Isotopic evidences for microbiologically mediated and direct C input to soil compounds from three different leaf litters during their decomposition

We show the potentiality of coupling together different compound-specific isotopic analyses in a laboratory experiment, where ¹³C-depleted leaf litter was incubated on a ¹³C-enriched soil. The aim of our study was to identify the soil compounds where the C derived from three different litter species is retained. Three ¹³C-depleted leaf litter (Liquidambar styraciflua L., Cercis canadensis L. and Pinus taeda L., δ¹³C_vsPDB ≈ ?43‰), differing in their degradability, were incubated on a C4 soil (δ¹³C_vsPDB ≈ ?18‰) under laboratory-controlled conditions for 8 months. At harvest, compound-specific isotope analyses were performed on different classes of soil compounds [i.e. phospholipids fatty acids (PLFAs), n-alkanes and soil pyrolysis products]. Linoleic acid (PLFA 18:2ω6,9) was found to be very depleted in ¹³C (δ¹³C_vsPDB ≈ from ?38 to ?42‰) compared to all other PLFAs (δ¹³C_vsPDB ≈ from ?14 to ?35‰). Because of this, fungi were identified as the first among microbes to use the litter as source of C. Among n-alkanes, long-chain (C27–C31) n-alkanes were the only to have a depleted δ¹³C. This is an indication that not all of the C derived from litter in the soil was transformed by microbes. The depletion in ¹³C was also found in different classes of pyrolysis products, suggesting that the litter-derived C is incorporated in less or more chemically stable compounds, even only after 8 months decomposition.     

Spatial and seasonal variations in bacterial communities of the Yellow Sea by T-RFLP analysis

Four typical coastal sites (rocky shore, sandy shore, mud flat shore, and artificial harbor) at the Yellow Sea were chosen to investigate the spatial and seasonal variations in bacterial communities. This was accomplished by using terminal restriction fragment length polymorphism (T-RFLP) analysis of PCR amplified 16S rDNA fragments. Two kinds of tetrameric restriction enzymes, HhaI and MspI, were used in the experiment to depict the bacterial community diversity in different marine environments. It was found that the community compositions digested by the two enzymes separately were different. However, the results of bacterial community diversity derived from them were similar. The MDA analysis results of T-RFLP profiles coming from HhaI and MspI both exhibited a significant seasonal community shift for bacteria and a relatively low spatial variation among the four locations. With HhaI as the sample, the pair wise T-tests also revealed that variations were minor between each pair of marine environments, with R ranging from 0.198 to 0.349. However, the bacterial community structure in the mud flat site depicted a larger difference than each of the other three sites (R ranging from 0.282 to 0.349).     

发展地方环保产业的思考

本文论述了发展地方环保产业的六大要素：优势、科技、龙头、基地、环境、创新。抓住了这六大要素,地方环保产业就可成为地方经济新的增长点。     

西部大开发与重庆市旅游业的可持续发展

重庆具有发展旅游业得天独厚的区位条件,而西部大开发进一步从交通环境、经济基础、市场开拓和生态保护几个方面为重庆旅游提供了良好的外部条件;但目前重庆的旅游业发展面临着严重的挑战。从战略方向和形象策划、客源定位、旅游产品的深层次开发、旅游基础设施的建设和旅游服务体系的完善、旅游管理和旅游人才的教育以及发展生态旅游几个方面,提出了重庆旅游业可持续发展的战略方向和战略对策。     

大气环境质量评价的未确知测度模型

给出大气环境质量综合评价的未确知测度模型 ,并用于某大型钢铁企业的大气环境质量评价 .模型严谨 ,测度函数的构造力求符合实际 ,并且针对评价空间分割的有序性 ,引入置信度识别准则使评判结果合理 ,是大气环境质量综合评价的实用模型 .     

考虑恐怖袭击下危险品运输安全监管的演化博弈与稳定性分析

为了提高恐怖袭击背景下的危险品运输安全水平和政府监管能力,首先构建政府监管部门、危险品运输企业和恐怖袭击者的三方演化博弈模型;其次引入政府动态惩罚机制和动态惩罚-补贴机制,进而采用系统动力学仿真分析动态惩罚和动态惩罚-补贴下的局中人的演化稳定策略。研究结果表明：给定情形下,引入动态惩罚机制能弥补原有模型没有稳定策略的不足;引入动态惩罚-补贴机制的模型可以演化出稳定的纯策略。     

储氢温度对加氢站泄漏爆炸事故的影响研究∗

通过降低氢气的温度,可以实现更高密度的氢气储存,进而有效提升存储及运输的效率。为探究储氢温度对加氢站泄漏爆炸事故的影响规律,利用FLACS 软件对加氢站内长管拖车在不同储氢温度条件下（50、100、200 与300 K）发生泄漏后的氢气扩散和爆炸事故进行分析。研究结果表明：随着储氢温度的降低,高压氢气射流撞击防爆墙后可燃气云达到稳定的时间、扩散范围和冻伤区域均逐渐增大,而最大爆炸超压和爆炸危险距离则呈现出先增大后减小的趋势;储氢温度为50 K 时的轻微冻伤距离比储氢温度100 K 和200 K 时分别增加了近1 倍和7 倍,严重冻伤距离也最大;储氢温度为100 K 时泄漏气云爆炸产生的超压峰值比常温氢气爆炸提高了近3 倍,危险区域也最大;储氢温度为200 K 时,达到爆炸超压峰值的时间最快,储氢温度为50 K 时最慢。     

摩托车后轮毂压铸模设计

摩托车后轮毂压铸模具精度要求高 ,且结构复杂。为满足铸件的技术要求 ,要合理选用压铸设备 ,合理地设计模具结构。分析了摩托车后轮毂的结构特点 ,介绍了摩托车后轮毂压铸模的结构 ,并详细说明了模具浇注系统、溢流系统、冷却系统、推出机构的设计。     

水体pH值时空变化条件下絮凝除藻剂的pH值优化

研究了由光照、水深等造成的水体pH值变化对絮凝剂除藻效果的影响,并监测絮凝前后不同深度的水体pH值。结果表明:1)当水体pH值无垂向分层,但随光照在8.5~10.5变化时,表层水体终点pH值为5.8~7.9,除藻效率均高于80%,此时中下层水体pH值为5.4~8.0;2)当水体pH值有垂向分层,表层水体终点pH值为7.0~7.3时,除藻效率均高于80%,此时中下层水体pH值为7.0~7.1;3)水池实验中,当表层水体终点pH为6.8时,除藻率高达99.33%,此时中下层水体pH值为7.0~7.1,池水清澈见底。上述结果说明:不论水体pH值是否垂向分层,控制表层水体终点pH值为6.8~7.3时既能有效除藻,也不会使底层水体pH值过低;水体pH值有垂向分层时,絮凝剂的pH值应高于无垂向分层时的情况。     

陕西省ODS使用量分布特征的分析

通过调查陕西省消耗臭氧层物质(ODS)的销售和使用量,分析了陕西省消耗臭氧层物质的行业和地区分布特征。根据各受控物质的特点,计算了这些物质的实际使用量的臭氧消耗潜能(ODP)值。结果表明,2008年陕西省使用的ODS总量约为679.95 t,按照ODP值折算,相当于约132.76 t当量CFC-11。ODS的使用主要集中在清洗行业和制冷行业,区域重点在西安市。