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1.
The denitrifying woodchip bioreactor is designed to remediate nitrate-rich water, including those produced from aquaculture effluents. Reuse of treated bioreactor outflows in recirculating aquaculture would offer considerable water savings and valuable alkalinity recuperation. However, such bioreactors may leach detrimental wood-bound contaminants, preventing outflow reuse. To determine water reuse potential, woodchip media from two hardwood species (white ash, Fraxinus americana; Norway maple, Acer platanoides) were evaluated for 206 d under a range of operating conditions (start-up, steady-state, reducing conditions, and drying-rewetting cycles) for a spectrum of potentially harmful dissolved contaminants. Aerated outflows also were evaluated for acute and chronic toxicity to the biologically sensitive invertebrate Ceriodaphnia dubia. Dissolved metal leaching subsided within the first few weeks of operation, though initial concentrations of copper and zinc were detected at concentrations of concern. Elevated concentrations of tannins-lignin and total ammonia nitrogen were detected throughout the study and were influenced by operational phase. Acute toxicity was not generally detected, though chronic toxicity was observed during drying-rewetting cycles in the maple outflows. The measured toxicity was not correlated with water chemistry, indicating an additive effect of several toxicants. Overall, significant differences in outflow water quality between ash and maple wood species were negligible. Results indicated that bioreactor outflows may be applicable for aquacultural reuse, though reusing outflows immediately following start-up or restarting after a dry period would not be recommended.  相似文献   
2.
【目的】 研究新疆主栽鲜食葡萄品种裂果特性差异和引起裂果生理原因,分析鲜食葡萄品种裂果特性差异,为生产过程中降低裂果发生率生产调控措施的选择提供理论依据。【方法】 以无核白、无核紫、无核白鸡心、新郁等12个鲜食葡萄品种为研究对象,分析成熟期浸水诱导裂果,对不同鲜食葡萄品种的裂果特性,通过石蜡切片测定果皮细胞结构特征,测定果皮强度、果胶、原果胶、纤维素等细胞壁结构物质含量及代谢关键酶活性。【结果】 不同鲜食葡萄品种裂果特性存在显著差异,浸水24 h裂果率分布在0~80%,12个品种可以分成4个裂果特性差异类群,其中极易裂果类群包括里扎玛特1个品种,易裂果类群包括新郁、无核白2个品种;较易裂果品种包括火州黑玉、新雅、无核白鸡心、无核紫4个品种,耐裂果类群包括红地球、京亚、夏黑、维多利亚、火焰无核5个品种。【结论】 果皮角质层完整性,果皮、亚果皮细胞大小和排列紧密度与果实易裂程度密切相关;水溶性果胶含量、水溶性果胶与原果胶比值与鲜食葡萄品种易裂性呈极显著的正相关关系;果皮强度、纤维素含量均与鲜食葡萄品种易裂性呈极显著负相关关系。  相似文献   
3.
本文主要用蔗糖、柠檬酸、硝酸钙配制的不同配方的保鲜剂对石竹梅鲜切花进行瓶插试验,观察了不同配方的保鲜剂在当地自然条件下对切花外观品质和瓶插寿命的影响,从中筛选出石竹梅切花的较佳保鲜配方。试验研究表明,2%的蔗糖+100mg/L柠檬酸+0.2%硝酸钙的保鲜剂配方对石竹梅切花保鲜效果是最好的,比未经处理的石竹梅鲜切花瓶插寿命延长6-8天。  相似文献   
4.
Abstract

The life history and fitness of Nilaparvata lugens being reared under ambient level (current CO2 concentration), medially elevated (550?µL/L) and highly elevated (750?µL/L) CO2 concentration for long-term generation were compared using two-sex life table instead of traditional age-specific life table. The results showed that significantly longer larval duration and lower fecundity of N. lugens were observed in 750?µL/L relative to 550?µL/L treatment (P?<?0.05). Accordingly, 550?µL/L CO2 significantly enhanced population parameters of N. lugens, including significantly higher intrinsic rate of increase (r), finite rate (λ) and net reproductive rate (RO), but not for 750?µL/L CO2. Taken together, N. lugens performs enhanced development rate, fecundity and survival in individual life history and higher potential in population multiplication under 550?µL/L CO2 level, while only indicates the less enhanced development rate and survival without significant increased capacity of population expansion under 750?µL/L CO2 level. These results should facilitate predicting the fitness and potential population damage of N. lugens, which is valuable for the integrated control of N. lugens in the future increasing CO2 concentration.  相似文献   
5.
6.
Alpine wetlands are hotspots of carbon (C) storage and methane emission, and they could be key contributors to global warming. In recent years, rapid warming has lowered the water table in alpine wetlands on the Tibetan Plateau, concurrent with intensified nitrogen (N) deposition via anthropogenic activities. We carried out a field experiment to investigate the ecological impacts of these two factors on soil bacterial and functional communities, which are essential drivers of greenhouse gas emissions. Nitrogen amendment alone decreased the phylogenetic alpha-diversity of bacterial communities which could be offset by lowered water table. In contrast, microbial functional alpha-diversity, revealed by a high-throughput microarray, remained unchanged. Both bacterial and functional beta-diversity responded to lowered water table, but only bacterial community responded to N amendment. The alpha-Proteobacteria, beta-Proteobacteria, and Bacteroidetes were the major responsive bacterial lineages, and C degradation, methanogenesis, alkaline shock, and phosphorus oxidation were the major responsive functional processes. Partitioning analysis revealed that N amendment changed bacterial community structure mainly via species loss processes but did not affect bacterial functional communities, with soil pH and ammonium as the key factors influencing changes in bacterial community structure. Conversely, lowered water table altered bacterial and functional communities through species substitution processes linked to soil pH and soil moisture. According to our results, the response mechanisms of microbial communities to lowered water table and N amendment are fundamentally different in alpine wetlands.  相似文献   
7.
【目的】探讨华北地区夏玉米-冬小麦轮作体系下氮肥减施与地下水埋深的交互作用。【方法】借助大型地中渗透仪和Logistic作物生长模型,采用二因素完全随机区组设计:地下水埋深(G1:2.0 m、G2:3.0 m、G3:4.0 m),施氮量(N1:减氮20%、N2:常规施氮),以及不施氮不控水作为对照(WN),研究了华北地区地下水埋深和施氮水平组合对夏玉米生长、干物质量积累和硝态氮量的影响。【结果】所有处理夏玉米叶面积指数(LAI)在灌浆期最大,成熟期相同施氮水平,G1处理LAI显著高于G2、G3处理;N2水平下,G1处理玉米株高快速生长时间较G2、G3处理分别增加了3.99%、12.91%,但最大增长速率相对降低了9.69%、14.65%;N1水平下,G1处理籽粒干物质量显著高于G2和G3处理,N2水平下,G3处理籽粒干物质量显著高于G1和G2处理;N2水平下,G1处理硝态氮增量显著高于G2、G3处理,0~20 cm分别高出75.92%、90.03%,20~40 cm分别高出30.56%、130.95%。同一地下水埋深下,成熟期LAI表现为N2处理显著高于N1处理;0~20 cm与20~40 cm土层N2处理下硝态氮增量是N1处理的1.4~5.3倍和2.4~11.2倍;在G1水平下,N2处理株高快速生长期较N1处理增加了7.52%,而N1处理单株籽粒干物质量显著高于N2处理,高出9.13%;Person相关性分析表明,N2水平下,随着地下水埋深变化,0~40 cm土层硝态氮增量与产量显著负相关,R2为0.827~0.883。【结论】高氮与较浅地下水埋深组合促进了玉米营养生长,不利于玉米生殖生长和产量形成;低氮与浅地下水埋深组合有利于产量形成和减氮增效。  相似文献   
8.
粮仓围护结构保温隔热性能对储粮安全和粮仓能耗有重要影响。粮仓屋顶面积大,是粮仓围护结构接受太阳辐射最强的部位,外界热量主要通过屋顶传入粮仓,因此屋顶是粮仓围护结构保温隔热设计的最重要部位。双层通风屋顶、高反射率的屋面隔热涂料和保温隔热材料等节能技术近年来在粮仓屋顶设计中得到迅速发展和应用。考虑屋顶不同外表面太阳辐射反射率和自然通风对双层通风屋顶传热的影响,该文给出并试验验证了多层屋顶非稳态传热模型和双层通风屋顶传热模型,利用经过验证的屋顶传热模型进行屋顶能耗计算,采用经济性模型和全生命周期理论对长沙地区低温粮仓普通屋顶和双层通风屋顶最佳保温隔热层厚度进行分析,并对采用最佳保温隔热层厚度时的生命周期总投资、净收益及回收周期进行计算和比较分析。研究结果表明:屋顶外表面太阳辐射反射率对长沙地区低温粮仓屋顶最佳保温隔热层厚度和经济性有较大影响,双层通风屋顶可以减小屋顶最佳保温隔热层厚度,长沙地区低温粮仓可采用双层通风屋顶和高反射率的屋面隔热涂料降低粮仓能耗,减少因能源消耗而引起的环境污染问题。长沙地区低温粮仓普通屋顶挤塑聚苯乙烯和膨胀聚苯乙烯最佳保温隔热层厚度为0.106~0.183 m,生命周期内最大净现值为417~633.38元/m2,投资回收年限为2.39~2.96 a。低温粮仓屋顶最佳保温隔热层厚度随屋顶外表面太阳辐射反射率的增大而减小,双层通风屋顶可以减少屋顶保温隔热层投资回收年限。该屋顶最佳保温隔热层厚度确定方法对于指导低温粮仓屋顶保温隔热设计具有一定指导意义。  相似文献   
9.
不同温度下褐带卷蛾茧蜂实验种群生命表   总被引:2,自引:0,他引:2  
为了探索温度对褐带卷蛾茧蜂Bracon adoxophyesi发育和繁殖的影响,研究了该蜂在6种温度下的实验种群生命表。结果表明,褐带卷蛾茧蜂各虫态发育历期随温度升高而缩短,在36℃下产卵前期略高于32℃下的产卵前期,说明温度过高或者过低均不利于卵巢发育。随温度降低,其世代历期显著延长,说明低温会显著抑制该蜂发育。各虫态的发育速率与温度的关系符合Logistic模型。该寄生蜂产卵前期的发育起点温度高于其他阶段的发育起点温度。在24℃下单雌产卵量最高,为619.86粒,16℃和36℃下的产卵量最低,分别为139.60粒和154.43粒。在24、28和32℃时,其种群趋势指数分别为101.78、74.25和73.41,在36℃和16℃时,其种群趋势指数较低,说明温度过高或者过低均不利于其种群繁殖,且低温的影响大于高温。在24~32℃下,褐带卷蛾茧蜂的种群趋势指数较高,说明24~32℃是适宜该寄生蜂种群增长的温度范围。  相似文献   
10.
A study was undertaken to investigate the remedial effect of some soil amendments (farmyard manure (FYM), press mud compost (PMC), cereal straw (CS) at 5 t ha?1 and fresh cow dung slurry (FCD) @ 0.5 t ha?1) on dissipation kinetics of imidacloprid and sulfosulfuron under laboratory conditions. Incorporation of CS or FCD was found to be most effective in degrading both the pesticides at faster rates. Dissipation of both the pesticides could be well accounted by two component (1 + 1) first order kinetics. The computed values of parameters revealed that use of organic amendments increased the dissipated fraction of imidacloprid and sulfosulfuron. Incorporation of CS or FCD in soil maintained relatively higher dissipation rate constants for both faster and slower dissipation processes of pesticides in comparison to control. Hence, eco-friendly practices of CS or FCD incorporation as soil amendment in soil can play a vital role in preventing soil and water pollution.  相似文献   
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