Impacts of n-alkane concentration on soil bacterial community structure and alkane monooxygenase genes abundance during bioremediation processes

Petroleum hydrocarbons, mainly consisting of n-alkanes and polycyclic aromatic hydrocarbons (PAHs), are considered as priority pollutants and biohazards in the environment, eventually affecting the ecosystem and human health. Though many previous studies have investigated the change of bacterial community and alkane degraders during the degradation of petroleum hydrocarbons, there is still lack of understanding on the impacts of soil alkane contamination level. In the present study, microcosms with different n-alkane contamination (1%, 3% and 5%) were set up and our results indicated a complete alkane degradation after 30 and 50 days in 1%- and 3%-alkane treatments, respectively. In all the treatments, alkanes with medium-chain length (C₁₁-C₁₄) were preferentially degraded by soil microbes, followed by C₂₇-alkane in 3% and 5% treatments. Alkane contamination level slightly altered soil bacterial community, and the main change was the presence and abundance of dominant alkane degraders. Thermogemmatisporaceae, Gemmataceae and Thermodesulfovibrionaceae were highly related to the degradation of C₁₄- and C₂₇-alkanes in 5% treatment, but linked to alkanes with medium-chain (C₁₁-C₁₈) in 1% treatment and C₂₁-alkane in 3% treatment, respectively. Additionally, we compared the abundance of three alkane-monooxygenase genes, e.g., alk_A, alk_P and alk_R. The abundance of alk_R gene was highest in soils, and alk_P gene was more correlated with alkane degradation efficiency, especially in 5% treatment. Our results suggested that alkane contamination level showed non-negligible effects on soil bacterial communities to some extents, and particularly shaped alkane degraders and degrading genes significantly. This study provides a better understanding on the response of alkane degraders and bacterial communities to soil alkane concentrations, which affects their biodegradation process.

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冷却塔塔筒荷载效应和简化设计方法——各荷载单独作用分析

为简化冷却塔塔筒配筋设计中的多风向计算问题,应明确塔筒在各荷载单独作用下的内力特征。以某冷却塔为例并配以代表性的荷载取值,对其自重、风、冬温和夏温、水平和竖向地震这6类荷载的内力状态进行了单独分析和系统对比,着眼于各自的主要内力和各内力环向分布特征。结果表明,自重、冬温和竖向地震作用下内力的环向均匀分布使其无碍于荷载效应的方向组合;夏温和水平地震的最不利内力固定在某一子午线上且各自分别以弯矩和轴力为主,两者方向一致时即自然形成最不利组合;风荷载方向的任意性、复杂的内力分布特征和轴弯联合作用使常规荷载效应组合中必须进行多风向计算,但其内力分布特征依然给荷载效应组合的简化提供了可能。     

微污染水源水中磷的去除

微量和限量的有毒有害有机污染物和城市污水中的氮磷进入水体，使饮用水水源受到轻度污染，这不仅威肋了人类的健康，也对传统净水工艺提出挑战。研究了电凝聚法对微污染水中磷的去除效果，并探讨了电流密度、电解时间、pH值等主要因素对除磷效果的影响。     

Endosulfan in China 2—emissions and residues

Background, aim, and scope  Endosulfan is one of the organochlorine pesticides (OCPs) and also a candidate to be included in a group of new persistent organic pollutants (UNEP 2007). The first national endosulfan usage inventories in China with 1/4° longitude by 1/6° latitude resolution has been reported in an accompanying paper. In the second part of the paper, we compiled the gridded historical emissions and soil residues of endosulfan in China from the usage inventories. Based on the residue/emission data, gridded concentrations of endosulfan in Chinese soil and air have been calculated. These inventories will provide valuable data for the further study of endosulfan. Methods  Emission and residue of endosulfan were calculated from endosulfan usage by using a simplified gridded pesticide emission and residue model—SGPERM, which is an integrated modeling system combining mathematical model, database management system, and geographic information system. By using the emission and residue inventories, annual air and soil concentrations of endosulfan in each cell were determined. Results and discussion  Historical gridded emission and residue inventories of α- and β-endosulfan in agricultural soil in China with 1/4° longitude by 1/6° latitude resolution have been created. Total emissions were around 10,800 t, with α-endosulfan at 7,400 t and β-endosulfan at 3,400 t from 1994 to 2004. The highest residues were 140 t for α-endosulfan and 390 t for β-endosulfan, and the lowest residues were 0.7 t for α-endosulfan and 170 t for β-endosulfan in 2004 in Chinese agricultural soil where endosulfan was applied. Based on the emission and residue inventories, concentrations of α- and β-endosulfan in Chinese air and agricultural surface soil were also calculated for each grid cell. We have estimated annual averaged air concentrations and the annual minimum and maximum soil concentrations across China. The real concentrations will be different from season to season. Although our model does not consider the transport of the insecticide in the atmosphere, which could be very important in some areas during some special time, the estimated concentrations of endosulfan in Chinese air and soil derived from the endosulfan emission and residue inventories are in general consistent with the published monitoring data. Conclusions  To our knowledge, this work is the first inventory of this kind for endosulfan published on a national scale. Concentrations of the chemical in Chinese air and agricultural surface soil were calculated for each grid cell. Results show that the estimated concentrations of endosulfan in Chinese air and soil agree reasonably well with the monitoring data in general. Recommendations and perspectives  The gridded endosulfan emission/residue inventories and also the air and soil concentration inventories created in this study will be updated upon availability of new information, including usage and monitoring data. The establishment of these inventories for the OCP is important for both scientific communities and policy makers.     

经济植物复层栽培对三峡库区水土保持和移民经济的作用

三峡库区森林覆盖率低，水土流失严重。三峡工程兴建后，由于大量耕地被淹，移民后靠，库区的生态环境与移民经济之间的矛盾将会更加突出。本文提出了经济植物复层栽培方法，对其在减少库区水土流失、改善库区生态环境和解决库区移民经济方面的作用作了全面的论述。经济植物复层栽培是解决三峡库区生态环境和移民经济的基本途径，采用扩大种植农作物的方法来解决三峡库区移民经济问题将会加剧水土流失，使生态环境更加恶化。     

智能交通与中国的交通安全

在交通运输中 ,安全是最重要的因素。近年来 ,中国交通运输事业的快速发展 ,给人民的生活带来诸多便利 ,但当前的交通安全状况却不容乐观 ,交通事故频繁发生 ,事故死亡人数逐年上升。智能交通系统是一个高科技集成系统 ,它综合运用各种高新技术于整个交通管理系统之中 ,可以系统、全面、高效地提高交通运输的安全性。笔者研究了我国的交通安全问题 ,尤其是公路交通安全问题 ,阐明了如何应用智能交通系统 ,有效地减少交通事故 ,改善交通安全状况 ;指出了我国发展智能交通对于改善交通安全 ,解决交通安全问题的重要意义并展望了我国发展智能交通的前景     

垃圾渗滤液中同步硝化反硝化的研究

对深圳市一坪垃圾填埋场渗滤液中同步硝化反硝化进行了深入研究，从理论方面综述了脱氮中同步硝化反硝化等技术的进展，分析了COD、DO、NH3-N对同步硝化反硝化所产生的影响，提出了在研究中发现的问题和需要努力加强的研究方向。     

开发洋口港的自然优势和宏观功能

本文根据近几年对洋口港的调查实测资料，分析了建深水港的可行性，并提出为解决长江口通海航道水深不足，充分发挥南通港港群机能等问题，供有关部门参考。     

水质评价中的宽域灰色决策法

依据灰色决策的基本原理，结合环境质量评价的实际情况，用宽域式结构建立隶属函数，提出宽域灰色决策法，并以水质评价为例进行了尝试。结果表明，宽域灰色决策法的评价结果比较符合实际状况，比模糊数学法和灰色聚类法的评价结果更为合理。     

氮肥工业中氨氮废水治理技术进展

介绍了氮肥厂对合成氨低温变换工艺冷凝液和尿素解吸废水的回收处理方法。认为选用热力水解法处理尿素吸废水是可行的。