Assessment of private economic benefits and positive environmental externalities of tea plantation in China

Tea plantations are rapidly expanding in China and other countries in the tropical and subtropical zones, driven by relatively high private economic benefit. However, the impact of tea plantations on the regional environment, including ecosystem services and disservices are unclear. In this study, we developed an assessment framework for determining the private economic benefits and environmental externalities (the algebraic sum of the regulating services and disservices) of tea plantations in China. Our results showed that tea plantations provided private economic benefits of 5,652 yuan ha^?1 year^?1 (7.6 yuan?=?1 USD in 2007) for tea farmers, plus positive environmental externalities of 6,054 yuan ha^?1 year^?1 for the society. The environmental externalities were calculated as the sum of the value of four regulating services, including carbon sequestration (392 yuan ha^?1 year^?1); soil retention (72 yuan ha^?1 year^?1); soil fertility protection (3,189 yuan ha^?1 year^?1) and water conservation (2,685 yuan ha^?1 year^?1), and three disservices, including CO₂ emission (?39 yuan ha^?1 year^?1), N₂O emission (?137 yuan ha^?1 year^?1) and nonpoint source pollution (?108 yuan ha^?1 year^?1). Before the private optimal level, the positive environmental externalities can be maintained by private economic benefits; if a social optimal level is required, subsidies from government are necessary.     

进水碳氮比对SUFR系统脱氮除磷影响的特性分析

考察了进水碳氮比（C/N）对螺旋升流式反应器（spiral up-flow reactor,SUFR）系统生物脱氮除磷的影响,试验设计了进水C/N在7～13范围的数种工况,研究了SUFR系统中COD、总磷和氮的变化规律。结果表明,进水C/N对SUFR系统去除COD与TP效果的影响不明显,平均去除率分别为95.2%和93.9%;当进水C/N<9.4时,TN的去除率随C/N的增大而快速提高,而当进水C/N>9.4时,TN的去除率稳定在81.1%～85.6%;SUFR系统的硝化效果较稳定,氨氮的去除率保持在90.5%～98.8%;系统的反硝化作用随C/N的增大有所增强,出水硝酸盐氮浓度逐渐降低。     

临江河回水区营养盐及富营养化特征分析

以2008年3～9月对库区次级河流临江河回水区水质的调查为依据,分析了临江河回水区氮、磷营养盐的污染分布及富营养化特征。结果表明,临江河回水区氨氮(NH₃-N)、总氮(TN)的浓度在7月中旬达到最小值,分别为1.963和5.128 mg/L, 之后在9月初出现峰值,而磷酸盐(PO^3-₄-P)和总磷(TP)的浓度却呈现出先增加后下降的变化规律;氮主要来自点源污染,而磷受面源污染影响较大;溶解性无机氮(DIN)和PO^3-₄-P是TN与TP的主要存在形态,平均分别占TN和TP的85.3%和77.8%,而DIN又以NH₃-N为主。营养盐浓度呈现出回水区中游最高,回水末端次之,河口处最低的空间分布特征。叶绿素a（Chl-a）的浓度在4月和9月出现峰值,其空间分布特征与营养盐的类似。研究表明,临江河回水区在重度污染的情况下,即便是河流型水体也可能发生富营养化;流速对Chl-a浓度的显著影响呈指数关系。     

OGO工艺处理城市污水的脱氮除磷效能与水力特性的试验研究

在OCO反应器的基础上改进得到了OGO反应器.在反应器改进前后脱氮除磷效能对比试验的基础上,进行了反应器水力特性的试验研究.城市污水对比试验研究结果表明,OGO工艺较改进前具有更为稳定、良好的生物同时脱氮除磷效果,工艺出水的平均值COD为22mg·L-1、NH4 -N为4.8mg·L-1、TN为11.2 mg·L-1、TP为0.80mg·L-1.反应器流态特征的试验结果表明,改进后形成的OGO反应器内,缺氧环区形成了良好的DO浓度梯度分布,且OGO反应器内推流流态所占比例从改进前的5.9%提高到改进后的12.9%,有效提高了反应器内推流流态的容积利用率和反应器效率.同时,反应器改进后能明显改善混合区水力条件,并有效避免了混合区内侧液流涡旋停滞造成的污泥沉积问题.     

不同气温层结条件下地面加热对街谷扩散能力的影响

利用CFD数值模拟方法研究了气温层结与地面加热作用对街谷环流和污染物扩散的影响.针对高宽比为0.5和1.0的两种街谷,总共进行了18组敏感性数值试验,结果表明相对于气温层结,地表加热是决定街谷附近污染物扩散能力的更为重要的因素,地表加热作用可显著提高街谷的扩散能力.在地表存在加热的情况下,流场结构、空气交换系数、湍流强度总体上均朝着有利于清除街谷内污染物的方向发展,即使是在稳定层结下,地表加热作用所产生的热力环流也会使得污染物能够被有效地输送和扩散到街谷之外,从而使得近地面的污染物浓度下降.     

Enhanced anaerobic digestion and sludge dewaterability by alkaline pretreatment and its mechanism

To investigate the influences of alkaline pretreatment on anaerobic digestion (AD) and sludge dewaterability after AD, waste activated sludge was adjusted to different pH values (8, 9, 10, 11, 12) and placed at ambient temperature for 24 hr. The samples were then adjusted to the initial pH and subjected to 25 days of AD. The results showed that, when compared with the control (pH 6.8), total suspended solids (TSS) and volatile suspended solids (VSS) reduction following pretreatment at pH 9-11 increased by 10.7%-13.1% and 6.5%-12.8%, respectively, while biogas production improved by 7.2%-15.4%. Additionally, significant enhancement of sludge dewaterability after AD occurred when pretreatment at pH 8-9 was conducted. The proteins and carbohydrates transferred from the pellet and tightly bound extracellular polymeric substances (TB-EPS) fractions to the slime and loosely bound EPS (LB-EPS) fractions after pretreatment and during the AD process, and the concentrations of proteins and carbohydrates in the slime fraction had a good linear relationship with the normalized capillary suction time (CST). During the AD process, the normalized CST was positively correlated with the organic materials in the loosely bound fraction of the sludge matrix (R^{2≥qslant 0.700, p < 0.01), while it was negatively correlated with the organic materials in the tightly bound fraction (R2≥qslant 0.702, p < 0.01). These results suggest that alkaline pretreatment could break the EPS matrix and release inner organic materials, thus influencing the efficiency of the AD process and dewaterability after AD.}     

北京空气重污染红色预警期间污染物与气象因子特征

揭示空气重污染红色预警期间污染物与气象因子的变化特征对空气质量预报和污染减排措施评估具有重要参考价值。利用大气污染和气象观测资料,研究了北京2015年11-12月空气重污染红色预警时期污染物浓度、气候特征及气象因子对空气质量影响。结果表明,PM2.5在大气颗粒物中占有较大比重,为首要空气污染物;在重污染峰值时段,城郊PM2.5与PM10比值（R）相差不大,可达0.9以上,空气呈均匀混合的高PM2.5浓度特征,而空气质量较好时城区R值明显高于郊区;研究时段气候特征与历史同期相比有明显差异,其中平均风速偏小19%,平均气温偏高0.23 ℃,气温日较差减小,而多次小型降水增加了空气湿度,导致相对湿度值偏高40%,垂直方向上的逆温层或等温层则加剧了空气重污染的形成和发展,重污染过程中的红色预警措施明显降低了颗粒物浓度;风速与污染物浓度呈指数相关,城郊风速分别低于2.0和2.5 m·s-1时,空气质量较差、污染物浓度随风速升高快速下降,而当城郊风速大于2.0和2.5 m·s-1时变化特征则相反;相对湿度与污染物浓度呈幂相关,相对湿度在65%左右为空气质量特征发生变化的转折点;由于气温日较差存在季节变化,其与空气质量相关关系不太显著。     

Toxicity evaluation in a paper recycling mill effluent by coupling bioindicator of aging with the toxicity identification evaluation method in nematode Caenorhabditis elegans

Toxicity identification evaluation (TIE) can be used to determine the specific toxicant(s) in industrial effluents.In the current study,the authors have attempted to combine the advantages of the model organism,Caenorhabditis elegans,with the virtues of the TIE technique,to evaluate and identify the toxicity on aging from a paper recycling mill effluent.The results indicate that only the toxicities from mixed cellulose (MC) filtration and EDTA treatment are similar to the baseline aging toxicity,suggesting ...     

铁/锰矿基人工湿地脱氮除磷性能及机理

铁氧化物和锰氧化物均可在缺氧条件下介导氨氮(NH₄⁺-N)的氧化去除,这2项技术被称为铁氨氧化(Feammox)和锰氨氧化(Mnammox)。此外,金属氧化物对总磷(TP)也有去除能力,因此,在人工湿地中具有良好的应用前景。为比较铁矿基和锰矿基人工湿地的脱氮除磷效果,本研究建立了铁矿基人工湿地(CW-Fe)、锰矿基人工湿地(CW-Mn)和砾石对照组人工湿地(CW-C)3组人工湿地。结果表明,CW-Fe和CW-Mn的脱氮除磷性能均优于CW-C。尽管锰矿对NH₄⁺-N的吸附作用最强,但CW-Fe却表现出了更优越的NH₄⁺-N长期去除性能。在基质对NH₄⁺-N的吸附饱和后,CW-Fe对NH₄⁺-N的去除率仍有39.93%~62.4%,而CW-Mn只有29.15%~35.4%。由于铁矿和锰矿溶出的金属离子能与磷酸盐结合形成稳定的沉淀,从而有效去除TP,CW-Fe和CW-Mn均有优异的TP去除性能。CW-Mn的TP去除率最高,为95.26%,其次是CW-Fe,为79.97%。在微生物方面,具有还原铁氧化物和氧化NH₄⁺-N潜力的Bacillus和Exiguobacterium在CW-Fe中均得到了显著富集。结合水质数据及脱氮相关功能菌的分析,推测出Feammox中可能更倾向于将NH₄⁺-N直接氧化为N₂,而Mnammox则是更倾向于先将NH₄⁺-N氧化为NO_x⁻-N。本研究可为探索同步脱氮除磷的低能耗污水处理工艺及人工湿地中基质的选择提供案例参考。     

基质粒径与排空时间对潮汐流人工湿地运行效能的影响

潮汐运行是强化人工湿地供氧的一种有效途径。为了解基质粒径对潮汐流人工湿地(TFCWs)处理效果及复氧过程的影响,研究了不同基质粒径TFCWs的处理性能,建立了TFCWs排空期氧转移过程的研究方法。结果表明基质粒径影响湿地对NH₄⁺的吸附性及排空期基质孔隙氧体积占比进而影响处理效果,7~9 mm基质粒径的湿地达到最佳的氨氮去除率82.6%,3~5 mm基质粒径的湿地达到最佳的COD去除率88.2%,粒径基质小的湿地中氨氧化菌属和反硝化菌属的相对丰度更高,脱氮能力强;分析排空期基质孔隙氧体积占比变化与湿地微生物耗氧过程的联系,能够优化潮汐流湿地系统的排空时间,湿地微生物的耗氧活动主要集中在氧体积占比快速下降阶段,更长的排空时间对复氧能力没有明显提升,本研究中8 h的排空时间即可满足湿地系统的氧需求。