合成骨质瓷负载TiO2光催化性能的研究

采用合成骨炭为主要原料制备的多孔陶瓷,能将纳米TiO_2催化活性与陶瓷载体的吸附性有机结合在一起,制备具有催化活性并能循环使用的载体型光催化剂,可有效催化降解水中有机污染物。通过实验研究了镀膜层数、多孔陶瓷球直径、致孔剂质量分数、骨炭合成中CaHPO_4和CaCO_3的质量比值等因素对催化性能的影响。试验结果表明:陶瓷球直径为3 mm,镀膜层数为4层,致孔剂质量分数为4%,CaHPO_4和CaCO_3的质量比值为2.6时,催化剂具有较好的催化活性。     

降解胆固醇马红球菌F21-1的分离、鉴定及其特性研究

利用以胆固醇为唯一碳源的选择性培养基,从豚鹿粪便样品中分离出1株降解胆固醇良好的菌株。经生理生化鉴定和16S rDNA基因序列分析,该菌株为马红球菌(Rhodococcus equi)。该菌株降解胆固醇的最佳碳源为胆固醇,最佳氮源为蛋白胨、硝酸铵复合氮;最佳培养条件:温度为32℃,初始pH值为8.0,胆固醇质量浓度为1.50 g/L。在该培养条件下培养24 h,胆固醇的降解率可达到71.95%。     

赣南红壤崩岗侵蚀区生态退化及其修复研究

崩岗侵蚀是危害性极大的一种快速水土流失,不仅影响侵蚀区的经济发展,而且直接威胁南方红壤丘陵山区的生态安全.本文以赣南红壤崩岗区为研究区域,从生态退化和生态恢复的角度来分析崩岗侵蚀区生态系统,定量分析了赣南红壤崩岗所在区县生态退化现状和成因,并就崩岗区的生态恢复提出相应对策,为赣南红壤崩岗侵蚀区治理以及其他地区崩岗发生区...     

农产品中农药残留化学降解方法研究进展

农药的大量使用,对环境和农产品造成的污染不可忽视,农产品中的农药残留问题是食品安全领域的研究热点。在诸多降解农药残留的方法中,化学降解方法受到研究者更多的关注。综述了几种化学降解农产品农药残留的典型方法,包括臭氧降解、过氧化氢降解和光催化降解的最新研究进展。对于油菜素内酯降解法和电生功能水降解法这2种新型降解农产品农药残留的方法也进行了重点介绍。     

牧业制度变迁对草地退化的影响及其路径

草地是牧民基本的生计资产,也是中国北方的生态屏障。然而,严重的草地退化威胁着牧区可持续发展和生态安全。维持高度可变的、脆弱干旱环境中的自然资本是发展绿色经济的要求。本文梳理了20世纪80年代以来草原牧区的主要牧业制度变迁,分析其对草地退化的影响及其路径,以探讨在现行草地经营制度下如何在不减少草地自然资本的情况下发展畜牧业。研究揭示,牧业制度变迁通过"分畜到户-牲畜增加-公地悲剧"、"分草到户/草地确权-草地细碎化-围栏陷阱"以及"三权分置/草地租赁-不完善契约/产权不安全-草地过度利用"三条路径影响草地退化。"交互规模"理论解释了草地细碎化对草地退化的影响机制。本文利用面上调研资料、定点观测数据以及自然试验证据支持了以上假说。研究表明,采用适合地区特点的确权方式、规范草地租赁市场以及减轻草地细碎化从而提高"交互规模",可更好地平衡牧业生产中的"劳动力-草地-牲畜-生产性资产-水资源",促进牧业的可持续发展。     

基于CA-Markov和InVEST模型的土地 利用格局变化对生境的影响研究——以北京 浅山区为例

在城市扩张蔓延和由此引起的生境变化过程中，研 究生境随土地利用/覆被变化(Land Use/Cover Change， LUCC)的适应性时空演变及预测已成为生态学的核心内容。 浅山区作为山区与平原的过渡地带，是天然生态屏障和生态敏 感地区，评估土地利用变化所引起的生境质量时空变化对于 浅山生态规划意义重大。以北京市浅山区为例，基于1999、 2017年的Landsat TM/ETM+遥感数据进行ENVI解译，并 采用CA-Markov模型模拟北京浅山区2035年自然增长情景 下的景观格局发展趋势。后结合InVest模型，评价3个时间下 的生境质量和退化度，以及1999—2017、2017—2035年 时间段下的生境稀缺度。结果表明：1999—2017年，浅山 区的景观空间愈加趋于碎片化，农田和建设用地趋于向浅山内 部扩张，预测2017—2035年仍将沿袭这一趋势，但变化速 度有所减缓。     

Sustainable agricultural intensification practices and cost efficiency in smallholder maize farms: Evidence from Ethiopia

Sustainable agricultural intensification (SAI) practices have been promoted in developing countries to improve farm productivity and environmental services. However, it is still unclear whether use of a combination of SAI practices has a significant influence on the cost efficiency of smallholder farms. This study investigates whether the cost efficiency of smallholder maize producers in Ethiopia depends on use of input-augmenting and agronomic SAI practices. Stochastic cost frontier models that account for heterogeneity across farms are used for estimation. We find that the use of individual SAI practices increases cost while the combined use of the practices reduces it. The marginal effect on cost reduction is substantial when SAI practices are set at their sample maximum levels. Overall, the results demonstrate the benefit of using a combination of SAI practices in minimizing production cost while addressing the adverse effects of soil degradation and climate variability. To enhance food security, smallholder farm incomes and the sustainability of production in developing countries, policy programs should focus on promoting packages of input-augmenting and agronomic SAI practices.     

老府河水体中有机污染物降解规律研究

在实验室条件下,模拟老府河水质状况,通过静态模拟实验,研究老府河中有机污染物的降解规律,确定有机污染物的降解系数,为老府河水环境容量的计算提供必要的参数,为河流综合整治方案的提出提供依据。     

Conservation Practices and the Growth of US Cash Rent Leases

Over the past 20 years the ratio of cash rent to cropshare land leases across the US has more than doubled. We test different theories that might explain this, and conclude that the shift is mostly the result of revolutionary changes in cultivation practices. The switch from conventional to conservation tillage brought about by changes in herbicide technologies, genetically modified seeds, increased fuel costs, and knowledge of the benefits of soil micro‐organisms, has reduced a tenant‐farmer's ability to exploit a landowner's soil. This removes a major incentive to cropshare and makes cash renting more attractive. Using USDA field‐level data from across the US, we find strong support for this hypothesis, and some evidence that increased corporate structure also influences cash renting. Alternatively, we cannot find evidence that changes in risk, risk‐aversion or insurance coverage explain the growth in cash renting.     

Challenges facing China's unbalanced urbanization strategy

China has taken a “great leap forward” in urbanization, but the resulting unbalanced development strategy seems likely to lead to unsustainable socioeconomic development, including increasing income disparities, waste of resources, environmental degradation, damage to China's natural and cultural heritages, growing social turbulence, and consequences for the rest of the world. To solve these problems, China's government must adjust its economic strategy to balance rural and urban development and to seek more sustainable socioeconomic development.