Soil water depletion under various leguminous cover crops in the derived savanna of West Africa

Leguminous cover crops have the potential of making cropping systems in the tropics sustainable if they would not deplete resources such as soil water and nutrients to the detriment of companion crops. Therefore, a study was carried out at Alabata, Ibadan, southwestern Nigeria, to evaluate the effects of leguminous cover crops on soil water suctions in 1993 and 1994 in order to assess the possibility of integrating them into the farming systems of the savanna zone of West Africa. In 1993, 13 leguminous cover crops (Aeschynomene histrix, Centrosema brasilianum, Centrosema pascuorum, Chamaecrista rotundifolia, Cajanus cajan, Crotalaria verrucosa, Crotalaria ochroleuca, Lablab purpureus, Mucuna pruriens, Psophocarpus palustris, Pseudovigna argentea, Pueraria phaseoloides and Stylosanthes hamata) were planted in a randomized complete block design with four replications. Maize and natural fallow (mainly Chromolaena odorata and Imperata cylindrica) were included as comparisons. Only six of the legumes (A. histrix, C. pascuorum, C. cajan, C. ochroleuca, M. pruriens, and P. phaseoloides) were included in the measurements in the 1994 new plots. Soil water suctions at various stages of legume growth were measured at daily or weekly intervals (depending on the frequency of rainfall events) using tensiometers installed at 0–15 and 15–30 cm soil depths. Soil water suctions exceeding 10 kPa (theoretical field capacity) were observed mainly between 6 and 12 weeks after planting (WAP), and by 20 WAP when cover crops had matured and rainfall frequency was very low. Soil water suctions were significantly related (r²>0.80) to dry matter between 8 and 10 WAP. The studied cover crops were classified in three groups which can be used as a guide for choosing the legumes in tropical farming systems. Soil water depletion was markedly influenced by growth characteristics of legumes and distribution of rainfall during the rainy season. Leguminous cover crops conserved soil water after their growth needs were satisfied.     

饮用水中致突变有机物的光化学氧化研究

以Ａｍｅｓ试验为指标，对城市自为水中致突变有机物的光分解和光催化氧化自理效果进行了研究对比，实验表明，在相同的光照强度下，固定膜光催化氧化对水中致突变物有良好的去除作用，效果优于直接光分解，在处理时间同为１ｈ的条件下，光催化氧化对ＴＡ９８菌株诱变指数的削减率为４７％，而光分解的削减率仅为３３％，对水样的有总有机炭，色谱图峰数和峰面积，及Ａｍｅｓ试验透变指数等３个指标的测定结果分析表明，Ａｍｅｓ试验     

城市建筑立体绿化建设初探

由于城市人稠地少环境污染严重，城市中的人们渴望回到大自然的怀抱，本文通过阐述城市立体绿化的必要性、绿化的方法等来说明城市建筑立体绿化已成为人们走向森林走向绿色的重要途径之一。     

公路建设项目环保投资核算研究

对公路建设项目环保投资的组成、机理和计量方法作了详细的论述，并以实例作了进一步说明。为建设项目的环境经济分析方法补充了一个新的内容，也为项目决策提供了更有利的支持。     

回注采出水深度除油复合配方的优选

胜利油田郝一站采出水在回注时油及悬浮物含量均不达标，采用正交实验对比了三种絮凝剂聚合铝、MAX-2、HLW003L的作用效果，确定最佳絮凝剂为MAX-2,50℃、pH 7．0时将其与反相除油剂FX复合后使用，可使处理后水中含油〈10mg／L，悬浮物〈5mg／L，能满足中低渗透油藏的注水水质指标。     

光催化氧化法去除水中有机氯化物的研究

以TiO_2为催化剂,研究了饮用水中常见的9种氯化有机物的光催化氧化、pH、复氧条件等对光催化氧化效果的影响及有关反应动力学问题。研究表明,光催化氧化法在饮用水深度处理领域。具有很好的应用前景。     

南岳森林群落生物多样性研究(Ⅱ)广济寺森林群落植物物种多样性测定

本文根据实地调查资料及其统计分析结果,选用了24个物种多样性指数公式,并采用重要值、株数或鲜重以及优势度或盖度等作为测度指标,对南岳广济寺森林群落植物物种多样性进行了研究。结果表明,南岳广济寺森林属落多样性较高,接近山地季雨林的水平;此外,不同测度指标对物种多样性指数计算值并无明显的规律性。     

南岳森林群落生物多样性研究(Ⅲ)广济寺森林群落植物物种相对多度分布格局

本文选用几何级数分布、分割线段、对数级数分布和对数正态分布等模型研究了南岳广济寺森林群落植物物种相对多度的分布格局。结果表明,对数级分布模型适于拟合南岳广济寺森林群落乔木层和灌木层物种相对多度的分布格局;分割线段中的序列一多度模型仅适合于乔木层;对数正态分布模型仅适合于草本层;几何级数分布模型完全适合于拟合任何层次。此外,α指数值亦显示出本群落接近山地季雨林的多样性水平。     

尿中1-羟基芘的同步荧光测定法

本文报告1-羟基芘的荧光光谱在碱性溶液中的红移现象,研究了在1mol/l NaOH溶液中的同步荧光光谱,得出最适△λ为35nm.以此为基础建立了尿中1-羟基芘的同步荧光测定法,回收率80%,精密度8.0%,检测下限0.05ng/ml.     

TiO2膜降解水中污染物的稳定性考察与再生方法研究

针对实际水处理中对催化剂性能的要求,以光催化降解苯酚溶液作为探针反应,考察了玻璃纤维网上负载的TiO2膜催化剂长期使用条件下的稳定性,研究了催化剂在自来水中使用失活后的再生方法.结果表明,经过50次使用之后,膜催化剂120 min反应对苯酚的降解率从100%下降至83%,总体上看,所制催化剂还是具有相当好的稳定性;在反应器中用蒸馏水浸泡配合光催化反应对TiO2膜催化剂进行原位再生是一种可行的再生途径.