Possible alkylation of inorganic Hg(II) by photochemical processes in the environment

Contamination of surface waters by pesticides continues to be the focus of concern for water authorities due to the growing evidence of their deleterious effects on aquatic life. In this context, the present work investigates the occurrence of 16 selected pesticides belonging to the classes of triazines, phenylureas, organophosphates, chloroacetanilides and thiocarbamates in surface waters from the Llobregat River (NE Spain) and some of its tributaries (Anoia and Rubí) and assesses their potential impact on the aquatic organisms by applying a recently developed index, the Short-term Pesticide Risk Index for the Surface Water System (PRISW-1), which takes into account the pesticides concentrations and their overall toxicity against three aquatic organisms (algae, Daphnia, and fish). Chemical analysis, performed by means of a fully automated method based on isotope dilution on-line solid phase extraction-liquid chromatography-electrospray-tandem mass spectrometry (on-line SPE-LC-ESI-MS/MS), revealed diuron and diazinon as the most ubiquitous and abundant compounds with levels up to 818 and 132 ng L⁻¹, respectively. Total pesticide concentrations, which in only 1 out of 66 samples surpassed 500 ng L⁻¹, were higher in the tributaries than in the river but their contribution in terms of mass-loads to the overall pesticide pollution of the Llobregat River was relatively small. Contamination increased downstream of the river and was clearly influenced by rainfall and hence river flow. Application of the PRISW-1 index indicated that, although pesticides levels fulfilled the European Union Environmental Quality Standards (EQS) for surface waters, the existing pesticide contamination poses a low to high ecotoxicological risk for aquatic organisms, that algae and macro-invertebrates are at higher risk than fish, and that the organophosphates diazinon and malathion and the phenylurea diuron are the major contributors to the overall toxicity and therefore the most problematic compounds.     

Brassinosteroid alleviates phenanthrene and pyrene phytotoxicity by increasing detoxification activity and photosynthesis in tomato

The present study was carried out to investigate the effects of exogenously applied 24-epibrassinolide (BR) on growth, gas exchange, chlorophyll fluorescence characteristics, lipid peroxidation and antioxidant systems of tomato seedlings grown under different levels (0, 10, 30, 100 and 300 μM) of phenanthrene (PHE) and pyrene (PYR) in hydroponics. A concentration-dependent decrease in growth, photosynthetic pigment contents, net photosynthetic rate (Pn), stomatal conductance (Gs), maximal quantum yield of PSII (Fv/Fm), effective quantum yield of PSII (Φ_PSII), photochemical quenching coefficient (qP) has been observed following PHE and PYR exposure. By contrast, non-photochemical quenching coefficient (NPQ) was increased. PHE was found to induce higher stress than PYR. However, foliar or root application of BR (50 nM and 5 nM, respectively) alleviated all those depressions with a sharp improvement in the activity of photosynthetic machinery. The activities of guaicol peroxidase (GPOD), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR) as well as content of malondialdehyde (MDA) were increased in a dose-dependent manner under PHE or PYR treatments. Compared with control the highest increments of GPOD, CAT, APX, GR and MDA by PHE/PYR alone treatments were observed following 300 μM concentration, which were 67%, 87%, 53%, 95% and 74% by PHE and 42%, 53%, 30%, 86% and 62% by PYR, respectively. In addition, both reduced glutathione (GSH) and oxidized glutathione (GSSG) were induced by PHE or PYR. Interestingly, BR application in either form further increased enzymatic and non enzymatic antioxidants in tomato roots treated with PHE or PYR. Our results suggest that BR has an anti-stress effect on tomato seedlings contaminated with PHE or PYR and this effect is mainly attributed by increased detoxification activity.     

Seasonal variations of CH(4) and N(2)O emissions in response to water management of paddy fields located in Southeast China

Water management is one of the most important practices that affect methane (CH₄) and nitrous oxide (N₂O) emissions from paddy fields. A field experiment was designed to study the effects of controlled irrigation (CI) on CH₄ and N₂O emissions from paddy fields, with traditional irrigation (TI) as the control. The effects of CI on CH₄ and N₂O emissions from paddy fields were very clear. The peaks of CH₄ emissions from the CI paddies were observed 1-2 d after the water layer disappeared. Afterward, the emissions reduced rapidly and remained low until the soil was re-flooded. A slight increase of CH₄ emission was observed in a short period after re-flooding. N₂O emissions peaks from CI paddies were all observed 8-10 d after the fertilization at the WFPS ranging from 78.1% to 85.3%. Soil drying caused substantial N₂O emissions, whereas no substantial N₂O emissions were observed when the soil was re-wetted after the dry phase. Compared with TI, the cumulative CH₄ emissions from the CI fields were reduced by 81.8% on the average, whereas the cumulative N₂O emissions were increased by 135.4% on the average. The integrative global warming potential of CH₄ and N₂O on a 100-year horizon decreased by 27.3% in the CI paddy fields, whereas no significant difference in the rice yield was observed between the CI and TI fields. These results suggest that CI can effectively mitigate the integrative greenhouse effect caused by CH₄ and N₂O emissions from paddy fields while ensuring the rice yield.     

Epilithic biofilm as a reservoir for functional virulence factors in wastewater-dominant rivers after WWTP upgrade

Virulence factors (VFs) confer upon pathogens the ability to cause various types of damage or diseases. Wastewater treatment plants (WWTPs) are important point sources for the emission of pathogens and VFs into receiving rivers. Conventional WWTP upgrades are often implemented to improve the water quality of receiving ecosystems. However, knowledge on the pathogens, VFs, and health risks to receiving aquatic ecosystems after upgrade remains limited. In this study, we investigated detailed pathogenic information, including taxa, pathogenicity, and health risk, in two wastewater-dominant rivers after WWTP upgrade. Using 16S rRNA gene sequencing, we screened 14 potential pathogens in water and epilithic biofilm samples, though they were significantly more enriched in the biofilms. Combining 16S rRNA and metagenomic sequencing data, we identified Pseudomonas and Aeromonas as the dominant pathogenic taxa carrying functional VFs (e.g., mobility and offensive) in the epilithic biofilm. Moreover, strong pathogen-specific VF-host co-occurrence events were observed in the epilithic biofilm samples, indicating the importance of biofilms as reservoirs and vehicles for VFs. Further, we demonstrated that mobility VF is crucial for biofilm formation and pathogens in biofilm carrying offensive VF may be highly invasive. Quantification and health risk assessment suggested that the skin contact risk of P. aeruginosa carrying VFs was higher than the acceptable probability of 10^?4 in both water and epilithic biofilm samples, which may threaten ecological and human health.     

散粒体斜坡上滚石法向碰撞恢复系数研究∗

国内外在研究滚石碰撞问题时多将碰撞目标假设为弹塑性体,从而推导出恢复系数计算公式。但是对于散粒体斜坡,由于具有结构松散、高压缩、低黏结力等物理力学特性,如果将其完全考虑为弹塑性体,那么低估了其自身的耗能潜力。为此,我们考虑了松散介质的孔隙压密特征,改进提出了散粒体斜坡上滚石法向碰撞恢复系数的计算式,并探讨了滚石碰撞再回弹的临界条件。同时以西藏昌都察达隧道进口散粒体斜坡为算例进行数值模拟,分析了5 种影响因素下滚石法向碰撞恢复系数变化规律,并与改进公式、已有相关公式计算结果进行了对比分析。结果表明改进公式与数值模拟结果较为吻合,优于假设为弹塑性体的公式计算值。研究思路及成果可为类似区域性问题提供参考。     

Identify the contribution of vehicle non-exhaust emissions: a single particle aerosol mass spectrometer test case at typical road environment

● A single particle observation was conducted in a high traffic flow road environment. ● Major particle types were vehicle exhausts, coal burning, and biomass burning. ● Contribution of non-exhaust emissions was calculated via PMF. ● Proportion of non-exhaust emissions can reach 10.1 % at road environment. A single particle aerosol mass spectrometer (SPAMS) was used to accurately quantify the contribution of vehicle non-exhaust emissions to particulate matter at typical road environment. The PM_2.5, black carbon, meteorological parameters and traffic flow were recorded during the test period. The daily trend for traffic flow and speed on TEDA Street showed obvious “M” and “W” characteristics. 6.3 million particles were captured via the SPAMS, including 1.3 million particles with positive and negative spectral map information. Heavy Metal, High molecular Organic Carbon, Organic Carbon, Mixed Carbon, Elemental Carbon, Rich Potassium, Levo-rotation Glucose, Rich Na, SiO₃ and other categories were analyzed. The particle number concentration measured by SPAMS showed a good linear correlation with the mass concentrations of PM_2.5 and BC, which indicates that the particulate matter captured by the SPAMS reflects the pollution level of fine particulate matter. EC, ECOC, OC, HM and crustal dust components were found to show high values from 7:00–9:00 AM, showing that these chemical components are directly or indirectly related to vehicle emissions. Based on the PMF model, 7 major factors are resolved. The relative contributions of each factor were determined: vehicle exhaust emission (44.8 %), coal-fired source (14.5 %), biomass combustion (12.2 %), crustal dust (9.4 %), ship emission (9.0 %), tires wear (6.6 %) and brake pads wear (3.5 %). The results show that the contribution of vehicle non-exhaust to particulate matter at roadside environment is approximately 10.1 %. Vehicle non-exhaust emissions are the focus of future research in the vehicle pollutant emission control field.     

Effect of the behavior and availability of heavy metals on the characteristics of the coastal soils developed from alluvial deposits

An investigation of the behavior and availability of heavy metals (HMs), i.e., Cu, Zn, Ni, Pb, Cr, and Cd, based on the analysis of correlation between HMs and physical and chemical properties of coastal soils developed from alluvial deposits in Shanghai, China, has been conducted, in order to reveal the effect of the soil formation and development and the unsuited human activities on the activities and mobility of HMs in agricultural soils. The results showed that (1) the soils still meet the needs of plant growth due to the moderate fertility with a soil texture of silty loam although the content of organic matters is lower, (2) total heavy metal content had a increase trend from the inland area to the coastal area, indicating the impact of alluvial deposits related to the soil formation on the distribution of HMs; (3) a significant positive correlation was found between HMs and some soil properties (i.e., clay content, cation exchange capacity, organic matters, total Phosphorous content, etc.), indicating that the regulation of these properties could give some great effect on the behavior and availability of HMs; (4) the positive correlation among Cu, Zn, Ni, and Cd, and between Pb and Cr is very significant, suggesting the most similar, if not the same, origins of HMs; These findings are helpful to the soil remediation, fertility adjustment, and plant cultivation.     

多米诺效应定量风险分析

根据多米诺效应的特点,提出了针对多米诺场景和效应后果的定量风险分析方法.首先辨识多米诺效应的事故场景,针对场景的复杂性和事故后果的严重性,运用数学模型和概率分析手段对主要事故场景进行分析; 其次根据初始事故的影响,运用设备损坏概率模型计算二次目标设备的损坏概率和场景的后果; 最后,运用人体脆弱性模型对效应后果进行分析,量化多米诺效应的风险,结合风险分析方法和理论得到直观的个人风险和F-N社会风险曲线.多米诺分析流程及计算的结果表明,多米诺效应对个人风险和社会风险都造成了显著的变化,加强多米诺效应分析有利于工厂规划布局和安全管理.     

小区域氯气扩散的CFD模拟研究

针对一个较小的工厂区域,应用CFD法,分别对氯气连续泄漏和瞬时泄漏的扩散过程进行了研究,并应用FLUENT软件,分别对两种情况下的氯气扩散情况进行了模拟.结果表明,连续泄漏时,建筑的阻挡和涡旋的存在会减慢氯气扩散速度,使得建筑后方氯气浓度比周围空间低很多;瞬时泄漏时,涡旋对氯气扩散的束缚作用非常明显,涡旋内部的氯气停留时间比其他区域长.这些结果可以为应急救援和工厂结构优化设计提供依据.