¹⁴C-phenyl-labeled herbicide clodinafop-propargyl (¹⁴C-CfP) was studied for 28 days in lab assays using a sediment–water system derived from a German location. Mineralization was 5.21% of applied ¹⁴C after 28 days exhibiting a distinct lag phase until day 14 of incubation. Portions of radioactivity remaining in water phases decreased at moderate rate to 18.48% after 28 days; 62.46% were still detected in water after 14 days. Soxhlet extraction of the sediment using acetonitrile released 35.56% of applied ¹⁴C with day 28, while 33.99% remained as non-extractable residues. A remarkable increase of bound ¹⁴C was observed between 14 and 28 days correlating with the distinct increase of mineralization. No correlation was found throughout incubation with microbial activity of the sediment as determined by dimethyl sulfoxide reduction. Dissolved oxygen and pH value of water phases remained almost constant for 28 days. Analyses of Soxhlet extracts of the sediment and ethyl acetate extracts of water phases by radio-TLC and radio-HPLC revealed that CfP was rapidly cleaved to free acid clodinafop (Cf), which was further (bio-) transformed. DT₅₀ values (based on radio-HPLC) were below 1 day (CfP) and slightly above 28 days (Cf). Further metabolites were not detected. Fractionation of humic and non-humic components of the sediment demonstrated that CfP's non-extractable residues were predominantly associated with fulvic acids up to 14 days of incubation (3.36%), whereas after 28 days, the majority of radioactivity was found in the humin/mineral fraction (13.30% of applied ¹⁴C). Due to high-performance size-exclusion chromatography of the fulvic acids fraction derived from assays incubated for 28 days, this portion of ¹⁴C was firmly, possibly covalently bound to fulvic acids and did not consist of CfP or Cf. Using an isolation strategy comprising preincubation of sediment with CfP and mineralization of ¹⁴C-CfP as criterion, a microorganism was isolated from the sediment examined. It grew on ¹⁴C-CfP as sole carbon source with evolution of ¹⁴CO₂. The bacterium was characterized by growth on commonly used carbon sources and 16S rDNA sequence analysis. Its sequence exhibited high similarity with that of Nocardioides aromaticivorans strain H-1 (98.85%; DSM 15131, JCM 11674).     

苏南水稻土有机碳矿化特征及其与活性有机碳组分的关系

通过对江苏省常熟市全市范围代表性水稻土采样并布置室内短期(20d)培育实验,研究土壤有机碳矿化过程动态,并分析其与微生物生物量碳和水溶性有机碳含量的关系。结果表明:研究区域水稻土有机碳含量变化为4.88～27.31g/kg,平均为18.07g/kg,全氮含量变化为0.58～2.84g/kg,平均为1.86g/kg;微生物生物量碳、氮及水溶性有机碳含量分别为294.0～1287.4,18.54～81.78和7.01～28.79mg/kg,且不同土属间存在显著差异(p<0.05);土壤呼吸强度为34.76～191.68mgCO2/(kg·d),平均为79.93mgCO2/(kg·d),不同土属间高低顺序为乌栅土>乌黄泥土>灰黄泥土>白土>黄泥土>乌沙土;培养期内有机碳日均矿化量为10.76～65.20mg-CO2/kg,平均为40.46mgCO2/kg,有机碳累计矿化量为215.25～1302.13mgCO2/kg,平均为807.20mgCO2/kg,不同土属间有机碳日均矿化量和累计矿化量变化趋势为乌栅土>乌黄泥土>乌沙土>白土>灰黄泥土>黄泥土;研究区域水稻土有机碳矿化率为3.07%～7.58%,但不同土属间差...     

施氮与凋落物去除影响下中亚热带阔叶林土壤氮素矿化潜势和硝化潜势研究

氮沉降影响土壤氮循环,而凋落物是土壤有机氮的主要来源,因此,为了探讨氮沉降和凋落物是否去除作用下,亚热带森林土壤潜在的氮素矿化与硝化作用,选择已进行8年模拟氮沉降试验的亚热带罗浮栲(Castanopsis fabri)常绿阔叶林土壤为研究对象,野外样地氮添加设置3个水平:对照(CK,0 kg·hm?2·a?1)、低氮(...     

生物质炭微生物矿化稳定性机制研究进展

生物质炭在碳封存和土壤改良等方面的应用潜力取决于其在土壤中的微生物矿化稳定性.明确生物质炭在土壤中微生物矿化稳定性是推进生物质炭在土壤固碳、改良等领域应用的关键.基于生物质炭在土壤中的微生物矿化稳定性研究进展,本文系统总结了不同类型生物质炭的微生物矿化速率和在土壤中的平均驻留时间,探讨了不同因素(生物质炭特性、土壤特性...     

水中放射性核素锶-90测量不确定度的评估

阐述了分析放射性核素产生不确定度因素比一般化学分析多的原因,通过采用鱼骨图法分析放射性核素锶-90测量实验中的不确定度和分析计算公式中的有关参数,了解到分析水中放射性核素锶-90时,主要受到样品测量、仪器探测效率、样品化学回收率和样品取样体积等4个方面的不确定度因素影响。     

Toxicity, uptake and metabolism of 4-n-nonylphenol in root cultures and intact plants under septic and aseptic conditions

4-Nonylphenol, a compound with estrogenic activity, has been shown to occur in sewage sludges and effluents of sludge treatment. This, as well as its use in the formulation of pesticides, may result in the contamination of crop plants and may therefore have an impact on the quality of food or feedstuff. The toxicity, uptake and metabolism of 4-n-nonylphenol (4-n-NP) were investigated as¹⁴C-labeled 4-n-NP in root cultures under septical and aseptical conditions and with intact plants grown in containers with soil and aseptically grown in nutrient media. 4-n-NP was toxic to all plant systems tested. The presence of microorganisms and the developmental state of the plant material appeared to have an influence on the EC₅₀ values. 4-n-NP was taken up by the roots and a metabolism to polar compounds was observed in the cases where sufficiently high uptake rates. With intact plants a transport from roots to the shoots was evident. Metabolism in roots changed quantitatively in the presence of microorganisms. The mineralization of 4-n-NP to₁₄CO₂ only occurred with microorganisms.     

Flocculant in wastewater affects dynamics of inorganic N and accelerates removal of phenanthrene and anthracene in soil

Recycling of municipal wastewater requires treatment with flocculants, such as polyacrylamide. It is unknown how polyacrylamide in sludge affects removal of polycyclic aromatic hydrocarbons (PAH) from soil. An alkaline-saline soil and an agricultural soil were contaminated with phenanthrene and anthracene. Sludge with or without polyacrylamide was added while emission of CO₂ and concentrations of NH₄⁺, NO₃⁻, NO₂⁻, phenanthrene and anthracene were monitored in an aerobic incubation experiment. Polyacrylamide in the sludge had no effect on the production of CO₂, but it reduced the concentration of NH₄⁺, increased the concentration of NO₃⁻ in the Acolman soil and NO₂⁻ in the Texcoco soil, and increased N mineralization compared to the soil amended with sludge without polyacrylamide. After 112 d, polyacrylamide accelerated the removal of anthracene from both soils and that of phenanthrene in the Acolman soil. It was found that polyacrylamide accelerated removal of phenanthrene and anthracene from soil.     

紫外光作用下氯酚的矿化程度比较

有关氯酚污染物光化学降解的研究,已有报道。ＨｕａｎｇＣＰ的工作较有系统性,他研究了四类深度化学氧化过程,检测指标是氯酚浓度。本文研究了在紫外光以及其它因素作用下,氯酚混合溶液的矿化程度,以溶液总有机磷浓度ＴＯＣ作为指标。所得结论,对于含有氯酚废水的治理,具有指导意义;对于难降解     

石油污染对土壤氮素矿化和硝化作用的影响

在实验室中用同位素示踪法,研究了土壤中不同石油污染量对氮矿化及硝化速率的影响。结果表明,石油对土壤中有机氮的矿化没有显著影响,但减缓了硝化反应的进程。土壤经过１０ｄ的培养,在未污染的土壤中硝化细菌数量由１．６×１０３增加到１．６×１０６,而在受石油污染的土壤上,硝化细菌数量仅增加到６．３×１０４;增加试验前土壤硝化菌数量为２．６×１０６,加油培养１０ｄ后,硝化细菌数量下降了近９０％。