Aerosol transmission,an indispensable route of COVID-19 spread: case study of a department-store cluster

• Aerosol transmission is an indispensable route of COVID-19 spread. • Different outbreak sites have different epidemiologic feature. • SRAS-CoV-2 can exist for a long time in aerosol. • SRAS-CoV-2 RNA can be detected in aerosol in diverse places. • Some environmental factors can impact SARS-CoV-2 transportation in aerosol. Patients with COVID-19 have revealed a massive outbreak around the world, leading to widespread concerns in global scope. Figuring out the transmission route of COVID-19 is necessary to control further spread. We analyzed the data of 43 patients in Baodi Department Store (China) to supplement the transmission route and epidemiological characteristics of COVID-19 in a cluster outbreak. Incubation median was estimated to endure 5.95 days (2–13 days). Almost 76.3% of patients sought medical attention immediately upon illness onset. The median period of illness onset to hospitalization and confirmation were 3.96 days (0–14) and 5.58 days (1–21), respectively. Patients with different cluster case could demonstrate unique epidemiological characteristics due to the particularity of outbreak sites. SRAS-CoV-2 can be released into the surrounding air through patient’s respiratory tract activities, and can exist for a long time for long-distance transportation. SRAS-CoV-2 RNA can be detected in aerosol in different sites, including isolation ward, general ward, outdoor, toilet, hallway, and crowded public area. Environmental factors influencing were analyzed and indicated that the SARS-CoV-2 transportation in aerosol was dependent on temperature, air humidity, ventilation rate and inactivating chemicals (ozone) content. As for the infection route of case numbers 2 to 6, 10, 13, 16, 17, 18, 20 and 23, we believe that aerosol transmission played a significant role in analyzing their exposure history and environmental conditions in Baodi Department Store. Aerosol transmission could occur in some cluster cases when the environmental factors are suitable, and it is an indispensable route of COVID-19 spread.     

磺胺类化合物对大肠杆菌突变QSAR预测模型初探

抗生素被广泛应用于医疗、农业和畜牧业等领域,但是长期滥用会促进细菌的突变作用。本文以大肠杆菌(E.coli)为受试生物,测定了10种磺胺类抗生素(SAs)单一暴露时对E.coli的突变效应,采用物化参数Ebinding(抗生素与其靶蛋白的相互作用能力)与突变效应参数lgRC0-2(最高可观测突变促进效应浓度)或lgRCmax(突变促进率最大值对应的浓度),建立了突变效应的QSAR模型,并采用雷达图进行验证。结果表明,lgRC0-2与Ebinding模型和lgRCmax与Ebinding、DMG(偶极矩)模型的拟合系数R2分别是0.888、0.873,即lgRC0-2或lgRCmax与Ebinding相关性均较好,可能由于磺胺类化合物(SAs)会作用于叶酸合成通路,影响嘌呤、嘧啶碱基的合成,从而对E.coli的突变具有促进效应,且雷达图验证表明,上述2个模型均具有良好的内部预测能力。本研究有望为抗生素使用带来的生态风险评价以及药物设计提供相关指导。     

我国区域空气污染治理效率及其影响机制——基于超效率SBM模型和门槛回归模型

随着人民对美好生活需求的日益增长,政府空气污染治理的效率问题日益得到重视。本文从地方政府空气污染治理效率及其影响因素的视角入手,以全国30个省份为研究对象,运用超效率SBM模型测算2003—2015年各省级区域的空气污染治理效率。在此基础上,运用门槛回归模型分析政府空气污染治理效率的影响机制。研究表明:①地区间空气污染治理效率差异性较为显著。中部、西部空气污染治理效率整体呈下降趋势。东部和东北地区空气污染治理效率则上升比较平稳。②政策规划、碳源、污染物排放和环境治理投入表现出双重门槛特征,其中碳源对空气污染治理效率影响显著,而以碳为首的能源消费结构则主要对中部和西部空气污染治理效率产生影响。落后地区政府应注重产业升级,财政上应对碳税等税目进行征收,产业上应鼓励企业创新,并对落后企业进行倒逼升级。     

Magnetotactic bacteria: Characteristics and environmental applications

• Magnetotactic bacteria (MTB) synthesize magnetic nanoparticle within magnetosomes. • The morphologic and phylogenetic diversity of MTB were summarized. • Isolation and mass cultivation of MTB deserve extensive research for applications. • MTB can remove heavy metals, radionuclides, and organic pollutants from wastewater. Magnetotactic bacteria (MTB) are a group of Gram-negative prokaryotes that respond to the geomagnetic field. This unique property is attributed to the intracellular magnetosomes, which contains membrane-bound nanocrystals of magnetic iron minerals. This review summarizes the most recent advances in MTB, magnetosomes, and their potential applications especially the environmental pollutant control or remediation. The morphologic and phylogenetic diversity of MTB were first introduced, followed by a critical review of isolation and cultivation methods. Past research has devoted to optimize the factors, such as oxygen, carbon source, nitrogen source, nutrient broth, iron source, and mineral elements for the growth of MTB. Besides the applications of MTB in modern biological and medical fields, little attention was made on the environmental applications of MTB for wastewater treatment, which has been summarized in this review. For example, applications of MTB as adsorbents have resulted in a novel magnetic separation technology for removal of heavy metals or organic pollutants in wastewater. In addition, we summarized the current advance on pathogen removal and detection of endocrine disruptor which can inspire new insights toward sustainable engineering and practices. Finally, the new perspectives and possible directions for future studies are recommended, such as isolation of MTB, genetic modification of MTB for mass production and new environmental applications. The ultimate objective of this review is to promote the applications of MTB and magnetosomes in the environmental fields.     

环境检测的作用及环保措施分析

本文对环境检测的作用进行了总结,包括环境检测是环境影响评价的基础、环境检测是环境保护的依据、环境检测促进环境管理工作等,提出了环境保护措施,需要增加资金投入力度、完善环境检测法律保障体系、合理使用环境检测新技术、构建环境检测质量控制体系、完善环境监管保护方法来有效地保护环境,提升人们的生活质量。     

Stabilization of Cd-, Pb-, Cu- and Zn-contaminated calcareous agricultural soil using red mud: a field experiment

Red mud (RM) was used to remediate heavy metal-contaminated soils. Experiments with two different dosages of RM added to soils were carried out in this study. It was found that soil pH increased 0.3 and 0.5 unit with the dosage of 3 and 5% (wt%), respectively. At the dosage of 5%, the highest stabilization efficiencies for Cd, Pb, Cu and Zn reached 67.95, 64.21, 43.73 and 63.73%, respectively. The addition of RM obviously transferred Cd from the exchangeable fraction to the residual fraction. Meanwhile, in comparison with the control (no RM added), it reduced 24.38, 49.20, 19.42 and 8.89% of Cd, Pb, Cu and Zn in wheat grains at the RM addition dosage of 5%, respectively. At the same time, the yield of wheat grains increased 17.81 and 24.66% at the RM addition dosage of 3 and 5%, respectively. Finally, the addition of RM did not change the soil bacterial community. These results indicate that RM has a great potential in stabilizing heavy metals in calcareous agricultural soils.

     

Health risk assessment of heavy metals in Cyprinus carpio (Cyprinidae) from the upper Mekong River

The purposes of this research are to quantify the concentration of heavy metals (Zn, Cu, As, Pb, Cd, and Hg) in the water and fish tissues of common carp (Cyprinus carpio) in the upper Mekong River and to thereby elucidate the potential dietary health risks from fish consumption of local residents. Surface water and fish tissues (gill, muscle, liver, and intestine) from four representative sample areas (influence by a cascade of four dams) along the river were analyzed for heavy metal concentrations. Results revealed that the levels of heavy metals in fish were tissue-dependent. The highest Cu and As levels were found in the liver; the highest Zn and Pb levels occurred in the intestine, and the highest Hg level was found in the muscle. The total target hazard quotient (THQ) value for residents is > 1 for long-term fish consumption, and local residents are, therefore, exposed to a significant health risk. Results from the current study provide an overall understanding of the spatial and tissue distribution of heavy metals in water and fish body along the upper Mekong River under the influence of cascade dams and highlight the potential health risk of As for the local residents of long-term fish consumption.

     

北京市城区挥发性有机物污染特征及其对臭氧影响分析

对2020年4月—2021年3月北京市建成区挥发性有机物（VOCs）的化学特征、污染来源及其对臭氧（O₃）污染的影响进行了研究。结果显示：O₃日最大8 h滑动平均值在臭氧季（4—9月）均值为134 μg/m³，是非臭氧季（10月至次年3月）均值（59.6 μg/m³）的2.2倍。臭氧季VOCs体积浓度均值为14.3×10^-9，明显低于非臭氧季（21.1×10^-9），可能与光化学反应速率和VOCs来源的季节性差异有关。臭氧生成潜势（OFP）贡献率排名前10位的物种在臭氧季和非臭氧季相似，均包括间/对-二甲苯、甲苯、乙烯、邻二甲苯、异戊烷、正丁烷、丙烯、反式-2-丁烯和1，2，4-三甲基苯，但排名有所差异，燃煤源特征明显的乙烯等物种在非臭氧季上升明显，与溶剂使用、油气挥发相关的间/对二甲苯、甲苯、异戊烷和正丁烷等物种在臭氧季上升明显。甲苯/苯的值和异戊烷/正戊烷的值在臭氧季明显高于非臭氧季，反映出机动车排放和油气挥发等在臭氧季影响突出，非臭氧季是燃煤影响显著。基于正交矩阵因子分解模型（PMF），臭氧季解析出机动车尾气排放（40.9%）、溶剂使用（20%）、油气挥发（16.4%）、工业排放（17.6%）和植物排放（5.1%）等5种污染源；非臭氧季解析出机动车尾气（38.9%）、燃烧源（26.3%）、工业排放（17.8%）和溶剂使用（17%）等4种污染源。     

Remediation of 2,4-dichlorophenol-contaminated groundwater using nano-sized CaO2 in a two-dimensional scale tank

• Nano CaO₂ is evaluated as a remediation agent for 2,4-DCP contaminated groundwater. • 2,4-DCP degradation mechanism by different Fe²⁺ concentration was proposed. • 2,4-DCP was not degraded in the system for solution pH>10. • The 2,4-DCP degradation area is inconsistent with the nano CaO₂ distribution area. This study evaluates the applicability of nano-sized calcium peroxide (CaO₂) as a source of H₂O₂ to remediate 2,4-dichlorophenol (2,4-DCP) contaminated groundwater via the advanced oxidation process (AOP). First, the effect and mechanism of 2,4-DCP degradation by CaO₂ at different Fe concentrations were studied (Fenton reaction). We found that at high Fe concentrations, 2,4-DCP almost completely degrades via primarily the oxidation of •OH within 5 h. At low Fe concentrations, the degradation rate of 2,4-DCP decreased rapidly. The main mechanism was the combined action of •OH and O₂^•−. Without Fe, the 2,4-DCP degradation reached 13.6% in 213 h, primarily via the heterogeneous reaction on the surface of CaO₂. Besides, 2,4-DCP degradation was significantly affected by solution pH. When the solution pH was>10, the degradation was almost completely inhibited. Thus, we adopted a two-dimensional water tank experiment to study the remediation efficiency CaO₂ on the water sample. We noticed that the degradation took place mainly in regions of pH<10 (i.e., CaO₂ distribution area), both upstream and downstream of the tank. After 28 days of treatment, the average 2,4-DCP degradation level was ≈36.5%. Given the inadequacy of the results, we recommend that groundwater remediation using nano CaO₂: (1) a buffer solution should be added to retard the rapid increase in pH, and (2) the nano CaO₂ should be injected copiously in batches to reduce CaO₂ deposition.     

武汉市都市发展区地表温度季节性空间分布与驱动力分析

基于2015年武汉市都市发展区30 m空间分辨率的Landsat 8遥感影像反演近地表温度(LST),运用地统计学、地理加权回归(GWR)等方法,分析都市发展区、生态绿楔以及主城区四季LST时空分布规律和各驱动因子的作用机制,以期为更全面、科学地规划城市发展空间布局和缓解热岛效应提供借鉴.结果 表明:(1)与单一的普通最小二乘回归(OLS)相比,线性逐步回归(LSR)可以寻找最优的多驱动因子组合模型,与LSR拟合的结果相比,GWR模型R2值提高了0.04～0.09,且AIC值均明显减小;(2) LST存在空间聚集关系,“高-高”聚集主要发生在主城区、新型城镇发展区、主要交通干线沿线等更容易造成高温聚集的人工表面,其中夏季“高-高”聚集网格数最多且占比最大,而“低-低”聚集四季均主要发生在各大湖泊水系;(3)绿楔生态用地降温幅度各异,春季降温幅度不明显,夏季降温幅度最显著,各绿楔生态用地降温均超过2℃,且在一定范围内,LST随着与绿楔距离增大而升高,达到一定距离时,会随着与绿楔距离增加而趋于平缓或呈下降趋势;(4)与前人研究相比,景观格局对LST变化的解释程度整体较低,其原因可能是快速城市化导致人工表面积增加,相应的人工绿地也将增加,使得城市景观格局更加零散,导致LST受多种相互作用因素的影响;(5)影响四季LST的驱动因子空间差异较大,夏季土地覆盖和景观格局与冬季土地覆盖、景观格局和人为活动的回归系数均为正值,说明高温或低温条件下这些驱动因子对全域升温作用明显.