Alterations of microbial populations and composition in the rhizosphere and bulk soil as affected by residual acetochlor

Acetochlor is a widely used herbicide in maize fields; however, the ecological risk of its residue in the soil–plant system remains unknown. We investigated the dissipation dynamics of field dose acetochlor and clarified its impact on microbial biomass and community structure both in the rhizosphere and bulk soil over 1 month after its application. Soil microbial parameters such as quantities of culturable bacteria and fungi represented by colony-forming units, soil microbial biomass carbon (SMB_C), and phospholipid fatty acids (PLFAs) were determined across different sampling times. The results showed that the dissipation half-lives of acetochlor were, respectively, 2.8 and 3.4 days in the rhizosphere and bulk soil, and 0.02–0.07 μg/g residual acetochlor could be detected in the soil 40 days after its application. Compared to the bulk soil, microbial communities in the rhizosphere soil were inclined to be affected by the application of acetochlor: SMB_C content and bacterial growth were most likely to be increased; however, fungal growth was prone to be inhibited. The principal component analysis of PLFAs, as well as the comparisons of fungi/bacteria and cy17:0/C16:1ω9c ratios between different treatments over sampling time, revealed that the soil microbial community composition was significantly affected by acetochlor at its early application stage (at day 15); thereafter, the effects of acetochlor were attenuated or even could not be detected. Our results suggested that residual acetochlor did not confer a long-term impairment on viable bacterial groups in the rhizosphere and bulk soil.     

基于生态水泥的再生混凝土中重金属浸出动力学研究

使用生态水泥、再生骨料制备再生混凝土.分别通过快速浸出实验和长期连续浸出实验对混凝土中的重金属进行浸取,并采用原子吸收光谱法检测浸出溶液中的重金属含量,对比研究再生混凝土与普通混凝土重金属浸出性能差异.研究发现,快速浸出实验条件下,再生混凝土浸出液各重金属浸出浓度高于普通混凝土浸出浓度,但仍低于《危险废物鉴别标准浸出毒性鉴别》(GB5085.3-2007)标准规定的限值.快速浸出实验条件下重金属浸出量与重金属总量相关性不显著,说明快速实验方法有局限性.长期连续浸出实验结果表明,再生混凝土各重金属元素的扩散系数高于普通混凝土(除Zn外),这是由再生混凝土独特的显微结构引起的.     

Dust Collection Efficiency Analysis in a Two-Dimensional Circulating Granular Bed Filter

Abstract

Dust collection efficiency data were analyzed to determine better operating conditions for a two-dimensional circulating granular bed filter (CGBF). The dust collection efficiency in the granular bed was affected by the following operating parameters: the louver angle, the solids mass flow rate, and the particle size of the bed material. Experimental results showed that higher dust collection efficiency occurs when the solids mass flow rates were 20.34 ± 0.24, 21.50 ± 0.11, and 30.51 ± 0.57 g/sec at louver angles of 45°, 30°, and 20°, respectively. Optimal dust collection efficiency peaked with a louver angle of 30°. Average particle sizes of bed material by sieve diameters (μm) of 795 μm had higher dust collection efficiency than the average collector particle size of 1500 μm. Dust collection efficiency is influenced by bed material attrition phenomenon, causing dust collection efficiency to decrease rapidly. The dust collection efficiency analysis not only found the system free of design defects but also assisted in the operation of the two-dimensional CGBF system.     

工业污水回用是节约新鲜水的重要途径

介绍了二级出水深度处理工艺、药剂选择、试运行处理效果及深度处理后出水的回用情况。     

Emission of ammonia from indoor concrete wall and assessment of human exposure

Addition of urea-based antifreeze admixtures during cement mixing can make it possible to produce concrete cement in construction of buildings in cold weather; this, however, has led to increasing indoor air pollution due to continuous transformation and emission from urea to gaseous ammonia in indoor concrete wall. It is believed that ammonia is harmful to human body and exposure to ammonia can cause some serious symptoms such as headaches, burns, and even permanent damage to the eyes and lungs. In order to understand the emission of ammonia from indoor concrete wall in civil building and assess the health risk of people living in these buildings, the experimental pieces of concrete wall were first prepared by concreting cement and urea-based antifreeze admixtures to simulate the indoor wall in civil building in this work. Then environmental chamber was adopted for studying the effect of temperature, relative humility and air exchange rate on emission of ammonia from experimental pieces of concrete wall. Also the field experiment was made at selected rooms in given civil buildings. Exposure and potential dose of adult and children exposed to indoor/outdoor ammonia in summer and in winter are calculated and evaluated by using Scenario Evaluation Approach. The results indicated that high air exchange rate leads to decreased ammonia concentration, and elevation of temperature causes increasing ammonia concentration and volatilizing rate in chamber. The complete emission of ammonia from the wall containing urea-based antifreeze admixtures needs more than 10 years in general. Ventilating or improving air exchange can play a significant role in reducing ammonia concentration in actual rooms in field experiments. Urea-based antifreeze admixtures in concrete wall can give rise to high exposure and potential dose, especially in summer. Generally, adults have a high potential dose than children, while children have personal average dose rate beyond adults in the same conditions.     

The Fuzzy Synthesizing Evaluation of City''''s Environmental Quality Based on GIOWA Operator:A Case of 13 Cities of Jiangsu Province

1 INTRODUCTION In China, cities have been undergoing a rapid development in recent years. On the one hand, the level of urbanization rises continuously and a large population gathers in a city. The number and the scale of city increase and enlarge continuously. On the other hand, large population gathering in a city brings a huge pressure to the ecological environment of the city. The environmental pollution of the city is becoming more serious. This is a terrible and heavy cost for city…     

二氧化碳灭火系统误喷事故分析及预防措施探讨

根据二氧化碳灭火系统在工程中的实际应用,系统分析灭火系统误喷事故原因,建立引起二氧化碳灭火系统误喷事故树。通过事故树计算各基本事件的结构重要度,确定基本事件对误喷事故产生的影响程度,最后为防止误喷事故发生制定了预防措施。     

2013年11月23日山东莱州4.6级地震序列初步分析

2013年11月23日山东省莱州市发生Ms4.6级地震,该地震发生在沂沭断裂带东侧.该地震序列类型为主余型,但是地震序列的h值小于1.根据地震的等震线长轴、震源机制解和地质资料分析认为发震断层呈NE向.该地震打破了华北地区6个月的ML4级地震平静,可能预示着华北地区中强地震活动复苏,拉开华北地区中强地震活动序幕,对华北地区6级地震具有指示意义.此外,该地震是1995年苍山Ms5.2级地震后,山东内陆地区发生的最大地震,引起了广泛的政府和社会关注,具有重要的社会影响.     

Emission factors of polycyclic aromatic hydrocarbons from domestic coal combustion in China

Domestic coal stove is widely used in China, especially for countryside during heating period of winter, and polycyclic aromatic hydrocarbons （PAHs） are important in flue gas of the stove. By using dilution tunnel system, samples of both gaseous and particulate phases from domestic coal combustion were collected and 18 PAH species were analyzed by GC-MS. The average emission factors of total 18 PAH species was 171.73 mg/kg, ranging from 140.75 to 229.11 mg/kg for bituminous coals, while was 93.98 mg/kg, ranging from 58.48 to 129.47 mg/kg for anthracite coals. PAHs in gaseous phases occupied 95% of the total of PAHs emission of coal combustion. In particulate phase, 3-ring and 4- ring PAHs were the main components, accounting for 80% of the total particulate PAHs. The total toxicity potency evaluated by benzo[a]pyrene-equivalent carcinogenic power, sum of 7 carcinogenic PAH components and 2,3,7,8-tetrachlorodibenzodioxin had a similar tendency. And as a result, the toxic potential of bituminous coal was higher than that of anthracite coal. Efficient emission control should be conducted to reduce PAH emissions in order to protect ecosystem and human health.     

蕹菜镉积累典型品种的根际土壤酶研究

通过在镉含量高、低不同的2种土壤上的自制根箱试验并对所种植作物的镉含量进行相关性分析,研究了两种蕹菜镉积累典型品种,强坤柳叶白骨（QK,Cd-PSC）和台湾308纯白柳叶（T-308,非Cd-PSC）的根际土壤酶区系.结果表明：品种间茎叶镉含量差异极显著;在高镉条件下,蕹菜茎叶Cd含量与根际转化酶活性呈显著正相关;在低镉条件下,与根际碱性磷酸酶活性呈显著负相关.