基于熵权模糊物元的高速公路路段安全综合评价

针对目前道路安全评价中信息屏蔽和主观性问题,利用模糊物元理论和熵权理论对高速公路安全水平进行了定量评价。在考虑影响道路安全水平多种因素基础上,构建了道路安全评价指标体系。以定量分析为主,将模糊物元、隶属函数及信息熵有机结合起来,建立了高速公路安全水平综合评价模型。以信息熵理论为基础确定了各评价指标的权重系数。将模型应用在新疆高速公路不同路段安全评价中,并与其它综合评价模型比较分析,验证该模型的有效性。研究结果表明该模型实用性强,计算过程简单,在道路安全评价中具有一定应用价值。     

采用固定化技术处理土壤中菲、芘污染物

采用动胶杆菌(Zoogloea sp.)固定化技术包埋来降解土壤中菲、芘污染物,在不同接种量、不同系列浓度下,对降解效果进行了测定.结果表明:5%的接种量最为合理,在168h时,固定化细菌对菲、芘的降解率达84.89%和76.94%;而在相同条件下土著菌降解仅达到27.85%和19.65%,因此动胶杆菌(Zoogloea sp.)具有更好的降解能力.另外,还用电镜观察研究了动胶杆菌在载体中的分布形态,表明了固定化细菌降解土壤中菲、芘具有较高的优势.     

油污染土壤气体抽排去污模型及影响因素

为了开展适合我国实际情况的有机污染土壤气体抽排净化技术研究,在对油污染土壤的通风去污过程机理进行分析的基础上,建立了一个简化机理模拟模型.以华北地区典型土壤为实验土样,油污染物为例,通过一维土柱实验,研究了抽排气体流速、土壤含水率和土质对去污过程的影响.实验表明抽排气体流速存在最佳值,土壤含水率对不同土质土壤净化时间影响不同,对粉砂土,含水率升高,净化效率增强;而对粘质土壤,结果正好相反.对模型预测结果进行实验验证表明,本文建立的模拟模型在实验限定条件范围内是准确和适用的.     

浅覆地层盾构开挖面被动破坏极限支护力及破坏模式研究

浅覆地层盾构掘进时支护力过大极易导致开挖面前方土体发生被动破坏,造成地表隆起。基于筒仓理论,通过优化传统三维楔形体模型,建立楔形块+倒棱台的土体被动破坏三维计算模型(修正三维楔形体模型),并推导被动极限支护力计算公式;对不同埋深下滑动破裂角β分析研究;采用有限元分析软件MIDAS-GTS对盾构隧道开挖面的被动破坏进行模拟,揭示被动破坏支护力变化规律及破坏模式。结果表明:本文研究计算模型更符合开挖面土体被动破坏模式;通过对破裂角β分析,解析土体被动破坏时其最优解30°左右;在浅覆盾构开挖面中,揭示S/(γD)受土体内摩擦角φ、埋深比K的影响,文中S/(γD)随内摩擦角φ的增大呈非线性增加,埋深比K越大,其幅度越明显;破坏模式分析中,K越小,土体位移变形对S/(γD)越敏感,越容易发生开挖面被动破坏;发生被动破坏时,土体纵向位移变形大于横向位移变形。     

Degradation of extracellular genomic,plasmid DNA and specific antibiotic resistance genes by chlorination

Extracellular DNA structure damaged by chlorination was characterized. Integrity of extracellular ARG genetic information after chlorination was determined. Typical chlorine doses will likely effectively diminish extracellular DNA and ARGs. Plasmid DNA/ARGs were less readily broken down than genomic DNA. The Bioanalyzer methodology effectively documented damage incurred to DNA. There is a need to improve understanding of the effect of chlorine disinfection on antibiotic resistance genes (ARGs) in order to advance relevant drinking water, wastewater, and reuse treatments. However, few studies have explicitly assessed the physical effects on the DNA. Here we examined the effects of free chlorine (1–20 mg Cl₂/L) on extracellular genomic, plasmid DNA and select ARGs. Chlorination was found to decrease the fluorometric signal of extracellular genomic and plasmid DNA (ranging from 0.005 to 0.05 mg/mL) by 70%, relative to a no-chlorine control. Resulting DNA was further subject to a fragment analysis using a Bioanalyzer, indicating that chlorination resulted in fragmentation. Moreover, chlorine also effectively deactivated both chromosomal- and plasmid-borne ARGs, mecA and tetA, respectively. For concentrations >2 mg Cl₂//L × 30 min, chlorine efficiently reduced the qPCR signal when the initial concentration of ARGs was 10⁵ copies/mL or less. Notably, genomic DNA and mecA gene signals were more readily reduced by chlorine than the plasmid-borne tetA gene (by ~2 fold). Based on the results of qPCR with short (~200 bps) and long amplicons (~1200 bps), chlorination could destroy the integrity of ARGs, which likely reduces the possibility of natural transformation. Overall, our findings strongly illustrate that chlorination could be an effective method for inactivating extracellular chromosomal- and plasmid-borne DNA and ARGs.     

Contamination characteristics of trace metals in dust from different levels of roads of a heavily air-polluted city in north China

Concentrations of eight trace metals (TMs) in road dust (RD) (particles?<?25 μm) from urban areas of Xinxiang, China, were determined by inductively coupled plasma mass spectrometry. The geometric mean concentrations of Zn, Mn, Pb, As, Cu, Cr, Ni and Cd were 489, 350, 114, 101, 60.0, 39.7, 31.6, and 5.1 mg kg^?1, respectively. When compared with TM levels in background soil, the samples generally display elevated TM concentrations, except for Cr and Mn, and for Cd the enrichment value was 69.6. Spatial variations indicated TMs in RD from park path would have similar sources with main roads, collector streets and bypasses. Average daily exposure doses of the studied TMs were about three orders of magnitude higher for hand-to-mouth ingestion than dermal contact, and the exposure doses for children were 9.33 times higher than that for adults. The decreasing trend of calculated hazard indexes (HI) for the eight elements was As?>?Pb?>?Cr?>?Mn?>?Cd?>?Zn?>?Ni?>?Cu for both children and adults.     

钻屑法测定煤层H_2S含量

为了测定煤层硫化氢(H2S)含量,防治矿井H2S涌出,提出一种通过钻屑法测定煤层H2S含量的方法。在未受采动影响的新鲜煤壁,采用钻屑法取样,通过测定煤样H2S解吸量、取样过程损失量和H2S残存量确定煤层H2S含量。根据溶于水中H2S的p H值和色谱分析解吸气体中H2S体积分数,确定H2S解吸量;根据煤样解吸规律和气样H2S体积分数,确定H2S损失量;根据色谱分析残存气体中H2S体积分数,确定其残存量。用此方法,对山西某矿H2S涌出煤层进行现场和实验室测定。研究表明,该矿H2S含量为(4.465~6.701)×10-3m3/t。钻屑法测定煤层H2S含量是可行的,可以为矿井H2S治理提供基础数据。     

可拓优度评价法在城市区域消防安全评价中的应用

为了解决城市区域消防安全评价的复杂性和不确定性,本文运用可拓优度评价法,根据相关文件并结合城市区域消防的实际情况,从火灾危险程度、城市区域特征、消防实力水平和社会管理状态4个方面选取17个指标,建立了城市区域消防安全评价指标体系并划分了消防安全等级,以洛阳市西工区为例对城市区域消防安全评价的可拓优度方法进行了验证。结果表明,可拓优度方法可以准确反映出该区域消防安全水平。     

Glyphosate application increased catabolic activity of gram-negative bacteria but impaired soil fungal community

Environmental Science and Pollution Research - Glyphosate is a non-selective organophosphate herbicide that is widely used in agriculture, but its effects on soil microbial communities are highly...