直筒型导叶直流式三相旋流器排气管上部内流场的实验研究

使用五孔球探针对一种用于分离锅炉净化烟气中含尘液滴的直筒型导叶直流式三相旋流器排气管上部的气相流场进行了实验测定。得到了这一区域的速度和静压分布。发现了排气管上部筒体中心存在强烈的内旋流;外层气体不断汇入内旋流,内旋流呈轴向加速运动;绝大部分气体不经过排气管外环形空间下行直接由排气管排出。主体段切向速度为Rankine组合涡。     

65 t/h煤粉锅炉除尘脱硫系统技术改造

对某电厂65 t/h煤粉锅炉水膜除尘器进行了旋流板塔脱硫除尘一体化改造研究,使其在保持原有水膜除尘器特点和功能的情况下增加其脱硫功能,提高除尘效率.通过本改造工程设计实例,探讨了除尘脱硫装置的选择及影响除尘脱硫系统效率的参数.改造实际运行表明:改造方案是经济的,技术上是可行的,脱硫效率80%以上,除尘效果达99%以上.水膜旋流板除尘脱硫系统是一种高效率、改造简单、运行可靠的湿式除尘脱硫系统.     

Isotopic Composition as a Tool for Assessment of Origin and Dynamic of Organic Matter in Tropical Freshwater

The isotopic composition (¹³C and ¹⁵N) and C:N ratio of sediment and particulate were investigated to assess the origin and dynamic of the organic matter in two river basins located in the Parana State, Brazil. The main sources of organic matter, plants, litter and soil, were analyzed in the study. This study was carried out during the dry and wet seasons. Although organic matter contribution for the particulate material has been mixed, the main contribution in the two seasons for both rivers was autochthonous characterized by δ¹³C and C:N ratio values ranging from −31.0 to −21.8‰ and from 5.1 to 11.4, respectively. The soil with δ¹³C values ranging from −25.9 to −20.6‰, and C:N ratio from 10.2 to 15.8, was the main carbon source for the river sediment for the two tributaries in the wet and dry seasons. The sediment δ¹⁵N values for both the rivers in the wet season showed an ¹⁵N enrichment trend in most of studied sites when compared to the dry season values, suggesting major input of nutrients as dissolved organic nitrogen and sewage nitrate. In the dry season, ¹⁴N enriched compounds, could have been used by phytoplankton, causing ¹⁵N enrichment. The isotope and C:N ratio data clearly showed that the agricultural activity has been influencing the origin and dynamic of organic matter in the two rivers, with potential biochemical consequences for the lower basin of the major Tibagi river.     

Value of Small Patches in the Conservation of Plant-Species Diversity in Highly Fragmented Rainforest

Abstract:  We evaluated the importance of small (<5 ha) forest patches for the conservation of regional plant diversity in the tropical rainforest of Los Tuxtlas, Mexico. We analyzed the density of plant species (number of species per 0.1 ha) in 45 forest patches of different sizes (1–700 ha) in 3 landscapes with different deforestation levels (4, 11, and 24% forest cover). Most of the 364 species sampled (360 species, 99%) were native to the region, and only 4 (1%) were human-introduced species. Species density in the smallest patches was high and variable; the highest (84 species) and lowest (23 species) number of species were recorded in patches of up to 1.8 ha. Despite the small size of these patches, they contained diverse communities of native plants, including endangered and economically important species. The relationship between species density and area was significantly different among the landscapes, with a significant positive slope only in the landscape with the highest deforestation level. This indicates that species density in a patch of a given size may vary among landscapes that have different deforestation levels. Therefore, the conservation value of a patch depends on the total forest cover remaining in the landscape. Our findings revealed, however, that a great portion of regional plant diversity was located in very small forest patches (<5 ha), most of the species were restricted to only a few patches (41% of the species sampled were distributed in only 1–2 patches, and almost 70% were distributed in 5 patches) and each landscape conserved a unique plant assemblage. The conservation and restoration of small patches is therefore necessary to effectively preserve the plant diversity of this strongly deforested and unique Neotropical region.     

Water budget and the consequent duration of canopy carbon gain in a teak plantation in a dry tropical region: Analysis using a soil–plant–air continuum multilayer model

A soil–plant–air continuum multilayer model was used to numerically simulate canopy net assimilation (A_n), evapotranspiration (ET), and soil moisture in a deciduous teak plantation in a dry tropical climate of northern Thailand to examine the influence of soil drought on A_n. The timings of leaf flush and the end of the canopy duration period (CDP) were also investigated from the perspective of the temporal positive carbon gain. Two numerical experiments with different seasonal patterns of leaf area index (LAI) were carried out using above-canopy hydrometeorological data as input data. The first experiment involved seasonally varying LAI estimated based on time-series of radiative transmittance through the canopy, and the second experiment applied an annually constant LAI. The first simulation captured the measured seasonal changes in soil surface moisture; the simulated transpiration agreed with seasonal changes in heat pulse velocity, corresponding to the water use of individual trees, and the simulated A_n became slightly negative. However, in the second simulation, A_n became negative in the dry season because the decline in stomatal conductance due to severe soil drought limited the assimilation, and the simultaneous increase in leaf temperature increased dark respiration. Thus, these experiments revealed that the leaflessness in the dry season is reasonable for carbon gain and emphasized the unfavorable soil water status for carbon gain in the dry season. Examining the duration of positive A_n (DPA) in the second simulation showed that the start of the longest DPA (LDPA) in a year approached the timing of leaf flush in the teak plantation after the spring equinox. On the other hand, the end appeared earlier than that of all CDPs. This result is consistent with the sap flow stopping earlier than the complete leaf fall, implying that the carbon assimilation period ends before the completion of defoliation. The model sensitivity analysis in the second simulation suggests that a smaller LAI and slower maximum rate of carboxylation likely extend the LDPA because soil water from the surface to rooting depth is maintained longer at levels adequate for carbon gain by decreased canopy transpiration. The experiments also suggest that lower soil hydraulic conductivity and deeper rooting depth can postpone the end of the LDPA by increasing soil water retention and the soil water capacity, respectively.     

影响红沿河核电厂区热带气旋特征及最大强度估算

红沿河核电厂区位于我国北方海域的辽东湾东海岸,经常受到北上热带气旋的侵袭和影响。观测和统计表明,在辽宁登陆的热带气旋,强度能够达到台风,不容忽略。影响红沿河的热带气旋基本出现在7、8月份,以进入渤海后向西北移动和穿越山东半岛向北在辽东半岛登陆的两类热带气旋对红沿河区域影响最大,建国56年来最强的热带气旋在红沿河附近区域造成的最大风速达到25～33m/s,极大风速达40m/s以上。使用概率论方法和梯度风公式估算红沿河核电厂区可能最大热带气旋的强度参数,得到:百年一遇的可能最低气压估值为961 hPa,最大风速为35.4m/s,极大风速为46.0m/s;千年一遇的可能最低气压估值为939 hPa,最大风速为42.2m/s,极大风速为54.9m/s。     

Climate Change, Elevational Range Shifts, and Bird Extinctions

Abstract:  Limitations imposed on species ranges by the climatic, ecological, and physiological effects of elevation are important determinants of extinction risk. We modeled the effects of elevational limits on the extinction risk of landbirds, 87% of all bird species. Elevational limitation of range size explained 97% of the variation in the probability of being in a World Conservation Union category of extinction risk. Our model that combined elevational ranges, four Millennium Assessment habitat-loss scenarios, and an intermediate estimate of surface warming of 2.8° C, projected a best guess of 400–550 landbird extinctions, and that approximately 2150 additional species would be at risk of extinction by 2100. For Western Hemisphere landbirds, intermediate extinction estimates based on climate-induced changes in actual distributions ranged from 1.3% (1.1° C warming) to 30.0% (6.4° C warming) of these species. Worldwide, every degree of warming projected a nonlinear increase in bird extinctions of about 100–500 species. Only 21% of the species predicted to become extinct in our scenarios are currently considered threatened with extinction. Different habitat-loss and surface-warming scenarios predicted substantially different futures for landbird species. To improve the precision of climate-induced extinction estimates, there is an urgent need for high-resolution measurements of shifts in the elevational ranges of species. Given the accelerating influence of climate change on species distributions and conservation, using elevational limits in a tested, standardized, and robust manner can improve conservation assessments of terrestrial species and will help identify species that are most vulnerable to global climate change. Our climate-induced extinction estimates are broadly similar to those of bird species at risk from other factors, but these estimates largely involve different sets of species.     

Long-term impacts of land-use change on dynamics of tropical soil carbon and nitrogen pools

Land-use changes, especially the conversion of native forest vegetation to cropland and plantations in tropical region, can alter soil C and N pools and N availability for plant uptake. Deforestation, followed by shifting cultivation and establishment of rubber tree plantation, is a common land-use change in Xishuangbanna, southwest China. However the influence of this kind of land-use change on soil C and N dynamics in this region remains poorly understood, This study was conducted to assess the effects of land-use change on soil C and N pools. Soil samples were collected on five adjacent plots, which belong to three land-use types including secondary forest-an acuminate banana( Musa itinerans) secondary forest and a male bamboo( Dendrocalamus membranaceae) secondary forest, shifting cultivation, and rubber tree ( Hevea brasiliensis (H. B. K. ) Muell. Arg. ) plantation(one plot is 3-year-old, and another is 7-year-old). We measured soil bulk density (BD), pH value, moisture content and concentrations of soil organic carbon(SOC), total soil nitrogen(TSN), and inorganic N(NO3^- -N and NH4^ -N) at 0--3, 3--20, 20--40 and 40--60cm depths, and calculated C and N pools in 0--20, 20--40, 40--60, and 0--60 cm soil layers. Compared with the adjacent secondary forests, shifting cultivation and establishment of rubber tree plantations resulted in significant decline in concentrations and stocks of SOC and TSN in 0--20 and 0--60cm soil layers, and increase in pH and bulk density at 0--3, 3--20, and 20--40cm depths. Soil moisture content decreased only in 0--20cm surface soils in shifting cultivation and plantations. The dynamics of mineral N was much more complex, which had different trends among depths and ecosystems. Compared with the secondary forests, SOC stocks in 0--20cm surface soils in shifting cultivation and rubber tree plantations(3-year-old plantation and 7-year-old plantation) decreased by 34.0%, 33%, and 23% ; and TSN stocks decreased by 32.2%, 20.4%, and 20.4%, respectively,whereas the decreases of SOC and TSN stocks in 0--60cm soil layers were much less. The results indicated that C and N losses were mainly occurred in 0--20cm surface soil, followed by 20--40cm layer.     

The environmental fate of thymol,a novel botanical pesticide,in tropical agricultural soil and water

In this study, the environmental fate of thymol, including hydrolysis, aqueous photolysis, soil sorption and soil degradation, was studied under conditions that simulated the tropical agricultural environment. This study was undertaken to supply basic information for evaluating the environmental risks of applying this new botanical pesticide to tropical crop production. The results showed that the hydrolysis of thymol was pH-dependent and accelerated by acidic conditions and high temperatures. However, the hydrolysis rate was far lower than the aqueous photolysis rate, indicating that direct photolysis is an important dissipation pathway for thymol in water. The sorption of thymol by three tropical soils was consistently well described by the Freundlich model, and the sorption coefficients increased in the order sandy soil < loamy soil < clay soil, a characterization that depended on the organic carbon contents of the soil. The soil degradation rate of thymol decreased in the order sandy soil > loamy soil > clay soil, which has a negative correlation with the sorption of thymol in soils. We concluded that the degradation rates of thymol in tropical soil and water are fast: thymol in water is photodegraded (50%) by sunlight within 28 h, and the thymol in soils is degraded (50%) within 8.4 d. Therefore, the environmental risk to the surrounding soils and water of thymol application for tropical crop production is low.     

Aminocyclopyrachlor sorption-desorption and leaching from three Brazilian soils

This study aimed to evaluate the sorption-desorption and leaching of aminocyclopyrachlor from three Brazilian soils. The sorption-desorption of ¹⁴C-aminocyclopyrachlor was evaluated using the batch method and leaching was assessed in glass columns. The Freundlich model showed an adequate fit for the sorption-desorption of aminocyclopyrachlor. The Freundlich sorption coefficient [K_{f (sorption)}] ranged from 0.37 to 1.34 µmol ^(1–1/n) L^1/n kg^?1 and showed a significant positive correlation with the clay content of the soil, while the K_{f (desorption)} ranged from 3.62 to 5.36 µmol ^(1–1/n) L^1/n kg^?1. The K_{f (desorption)} values were higher than their respective K_{f (sorption)}, indicating that aminocyclopyrachlor sorption is reversible, and the fate of this herbicide in the environment can be affected by leaching. Aminocyclopyrachlor was detected at all depths (0?30 cm) in all the studied soils, where leaching was influenced by soil texture. The total herbicide leaching from the sandy clay and clay soils was <0.06%, whereas, ～3% leached from the loamy sand soil. The results suggest that aminocyclopyrachlor has a high potential of leaching, based on its low sorption and high desorption capacities. Therefore, this herbicide can easily contaminate underground water resources.