Agroforestry as alternative land-use production systems for the tropics

The science of agroforestry has progressed significantly during the past three decades. This article describes and documents various prominent traditional agroforestry systems. In-depth research on interactive processes of some agrisilvicultural systems have been undertaken and quantified. It has been found that the presence of woody species can enhance nutrient cycling, and can improve soil productivity, soil conservation and soil biotic andfaunal activities. In simultaneous systems however, their presence can also cause competition with the associated food crops. Most agroforestry systems constitute ecologically and bio-physically sustainable land use systems. Some are highly sustainable and economically viable, in particular the highly complex and specialized types, such as the damar and rubber agroforests in Indonesia. Agroforestry systems have potential uses in stabilization of sloping lands and buffer zones around forest reserves, for recovering degraded lands, and for improving the productivity of the bush fallow system. Despite rapid progress in biophysical research, field application of the science of agroforestry is still minimal. This article examines the possibilities of exploring the multiple contributions of trees to food security, rural income generation, diversity of products and ecosystem conservation within sustainable agroforestry contexts. Research efforts in the new millennium need to focus more on practical research and also on socio-economic and policy factors that can enhance beneficial application of the science in the near future to smallholder farmers in the tropics.     

荆江分洪区1998年洪水转移调查分析

对荆江分洪区１９９８年洪水期间安全转移的调查表明,叶然有分洪预案,但实际转移时仍出现了相当程度的拥挤与混乱。完善分洪转移的组织与管理,已成为分洪区居民１９９８年转移后关注的焦点,分洪区居民普遍表现出对分洪洪水情不甚了解,通过各种方式开展有关洪水的宣伟,提高区内居民的防洪意识,是荆江分洪区未来防洪减灾的重点工作之一,由于是国家为保护更重要的地区而主动分洪。对分洪区历分洪蒙受的损失给预某种形式的补偿已     

依靠科学进步,促进防灾减灾

以科学技术工作为主线 ,系统地总结了陕西省减灾协会 10年来 ,从事自然灾害综合预测、防灾减灾科学研究、学术交流和科普宣传教育等方面的做法、经验和所取得的初步成效 ,以及如何建设好减灾科技社团的体会     

Tissue retention and metabolism of 2,3,4,3′,4′-pentachlorobiphenyl in mink and mouse

2,3,4,3′,4′-Pentachlorobiphenyl was retained as the unmetabolized parent compound in liver and fat from mouse and mink. In contrast, in mouse plasma - 4-hydroxy-2,3,5,3′,4′-pentachlorobiphenyl - was present in concentrations 15 times higher than that of the parent chlorobiphenyl. In mink plasma the parent compound and the 4-hydroxylated metabolite were present in similar concentrations. Faeces was the major excretion pathway in both animals. Both the mouse and the mink excreted mainly the parent compound accompanied by trace amounts of hydroxylated metabolites but the mink also excreted significant amounts of hydrophilic metabolites, that gave hydroxylated products after acidic hydrolysis. Five hydroxylated metabolites, 4-hydroxy-2,3,5,3′,4′-pentachlorobiphenyl, 4-hydroxy-3,5,2′,3′,4′-pentachlorobiphenyl, 2-hydroxy-3,4,2′,3′,4′-pentachlorobiphenyl, 5-hydroxy-3,4,2′,3′,4′-pentachlorobiphenyl and 5-hydroxy-2,3,4,3′,4′-pentachlorobiphenyl, were identified in excreta of mink and mouse.     

Butyltins in sediments from Boston Harbor, USA

Sediments from 12 sites in Boston Harbor were assayed for butyltins. The highest levels of tributyltin (TBT) were found at sites where commercial or pleasure boats were moored, where ocean going vessels dock, and at a former shipyard. Little or no TBT was detected at sites which do not have a history of significant boating activity. Dibutyltin and monobutyltin were also detected at most sites, indicating that degradation of TBT occurs at these sites.     

The role of soil and active ingredient properties in degradation of pesticides: A preliminary assessment

Pesticide disappearance from soils was observed in laboratory studies in which leaching and runoff were impeded, and volatilisation and degradation evaluated. Advection by volatilisation was negligible for the less volatile chemicals, and significant for the more volatile (Trifluralin and Heptachlor). Basic statistics applied to degradation DT50 data of 14 active ingredients in four different soils showed that the properties of pesticides play a major role in determining their degradability.     

水和废水中多氯联苯(PCBs)的测定方法及进展

本文引用了七十余篇近几年国内外的有关著文,对水和废水中的多氯联苯(PCBs)的测定方法进行了评述,全面系统地介绍了水样的采集、富集、净化和分析测定等操作程序,着重于样品的前处理和气相色谱分析,并提出了这一领域今后的发展趋势。