水泥灰三相泡沫的形成机理与稳定性试验研究

针对高硫矿石容易发生氧化自燃的危险,通常的灌浆、注砂、注惰气和喷洒阻化剂等技术还存在一些不足,提出一种以水泥灰为基料的三相泡沫来预防硫化矿石自燃的新技术。该技术是将水泥灰和水按一定的比例混合,同时加入一定比例的发泡剂和稳泡剂后,经物理机械方式发泡形成,集固、液、气三相材料的防灭火性能与一体。理论分析了水泥灰三相泡沫的形成与衰变机理,并通过正交试验,对三相泡沫的发泡倍数与半衰期进行研究,最后采用单因素实验,定量分析灰水质量比,发泡剂和稳泡剂浓度对三相泡沫稳定性能的影响,得到最佳泡沫配方。结果表明:当灰水质量比为1:5,发泡剂浓度为5g/L,稳泡剂浓度为8g/L时,制得的三相泡沫发泡倍数达到6倍,半衰期达到6h以上。     

基于油耗调查的2010年天津市农业机械排放研究

通过问卷调查,采用基于燃油消耗量的方法估算出天津市2010年农业机械氮氧化物(NOx)和颗粒物(PM)的总排放量.2010年天津市农业机械总保有量为57.5万台,其中种植业机械最大约占52.5%;总动力为588万kW,运输机械占比最大为47.3%.估算出2010年天津市农业机械总油耗(主要为柴油)为6.7万t,其中运输机械耗油量为4.5万t.再根据燃油消耗量估算了天津2010年农业机械污染物排放量,NOx和PM年排放量分别为3470t和303t.     

不同类型区农用地整治对农田生产能力的影响

以产能提高为核心的农用地整治已上升为国家层面的重要战略之一。通过建立农用地整治影响下的农田生产能力估算模型,定量评价湖北省内平原、丘陵及山地3种不同类型区农用地整治对农田生产能力的影响,结果表明:①农用地整治后,山地型整治区农田生产能力提高168.91%,丘陵型整治区提高57.78%,平原型整治区提高38.32%;②平原型整治区基础设施要素提高最大,为78.62%;丘陵型整治区水资源要素提高最大,为75%;山地型整治区基础设施要素提高最大,为199.12%;③总体上,基础设施要素对农田生产能力的贡献率都最大。建议国家农用地整治在政策上适当增加对山地型和丘陵型整治区的重视,项目区应合理配套农村居民点整治工程,并尽量避免生态损失。     

Oxidative stress in the freshwater cyprinid crucian carp (Carassius carassius L.) upon chronic exposure to endosulfan

Oxidative stress and antioxidant responses of crucian carp, upon chronic exposure to endosulfan, were evaluated in vivo. The lethal concentration (LC_50–96?h) was 70 μg L^?1; on its basis, the fish were exposed to endosulfan at 20, 35, and 50 μg L^?1 and autopsy was done on days 1, 2, 3, 4, 7, 14, 21, 28, and 35. Lipid peroxidation was induced in a concentration-dependent manner, being highest at 50 μg L^?1 (3/4 LC_{50–96 h}, sub-lethal concentration-I, SL-I) on day 4 (720% versus control), followed in its extent (490%) at 30 μg L^?1 (1/2 LC_{50–96 h}, sub-lethal concentration-II, SL-II) on day 7 and lowest (260%) at 10 μg L^?1 (1/4 LC_{50–96 h}, sub-lethal concentration-III, SL-III) on day 14. Glutathione showed a concentration- and time-dependent elevation in the initial phase, with highest level on day 4 (180%) at SL-I, but showed significant reduction in all test concentrations from day 21 of post-exposure. Superoxide dismutase was decreased significantly throughout the study, with highest reduction (63%) on day 4 at SL-I; catalase increased in all test concentrations up to day 14 but showed a significant decrease from the day 28 of post-exposure. The potential role of these parameters as indicators of pesticide pollution in aquatic systems is discussed.     

Are indigenous forest reserves sustainable? An analysis of present and future land-use trends in Bosawas,Nicaragua

SUMMARY

In recent years, indigenous tenure over forest lands has emerged as a means to conserve forests while recognizing indigenous rights. There is concern, however, that indigenous reserves may not be an appropriate policy tool for sustained forest conservation. Our research examined how recognition of indigenous common-property rights has controlled agricultural expansion and conserved forests in Bosawas Biosphere Reserve, Nicaragua. We used satellite imagery with empirical data gathered in the field on land-use institutions, population pressures, and land-use practices to compare whether indigenous communities under territorial management or public management are better able to (1) control the ‘fast threat’ of frontier expansion and (2) address the long-term ecological threats posed by indigenous land-use practices and institutional changes in the region. Our findings are that indigenous residents who share common-property rights over their territories are better able to control agricultural expansion than are indigenous residents living on public lands. With respect to the long-term threats to the region, a series of simulations of possible land-use pressures demonstrate that the enforcement of territorial boundaries and further development of indigenous forest management rules will prove crucial in determining land-use capacity and deforestation over the next 50 years.     

Empirical analysis on the influence of the Shaanxi fruit industry on regional food security

As part of its development policy to relieve rural poverty in west China, the Chinese government has introduced measures such as agricultural tax exemptions, agricultural subsidies, and scientific, technological and restructuring improvements to agriculture. Following these actions, farmers’ incomes have increased greatly and the economy in poor areas of west China has seen rapid improvements. However, agricultural restructuring, infrastructure construction and ecological restoration projects have reduced the area of land under arable farming, restricting opportunities for increasing total grain yield. Regional food security is therefore threatened and an imbalance between economic development and food security is created. Shaanxi is a representative province in west China where agricultural restructuring has resulted in large areas of arable land being converted into orchards that produce higher economic returns. This study randomly surveyed 1430 farm households in three counties in the apple-producing region of Shaanxi Province (Luochuan, Changwu and Baishui). The standard of living and household income of farmers in the fruit production areas were higher than in grain-producing areas, thus discouraging grain production. Land under agriculture in the counties studied comprised 59% orchards and 39% arable, with 2% under other uses. Per capita, 204.3 kg of grain was produced, 51% of that required for self-sufficiency. Other staple foods produced amounted to only 13.9% of that needed for self-sufficiency. As a result, nearly half of the grain needed by the community was purchased from outside, resulting in very poor regional food security. Clearly, fruit production in this region seriously affects regional food security. Coordination of relationships between rural economic development and regional food security is key for sustainable development of the regional agriculture and economy of west China.     

加拿大最佳管理措施流域评价项目评述

可持续农业的目的是在保持良好环境质量的同时获得较高的农业生产率。最佳管理措施(BMPs)在世界范围内已得到广泛应用,以减少农业污染物对水环境的影响。自2004年以来,加拿大农业部实施了最佳管理措施流域评价(WEBs)项目,在全国各地选择了有代表性的9个小流域,对BMPs的环境和经济效益进行评价。笔者对过去几年来WEBs项目的进展、研究方法及主要成果进行简要的回顾,并对在中国开展类似项目的必要性和启示进行了探讨。     

三江平原农田源头排水沟渠截留排水中氮素动态

通过小尺度野外原位试验,研究排水沟渠水体、底泥和植物中氮含量的变化规律.结果表明,随水体停留时间增加,沟渠对水体氮素的净化能力增强,认为停留8d左右较适宜.沟渠对NH4-N的截留率大于TN和NO3--N.渠水停留11d时,4条试验沟渠[氮浓度高、磷浓度低(NHPL),氮浓度高、磷浓度高(NHPH),氮浓度低、磷浓度低(NLPL),氮浓度低、磷浓度高(NLPH)]对NH4+-N的截留率均达100％,对NO3--N的截留率分别为84.63％、84.35％、75.67％和76.14％,对TN的截留率分别为88.02％、89.89％、90.88％和88.53％.试验结束时沟渠表层(0～15 cm)底泥氮含量降低,植物氮累积量远大于进水TN总量,说明植物生长同时吸收了水体、土壤和底泥中的氮,建议在秋季适时收割植物,以避免植物分解导致二次污染.     

南疆近60a来寒潮气候特征及其对农业生产的影响

寒潮是我区主要灾害性天气之一,南疆植被稀少,温差大,强冷空气南下,容易形成寒潮。论文利用南疆5地(州)1949-2008年间的寒潮发生频次、 持续时间及其造成的受灾农田面积、 死亡牲畜、 经济损失数据资料,对南疆寒潮空间分布、 年际变化、 季节变化、 形成原因及其对农业生产影响进行深入分析。分析得出:①近60 a来,南疆寒潮发生频次山区多于平原、 北部多于南部,而寒潮过程降温幅度天山南麓绿洲带大于北部山区;对地(州)而言,巴州发生频次最多,受灾最严重,阿克苏次于巴州,克州与和田寒潮频次与受灾最少,喀什居中。②近60 a来,寒潮发生频次年际变化幅度较大,总体上呈现略有减少趋势,特别是1999年来频次明显减少;每年9月至翌年5月是寒潮活动期,以5月和4月发生频次最高,极端最大降温以4-5月和9-10月居多。③在气候变暖背景下,虽寒潮频次总体上呈略有减少趋势,但由于4-5月寒潮较多,而且小麦返青拔节,棉花出苗蕾铃,果树生芽开花,其抗寒能力下降,遇到明显降温,就会发生冻害,加上绿洲种植面积扩大,社会经济发展,承载体单位面积的受灾成本提高,使南疆寒潮低温冻害灾害呈显著增多趋势。     

哈尼梯田地区农户粮食作物种植结构及驱动力分析

哈尼稻作梯田系统作为全球重要农业文化遗产（GIAHS）,具有极高的生态、经济、文化价值。近年来,以粮食产量增长为导向的农耕技术和作物品种单一化趋势,给哈尼梯田地区带来了严重的生态和食品安全问题。论文以农户生产行为作为切入点,从主要粮食作物的经济效益、耕地资源特征、村落发展类型、农户的家庭特征与资源禀赋进行实证研究,分析了哈尼梯田地区农户粮食作物种植结构现状及驱动因素。结果表明：1）调查涉及的41.23 hm²有效耕地中,按种植总面积排序,杂交稻、玉米、水果类作物位居前三。2）本地传统粮食作物--梯田红米,种植总面积和户均种植面积远小于经济效益较高的杂交稻和兼有饲料用途的玉米。同时,农户倾向于将其种植在质量较差、海拔较高的耕地上。3）作物的经济效益和耕地海拔及质量对替代性作物（如杂交稻和红米）的种植选择影响较大;个体农户层面上,农户特征与资源禀赋在不同程度上对不同作物的种植选择产生影响。