城市二级污水灌溉对几种园林植物生长的影响

以新疆乌鲁木齐市东郊七道弯污水处理厂二级出水为研究对象．开展了二级污水对几种园林植物(万寿菊、紫穗槐、高羊茅、早熟禾)生理、生态的影响研究。与对照组相比，结果表明，草坪草、紫穗槐叶绿素含量、净光合速率、地上部分生物量增加。     

Combined alkaline and ultrasonic pretreatment of sludge before aerobic digestion

Alkaline and ultrasonic sludge disintegration can both be used as pretreatments of waste activated sludge (WAS) for improving the subsequent anaerobic or aerobic digestion. The pretreatment has been carried out using different combination of these two methods in this study. The effect was evaluated based on the quantity of soluble chemical oxygen demand (SCOD) in the pretreated sludge as well as the degradation of organic matter in the following aerobic digestion. For WAS samples with combined pretreatment, the released COD was in high level than those with ultrasonic or alkaline treatment. When combined with the same ultrasonic treatment, NaOH treatment resulted in more solubilization of WAS than Ca(OH)2. For combined NaOH and ultrasonic treatments with different sequences, the released COD were in the order: simultaneous treatment > ultrasonic treatment following NaOH treatment > NaOH treatment following ultrasonic treatment. For simultaneous treatment, low NaOH dosage (100 g/kg dry solid), short duration (30 min) of NaOH treatment, and low ultrasonic specific energy (7 500 kJ/kg dry solid) were beneficial for sludge disintegration. Using combined NaOH and ultrasonic pretreatment with the optimium parameters, the degradation efficiency of organic matter was increased from 38.0% to 50.7%, which is much higher than with ultrasonic (42.5%) or with NaOH pretreatment (43.5%) in the subsequent aerobic digestion at the same retention time.     

Phragmites australis and Typha orientalis in removal of pollutant in Taihu Lake, China

Two plant populations of Phragmites australis and Typha orientalis grown in gravel and sediment substrate were studied to assess their capabilities for purifying polluted water in Taihu Lake, China. The substrate displayed most significant effects on the suspended matter (P < 0.01), with the reduction of 76%-87% and 52%-63% for P. australis, and 83%-86% and 45%-62% for T. orientalis in gravel substrate and sediment substrate, respectively. Both species and substrates significantly decreased the N and P conc...     

Optimization of gasoline hydrocarbon compositions for reducing exhaust emissions

Effects of hydrocarbon compositions on raw exhaust emissions and combustion processes were studied on an engine test bench. The optimization of gasoline hydrocarbon composition was discussed. As olefins content increased from 10.0% to 25.0% in volume, the combustion duration was shortened by about 2 degree crank angle ( CA), and the engine-out THC emission was reduced by about 15%. On the other hand, as aromatics content changed from 35.0% to 45.0%, the engine-out NOx emissions increased by 4%. An increment in olefins content resulted in a slight increase in engine-out CO emission, while the aromatics content had little e ect on engine-out total hydrocarbon (THC) and CO emissions. Over the new European driving cycle (NEDC), the THC, NOx and CO emissions of fuel with 25.0% olefins and 35.0% aromatics were about 45%, 21% and 19% lower than those of fuel with 10.0% olefins and 40.0% aromatics, respectively. The optimized gasoline compositions for new engines and new vehicles have low aromatics and high olefins contents.     

水热改性污泥的水分布特征与脱水性能研究

采用差示扫描量热法（DSC）考察了水热改性污泥束缚水含量及水热改性影响下的污泥固体颗粒对水的束缚强度,分析了水热改性污泥水分布特征与脱水性能变化的关系.结果表明,水热处理将污泥的束缚水含量由3.6　g/g降低至1.0　g/g以下,随着热处理时间的增加束缚水含量降低,在水热处理条件为170℃/90　min时束缚水含量降低至0.592　g/g.水热处理将污泥中大部分的束缚水转变为可被机械力去除的自由水,污泥中自由水、束缚水及固体含量发生变化.泥饼中自由水的含量基本不变,约为10%.对污泥中的水分进行热力学分析发现,污泥脱水泥饼的水分束缚强度约为65　kJ/kg,机械脱水不能再进行.在170℃下进行水热改性污泥压滤脱水的含水率从80%降低至50%左右.     

教您选择放心菜

蔬菜营养丰富,其中含有多种人体必需的微量元素。蔬菜安全是老百姓街头巷尾热议的话题之一。当前蔬菜质量安全问题主要有三个方面：一是农药残留超标;二是重金属含量超标;三是硝酸盐、亚硝酸盐含量超标。作为普通消费者,怎样选择蔬菜才能减轻这些危害,吃的放心呢？     

矿区周围稻米重金属积累及健康风险分析

选用杂交稻、常规稻和糯稻3个水稻品系共21个水稻品种在广东大宝山矿区周围重金属污染土壤中进行大田试验,研究Cu、Zn、Pb、As和Cd 5种重金属元素在不同水稻品种(品系)稻米中的积累状况,并进行健康风险评价分析。结果表明,供试水稻稻米中Cd和Pb超标率很高,分别为100%和71.43%;Cu和As超标现象不严重,超标率分别为4.76%和14.29%;Zn含量均不超标。供试水稻品系中常规稻和糯稻稻米对Cu、Zn、Pb、Cd的积累能力较高,杂交稻则较低;但杂交稻稻米对As的积累能力高于其他2个品系。稻米中Cu、Zn、Pb、As和Cd含量与稻谷生物量均呈负相关关系,其中Pb含量与稻谷生物量呈显著负相关。供试水稻稻米对5种重金属的富集能力由高到低排序为Cd>Zn>Cu>As>Pb。本研究表明供试土壤中Cd和Pb对人体健康存在比较严重的潜在威胁,Cu、Zn和As对人体健康的潜在危害较小,应重点关注大宝山矿区稻米Cd和Pb的重金属污染问题及其对人体健康的潜在危害。     

模拟酸雨对薇甘菊种子萌发和幼苗生长的影响

薇甘菊是入侵性杂草,已在我国华南地区及云南部分地区造成严重危害。我国华南地区同时也是强酸雨分布区域。采用不同pH值的模拟酸雨对薇甘菊种子及幼苗进行处理,测定其对种子萌发和幼苗生长的影响。测定了不同pH值下薇甘菊幼苗叶绿素含量、丙二醛含量、脯氨酸含量、超氧阴离子产生速率、超氧化物歧化酶和过氧化物酶活性。结果表明,薇甘菊种子具有较强的耐酸能力,pH≥3．5时均能正常萌发,pH≤3．0时不能萌发。不同pH值模拟酸雨对薇甘菊幼苗叶绿素含量影响不显著。随着模拟酸雨pH值下降,超氧阴离子产生速率上升,丙二醛含量、脯氨酸含量、超氧化物歧化酶活性和过氧化物酶活性呈先上升后下降。pH3．5时,丙二醛含量、脯氨酸含量、过氧化物酶活性均达最大值;pH4．0时超氧化物歧化酶活性达最大值。结果表明薇甘菊对华南地区酸雨胁迫表现出适应。     

雷州半岛桉林-砖红壤水分动态变化特征研究

根据定位观测数据,对雷州半岛浅海沉积物发育的桉林地砖红壤水分状况及其动态变化进行了初步探讨.结果表明,受水分蒸发量大等因素的影响,0～100 cm土层月均贮水量较低;主要受降雨分布的影响,土壤水分呈明显的季节性变化特征且季节性干旱时间较长,8～     

杉木观光木混交林群落的能量生态

对杉木观光木混交林群落能量的研究结果表明：混交林中观光木地上部分灰分含量以皮最高,而杉则以叶最高,两者GCV（干重热值）和AFCV（去灰分热值）均以叶为最高;观光木、杉木地下各部分的灰分含量均随径级的减小而增加,GCV均以粗根最高,细根最低;观光木的平均灰分含量高于杉木,但GCV和AFCV均低于杉木;从乔木层、灌木层到草本层,灰分含量依次增加,GCV和AFCV则依次降低,混交林群落的能量现存量公占群落的很小一部分,而其能量年净增量、归还量和净固定量却占有一定比重,混交林群落的太阳能转化率为1.57%,而纯林为1.44%,表明杉观混交林是一种能量生产力较高和维持地力能力较强的杉阔混交类型。同时,混交林的能量累积比大于纯林,能量流动速率则低于纯林;乔木层的能量累积比高于林下植被,能量流动速率则低于林下植被,从能量的角度看,构建合理的群落结构必须选择高能量累积比的乔木层树种,同时须促进能量流动速率快的林下植被的发育以维持和提高地力。