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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.
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   
3.
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   
4.
5.
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   
6.
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   
7.
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   
8.
为明确山苍子精油防治植物疫病的应用前景,在室内离体条件下测定其对辣椒疫霉Phytophthora capsici菌丝生长、孢子囊形成与萌发、游动孢子萌发的毒力,观测经山苍子精油处理后菌丝生长量及形态结构、细胞膜通透性和可溶性蛋白含量的变化;采用离体叶片法和灌根法分别测定山苍子精油对辣椒疫病的预防效果和治疗效果。结果表明,山苍子精油对辣椒疫霉的菌丝生长、孢子囊形成与萌发以及游动孢子萌发的有效中浓度EC_(50)分别为161.49、29.68、231.80、90.68 mg/L;EC_(50)和EC_(75)的山苍子精油处理显著降低了辣椒疫霉菌丝的鲜重和干重,抑制率均在49.71%以上,亦可显著降低菌丝中可溶性蛋白含量,抑制率分别为10.77%和18.47%;用山苍子精油处理菌丝后,其顶端生长受到抑制,分枝明显增多、间距缩短;细胞膜通透性增大。1 000 mg/L山苍子精油对辣椒疫病的预防效果达63.33%(离体叶片法),2 000 mg/L精油对辣椒疫病的预防效果和治疗效果分别达80.00%和68.00%(灌根法,7 d),均显著高于对照药剂嘧菌酯。表明山苍子精油是辣椒疫霉的有效抑制剂,在辣椒疫病综合治理中具有较大的应用潜力。  相似文献   
9.
European nase (Chondrostoma nasus) is a specialist riverine fish, characterised by a complex life cycle making it vulnerable to habitat degradation. Recent findings indicate that, analogously to salmonids, the interstitial zone quality may pose a serious bottleneck for successful recruitment of this species. In this study, nase eggs were exposed to different substrate qualities. First, standardised substrate mixtures with differing fine sediment additions were used. Second, we tested different homogenous gravel fractions for their influence on egg development and emergence success. In both setups, substrate composition significantly affected emergence success, timing of emergence and larvae size at emergence. In the substrate mixtures, emergence was most successful in substratum with no fine sediment addition (98%) and decreased to 55% in substratum with 20% fine sediment addition. Emergence was most successful in the coarsest fraction (93%) and decreased to 47% in the finest fraction. Over all treatments, the time between hatching and emergence from substrate differed by up to 156 degree days, thereby indicating that free embryos of nase use the shelter of the interstitial zone for early ontogeny. These results suggest that a loose and porous stream bed can positively contribute to the development success of eggs and larvae and thereby potentially improve the recruitment of nase populations. It is thus important to consider the substrate and interstitial conditions in the conservation and restoration management of this rheophilic cyprinid.  相似文献   
10.
Charybdis feriatus is a highly prized crab in the local and international markets of East Asian countries. In local markets, crabs are sold live, iced, or refrigerated at 2°C – 4°C. The present study was carried out to determine the shelf life of whole crab stored at 4°C for 192 h using a set of biochemical, microbiological, and sensorial parameters. Biochemical indicators such as the total volatile base nitrogen (TVB-N) and trimethylamine nitrogen (TMA-N) increased significantly during storage and within an acceptable limit up to 144 h. Regarding the biogenic amines, cadaverine and spermidine increased significantly (p < 0.05) during the storage period. Among them, cadaverine could be proposed as a useful spoilage indicator for this crab species. The mesophilic and psychotropic bacterial count exceeded the limit of acceptance after 144 h of storage. Sensory attributes were gradually diminished with the storage time. Sensory scores were found to correlate well with both mesophiles and psychrotrophs. Based on the results of this study, the meat quality of Charybdis feriatus can be maintained up to 144 h when properly stored at a temperature of 4°C ± 1°C.  相似文献   
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