Ionic composition of submicron particles (PM1.0) during the long-lasting haze period in January 2013 in Wuhan, central China

In January 2013, a long-lasting severe haze episode occurred in Northern and Central China; at its maximum, it covered a land area of approximately 1.4 million km². In Wuhan, the largest city in Central China, this event was the most severe haze episode in the 21st century. Aerosol samples of submicron particles (PM_1.0) were collected during the long-lasting haze episode at an urban site and a suburban site in Wuhan to investigate the ion characteristics of PM_1.0 in this area. The mass concentrations of PM_1.0 and its water-soluble inorganic ions (WSIIs) were almost at the same levels at two sites, which indicates that PM_1.0 pollution occurs on a regional scale in Wuhan. WSIIs (Na⁺, NH₄⁺, K⁺, Mg²⁺, Ca²⁺, Cl^-, NO₃^- and SO₄^2-) were the dominant chemical species and constituted up to 48.4% and 47.4% of PM_1.0 at WD and TH, respectively. The concentrations of PM_1.0 and WSIIs on haze days were approximately two times higher than on normal days. The ion balance calculations indicate that the particles were more acidic on haze days than on normal days. The results of the back trajectory analysis imply that the high concentrations of PM_1.0 and its water-soluble inorganic ions may be caused by stagnant weather conditions in Wuhan.     

Sorption and degradation of pesticides in nursery recycling ponds

Knowledge of pesticide distribution and persistence in nursery recycling pond water and sediment is critical for preventing phytotoxicity of pesticides during water reuse and to assess their impacts to the environment. In this study, sorption and degradation of four commonly used pesticides (diazinon, chlorpyrifos, chlorothalonil, and pendimethalin) in sediments from two nursery recycling ponds was investigated. Results showed that diazinon and chlorothalonil were moderately sorbed [K(OC) (soil organic carbon distribution coefficient) from 732 to 2.45 x 10(3) mL g(-1)] to the sediments, and their sorption was mainly attributable to organic matter content, whereas chlorpyrifos and pendimethalin were strongly sorbed (K(OC) > or = 7.43 x 10(3) mL g(-1)) to the sediments, and their sorption was related to both organic matter content and sediment texture. The persistence of diazinon and chlorpyrifos was moderate under aerobic conditions (half-lives = 8 to 32 d), and increased under anaerobic conditions (half-lives = 12 to 53 d). In contrast, chlorothalonil and pendimethalin were quickly degraded under aerobic conditions with half-lives < 2.8 d, and their degradation was further enhanced under anaerobic conditions (half-lives < 1.9 d). The strong sorption of chlorpyrifos and pendimethalin by the sediments suggests that the practice of recycling nursery runoff would effectively retain these compounds in the recycling pond, minimizing their offsite movement. The prolonged persistence of diazinon and chlorpyrifos, however, implies that incidental spills, such as overflows caused by storm events, may contribute significant loads of such pesticides into downstream surface water bodies.     

广州市白云山降水的化学特征及源解析

以2006年广州市白云山降水监测资料为基础,对其降水样品的化学特征进行了分析。结果表明,白云山降水样品pH值分布为3.04—6.41,雨量加权pH平均值为4.26,酸雨频率为70.2％,降水中的主要阳离子是Ca^2＋和NH^＋4分别占阳离子总量的46.4％和17.5％;主要阴离子为SO^2-4和NO^-3,分别占阴离子总量的59.0％和19.9％。相对酸度（FA）和中和因子（NF）计算结果表明,约有84.7％的降水酸度被碱性成分Ca^2＋和NH^＋4中和。利用富集系数方法,计算结果表明SO^2-4和NO^-3主要来源于人类活动,而Ca^2＋和K^＋主要来源于岩石／土壤风化。     

Polybrominated diphenyl ethers in house dust in Singapore

The use of polybrominated diphenyl ethers (PBDEs) as flame retardants in Singapore is not strictly regulated; therefore these compounds can be readily found in furniture, electronic devices, and building materials. This study was the first of its kind to be conducted in Singapore to measure concentrations of PBDEs in house dust. Samples were collected from 31 homes in various locations across the island-state of Singapore, and a total eight PBDEs congeners were measured. PBDEs were detected in all 31 dust samples and the number of BDE congener detected per home ranged between 3 and 8. The most abundant BDE congeners found were BDE 47, 99 and 209, with a median value of 20 ng g(-1) dust, 24 ng g(-1) dust and 1000 ng g(-1) dust, respectively. BDE 209 contributed 88% to the median of all the congeners, and BDE 47 and 99 contributed 1.8% and 3.5%, respectively. Different congener profiles were observed between this and studies conducted elsewhere, which is consistent with the use of different commercial PBDE around the world. No significant correlations between PBDE dust levels and residential characteristics (number of TVs and computers, floor area or flooring material) were observed. The daily intake of PBDEs via the inhalation pathway was estimated. House dust may be regarded as the most important exposure route of PBDEs for children.     

Selected organochlorine pesticide and polychlorinated biphenyl residues in house dust in Singapore

Although the use of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) has been prohibited in Singapore since 1980, OCPs and PCBs still can be detected in the environment and represent a potential threat to public health. In this study, OCPs and PCBs were measured in house dust samples collected from 31 homes across the island-state of Singapore. Organochlorine pesticides, such as hexachlorocyclohexanes (HCHs), chlordanes and dichlorodiphenyltrichloroethanes (DDTs) were tested, with a range of 相似文献   

Response of microcystis to copper stress: do phenotypes of microcystis make a difference in stress tolerance?

To elucidate the role of phenotype in stress-tolerant bloom-forming cyanobacterium Microcystis, two phenotypes of M. aeruginosa - unicellular and colonial strains were selected to investigate how they responded to copper stress. Flow cytometry (FCM) examination indicated that the percents of viable cells in unicellular and colonial Microcystis were 1.92-2.83% and 72.3-97.51%, respectively, under 0.25 mgl(-1) copper sulfate treatment for 24h. Upon exposure to 0.25 mgl(-1) copper sulfate, the activities of antioxidative enzyme, such as superoxide dismutase (SOD) and catalase (CAT), were significantly increased in colonial Microcystis compared to unicellular Microcystis. Meanwhile, the values of the photosynthetic parameters (F(v)/F(m), ETR(max), and oxygen evolution rate) decreased more rapidly in unicellular Microcystis than in colonial Microcystis. The results indicate that colonial Microcystis has a higher endurance to copper than unicellular Microcystis. This suggests that the efficient treatment concentration of copper sulfate as algaecides will be dependent on the phenotypes of Microcystis.     

省域高速公路交通应急救援联动机制探讨

在系统分析省域高速公路应急救援组织体系存在问题的基础上,通过广泛调研和系统研究,结合我国国情,提出省域高速公路交通应急救援的组织指挥体系、可靠联动模式、运行机制、联动保障、技术路线等方案与措施。建立了基于领导机构、办事机构、工作机构、专家组4个层次的救援组织指挥体系,构建了高速公路交通应急救援的协调管理的基本机制,设计了对应协调管理基本机制的联动处置流程,并提出建设先进的高速公路交通应急救援调度信息中心的具体内容,为建立高效、稳健的高速公路交通应急救援组织体系与联动机制提供科学依据。该方案与措施有助于统一协调指挥多个救援部门之间的工作,实现救援部门之间的信息共享,确保交通应急救援调度和协调管理工作的顺利实施。     

公路交通事故黑点成因的对应分析法

为了便捷获取公路事故黑点的形成原因,应用对应分析构建立事故黑点成因分析模型。该模型设立事故样本和事故影响因素之间的列联表,将列联表中影响变量的状态呈现于二维对应分析散点图中,以直观简洁的形式描述事故样本与影响因素之间的对应关系。进而设定相关系数判定对应分析模型的收敛性,应用点子排除法剔除特殊影响变量,增强了分析结果的鲁棒性。通过G205事故黑点路段(K954+50-K954+900)的实例分析表明,运用对应分析法所建立的模型与算法可以获得公路事故黑点形成的主要和次要因素,准确确定直接原因与根本原因的对应关系。     

Selected organochlorine pesticides (OCPs) in surface soils from three major states from the northeastern part of India

Eighty-two surface soil samples were collected from forest, grassland, tea estate, wildlife sanctuary, wetland, and roadside areas from the northeastern states of India, viz., Tripura, Manipur, and Assam. Thirteen different organochlorine pesticides (OCPs) were detected from background soils using gas chromatography electron capture detector. Manipur soils were found to be with higher concentration of dichlorodiphenyltrichloroethanes (DDTs), hexachlorocyclohexanes (HCHs), and endosulfan followed by Tripura and Assam. The spearman correlation coefficient shows significant correlation between HCHs, DDTs, and endosulfan isomers (r ²?>?0.5 and p?<?0.05). Additionally, α-HCH, δ-HCH, o,p′-DDE, and endosulfan-sulfate shows good correlation with total organic carbon in soil (r ²?=?0.5, p?=?0.05), indicating that the soil organic matter could enhance adsorption of these compounds, also demonstrating that the present OCPs in the background soil were from similar source. Further principal component analysis evaluates that most of the higher volatile compounds where clustered together in soil. However, after comparing with different states of Indian soil samples, the concentrations of OCPs in the present study areas are much lower and comparable with background soil across the globe.     

Environmentally Friendly Oil-Modified Polyesters as Polymeric Plasticizers for Poly(vinyl chloride)

Oil-modified polyesters were synthesized to serve as polymeric plasticizers for PVC. A total of four polymeric plasticizers with different average molecular weights were prepared. Characterizations were done using Fourier-transformed infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, and gel permeation chromatography. Some of the tests conducted on PVC films include thermal stability test using thermogravimetric analyser, determination of glass transition temperature (T_g), plasticizer migration and leaching resistance test, morphology study of plasticized PVC films using field emission scanning microscope, toxicity test, and tensile test. Owing to the plasticizing effect of the palm oil-based compound, T_g of the plasticized PVC has decreased to an average of 65 °C at 20 wt% loading. The polymeric plasticizer is also able to contribute positively to the thermal stability and mechanical properties of the PVC films. Some of the advantages of incorporating polymeric plasticizer with high molecular weight includes lower rate of leaching from plastic, and improved tensile strength and elongation at break. Besides, thermal stability of the plastic studied using Kissinger’s and Flynn–Wall–Ozawa’s approaches shows that PVC blended with high molecular weight oil-modified polyester is more thermally stable, evidenced by the increase in the activation energy of decomposition, E_d. Toxicity test using brine shrimp egg shows encouraging results, where the oil-based plasticizer is considerably less toxic compared to some of the commercial plasticizers.