Effects of organic matter on Leymus chinensis germination,growth, and urease activity and available nitrogen in coastal saline soil

ABSTRACT

The present study was carried out to investigate the effect of three organic matters (stalk powder, microbial fertilizer, and manure) on Leymus chinensis germination, growth, and urease activity and available nitrogen (N) in coastal saline soil. The study was conducted in a completely randomized design with eight treatments: J₀V₀Y₀, J₁V₀Y₀, J₀V₁Y₀, J₀V₀Y₁, J₁V₁Y₀, J₁V₀Y₁, J₀V₁Y₁, J₁V₁Y₁. The notations were based on the quantities of each agent added to 1 kg of coastal saline soil: J₀ – no straw powder, J₁ – 0.2 kg straw powder, Y₀ – no manure, Y₁ – 0.3 kg manure, V₀ – no microbial fertilizer, V₁ – 0.2 L microbial fertilizer, each in quantic repeat. L. chinensis was sown as 50 seeds per pot. Results indicated that addition of organic agents exerted a significantly enhanced germination, increase in fresh weight and elevated soil urease activity. Soil available N levels were significantly positively correlated with soil urease activity and fresh weight, but not with germination rate. It is noteworthy that the halophyte L. chinensis showed improved characteristics when grown in coastal saline soil with addition of organic amendments.     

Discounting in the presence of scarce ecosystem services

The discount rate for cost-benefit analysis has to take account of future scarcity of ecosystem services in consumption and production. Previous literature focuses on the first aspect and shows the importance of the relative price effect, for given growth rates of consumption and ecosystem services. This paper focuses on intermediate ecosystem services in production and shows that for limited substitutability and a low growth rate of these ecosystem services, the growth rate of consumption, and thus the discount rate, declines towards a low value. Using a Ramsey growth model, the paper distinguishes three cases. If ecosystem services can be easily substituted, the discount rate converges to the usual value in the long term. Secondly, if ecosystem services can be easily substituted in production but not in consumption, the relative price effect is important. Finally, and most interestingly, if ecosystem services cannot be easily substituted in production, the discount rate declines towards a low value and the relative price effect is less important. Another part of the previous literature has shown that a declining discount rate is the result of introducing several forms of uncertainty, but this paper reaches that conclusion from an endogenous effect on the growth rate of the economy.     

Co-treatment of fruit and vegetable waste in sludge digesters. An analysis of the relationship among bio-methane generation,process stability and digestate phytotoxicity

The co-digestion of a variable amount of fruit and vegetable waste in a waste mixed sludge digester was investigated using a pilot scale apparatus. The organic loading rate (OLR) was increased from 1.46 kg VS/m³ day to 2.8 kg VS/m³ day. The hydraulic retention time was reduced from 14 days to about 10 days. Specific bio-methane production increased from about 90 NL/kg VS to the maximum value of about 430 NL/kg VS when OLR was increased from 1.46 kg VS/m³ day to 2.1 kg VS/m³ day. A higher OLR caused an excessive reduction in the hydraulic retention time, enhancing microorganism wash out. Process stability evaluated by the total volatile fatty acids concentration (mg/l) to the alkalinity buffer capacity (eq. mg/l CaCO₃) ratio (i.e. FOS/TAC) criterion was <0.1 indicating high stability for OLR <2.46 kg VS/m³ day. For higher OLR, FOS/TAC increased rapidly. Residual phytotoxicty of the digestate evaluated by the germination index (GI) (%) was quite constant for OLR < 2.46 kg VS/m³ day, which is lower than the 60% limit, indicating an acceptable toxicity level for crops. For OLR > 2.46 kg VS/m³ day, GI decreased rapidly. This corresponding trend between FOS/TAC and GI was further investigated by the definition of the GI ratio (GIR) parameter. Comparison between GIR and FOS/TAC suggests that GI could be a suitable criterion for evaluating process stability.     

Development of heat transfer and evaporation model of LNG covered by Hi-Ex foam

Natural gas is a kind of clean, efficient green energy source, which is used widely. Liquefied natural gas (LNG) is produced by cooling natural gas to −161 °C, at which it becomes the liquid. Once LNG was released, fire or explosion would happen when ignition source existed nearby. The high expansion foam (Hi-Ex foam) is believed to quickly blanket on the top of LNG spillage pool and warm the LNG vapor to lower the vapor cloud density at the ground level and raising vapor buoyancy. To identify the physical structure after it contacted with LN₂ and to develop heat transfer model, the small-scale field test with liquid nitrogen (LN₂) was designed. In experiment, three layers including frozen ice layer, frozen Hi-Ex layer and soft layer of Hi-Ex foam were observed at the steady state. By characterizing physical structure of the foam, formulas for calculating the surface of single foam bubble and counting foam film thickness were deduced. The micro heat transfer and evaporation model between cryogenic liquid and Hi-Ex foam was established. Indicating the physical structure of the frozen ice layer, there were a certain number of icicles below it. The heat transfer and evaporation mathematical model between the frozen ice layer and LNG was derived. Combining models above with the heat transfer between LNG, ground and cofferdam, the heat transfer and evaporation mathematical model of LNG covered by Hi-Ex foam was developed eventually. Finally, LN₂ evaporation rate calculated by this model was compared with the measured evaporation rate. The calculated results are 1.2–2.1 times of experimental results, which were acceptable in engineering and proved the model was reliable.     

电化学氢化物发生法处理含锑废水及对锑的回收

采用电化学氢化物发生法对模拟含锑废水进行处理,锑与水电解产生的氢形成氢化物从溶液中脱除,而后收集并加热分解锑化氢得到金属锑.实验表明,在酸性条件下对Sb(Ⅲ)去除效果较好,p H=4时去除率为76.1%.Sb(Ⅲ)与电解水产生的氢结合形成锑化氢从溶液中逸出是溶液中锑去除的最主要途径(回收率为66.2%),电沉积和吸附也对锑的去除做出少量贡献.Sb(Ⅴ)须预还原为Sb(Ⅲ)再氢化进行去除.试用了铅、石墨、钨这3种电解阴极材料,铅电极处理效果最佳.     

蠡河底泥中反硝化复合菌群富集及菌群结构研究

从无锡市滨湖区蠡河底泥中富集培养反硝化复合菌群,研究其在不同富集培养阶段TN、NO-3-N、NO-2-N、NH+4-N和COD动态变化,分析反硝化过程中气体释放总量、释放速率和成分,通过构建全长16S r DNA克隆文库研究其菌落结构.结果表明,反硝化复合菌群富集在阶段4时脱氮效果最佳,仅在9 h内,330 mg·L-1的TN负荷下,TN去除率达90.9%,NO-3-N去除率达100%,中间产物NO-2-N和NH+4-N积累量最少,分别为3.39 mg·L-1和16.64 mg·L-1,COD去除率达85%;释放气体260m L,气体主要成分为N2,同时还有少量的CH4和CO2等.富集培养反硝化复合菌群细菌属于Pseudomonadaceae科和Rhodocyclaceae科,为Proteobacteria门,OUT丰度分别为57.8%和31.6%,Pseudomonadaceae科是优势类群.     

容积负荷对ABR-MBR工艺反硝化除磷性能的影响

采用连续流ABR-MBR组合工艺处理生活污水,研究不同容积负荷(volume loading rate,VLR)对该工艺反硝化除磷性能的影响,获得最佳工艺参数.试验考察ABR进水容积负荷(以COD计,下同)分别为0.76、1.01、1.51和2.27 kg·(m~3·d)~(-1)时系统去碳脱氮除磷的性能,并在各ABR容积负荷条件下考察MBR容积负荷对MBR反应器硝化性能的影响.结果表明,在ABR进水容积负荷为1.51 kg·(m~3·d)~(-1)的条件下,系统A2隔室COD去除量最大,并在MBR容积负荷为0.462 kg·(m~3·d)~(-1)时,MBR反应器中实现了短程硝化,系统NH_4~+-N和TN去除率分别达到90%和72%以上,厌氧释磷量为7.41 mg·L~(-1),缺氧吸磷量达到15.42 mg·L~(-1),出水PO_4~(3-)-P浓度低于0.5 mg·L~(-1),这表明短程硝化更有利于强化ABR-MBR系统的反硝化除磷性能.     

常规施肥条件下农田不同途径氮素损失的原位研究:以长江中下游地区夏玉米季为例

为了解农田常规施肥条件下的不同途径氮素损失特征,本文通过田间原位试验同步研究了长江中下游地区夏玉米生长季氮肥施用后的农田N2O排放、NH3挥发、氮渗漏和地表径流的变化.结果表明,在复合肥为基肥,尿素为追肥,基追肥氮素水平均为150 kg·hm-2的条件下,整个玉米生长季N2O排放系数为3.3%,NH3挥发损失率为10.2%,氮渗漏和地表径流损失率分别为11.2%和5.1%.此外,基肥施用以氮素渗漏损失为主,而追肥氮素损失以氨挥发和渗漏为主,表明不同途径化肥氮素损失主要受氮肥品种影响,玉米季追肥可改用低氨挥发氮肥品种以减少氮素损失.     

Ethanol mediated As(III) adsorption onto Zn-loaded pinecone biochar: Experimental investigation, modeling, and optimization using hybrid artificial neural network-genetic algorithm approach

Organic matters (OMs) and their oxidization products often influence the fate and transport of heavy metals in the subsurface aqueous systems through interaction with the mineral surfaces. This study investigates the ethanol (EtOH)-mediated As(III) adsorption onto Zn-loaded pinecone (PC) biochar through batch experiments conducted under Box–Behnken design. The effect of EtOH on As(III) adsorption mechanism was quantitatively elucidated by fitting the experimental data using artificial neural network and quadratic modeling approaches. The quadratic model could describe the limiting nature of EtOH and pH on As(III) adsorption, whereas neural network revealed the stronger influence of EtOH (64.5%) followed by pH (20.75%) and As(III) concentration (14.75%) on the adsorption phenomena. Besides, the interaction among process variables indicated that EtOH enhances As(III) adsorption over a pH range of 2 to 7, possibly due to facilitation of ligand–metal(Zn) binding complexation mechanism. Eventually, hybrid response surface model–genetic algorithm (RSM–GA) approach predicted a better optimal solution than RSM, i.e., the adsorptive removal of As(III) (10.47 μg/g) is facilitated at 30.22 mg C/L of EtOH with initial As(III) concentration of 196.77 μg/L at pH 5.8. The implication of this investigation might help in understanding the application of biochar for removal of various As(III) species in the presence of OM.     

Assessment of the clear-sky bias issue using continuous PM10 data from two AERONET sites in Korea

A bias in clear-sky conditions that will be involved in estimating particulate matter(PM)concentration from aerosol optical depth(AOD) was examined using PM_(10) from two Aerosol Robotic Network sites in Korea. The study periods were between 2004 and 2007 at Anmyon and between 2003 and 2011 at Gosan, when both PM_(10) and AOD were available. Mean PM_(10) when AOD was available(PM AOD) was higher than that from all PM_(10)data(PM all) by 5.1 and9.9 μg/m~3 at Anmyon and Gosan, which accounted for 11% and 26% of PM all, respectively.Because of a difference between mean PM_(10) under daytime clear-sky conditions(PM clear)and PM AOD, the variations in ΔPM_(10), the difference of PM all from PM clear rather than from PM AOD, were investigated. Although monthly variations in ΔPM_(10)at the two sites were different, they were positively correlated to those in ΔT, similarly defined as ΔPM_(10)except for temperature, at both sites. ΔPM_(10)at Anmyon decreased to a negative value in January due to an influence of the Siberian continental high-pressure system while ΔPM_(10)at Gosan was high in winter due to an effect of photochemical production at higher temperatures than at Anmyon.