塔河油田原油甾藿烷系列化合物地球化学再认识

生物标志化合物是油气油源、成熟度、运移等领域研究中的一项得力工具。运用生物标志物色谱质谱技术，对比研究了塔河油田各油区原油生物标志化合物中甾、藿烷系列化合物特征。研究表明，塔河油田为一由晚期成熟高、轻微改造的原油与早期成熟度低、遭受较强降解原油混合而成的复合油藏，该油藏各区原油C27—C29甾烷同系物以及C27—C29重排甾烷特征反映出该区不同成熟度原油来自同一母源，原油Ts/(Tm+Ts)、重排甾烷/规则甾烷和ββ/(ββ+αα) C29比值关系立体图指示出原油的充注方向，印证了“塔河地区的油气主要来自于南部的满加尔坳陷”这一论点。     

Financial efficiency of major soil and water conservation measures in West Usambara highlands, Tanzania

Soil and Water Conservation (SWC) measures are needed to control soil erosion and sustain agricultural production on steep slopes of West Usambara mountains. However, the adoption by farmers of the recommended soil and water conservation measures is low and soil erosion continues to be a problem. It could well be that the reason for the low adoption is that the costs to invest in soil and water conservation are higher than the eventual benefits. This research assessed the costs and benefits of bench terraces, grass strips and fanya juu, which are major SWC measures. Financial Cost Benefit Analysis (FCBA) was undertaken for farmers with low, moderate and high opportunity costs of labour at different slopes and soil types. The results show that labour is the major cost item in implementing SWC measures and is higher with bench terraces than with fanya juu and grass strips. The results also show that the costs of establishing the three SWC measures exceed the returns in the initial 2 years. However, in the long term, the three SWC measures are profitable to farmers with low to medium opportunity costs of labour on gentle to moderate slopes. It was also found that SWC measures are not financially attractive to most farmers with off-farm activities and other sources of income. It is concluded that high investment costs and initial negative returns are the major hindrances to the adoption of SWC measures by smallholder farmers in West Usambara mountains. Options to overcome the initial investment costs include the gradual investment in SWC measures, introduction of high value crops and small credit facilities. The promotion of dairy cattle under zero grazing system can also increase the adoption of SWC measures because of the high benefits from grasses used to stabilise SWC measures.     

Factors influencing adoption and continued use of long-term soil and water conservation measures in five developing countries

Many regions in the world are affected by land degradation. Successive development projects have promoted a variety of soil and water conservation (SWC) measures to prevent further land degradation. However, these measures have seldom been adopted on a large scale. This paper deals with the adoption process of investments in SWC measures, and with the factors influencing adoption and continued use of these measures. After a theoretical introduction, whereby three phases in the adoption process are distinguished, it presents and compares some results of independent empirical research projects on adoption of SWC measures in five developing countries. Some general conclusions are drawn from these diverse research results.