Origin of major ions in monthly rainfall events at the Bamenda Highlands, North West Cameroon

Rainwater characteristics can reveal emissions from various anthropogenic and natural sources into the atmosphere. The physico-chemical characteristics of 44 monthly rainfall events （collected between January and December 2012） from 4 weather stations （Bamenda, Ndop plain, Ndawara and Kumbo） in the Bamenda Highlands （BH） were investigated. The purpose was to determine the sources of chemical species, their seasonal inputs and suitability of the rainwater for drinking. The mean pH of 5 indicated the slightly acidic nature of the rainwater. Average total dissolved solids （TDS） were low （6.7 mg/L）, characteristic of unpolluted atmospheric moisture/air. Major ion concentrations （mg/L） were low and in the order K＋ 〉 Ca2＋ 〉 Mg2~ 〉 Na＋ for cations and NO3 〉〉 HCO3 〉 SO] 〉 CI- 〉 PO3- 〉 F- for anions. The average rainwater in the area was mixed Ca-Mg-SO4-CI water type. The CI-/Na＋ ratio （1.04） was comparable to that of seawater （1.16）, an indication that N a＋ and CI originated mainly from marine （Atlantic Ocean） aerosols. High enrichments of Ca2＋, Mg2＋ and SO2- to Na＋ ratios relative to seawater ratios （constituting 44% of the total ions） demonstrated their terrigenous origin, mainly from Saharan and Sahelian arid dusts. The K＋/Na＋ ratio （2.24）, which was similar to tropical vegetation ash （2.38）, and NO3 was essentially from biomass burning. Light （〈 100 mm） pre-monsoon and post-monsoon convective rains were enriched in major ions than the heavy （〉 100 mm） monsoon rains, indicating a high contribution of major ions during the low convective showers. Despite the acidic nature, the TDS and major ion concentrations classified the rainwater as potable based on the WHO guidelines.     

Hunter Reporting of Catch per Unit Effort as a Monitoring Tool in a Bushmeat‐Harvesting System

Abstract: Growing threats to biodiversity in the tropics mean there is an increasing need for effective monitoring that balances scientific rigor with practical feasibility. Alternatives to professional techniques are emerging that are based on the involvement of local people. Such locally based monitoring methods may be more sustainable over time, allow greater spatial coverage and quicker management decisions, lead to increased compliance, and help encourage attitude shifts toward more environmentally sustainable practices. Nevertheless, few studies have yet compared the findings or cost‐effectiveness of locally based methods with professional techniques or investigated the power of locally based methods to detect trends. We gathered data on bushmeat‐hunting catch and effort using a professional technique (accompanying hunters on hunting trips) and two locally based methods in which data were collected by hunters (hunting camp diaries and weekly hunter interviews) in a 15‐month study in Equatorial Guinea. Catch and effort results from locally based methods were strongly correlated with those of the professional technique and the spatial locations of hunting trips reported in the locally based methods accurately reflected those recorded with the professional technique. We used power simulations of catch and effort data to show that locally based methods can reliably detect meaningful levels of change (20% change with 80% power at significance level [α]= 0.05) in multispecies catch per unit effort. Locally based methods were the most cost‐effective for monitoring. Hunter interviews collected catch and effort data on 240% more hunts per person hour and 94% more hunts per unit cost, spent on monitoring, than the professional technique. Our results suggest that locally based monitoring can offer an accurate, cost‐effective, and sufficiently powerful method to monitor the status of natural resources. To establish such a system in Equatorial Guinea, the current lack of national and local capacity for monitoring and management must be addressed.     

壁面粗糙度对旋风分离器内流场影响的数值模拟

利用计算流体动力学软件FLUENT6.2.16对壁面粗糙度不同的旋风分离器内流场进行了数值模拟,得到了切向速度、轴向速度、径向速度和静压力分布规律。旋风分离器内的切向速度随着壁面粗糙度的增大而明显减小;轴向速度没有明显的规律性变化,只在上部筒体涡核区轴向速度增加,削弱了涡核区滞留现象;在流场大部分区域径向速度随粗糙度的...     

Changing Drivers of Deforestation and New Opportunities for Conservation

Abstract: Over the past 50 years, human agents of deforestation have changed in ways that have potentially important implications for conservation efforts. We characterized these changes through a meta‐analysis of case studies of land‐cover change in the tropics. From the 1960s to the 1980s, small‐scale farmers, with state assistance, deforested large areas of tropical forest in Southeast Asia and Latin America. As globalization and urbanization increased during the 1980s, the agents of deforestation changed in two important parts of the tropical biome, the lowland rainforests in Brazil and Indonesia. Well‐capitalized ranchers, farmers, and loggers producing for consumers in distant markets became more prominent in these places and this globalization weakened the historically strong relationship between local population growth and forest cover. At the same time, forests have begun to regrow in some tropical uplands. These changing circumstances, we believe, suggest two new and differing strategies for biodiversity conservation in the tropics, one focused on conserving uplands and the other on promoting environmental stewardship in lowlands and other areas conducive to industrial agriculture.     

Canopy Seed Banks as Time Capsules of Biodiversity in Pasture-Remnant Tree Crowns

Abstract: Tropical pastures present multiple barriers to tree regeneration and restoration. Relict trees serve as “regeneration foci” because they ameliorate the soil microclimate and serve as safe spots for dispersers. Here, we describe another mechanism by which remnant trees may facilitate pasture regeneration: the presence of seed banks in the canopy soil that accumulates from decomposing epiphytes within the crowns of mature remnant trees in tropical cloud forest pastures. We compared seed banks of canopy soils (histosols derived from fallen leaves, fruits, flower, and twigs of host trees and epiphytes, dead bryophytes, bark, detritus, dead animals, and microorganisms, and dust that accumulate on trunks and the upper surfaces of large branches) in pastures, canopy soils in primary forest trees, and soil on the forest floor in Monteverde, Costa Rica. There were 5211 epiphytic and terrestrial plant seeds in the three habitats. All habitats were dominated by seeds in a relatively small number of plant families, most of which were primarily woody, animal pollinated, and animal dispersed. The density of seeds on the forest floor was greater than seed density in either pasture‐canopy or forest‐canopy soils; the latter two did not differ. Eight species in 44 families and 61 genera from all of the habitats were tallied. There were 37 species in the pasture‐canopy soil, 33 in the forest‐canopy soil, and 57 on the forest floor. Eleven species were common to all habitats. The mean species richness in the pasture canopy was significantly higher than the forest canopy (F =83.38; p < 0.02). Nonmetric multidimensional scaling ordination revealed that the communities were distinct. Greenhouse experiments verified that many of these seeds were viable, with 29 taxa germinating (23 taxa in pruned mats [mimic of exposed conditions] and 16 taxa in control mats [intact conditions]) within 2 months of observation. Nearly half the species that germinated were characteristic of primary forests (primary forest samples, 19%; pasture samples, 29%). This supports the idea that canopy seed banks of pasture trees can function as time capsules by providing propagules that are removed in both space and time from the primary forest. Their presence may enhance the ability of pastures to regenerate more quickly, reinforcing the importance of trees in agricultural settings.     

Evaluating the Success of Conservation Actions in Safeguarding Tropical Forest Biodiversity

Abstract: We reviewed the evidence on the extent and efficacy of conservation of tropical forest biodiversity for each of the classes of conservation action defined by the new International Union for Conservation of Nature (IUCN) classification. Protected areas are the most tested conservation approach, and a number of studies show they are generally effective in slowing deforestation. There is some documentation of the extent of sustainable timber management in tropical forest, but little information on other landscape‐conservation tactics. The extent and effectiveness of ex situ species conservation is quite well known. Forty‐one tropical‐forest species now survive only in captivity. Other single‐species conservation actions are not as well documented. The potential of policy mechanisms, such as international conventions and provision of funds, to slow extinctions in tropical forests is considerable, but the effects of policy are difficult to measure. Finally, interventions to promote tropical conservation by supporting education and livelihoods, providing incentives, and furthering capacity building are all thought to be important, but their extent and effectiveness remain poorly known. For birds, the best studied taxon, the sum of such conservation actions has averted one‐fifth of the extinctions that would otherwise have occurred over the last century. Clearly, tropical forest conservation works, but more is needed, as is critical assessment of what works in what circumstances, if mass extinction is to be averted.     

旋风除尘器设计中压力降模型的研究

从理论上探讨了旋风除尘器压力降的成因及影响因素,构造了旋风除尘器压力降的数学模型,解决了旋风除尘器设计过程中压力降的计算问题,将所得模型与实际工业型旋风除尘器的数据进行了比较,结果吻合良好。模型对旋风除尘器的设计有较大的参考价值。     

旋流气浮除油装置预处理含油污水

在河南油田开展旋流气浮除油装置的现场试验,考察进水流量和曝气量对旋流气浮除油装置除油效果的影响。试验结果表明:在进水流量为1.8 m³/h、曝气量为0.5 L/min时,除油率最高达到96.03%;在不添加任何药剂的条件下,装置处理效果稳定;连续运行6 d内,进水含油量为174.57~1 193.15 mg/L时,出水含油量可以保持在137.38 mg/L以下,除油率为58.58%~94.53%。     

气旋活动对福岛核污染物扩散影响的模拟研究

基于拉格朗日粒子扩散模式FLEXPART-WRF,根据Stohl推导的日本福岛第一核电站核事故(下称福岛核事故)发生后40 d内的137Cs排放量数据,对核污染物在中尺度区域的扩散传输进行数值模拟研究,并选取近5年3次典型气旋个例(北方气旋、南方气旋和缓慢移动气旋)进行敏感性试验,以分析不同气旋系统对污染物扩散的影响. 结果表明:福岛核事故发生后,受中纬度西风带影响,核污染物主要向东部太平洋方向扩散;核事故发生后的5 d,受北方气旋和日本南部局地中尺度气旋2次气旋过程的影响,核污染物对日本本土部分地区影响较大,但影响时间不长. 典型气旋个例的敏感性模拟试验结果表明:北方气旋和南方气旋均可使核污染物对日本本土造成一定的影响,但由于气旋移动速度较快,影响日本岛的时间较短,沉降量也较小;当出现缓慢移动气旋影响日本和周边地区时,可致污染物影响日本岛的时间延长,并直接进入东亚大陆.      

The distribution,metabolism and toxicity of 14c-DDT in model aquarium tanks with fish and sediment simulating a tropical marine environment

Studies conducted on the distribution, fate and metabolism of DDT in a model ecosystem simulating a tropical marine environment of fish, Gobious nudiceps, Lethrinus harak, Gobious keinesis, Gobious nebulosis and white shrimp (Panaeus setiferus), show that DDT concentration in the water decreases rapidly within the first 24?h. Rapid accumulation of the pesticide in the biota also reaches a maximum level in 24?h before gradually declining. The bioaccumulation factors calculated for the fish species (G. keinesis) and white shrimp (P. Setiferus) were 270 and 351, respectively, after 24?h. There was a steady build up of DDT residues in the sediment during the first 24?h which continued to a maximum concentration of 6.66?ng/g in the seawater/fish/sediment ecosystem after 3 weeks and 5.27?ng/g in the seawater/shrimps/sediment ecosystem after 2.7 days. The depuration of the accumulated pesticide was slow with only 54% lost in G. nudiceps within 3 days of exposure in fresh sea water. By contrast, depuration was fast in the white shrimp, which lost 97% of the accumulated pesticide under the same conditions. DDT was found to be toxic to two of the fish species (G. nebulosis and L. harak) and to white shrimp, and the degree of toxicity was dependent on the particular species. The 24?h LC₅₀ at room temperature for the fish species G. nebulosis and white shrimp was found to be 0.011 and 0.116?mg/kg, respectively. These levels are comparable to the ones recorded for the temperate organisms. Degradation of DDT to its primary metabolites, DDE and DDD, was found in all the compartments of the ecosystem with DDE being the major metabolite in the fish, shrimps and sediment, while in seawater, DDD dominated as the major metabolite.