近20年天津地区植被变化及其对气候变化的响应

植被与气候变化的相互关系在全球或区域尺度上得到了证明.研究特定地区植被动态变化及其与气候变化的关系,找出影响植被变化的     

农田生态系统服务功能研究进展

农田生态系统是人类社会存在和发展的基础,研究农田生态系统服务功能及其价值评估具有重要的意义.文章综述了国内外有关农田生态系统服务功能及其价值评估的研究进展;提出了农田生态系统服务功能的特点;将其服务功能类型划分为生产功能、生态功能和生活功能.分析了当前研究中存在的问题,如服务功能形成的微观机制及其参数研究欠缺;评价结果不准确;评价指标和方法有待完善等.因此,今后农田生态系统服务功能价值评估研究重点应着重于理论探索和方法完善方面,从农田生态系统微观形成机制入手,开展不同尺度和类型的农田生态系统功能价值评估研究,充分考虑影响其功能价值的因素,改进评估的手段、方法和技术,使评估结果更具可比性和实用性,为合理开发利用农业资源、管理农田生态系统,实现农业的永续发展提供理论依据和技术支持.     

矽卡岩型钼矿尾砂中重金属Mo的淋滤实验研究

运用动态淋滤法实验研究了辽宁葫芦岛地区矽卡岩型辉钼矿浮选法产生的尾矿中重金属钼的淋滤行为(15 ℃和35 ℃,淋溶液pH值4～9).结果表明:淋滤液均呈碱性,钼的质量浓度为7.5～14.2 mg·L-1,淋滤累积质量为54～69 mg,占总钼的12.56%～16.54%;与Pb、Cu和Zn等重金属随酸性排水淋滤迁移不同,钼在碱性环境中具有较强迁移性;尾砂中斜长石和钠长石等矿物因具有较强的产碱能力形成了尾砂内部的碱性环境;尾矿中MoS2和MoO3在碱性环境下转化为MoO42-是迁移的主要机制.pH值为5～9时,淋滤累积质量与pH值正相关.因酸可溶态钼发生溶解,pH值为4淋滤累积质量大于pH值为5时的淋滤累积质量,排水仍为碱性.温度能够加速淋滤速率,35 ℃淋滤液中钼质量浓度比15 ℃的高7%～10%.因此,对该区尾砂应该设置标准尾矿库封存管理,否则将对环境造成严重影响.     

膨润土负载壳聚糖修复土壤镉污染的效果

随着重金属污染土壤日益加剧,污染土壤修复和控制技术的研究越来越迫切.为利用膨润土原位修复土壤镉污染提供理论依据,采用平衡吸附试验研究了Cd2 在膨润土负载壳聚糖上的吸附行为.以90%脱乙酰度壳聚糖为原料,制备了膨润土负载壳聚糖颗粒吸附剂,用于吸附溶液中Cd2 .试验探讨了壳聚糖质量浓度对负载率的影响,结果表明,质量浓度3%的壳聚糖负载量最大,壳聚糖最大负载率达32.6%.吸附Cd2 最佳工艺条件是:壳聚糖与膨润土质量比为1∶20,膨润土负载壳聚糖颗粒吸附剂用量为15 g·L-1,溶液中Cd2 含量不大于200 mg·L-1, pH 值为6～8,吸附平衡时间为8 min,Cd2 去除率为99%.动态吸附Cd2 试验结果表明:质量浓度为 200 mg·L-1的含Cd2 溶液,流速为4～6 m(h-1,经壳聚糖-膨润土吸附剂一次处理后,溶液中Cd2 的残留量为0.7 mg(L-1.     

萘乙酸和Zn对大豆Cd胁迫伤害的缓解效应

为探讨植物生长调节剂对大豆Cd胁迫伤害的缓解效应,采用营养液培养试验方法,研究了喷施萘乙酸(NAA)和加Zn处理对3个Cd胁迫大豆幼苗的影响.结果表明,加Zn和喷施NAA均可降低Cd胁迫大豆幼苗叶片丙二醛(MDA)和脯氨酸(PRO)含量,可减轻膜脂的过氧化作用及蛋白质的水解;喷施NAA还可降低Cd胁迫大豆幼苗POD活性,提高硝酸还原酶(NR)活性;加Zn对Cd胁迫大豆幼苗NR活性的降低缺乏抑制作用,但降低沔1101叶片中POD活性,提高湘04-6和特早熟毛豆的POD活性,品种之间表现明显的差异性.     

城市景观河道不同类型驳岸界面微生物生态研究

对某景观河道鹅卵石驳岸、泥岸、石砌驳岸和砼仿木桩驳岸4种类型驳岸的河水/河床界面上覆水质及界面功能微生物生态多样性进行了研究.结果表明:4种驳岸的界面上覆水质以鹅卵石驳岸和泥岸较好,而石砌驳岸和砼仿木桩驳岸较差;界面上覆水和界面泥样的功能微生物菌群数量都以鹅卵石驳岸最多,泥岸次之,砼仿木桩驳岸最少.在鹅卵石驳岸上鹅卵石的堆砌增加了水体与驳岸的接触面积,为微生物提供了更多的生存空间.泥岸对污染物的吸附能力较强,为微生物提供了有利的生存环境,微生物数量较大.     

福建沿海水稻Cd、Pb、Hg等重金属含量变化规律

文章研究了福建沿海重金属高含量的水稻样品的区域分布规律,分析了不同品种的水稻对重金属吸收的差异.以该区10个流域两侧的水稻种植区为研究对象,系统采集了福建沿海水稻样品185件,采用干灰石墨炉原子吸收光谱法和原子荧光光谱法,分析了籽粒中的Cd、Hg、Pb、As、Cu、Zn等重金属元素的含量,结果表明其平均值分别为0.005、0.08、0.33、0.17、2.94和14.62 mg·kg-1,显著高于台湾地区稻米的平均含量.对比大米国家食品限制值,有16.8%的样品的Pb超标;有11.4%的样品Cd超标.Hg、As的超标率相对较低,均只为0.5%.Cd、Pb含量高的样品主要集中分布在漳州、福州、福清等工业发达的城市周边地区.不同的水稻品种对重金属的吸收率完全不同,昌优964对Cd、Cu、Zn和Pb表现出高的吸收率,而糯米、803A1527等则表现出对Cd、As、Pb等低的吸收率.这些结果的获得为水稻安全标准评价和品种的优选提供了理论基础.     

基于GIS数字城市规划的应用研究

介绍了GIS在数字城市规划中的应用模式,针对数字城市建立了GIS数据模型、数字城市规划模型、数字城市基本模型、公众参与冲突的协调机制理论模型,在GIS概念的基础上,给出了数字城市的框架与关键技术,并对解决城市规划中的优势进行了分析.该方法表明,GIS技术在城市规划中能起到重要的作用.图2,参5.     

水压力对填石路堤稳定性的影响

基于极限平衡理论和Ordinary方法,采用Geo-slope软件分析了不同临界水位时水压力对高填石路堤稳定性的影响.结果表明:填石路堤稳定性系数随着临界水位的降低而增大.对于干沟高填石路堤,当临界水位低于路肩52 m时,水压力对路堤稳定性的影响可以忽略不计.在最低临界水位时的稳定系数为1.371,满足有关规范的要求.在最高临界水位时,稳定系数为0.921,比低水位时降低了32.8%,路堤的稳定性降低,且稳定系数不能满足有关规范的要求.因此,在进行填石路堤设计或施工时必须考虑水压力对其稳定性的影响,采取相应的工程措施保证路堤安全.     

Optimal oil tanker size with regard to environmental impact of oil spills

This paper considers optimal tanker size in view of the environmental effects of oil spills. A model is developed that incorporates the tradeoff between small but frequent spills with many tankers, and the relatively less frequent but larger and more concentrated spills with a smaller fleet of larger ships. A procedure is suggested to incorporate the environmental impact of oil spills in the model without quantifying them in monetary units. A closed form solution set for optimal tankers size is obtained and some numerical results are presented.     

石油污染生物修复研究进展

石油污染多见于油田附近的土壤污染和海上油轮泄漏造成的海域污染,自1970s便出现了利用微生物降解石油污染物的生物修复研究,总结了1970s至今的相关文献发现石油污染生物修复技术受到越来越多的关注,其目前的主要研究方向包括:添加辅助营养物质或辅助乳化剂、石油污染降解过程的生物标记研究、菌株具体降解途径、工程示范研究.而由于石油污染成分复杂,不同微生物可利用的石油底物不同,降解途径也不同,因此传统的石油污染生物修复研究存在效率不高、难以维持等问题,而随着1990s以来分子生物学技术的迅速发展,其在石油污染生物修复中得到越来越多的应用,并有效地提高了修复效率.其应用主要包括以下两方面:(1)在掌握已有石油污染物生物降解途径和降解基因的基础上,研究针对石油污染不同底物的高效降解菌株,构建高效基因工程菌或功能互补的混合菌剂.譬如石油污染物的生物降解过程中,一系列的加氧酶/羟化酶起着最重要的作用,其中包括了单加氧酶和双加氧酶等.它们一般作用于降解的加羟基或后续的开环过程.而不同的脱氢酶、脱羧基酶、辅酶A连接酶等,则对底物加氧后的降解起着重要作用.因此本文重点分析整理了一系列典型石油污染物降解途径中的加氧酶及其参考菌株.(2)由于下游多态性分析方法的进步,越来越多的研究利用PCR对修复过程中群落的重要降解基因进行扩增,譬如对芳烃开环有重要作用的儿茶酚1,2-双加氧酶(C120)、儿茶酚2,3-双加氧酶(C23O)以及对长链烷烃降解起作用的alkB,alkM等基因,并进而应用rDNA扩增及限制性位点分析、梯度凝胶电泳、末端限制性片段长度多态性分析等方法监测研究石油污染的生物降解过程.本文总结了近年来石油污染修复中应用上述方法的研究,为今后的石油污染生物修复工作提供参考.     

Mid-depth oil concentration due to vertical oil dispersion in a regular wave field

An experimental program is organized to investigate the vertical oil dispersion of surface oil spills in a regular wave field. Various waves characteristics and different volumes of oil spills are tested to assess the oil concentration variations at two sampling stations. It is found that the oil concentration due to vertical oil dispersion follows an ascending diagram to reach a maximum and then decreases while oil slick passes the location. The maximum mid-depth oil concentration (C_max) at the farther sampling station is 30–50 % less than the concentration at the closer sampling station to the spill location. A 50 % increase in oil spill volume causes 30–60 % growth in oil concentrations. The relations between oil concentration and important parameters such as wave characteristics, amount of spilled oil and the distance of sampling stations from the spill location are indicated and also oil concentration variations are quantified. Two equations are derived through statistical analysis of the obtained experimental data, which estimate the magnitude and time of maximum oil concentration.     

Enhanced oil recovery water requirements

Water requirements for enhanced oil recovery (EOR) are thoroughly evaluated using publicly available information, data from actual field applications and information provided by knowledgeable EOR technologists in fourteen major oil companies. Water quanity and quality requirements are estimated for individual EOR processes (steam drive,in situ combustion and carbon dioxide, micellar-polymer, polymer and caustic flooding) in those states and specific geographical locations where these processes will likely play major roles in future petroleum production by the year 2000. The estimated quantity requirements represent thetotal water needed from all sources, e.g. aquifers, lakes and produced water. A reduction in these quantities can be achieved by reinjecting all of the produced water potentially available for recyle, e.g. some is lost in oil and water separation and water treatment processes, in the oil recovery method. For injection water quality requirements, it is noted that not all of the water used for EOR needs to be fresh. The use oftreated produced water can significantly reduce the quantities of fresh water that would be sought from other sources. Although no major EOR project to date has been abandoned because of water supply problems, competing regional uses for water, drought situations, and scarcity of high quality, e.g. low total dissolved solids, surface water and ground water could be impediments to certain projects in the near future.     

Antiaflatoxigenic activity of Carum copticum essential oil

Plants are unique sources of useful metabolites. Plant essential oils display a wide range of antimicrobial effects against various pathogens. Here, we studied the essential oil from the seeds of Carum copticum. We monitored aflatoxin by high-performance liquid chromatography. Results show that Carum copticum essential oil inhibits Asergillus parasiticus growth and prevents aflatoxin production. The half-maximal inhibitory concentration (IC₅₀) is 127.5 μg mL^?1 for aflatoxin B₁ and 23.22 μg mL^?1 for aflatoxin G₁. Our findings show that Carum copticum essential oil is a potential candidate for the protection of foodstuff and feeds from toxigenic fungus growth and their subsequent aflatoxin contamination.     

An environmental assessment of enhanced oil recovery

The objective of this assessment is to quantify some of the environmental effects of a significant increase in United States oil production by tertiary or enhanced oil recovery (EOR) methods. The problems associated with each EOR technology are discussed and controls and regulations are briefly summarised. A tertiary oil production scenario for the United States was developed focussing only on mainland fields in the lower 48 states. It included all of the EOR methods expected to be in use during the next two decades. The environmental impacts, including water requirements, air emissions and generation of solid wastes, are then scaled to this scenario. The effects of control technologies and state regulations are considered. A comparison is also made between the impacts of EOR as an energy source and impacts associated with coal and synthetic fuels which concludes that EOR is preferable in many respects. There are environmental risks associated with EOR technologies, specific projects and specific fields in the production scenario; however, most problems are solvable by responsible regulation, enforcement of regulations and application of the best professional engineering by project operators.     

Saturday effects in tanker oil spills

This paper documents a “Saturday effect” in the timing of tanker oil spills—certain types of spills happen much more frequently on this day than one would expect if the spills were uniformly distributed. The phenomenon is restricted to Europe and North America, and is associated with “vessel guidance” accidents—groundings, collisions, and rammings. Eliminating the Saturday effect would reduce tanker oil spills by around 163,000 gallons per year. Several policy responses are considered, including a Saturday harbor tax. A lower bound for an efficient tax is estimated to be $780 for a 20 million gal cargo.     

Arsenic management in shale oil upgrading

Although the timing remains uncertain, the production of synthetic crude from oil shale seems to be a likely response to diminishing petroleum reserves. Although not unique to shale oil, the presence of arsenic, ranging in concentration from a few to over 100 parts per million, poses a special concern.Arsenic is typically removed from the shale oil by a hydro-processing technique and is concentrated on a catalyst as thermally stable metal arsenides and metal arsenous sulfides. Because this arsenic is still slightly soluble in water, making the spent catalyst a hazardous material, passivation and extraction techniques were investigated to make the catalyst safe for disposal. Passivation techniques were not successful. While extraction procedures were capable of removing over 75% of the arsenic, treated material may still be acceptable.