Sequestration of organochlorine pesticides in soils of distinct organic carbon content

In the present study, five soil samples with organic carbon contents ranging from 0.23% to 7.1% and aged with technical dichlorodiphenyltrichloroethane (DDT) and hexachlorocyclohexane (HCH) for 15 months were incubated in a sealed chamber to investigate the dynamic changes of the OCP residues. The residues in the soils decreased over the incubation period and finally reached a plateau. Regression analysis showed that degradable fractions of OCPs were negatively correlated with soil organic carbon (SOC) except for α-HCH, while no correlation was found between degradation rate and SOC, which demonstrated that SOC content determines the OCP sequestration fraction in soil. Analysis of the ratio of DDT and its primary metabolites showed that, since it depends on differential sequestration among them, magnitude of (p,p′-DDE + p,p′-DDD)/p,p′-DDT is not a reliable criterion for the identification of new DDT sources.     

Changes of polyamine levels in roots of Sagittaria sagittifolia L. under copper stress

Introduction

The goal of the present study was to investigate the effects of Cu contamination on the above-mentioned biochemical and physiological parameters in order to explore possible prevention strategies against heavy metal stress.

Materials and methods

Effects of copper (Cu) on the roots of Sagittaria sagittifolia L. were studied after 10 days of treatment at five concentration levels. The accumulation of Cu, the generation rate of O₂ ^·?C, the contents of thiobarbituric acid reactive substances (TBARS) and polyamines, as well as the activities of arginine decarboxylase (ADC) and polyamine oxidase (PAO) in the roots were measured and analyzed.

Results and discussion

It was observed that endogenous Cu content increased in roots of S. sagittifolia L. in a concentration-dependent manner, along with an increased production of O₂ ^·?C. TBARS content increased progressively up to 5 ??mol l^?1 Cu. A constant increase in ADC activity was also observed. The results indicated that lower Cu concentrations (2.5 and 5 ??mol l^?1, respectively) had greater enhancing effect on the contents of free Put and perchloric acid-soluble conjugated (PS-conjugated) putrescine (Put), while Cu treatments at different concentration levels had similar enhancing effect on the content of perchloric acid-insoluble bound Put. In total, Put content in each Cu-treated group was higher than that in the control group. PAO activity was inhibited up to 10 ??mol l^?1 Cu but enhanced at higher Cu concentrations (20 and 40 ??mol l^?1). This explained the initial rise and subsequent decline of the contents of all forms of spermine (Spm), free and PS-conjugated spermidine (Spd). However, with the increase of Cu concentration, total Spm content increased gradually while total Spd content decreased. Our results suggest that Cu is phytotoxic to the roots of S. sagittifolia L. at high concentrations, and that the increased Spm level is not sufficient to resist Cu-induced oxidative damages.     

Effects of perfluorinated compounds on development of zebrafish embryos

Perfluorinated compounds (PFCs) have been widely used in industrial and consumer products and frequently detected in many environmental media. Potential reproductive effects of perfluorooctanesulfonate (PFOS), perfluorooctanoic acid (PFOA) and perfluorononanoic acid (PFNA) have been reported in mice, rats and water birds. PFOS and PFOA were also confirmed developing toxicants towards zebrafish embryos; however, the reported effect concentrations were contradictory. Polyfluorinated alkylated phosphate ester surfactants (including FC807) are precursor of PFOS and PFOA; however, there is no published information about the effects of FC807 and PFNA on zebrafish embryos. Therefore, this study was conducted to determine the effects of these four PFCs on zebrafish embryos. Normal fertilized zebrafish embryos were selected to be exposed to several concentrations of PFOA, PFNA, PFOS or FC807 in 24-well cell culture plates. A digital camera was used to image morphological anomalies of embryos with a stereomicroscope. Embryos were observed through matching up to 96-h post-fertilization (hpf) and rates of survival and abnormalities recorded. PFCs caused lethality in a concentration-dependent manner with potential toxicity in the order of PFOS > FC807 > PFNA > PFOA based on 72-h LC(50). Forty-eight-hour post-fertilization pericardial edema and 72- or 96-hpf spine crooked malformation were all observed. PFOA, PFNA, PFOS and FC807 all caused structural abnormalities using early stages of development of zebrafish. The PFCs all retarded the development of zebrafish embryos. The toxicity of the PFCs was related to the length of the PFC chain and functional groups.     

Reprint of: Concentrations, distribution, and bioaccumulation of synthetic musks in the Haihe River of China

Seven typical synthetic musks (SMs) in the samples from the surface water, sediment and fish of the Haihe River were measured. The SM concentrations in the sediment and surface water of the Haihe River were significantly lower than those in the Dagu Drainage River and Chentaizi Drainage River (p < 0.05). Along the flow direction, the SM concentrations in surface water and sediment tended to increase from the upstream to the downstream of Dagu Drainage River. The Bioaccumulation factors (BAFs) of galaxolide (HHCB) and tonalide (AHTN) were calculated at high levels in the muscles of crucian carp, common carp, and silver carp. Most of the biota-sediment accumulation factors (BSAFs) for HHCB and AHTN were higher than 1.7, suggesting magnification possibly exist in the musk bioaccumulations of the three fishes in the Haihe River. No significant differences in HHCB/AHTN ratios were observed among the water, fish, and sediment samples (p > 0.05). However, the HHCB/AHTN values in the Haihe River were much lower than those in the Dagu Drainage River and Chentaizi Drainage River (p < 0.05). Compared with several typical persistent organic pollutants (POPs), the musk concentrations were higher or comparable in the Haihe River.     

Bioanalytical and instrumental analysis of thyroid hormone disrupting compounds in water sources along the Yangtze River

Thyroid hormone (TH) agonist and antagonist activities of water sources along the Yangtze River in China were surveyed by a green monkey kidney fibroblast (CV-1) cell-based TH reporter gene assay. Instrumental analysis was conducted to identify the responsible thyroid-active compounds. Instrumentally derived l-3,5,3′-triiodothyronine (T₃) equivalents (T₃-EQs) and thyroid receptor (TR) antagonist activity equivalents referring to dibutyl phthalate (DBP-EQs) were calculated from the concentrations of individual congeners. The reporter gene assay demonstrated that three out of eleven water sources contained TR agonist activity equivalents (TR-EQs), ranging from 286 to 293 ng T₃/L. Anti-thyroid hormone activities were found in all water sources with the TR antagonist activity equivalents referring to DBP (Ant-TR-EQs), ranging from 51.5 to 555.3 μg/L. Comparisons of the equivalents from instrumental and biological assays suggested that high concentrations of DBP and di-2-ethylhexyl phthalate (DEHP) were responsible for the observed TR antagonist activities at some locations along the Yangtze River.     

改性氧化铝微波诱导催化氧化处理高浓度苯酚废水的研究

采用微波诱导催化氧化技术,以改性氧化铝为催化剂,对高浓度模拟苯酚废水进行氧化处理。考察了微波功率、催化剂投加量、H202投加量、废水pH值和微波反应时间等因素对苯酚去除效果的影响。实验结果表明,处理30mL质量浓度为1 100mg/L的苯酚模拟废水,在微波功率500W,催化剂加入量1 g(液固比30∶1),30％双氧水...     

A2O工艺好氧末段溶解氧变化对脱氮除磷影响

采用连续流A2O工艺处理实际的生活污水,研究好氧末段在不同溶解氧(DO)浓度条件下对污泥沉降性能、系统脱氮除磷的影响,同时考察了DO对污泥硝化活性、厌氧释磷速率和反硝化脱氮速率的影响.结果表明,随着末段溶解氧的提高,污泥容积指数SVI从140降至100左右,后又升高到120～170;系统的硝化效果提高,氨氮的去除率从6...     

油田回注水中优势硫酸盐还原菌的分离鉴定与生理特性研究

从胜利油田回注水中筛选得到一株硫酸盐还原菌,命名为zsz1209。经过16SrDNA序列分析,鉴定zsz1209为梭菌属（Clostridium）。实验研究了zsz109的生理特性,并对通过调节环境pH来抑制菌株zsz1209生长繁殖的可行性进行了探讨。实验结果表明：菌株zsz1209的理想碳源为乙酸钠,在30～60℃之间可较好地生长;SOi浓度低至50mg／L时,生长未受到明显抑制。当培养环境pH高至8．5～9．0或低至3．5～4．0时,检测菌株zsz1209对SO4^2-和碳源（COD）的利用情况,发现zsz1209的生长受到明显抑制,结果表明利用改变环境pH来抑制微生物对油田的腐蚀具有可行性。     

Evaluation of photolysis and hydrolysis of pyraclostrobin in aqueous solutions and its degradation products in paddy water

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.     

Determination of the residue dynamics and dietary risk of thiamethoxam and its metabolite clothianidin in citrus and soil by LC-MS/MS

A modified quick, easy, cheap, effective, rugged and safe (QuEChERS) method was developed for the determination of thiamethoxam and its metabolite clothianidin in citrus (including the whole citrus, peel and pulp) and soil samples by liquid chromatography-tandem mass spectrometry. The sample was extracted with acetonitrile and purified with octadecylsilane. The detection limits of both compounds were 0.0001–0.0002?mg kg^–1, while the limit of quantification of thiamethoxam was 0.002?mg kg^–1 and the limit of quantitation of metabolites was 0.001?mg kg^–1. The recovery was 70.37%–109.76%, with inter-day relative standard deviations (RSD) (n?=?15) values ≤9.46% for the two compounds in the four matrices. The degradation curve of thiamethoxam in whole citrus and soil was plotted using the first-order kinetic model. The half-life of the whole citrus was 1.9–6.2?days, and the half-life of the soil was 3.9–4.2?days. The terminal residue of thiamethoxam (the sum of thiamethoxam and clothianidin, expressed as thiamethoxam) was found to be concentrated on the peel. The final residual amount of thiamethoxam in the edible portion (pulp) was less than 0.061?mg kg^–1. The risk quotient values were all below 1, indicating that thiamethoxam as a citrus insecticide does not pose a health risk to humans at the recommended dosage.