将田间调查与分析相结合,测定了杨凌示范区164个农田土壤样品和88个主要农作物样品中重金属As、Cd、Hg、Cr、Pb、Ni、Cu和Zn的含量,采用单因子指数法、内梅罗指数法、地质积累指数法和潜在生态危害指数法评价了重金属的积累和风险,用ArcGIS技术对重金属的空间分布进行了分析.结果表明:杨凌示范区土壤中上述8种重金属的平均含量分别为15.67、0.18、0.08、51.40、27.34、43.25、28.08、79.32 mg?kg-1,除Hg和Cr外,其余重金属的平均含量均超过陕西关中塿土背景值,说明其在土壤中有一定累积;但8种重金属的平均含量均低于土壤环境质量农用地土壤污染风险管控标准规定的风险筛选值.Cd和Cr的点位超标率分别为10.98％和3.05％,其他重金属均未超标.所有土壤样品中As、Cr、Hg、Pb、Ni、Cu、Zn的潜在生态危害指数Eir均低于40,为轻度风险.土壤样品中Cd的Eir值范围为0.00～49.00,平均值为22.76±7.60,有3.66％的土壤样品中Cd含量达到轻度生态危害.农作物中上述8种重金属含量均值分别为0.016、0.019、0.005、0.108、0.033、0.090、4.880、29.272 mg?kg-1,均低于我国食物中污染物的卫生限量标准.在谷物、蔬菜和水果内,同一种重金属的含量无显著差异,作物的重金属污染指数MPI为0.11.重金属的内梅罗指数为0.89,达到警戒水平范围;潜在生态危害综合指数RI=36.5,存在轻度生态危害.这些研究结果表明,杨凌示范区的农田土壤整体仍处于清洁安全水平,属于应予优先保护类土地.

随着人们环境保护意识的不断增强和国家对环境的高度重视，如何有效地控制大气污染已成为环境工程专业学生迫切需要解决的问题。大气污染控制工程是环境工程专业学生的核心课程，实验课程的教学设计关系到未来环保人才的培养质量。根据大气污染与控制课程的体系和培养目标，实验课的教学设计类型关注热点，贴近实际，设置颗粒物污染监测；汽车尾气监测；氮氧化物和硫氧化物气体监测与控制；除尘器的设计与应用等四个方向。让学生通过实验观察、模拟、验证和探索等方式强化大气污染控制工程核心内容，培养和提升学生工程应用能力，为培养创新型环境专业人才打下坚实基础，对提高人才培养质量具有重要意义。

通过对哈尔滨工业大学、吉林建筑大学、吉林大学、辽宁大学、东北石油大学和西北农林科技大学等6所大学环境工程专业就业方向进行调研,发现不同类型学校就业方向各有不同.哈尔滨工业大学和吉林建筑大学环境工程专业设计方向就业比例分别达到34.48％和26.55％.吉林建筑大学施工方向就业比例占25.66％.综合类大学就业略有不同,吉林大学在设计和环评方向占据优势,辽宁大学在环评、科研和环保综合类不相上下.东北石油大学设计和施工方向,更多的偏向石油类企业的环境工程方向.西北农林科技大学环境工程偏向于土壤污染与修复.结合调研结果,对环境工程专业实习进行合理规划与设计,提高本科生专业素养,培养高层次环境工程应用型人才,具有实际意义.

实验室是高校实验教学和科研实验的重要场所,它的建设与管理关系到高校的教学质量、教学水平、科研水平和管理水平.在高校教育改革和教学管理升级的时代背景下,现代高校实验室的建设与管理日益专业化和规范化,要求高校加强重视,不断提高实验室建设与管理的理论认识,进而促进实验室组织结构、人员建设、技术创新、管理操作水平的全面提升.胡征编著的《现代实验室建设与管理指南》(天津科技翻译出版有限公司2014年出版),归纳和总结了实验室建设与管理的一线工作经验,以专业、实用和创新的编写方式与编写内容全面梳理了现代实验室建设与管理的科学策略与有效办法.该书实用操作性强,对各类实验室的建设与管理都提出了切合实际的技术意见,有着较高的参考价值和实用价值.

[目的]海拔高度、成土母质、气候条件、种植品种、耕作方式和施肥水平等因素对农田土壤肥力产生深刻影响.调查明确青海省春油菜区土壤养分的空间分布现状,有助于制定合理的施肥策略和实现该地区春油菜高产优质以及农业的可持续发展.[方法]2015年在青海省东部的湟中、大通和互助三个春油菜主产县,依据各乡镇油菜种植面积大小,共采集了103个耕层土壤样品.测定土壤主要养分含量,并结合ArcGIS中的Kriging插值法研究春油菜田土壤肥力现状及其空间分布特征.[结果]土壤各养分平均含量分别为有机质26.81 g/kg(中等)、全氮1.97 g/kg(丰富)、速效磷19.03 mg/kg(中等)、速效钾164.27 mg/kg(丰富)、有效铁12.02mg/kg(丰富)、有效锰6.43 mg/kg(中等)、有效铜0.70 mg/kg(中等)、有效锌1.81 mg/kg(中等)、有效硼0.27mg/kg(缺乏).三县土壤全氮和速效磷含量达到中等水平以上的比例分别为94％和91％.速效钾和有效锌含量区域差异较大,速效钾缺乏及以下比例有23.0％,主要分布在湟中和互助县,有效锌缺乏及以下比例有36.9％,主要分布在互助县;有效硼缺乏及以下比例高达93.2％,主要分布在互助和大通县.[结论]青海省春油菜土壤氮磷钾养分含量整体偏高,相应化肥减量空间较大.大通、互助两县应合理减施氮肥;湟中、大通两县应降低磷肥施用量;针对湟中和互助县的速效钾含量缺乏地区应适当增施钾肥.土壤有效硼除湟中县的部分地区外均缺乏严重,有效锌含量缺乏的土壤主要分布在互助县,针对以上区域应合理增施硼肥和锌肥,防止作物因缺素而限制产量和品质的提高.养分的平衡供应将有利于提高肥料利用率,实现春油菜产业的可持续发展.

Cu(i)-Catalyzed diastereoselective carboboration of α-alkyl-substituted α,β-unsaturated carboxylic esters to produce β-boryl-α-quaternary carbon esters was developed. The carbon skeletons of dialkyl sulfates, primary allyl halides, and benzyl bromides were transferred to the α-position of the substrates to provide products in moderate to good yields with a diastereoselectivity of >95% in most cases. Substrates bearing a β-(hetero)aryl substituent gave higher diastereoselectivities than those bearing a linear β-alkyl substituent. The crystal structure of the potassium trifluoroborate derivative shows that the reactions probably go through a copper(i) enolate intermediate and the diastereoselectivity arises from the electrophilic attack of electrophiles to the less hindered side of the enolates.

近年来空气质量受到了人们的日益关注,然而目前尚缺乏针对西安市空气质量的系统分析.通过西安市2014-2017年环境监测的实时数据以及环境空气质量指数(AQI),可分析西安市雾霾天气的时空分布特征以及污染变化趋势.从年度变化看,西安市AQI呈现明显的单峰特征,取暖季重度污染和严重污染约占总天数的40％,PM2.5作为首要污染物的天数增加到72 d,非取暖季2016年重度污染天数比2014年提高了4.4％.从空气污染物成分看,PM2.5和PM10的正相关性最强,而与臭氧则呈负相关关系.研究结果可预测未来几年污染趋势,为政府部门采取有针对性的大气污染治理措施提供了参考.

Nitrate that originates from agriculture is linked to a series of deleterious environmental consequences that are closely related to human health. Therefore, it is vital to design cropping systems that can produce acceptable crop yields while minimizing the impact of surplus soil nitrate. To develop quantitative estimations, data from 2008 to 2016 were evaluated using multiple regression models. A split-plot field experiment was conducted, with the main treatments of growing Huai bean, soybean and mung bean in summer as leguminous green manure (LGM) while fallow as the control. Four synthetic N rates (0, 108, 135 and 162kgha-1) were applied as sub-treatments at wheat seeding. The N accumulation for LGMs ranged from 61 to 90kgha-1, and that of Huai bean was 46% higher than the average value of soybean and mung bean (P<0.05). The threshold of total N for wheat to produce the highest yields was 141kgha-1. For the LGM treatments, residual nitrate accumulated below the root-zone soil was not significantly increased even when their total N inputs were higher than that of fallow with 162kgha-1 of synthetic N. The estimated nitrate-holding capacity of the root-zone soil for the LGM treatments ranged from 104 to 117kgha-1, and the corresponding synthetic N limits were 97-130kgha-1. Considering the target of producing high wheat yields while keeping the residual nitrate in the root-zone soil, the optimal synthetic N rates for LGM treatments were 52-80kgha-1. In conclusion, growing LGMs can maintain high crop yield and mitigate the environmental impact of residual nitrate by substantially replacing the synthetic N to avoid nitrate leaching to deeper soils.

The Cu(i)-catalyzed stereoconvergent borylative cyclization of ω-mesylate-α,β-unsaturated compounds is facilitated by a simple Cu-bisphosphine catalyst. This reaction provides a novel route to cis-β-boron-substituted five- and six-membered carbocycle and heterocycle esters. Mechanistic studies indicate that stereoconvergence and cis-substitution likely stem from the rapid enolation of the borylcopper adduct with the substrate double bond and the formation of a five-membered intermediate, respectively.

The deoxydehydration of polyols to alkenes is one of the important methods for the conversion of biomass-based platform molecules to useful chemicals and liquid fuels. A new imidazolinium perrhenate catalytic system for the deoxydehydration of vicinal diols to alkenes was reported. The reaction conditions, including reductants, solvents and imidazolinium cations were investigated. The best result was obtained with 3 equiv. of 3-octanol as the reductant in chlorobenzene at 180 degrees C under argon atmosphere, affording the 1-tetradecene product in 85% yield after 24 h. The catalyst shows moderate activity for several vicinal diols and can be reused after recoverd.

The knowledge service in research universities can be extended to any fields concerning knowledge management and production,teaching and research.The knowledge service with the librarian as the main body can be classified into routine and project service which can apply project system management.The article explores the sources of project service and its generative mechanism,discusses some fundamental problems in the course of application of knowledge service for project system,and reveals the role that the management mode of project system plays in promoting knowledge service in library.