Manure and adoption of modern seeds in cereal‐based systems in West African drylands: linkages and (non)complementarities

Using a stepwise approach that combines several econometric methods, we assessed whether or not the adoption of modern seeds and the use of manure in cereal‐based systems are linked and, if so, what are the driving forces of the linkages between these two agricultural technologies under dry‐climate conditions in West Africa. We found complementary and substitutability linkages arising from jointness and endogeneity between the two technologies. Specifically, our findings reveal positive joint determination along with negative endogeneity between the two technologies indicating that, controlling for observable variables, both technologies are positively linked, but unobserved factors that affect one adoption decision are negatively correlated with the other. After controlling for jointness and endogeneity, we found significant complementarity linkages showing a significant positive effect of manure use on the adoption of modern seeds, which is also significantly and positively affected by the number of cash crops grown and remittances. The two technologies are reversely affected by schooling and the incidence of soil fertility problems within the farm, whereas the amount of healthy land has a positive effect on both. The study suggests that organic fertilizer can serve as an enabling factor for greater adoption of modern seeds, especially in less favourable climate areas, and strongly supports the argument behind the need to breed seeds suitable for the use of organic fertilizers. These findings provide avenues for re‐orientation of policies that promote the use of modern seeds in dryland areas in sub‐Saharan Africa, with a possibility of breeding and promoting them in packages with organic fertilizers to upscale their adoption.     

基于调查的中国秸秆露天焚烧污染物排放清单

基于2010年初农村能源消费情况的问卷调查,获得全国分省秸秆露天焚烧比例,在此基础上确定秸秆露天焚烧的活动水平,采用排放因子法建立中国秸秆露天焚烧的污染物排放清单. 结果表明,中国农村秸秆露天焚烧平均比例为20.8%. 2009年全国28个省区(不包括西藏自治区、天津市、上海市、港澳台地区,下同)秸秆露天焚烧的PM_2.5、BC、OC、SO₂、NO_x、CO、NMVOC、NH₃、CH₄和CO₂排放量分别138.1×104、6.4×104、41.1×104、8.7×104、41.8×104、594.6×104、94.4×104、8.0×104、44.2×104和14 355.4×104 t. 稻谷、玉米和小麦是露天焚烧的三大作物秸秆,其对污染物排放的贡献合计约为87%. 秸秆露天焚烧排放量最高的前3位分别为湖南省、河南省和安徽省, 秸秆露天焚烧比例分别43.1%、20.8%和39.7%. 污染排放的高值区主要集中在华北和华中地区. 95%置信区间下的不确定性分析结果显示,PM_2.5、BC、OC、SO₂、NO_x、CO和NMVOC排放的不确定性范围分别为-60%~83%、-78%~147%、-73%~135%、-48%~75%、-49%~78%、-91%~155%和-67%~94%. 2015年初对六省(湖南省、广东省、江苏省、河南省、黑龙江省和辽宁省)农村能源消费调查的结果显示,2014年江苏省、湖南省和广东省的秸秆露天焚烧比例较2009年均有下降,而辽宁省、黑龙江省和河南省则相对上升. 研究显示,秸秆禁烧政策已取得初步成效,建议国家有关部门进一步加大秸秆禁烧政策的推行力度,完善相关政策措施.      

Positively charged microporous ceramic membrane for the removal of Titan Yellow through electrostatic adsorption

To develop a depth filter based on the electrostatic adsorption principle, positively charged microporous ceramic membrane was prepared from a diatomaceous earth ceramic membrane.The internal surface of the highly porous ceramic membrane was coated with uniformly distributed electropositive nano-Y_2O_3 coating. The dye removal performance was evaluated through pressurized filtration tests using Titan Yellow aqueous solution. It showed that positively charged microporous ceramic membrane exhibited a flow rate of 421 L/(m~2·hr) under the trans-membrane pressure of 0.03 bar. Moreover it could effectively remove Titan Yellow with feed concentration of 10 mg/L between pH 3 to 8. The removal rate increased with the enhancement of the surface charge properties with a maximum rejection of 99.6%. This study provides a new and feasible method of removing organic dyes in wastewater. It is convinced that there will be a broad market for the application of charged ceramic membrane in the field of dye removal or recovery from industry wastewater.     

浊度与悬浮颗粒携带污染物之间的规律研究

以4种不同工艺系统为例,分别在反硝化产生浮泥(甲)及厌氧发酵产生浮泥(乙)两种条件下,研究了出水浊度与悬浮固体浓度(SS)以及浊度与悬浮颗粒携带污染物COD、TN及TP之间的相关性规律。结果表明:浊度与SS、COD、TN及TP之间存在显著的线性关系,在反硝化产生浮泥条件下,SS、COD、TN及TP随单位浊度(1 NTU)的增加分别增加2.737,3.134,0.265,0.063 mg/L,厌氧发酵产生浮泥条件下,各指标则分别增加2.656,3.130,0.187,0.057 mg/L。SS和COD增加量与泥龄呈相关。TN和TP增加量因不同工艺系统特性而异。在浊度大于3.71 NTU,且液相各指标与排放标准相差不大时,出水综合水质指标的提高可通过物理强化降低浊度实现。     

京津冀国家干线公路污染空间特征分析

以国家干线公路交通量信息和单车排放因子为基础,基于GIS的路网线性参考系统,采用动态分段技术和核密度分析方法,从路段、污染物和车型这3个层次对2014年京津冀国家干线公路交通污染排放强度的空间差异进行分析.结果表明,车流量、车型构成和路网布局是引起排放强度空间分布差异的主要因素,排放强度高的路段集中在路网密度大且公路使用率高的京津地区,中小客车和特大货车对污染物排放强度影响显著.因使用燃料和车型的不同,NO_x、PM_(10)和PM_(2.5)排放强度分布大体一致,HC、CO空间分布更为相似.此外,经济发展水平、产业结构特征也是重要影响因素.北京除特大货车和集装箱以外的其他车型排放强度均很高,天津货车和客车排放强度均较高,河北货车排放强度高于客车.     

乌鲁木齐城市群内部大气污染特征及趋势对比

为了更好地协调乌鲁木齐城市群内部环境、经济的可持续发展,采用2011—2013年乌鲁木齐市、阜康市、五家渠市、昌吉市、石河子市5个城市的API日数据、日气象数据、PM10、SO2、NO2日均浓度值,对比分析大气污染特征,首要污染物及其变化趋势,再结合经济因素、气象因素、城市群内部之间相互影响等讨论防止空气污染的措施。     

Organochlorine levels in viperine snake Natrix maura carcasses from the ebro delta (NE Spain): Sexual and size-related differences

Organochlorine compounds (PCBs, DDTs and HCB) in carcasses from a population of the Viperine Snake (Natrix maura) living in the Ebro Delta were analyzed. This is a wetland area on the Mediterranean coast where the natural ecosystem has been partially substituted by rice fields. High levels of pollutants (mainly DDTs and PCBs) have been detected in several species living in this area, due to the production of these compounds by a former industrial activity upstream as well as agricultural activity in the Delta. Organochlorines were analyzed in adult males and females, and in immature snakes. DDTs (mainly p,p′-DDE) were the most abundant pollutant present. The DDT/PCB ratio was higher than expected, which is consistent with the position of the Viperine Snake in the trophic web as well as the type of prey consumed. Immature snakes had more organochlorines than adults. However, the broad range of concentrations shown by immature snakes, suggested that part of the organochlorine load is transferred from gravid females to their eggs. In adults, organochlorine concentrations increased with carcass weight in both males and females. This increase was higher in males since females lost contaminants through fat investment during vitellogenesis. Seasonally, PCBs and DDTs levels increased in spring when snakes showed higher feeding activity, whereas higher levels of HCB were present at the end of summer, when the river input increased. Furthermore, HCB does not seem to biomagnify well across the trophic chain. Organochlorine concentrations in Viperine Snake carcasses were high since: 1) the dry tissue had less than 5% of fat, and 2) snakes were caught many years after the DDT ban, supporting the fact that cleaning of the ecosystem does not occur easily. These results indicate that snakes are adequate as indicators of the contamination in natural ecosystems but sex and body size of the samples should be taken into account for interpretation of results.     

Distribution of tritium in estuarine waters: the role of organic matter

Tritium is an important environmental radionuclide whose reactivity with ligands and solids in aquatic systems is assumed to be limited. We studied the fractionation and sorption of tritium (added as tritiated water) in river water and seawater, and found that its distribution appears to be influenced by its affinity for organic matter. Tritium rapidly equilibrates with dissolved organic ligands that are retained by a reverse-phase C18 column, and with suspended sediment particles. Significantly, a measurable fraction of sorbed tritium associates with proteinaceous material that is potentially available to sediment-feeding organisms. These characteristics have not been reported previously and cannot be accounted for solely by isotopic exchange with hydrogen. Nevertheless, they are in qualitative agreement with available measurements of tritium in estuarine and coastal waters where its principal discharge is as tritiated water. Further research into the estuarine biogeochemical behaviour of tritium is required and radiological distribution coefficients and concentration factors that are assumed for this radionuclide may require reconsideration.     

Microbial fuel cell (MFC) for bioelectricity generation from organic wastes

Microbial fuel cells (MFCs) have gained a lot of attention recently as a mode of converting organic matter into electricity. In this study, a compost-based microbial fuel cell that generates bioelectricity by biodegradation of organic matter is developed. Grass cuttings, along with leaf mold, rice bran, oil cake (from mustard plants) and chicken droppings (waste from chickens) were used as organic waste. The electric properties of the MFC under anaerobic fermentation condition were investigated along with the influence of different types of membranes, the mixing of fly ash, and different types of electrode materials. It is observed that the maximum voltage was increased by mixing fly ash. Cellophane showed the highest value of voltage (around 350 mV). Bamboo charcoal is good for anode material; however carbon fiber is better for the cathode material in terms of optimization of power generated. This developed MFC is a simple cell to generate electricity from organic waste.     

Uptake of Polycyclic Aromatic Hydrocarbons (PAHS) by Broad Leaves: Analysis of Kinetic Limitations

A kinetic model for the uptake ofpolycyclic aromatic hydrocarbons (PAHs) wasdeveloped from the anatomical structure of broadleaves. The model, which is supported by fielddata, includes the uptake from two pathways: outercuticle pathway and stomatal pathway, and withgrowth rate incorporated as a dilution term. Allthe parameters for the calculation of total masstransfer coefficient, k_OL, were estimated fromthe conductance of water vapor diffusion throughleaves. The results indicate that the stomatalpathway is a dominant pathway for dry gaseousdeposition of POPs on leaves and the uptake fromouter cuticle pathway can be neglected for the PAHsof molar volumes larger than phenanthrene becauseof the rate limitation in outer layer cuticle. Model sensitivity analyses demonstrates that withinthe range of environmental conditions and normalleaf structure, the surface area in stomata has themost significant effect on the uptake rate. If thestomatal pathway is closed, the kinetics of uptakeare so slow that accumulation appears independentof compound lipophilicity or molecular size. Ineither case, the leaf growth rate has little effecton the predicted accumulation