Amelioration of a highly degraded tropical alfisol by planting I. Changes in soil physical and chemical properties 1989-91

This paper examines soil amelioration by planting 15 leguminous and graminaceous plant species, including herbaceous annuals, perennials and biennials, and woody perennials and biennials. Disturbed and undisturbed natural regrowth were planted with leguminous species, in some cases with fertilizer applied at planting (400 kg ha⁻¹ of 15:15:15 NPK). The studies were made on two highly degraded sites in southwestern Nigeria which had been subjected to intensive mechanized cropping for a period of 10 years. Changes in soil physical and chemical properties were monitored from 1989 to 1991. Acacia difficilis, Brachiaria lata and Mucuna utilis had the lowest survival rates by the following growing season. Soil fertility and compaction levels differed between sites. Planting had no effect on the latter. The decreases in compaction (i.e. macroporosity) between 0.00 and 0.10 m depth at both sites one month before and five and 17 months after planting were 43, 59 and 61 per cent, respectively were attributed to exclusion of heavy machinery from the sites. Large decreases in fertility occurred at both sites and were attributed to a combination of nutrient extraction and to leaching. Between fallow species, exchangeable Ca, pH and the cation-exchange capacity (CEC) were greater and total acids lower for herbaceous cover compared with woody perennials, and was attributed to a higher Ca demand by the latter. Highest and lowest values of Ca, CEC and pH occurred in plots where plant material was returned to the soil (i.e. by cutting or die-back) and in cropped plots, respectively. Natural regrowth was as effective or better than planted species in improving soil physical and chemical properties. Therefore the use of exotic plant species for ameliorating highly degraded alfisols is unnecessary. Amelioration of highly degraded alfisols may be best effected by allowing natural regrowth to occur while excluding all mechanized traffic from the site.     

土著B[a]P降解菌群的富集及最佳降解条件研究

为了获得能够降解苯并[a]芘(BaP)的微生物菌群,为生物修复多环芳烃污染的土壤提供菌种资源,本试验从长期石油污染的土壤中,富集了一个能够降解BaP的微生物菌群,并研究了其最佳降解条件,通过高通量测序研究了其群落结构。该菌群可以在15 d内将30 mg·L^-1的BaP降解33.34%。高通量测序的结果表明,该菌群主要由Bacillus、Zobellella、Gordonia和Rheinheimera组成,其中Bacillus是主要的降解菌。试验结果表明,该菌群的最佳降解条件为1%盐度,酵母浓度为80 mg·L^-1,pH值7.0。该菌群对芘、菲、荧蒽等多环芳烃也有一定的降解效果,其中荧蒽的降解效果最好,降解率达到99%。试验结果表明,该菌群在实际应用中具有很大的潜力。     

低温木质纤维素分解复合菌系PLC-8对玉米秸秆的分解特性

为提高东北寒区玉米秸秆的分解效率,突破低温的瓶颈,探讨了低温木质纤维素分解复合菌系PLC-8对玉米秸秆的分解效果及其微生物多样性.通过pH、玉米秸秆的减重、木质纤维素的含量、酶活性、有机酸含量等指标评价玉米秸秆的分解效果,采用变性凝胶电泳(DGGE)和高通量测序技术研究其微生物多样性.结果表明:pH先下降后回升至接近初...     

Screening of Feather Degrading Bacteria and Optimization of Fer-mentation Conditions from Poultry

The purpose of this experiment was to isolate and screen the microorganisms from the soil where chicken feathers were piled for a long time and identify them bi...     

市售氯硝柳胺在斑点叉尾组织中的残留消除规律研究

为了研究氯硝柳胺在斑点叉尾(Ictalurus punctalus)组织中的残留消除规律,在静水条件下经安全性试验确定安全浓度后,直接对水族箱泼洒25%氯硝柳胺乙醇胺盐(NES)粉剂后采集斑点叉尾皮肤、肌肉和水样。采用高效液相色谱-质谱联用法(HPLC-ESI/MS/MS)测定样品中氯硝柳胺的浓度,结果表明,静水条件下25%氯硝柳胺乙醇胺对斑点叉尾的安全浓度为0.113 mg/kg;养殖水环境中氯硝柳胺能快速消解,实验第2天即低于1μg/L,并呈无规律性持续较长时间;用药24 h内,氯硝柳胺在鱼体肌肉和鱼皮中具有较强的蓄积能力,但48 h后,其在鱼皮和肌肉中呈现快速消除至较低浓度,但后期消除缓慢,并会持续一定时间;氯硝柳胺(NIC)在斑点叉尾肌肉和鱼皮中的消除半衰期T1/2分别为10.66和9.24 d,显著大于在水体中的消除半衷期。     

养殖水体中高效氨氮降解菌的分离与鉴定

以(NH4)2SO4为惟一氮源的选择性培养基,从养鱼池水中分离筛选到1株高效氨氮降解菌X2。当NH4 -N初始质量浓度为50 mg/L时,该菌株在24 h内的氨氮降解率>95%,并具有硝酸还原和亚硝酸还原能力。初步鉴定该菌株为巨大芽孢杆菌(Bacillus megaterium)。     

Effects of shrimp pond water on phytoplankton: importance of salinity and trophic status of the receiving environment

Aquaculture generates a large load of effluents rich in organic matter and nutrients that may be introduced into the environment. This study aimed to assess in a microcosm experiment, the effect of shrimp pond water mixed with Patos Lagoon estuary water on phytoplankton chlorophyll a and primary production, simulating two salinities. Chlorophyll a, dissolved inorganic nutrients and primary production were measured in two experiments. In Harvest I, salinity of shrimp pond and environment water was similar, and chlorophyll a showed different trends over time, according to the amount of nitrogen available. In Harvest II, with different salinities and high nutrient concentrations in environment water, chlorophyll a levels showed a similar increasing trend over time in all mixtures. Net primary production showed differences among treatments in the first sampling in Harvest I, but not in the second, whereas no differences were observed among treatments in Harvest II. We conclude that shrimp pond effluent can lead to short‐term variations in chlorophyll a and primary production levels, with similar salinities. Salinity differences result in lower chlorophyll a and primary production values than expected according to the nutrient input. Differences in salinity can be an important management strategy to choose the best harvest period.     

Degradation and effect of hydrogen peroxide in small‐scale recirculation aquaculture system biofilters

From an environmental point of view, hydrogen peroxide (HP) has beneficial attributes compared with other disinfectants in terms of its ready degradation and neutral by‐products. The rapid degradation of HP can, however, cause difficulties with regard to safe and efficient water treatment when applied in different systems. In this study, we investigated the degradation kinetics of HP in biofilters from water recirculating aquaculture systems (RAS). The potential effect of HP on the nitrification process in the biofilters was also examined. Biofilter elements from two different pilot‐scale RAS were exposed to various HP treatments in batch experiments, and the HP concentration was found to follow an exponential decay. The biofilter ammonia and nitrite oxidation processes showed quick recuperation after exposure to a single dose of HP up to 30 mg L^?1. An average HP concentration of 10–13 mg L^?1 maintained over 3 h had a moderate inhibitory effect on the biofilter elements from one of the RAS with relatively high organic loading, while the nitrification was severely inhibited in the pilot‐scale biofilters from the other RAS with a relatively low organic loading. A pilot‐scale RAS, equipped with two biofilter units, both a moving‐bed (Biomedia) and a fixed‐bed (BIO‐BLOK^®) biofilter, was subjected to an average HP concentration of ～12 mg L^?1 for 3 h. The ammonium‐ and nitrite‐degrading efficiencies of both the Biomedia and the BIO‐BLOK^® filters were drastically reduced. The filters had not reverted to pre‐HP exposure efficiency after 24 h, suggesting a possible long‐term impact on the biofilters.     

滇池水环境退化与区域内物种多样性的丧失

本文论述了滇池草海的物种多样性指数由20世纪50年代的2.70(ShannonˉW iener Index)降到90年代的0.29;滇池外海在20世纪50年代末,湖水面积90%以上为海菜花群落、马来眼子菜群落等,70年代仅占20%弱,20世纪90年代末的水生植物覆盖率不及3%;分析了藻类的种群优势度向着蓝藻种群优势度不断增加的方向发展,浮游动物的多样性增加,大型底栖无脊椎动物物种结构趋向单一化,鱼类多样性指数由1957年的1.81降为1997年的0.11,滇池的物种多样性指数由20世纪60年代的1.08降到90年代的0.67,认为滇池水环境退化与物种多样性丧失呈双向恶化效应,物种多样性重建是滇池生态恢复的重要指标。