土地利用转型背景下的乡村景观格局演变响应——基于草堂溪流域的样带分析

研究山区土地利用转型背景下乡村景观格局演变与转型,对山区现代化农业可持续发展和景观格局优化具有一定的指导意义。以三峡库区草堂溪流域为研究对象,利用ArcGIS 10.2和Fragstats 4.2软件,采用样带梯度分析结合景观格局分析方法,基于地形和社会经济因素,分别在河谷地区和山地丘陵地区设置5条样带,对研究区2000—2018年不同方向样带上景观格局梯度演变和驱动机制进行分析比较。结果表明：（1）景观类型整体变化幅度大致可分为较稳定型、逐年递减型和波动递增型,且景观转型的重点主要体现在耕地收缩、果园扩张和林地恢复性增长。（2）2000—2018年,研究区河谷地区的景观类型逐渐多样化,土地利用集聚,呈现空间集约化;而山地丘陵地区景观类型逐渐单一化,林地恢复。整体上由生产型景观格局转型成生态经济型、生态调节型为主的景观格局。（3）社会经济发展和政府政策导向等因素导致研究区内土地利用发生转型,在土地利用转型背景下的乡村景观格局也发生了相应的转变。研究结果可为类似山区土地资源的合理利用、生态治理和乡村振兴提供借鉴价值。     

Transformation and migration of phosphorus in excess sludge reduction pretreatment by alkaline ferrate oxidation combined with anaerobic digestion

Recently,more and more attention has been paid to the strong oxidation ability of newly prepared potassium ferrate(NAPF) in sludge reduction process,but less attention has been paid to the change of phosphorus in this process.The feasibility of phosphorus migration and transformation during excess sludge reduction pretre atment using NAPF pre-oxidation combined with anaerobic digestion was investigated.After 70 mg/g suspended solids NAPF pretreatment and 16 days anaerobic digestion,the solid-phase volatile suspended solids decreased by 44.2%,and much organic matter had been released into the liquid-phase and then degraded during digestion by indigenous microorganisms.As the sludge pre-oxidation process was performed,solid-phase organic phosphorus and chemically combined phosphorus also released into the liquid-phase as PO_4~(3-),peaking at 100 mg/L.During anaerobic digestion,the Fe~(3+)in the liquid-phase was gradually reduced to Fe~(2+),and then formed Fe~(2+)-PO_4~(3-) compound crystals and re-migrated to the solid-phase.The concentration of PO_4~(3-) decreased to 17.08± 1.1 mg/L in the liquid-phase after anaerobic digestion.Finally,the phosphorus in the Fe~(2+)-PO_4~(3-) compound accounts for 80% of the total phosphorus in the solid-phase.A large number of vivianite crystals in sludge were observed.Therefore,this technology not only effectively reduces sludge,but also increases the proportion of PO_4~(3-)in the sludge in the form of Vivianite.     

Drought can offset potential water use efficiency of forest ecosystems from rising atmospheric CO2

Increasing atmospheric CO₂ is both leading to climate change and providing a potential fertilisation effect on plant growth. However, southern Australia has also experienced a significant decline in rainfall over the last 30 years, resulting in increased vegetative water stress. To better understand the dynamics and responses of Australian forest ecosystems to drought and elevated CO₂, the magnitude and trend in water use efficiency (WUE) of forests, and their response to drought and elevated CO₂ from 1982 to 2014 were analysed, using the best available model estimates constrained by observed fluxes from simulations with fixed and time-varying CO₂. The ratio of gross primary productivity (GPP) to evapotranspiration (ET) (WUEe) was used to identify the ecosystem scale WUE, while the ratio of GPP to transpiration (Tr) (WUEc) was used as a measure of canopy scale WUE. WUE increased significantly in northern Australia (p < 0.001) for woody savannas (WSA), whereas there was a slight decline in the WUE of evergreen broadleaf forests (EBF) in the southeast and southwest of Australia. The lag of WUEc to drought was consistent and relatively short and stable between biomes (≤3 months), but notably varied for WUEe, with a long time-lag (mean of 10 months). The dissimilar responses of WUEe and WUEc to climate change for different geographical areas result from the different proportion of Tr in ET. CO₂ fertilization and a wetter climate enhanced WUE in northern Australia, whereas drought offset the CO₂ fertilization effect in southern Australia.     

Linkage between water soluble organic matter and bacterial community in sediment from a shallow, eutrophic lake, Lake Chaohu, China

Lacustrine sediment played important roles in migration and transformation of its water soluble organic matter (WSOM), and the source and composition of WSOM would affect water trophic status and the fate of pollutants. However, we know little about the pathway of WSOM transformation and its driving bacterial communities in lacustrine sediment. In the present study, we investigated the spatial distribution patterns of sediment WSOM and its fluorescent fractions across Lake Chaohu using fluorescence spectroscopy, and explored WSOM compositional structure through our proposed calculated ratios. In addition, we also analyzed sediment bacterial community using Illumina sequencing technology, and probed the possible pathway of sediment WSOM transformation under the mediate of indigenous bacteria. Our results showed that the inflowing rivers affected the spatial distribution patterns of WSOM and its five fractions (including tyrosine-, tryptophan-, fulvic acid-, humic acid-like substances and soluble microbial productions), and sediment WSOM originated from fresh algae detritus or bacterial sources. In parallel, we also found that Proteobacteria (mainly γ-Proteobacteria and δ-Proteobacteria), Firmicutes (mainly Bacilli), Chloroflexi, Acidobacteria, Planctomycetes and Actinobacteria dominate sediment bacterial community. Furthermore, these dominant bacteria triggered sediment WSOM transformation, specifically, the humic acid-like substances could be converted into fulvic acid-like substances, and further degraded into aromatic protein-like and SMP substances. In addition, our proposed ratios (P-L:H-L, Ar-P:SMP and H-L ratio), as supplementary tool, were effective to reveal WSOM composition structure. These results figured out possible pathway of WSOM transformation, and revealed its microbial mechanism in lacustrine sediment.     

我国农村生活污水污染排放及环境治理效率

当前我国农村生活污水治理形势依然严峻.利用第二次全国污染源普查成果,分析了我国2017年农村生活污水排放情况,并基于熵值法和数据包络分析（DEA）模型从技术效率、经济效率两个角度对治理效率进行评价.结果表明:①我国农村生活污水中COD排放量约占生活源排放总量的50.8%,NH₃-N、TN和TP排放量分别占生活源排放总量的35.0%、30.5%、38.7%,污水及污染物排放去向以直排入水体、直排入农田和其他途径为主,三者占80%以上.②我国沿海用水量较大地区的水冲式厕所比例超过80%,且农村生活污水有效治理比例仅为11.0%,导致我国农村生活污水治理的技术效率仅为8.6%,且区域差异较大,其中有23个省份小于10%,技术效率普遍较低.③相比浙江省、上海市、山西省、内蒙古自治区、青海省、西藏自治区等地（经济效率均为1）,我国其他省份农村生活污水治理的经济效率有很大改善空间.农村生活污水中人均COD排放强度、人均NH₃-N排放强度与农村居民人均可支配收入之间的环境库兹涅茨曲线（EKC）均呈一定的倒“U”型关系,人均TN排放强度、人均TP排放强度与农村居民人均可支配收入之间的EKC则均呈“N”型特征,有波动上升趋势.研究显示,我国农村生活污水治理效率存在较大的提升空间,与城镇相比,农村的环境保护基础设施建设还比较落后,应以源头减量、分类处理、循环利用为导向,加强统筹规划,梯次推进,加快提升我国农村污水治理水平.      

部分亚硝化-厌氧氨氧化处理磁混凝生活污水

以磁混凝预处理后的生活污水为处理对象,构建了部分亚硝化-厌氧氨氧化分体式反应器,通过曝气调控与生物强化促进部分亚硝化反应的稳定进行,并耦合厌氧氨氧化反应进行深度脱氮.近100d的运行结果表明,在生物强化和间歇曝气的控制条件下,亚硝酸盐积累率达到了89.93%;提高亚硝化反应器中曝气阶段溶解氧浓度（从0.6~0.8mg/L升高至1.0~1.2mg/L）有利于氨氮与总氮去除.该系统最高能够去除95.45%的氨氮和86.28%的总氮,实现了稳定、高效脱氮;磁混凝预处理后的生活污水在亚硝化反应器中,间歇曝气条件促进了残留的溶解性有机物为反硝化提供碳源,COD总去除率达到64.65%~74.42%,并且亚硝化反应器出水与系统最终出水的有机物组分相似,主要为难降解有机物.     

基于配额指标重要性视角的中国碳排放配额再分配

提出用与碳排放“同步变化程度”来衡量配额指标重要性的思想,对中国各省份碳排放配额进行再分配.首先在公平和效率原则基础上选取碳排放的影响因素作为分配指标,其次采用灰色关联分析法分别测算出各地区各指标与碳排放量的同步变动程度,以得到各地区各指标在配额分配中的比重.最后测算出我国29个省区2020~2030年的碳排放配额与排放空间.结果表明,人口基数及经济发展指标对各地碳排放有较强的同步变动关联性,因此应该被赋予更高的权重;配额最多的地区包括广东、北京、江苏、山东、上海,最少的地区则包括宁夏、贵州、青海、吉林、新疆.盈余分析发现,北京地区的碳排放空间有较多盈余;浙江等5个省区已达较饱和状态;山东等4个省区则处于较严重的溢出状态,在未来10年内需承担较重的减排压力.     

Assessment of sunflower germplasm for phytoremediation of lead-polluted soil and production of seed oil and seed meal for human and animal consumption

Phytoremediation is a valuable technology for mitigating soil contamination in agricultural lands, but phytoremediation without economic revenue is unfeasible for land owners and farmers. The use of crops with high biomass and bioenergy for phytoremediation is a unique strategy to derive supplementary benefits along with remediation activities. Sunflower (Helianthus annuus L.) is a high-biomass crop that can be used for the phytoremediation of polluted lands with additional advantages (biomass and oil). In this study, 40 germplasms of sunflower were screened in field conditions for phytoremediation with the possibility for oil and meal production. The study was carried out to the physiological maturity stage. All studied germplasms mopped up substantial concentrations of Pb, with maximum amounts in shoot?>?root?>?seed respectively. The phytoextraction efficiency of the germplasm was assessed in terms of the Transfer factor (TF), Metal removal efficiency (MRE) and Metal extraction ratio (MER). Among all assessed criteria, GP.8585 was found to be most appropriate for restoring moderately Pb-contaminated soil accompanied with providing high biomass and high yield production. The Pb content in the oil of GP.8585 was below the Food safety standard of China, with 59.5% oleic acid and 32.1% linoleic acid. Moreover, amino acid analysis in meal illustrated significant differences among essential and non-essential amino acids. Glutamic acid was found in the highest percentage (22.4%), whereas cysteine in the lowest percentage (1.3%). Therefore, its efficient phytoextraction ability and good quality edible oil and meal production makes GP.8585 the most convenient sunflower germplasm for phytoremediation of moderately Pb-contaminated soil, with fringe benefits to farmers and landowners.     

施用牛粪对As污染稻田水稻As吸收的影响

为探究牛粪施肥对污染稻田水稻As吸收的影响,采用盆栽培养试验研究了施加牛粪对土壤Fe和As的活性、水稻根表铁膜形成及籽粒As含量的影响。实验所用受高As矿山废水污染土壤(As:92. 3 mg/kg)施加10%～30%的牛粪,土壤溶解性有机碳含量增加8. 41～24. 5 mg/kg,土壤孔隙水pH提高0. 14～0. 59,土壤氧化还原电位降低93. 5～174 m V,与背景土(As:18. 1 mg/kg)变化趋势相同;施用牛粪还会活化土壤中的Fe和As,污染土壤Fe(II)、AO-Fe和HCl-As含量分别增加13. 5%～149%、35. 9%～90. 9%和70. 1%～181%,分别为背景土壤的0. 86～1. 66倍、1. 17～2. 15倍、4. 29～8. 91倍;施加牛粪能促进根表铁膜的形成,拔节期污染土壤和背景土壤水稻根表Fe分别是其对照的1. 56～1. 96倍和2. 09～3. 07倍,根表吸附As含量是其对照的3. 04～5. 18、3. 82～4. 08倍,根表附着Fe随牛粪的增加先增加后降低,至成熟期污染土壤水稻根表吸附Fe和As分别是背景土壤的1. 35～2. 91和8. 45～16. 6倍,根表As和Fe的物质量比为污染区(3. 49×10~(-3)～3. 55×10~(-3))背景区(4. 41×10~(-4)～6. 17×10~(-4));背景土壤施加牛粪后水稻籽粒As含量降低,最大降低36. 4%,而污染土壤水稻籽粒As含量增加,最大增加127%。牛粪对土壤As、Fe的活性及根表铁膜的形成都具有重要影响,会提高污染稻田籽粒中As的含量,含As矿山废水污染稻田应当谨慎施用牛粪。     

旋翼结冰对直升机悬停性能影响的数值分析

目的 研究旋翼结冰对直升机悬停性能的影响。方法 选取具有充分试验数据的UH-1H直升机为算例,采用Fluent计算旋翼流场,将收敛后的流场文件导入Fensap-ICE中进行水滴撞击和结冰计算,得到结冰后的旋翼外形后,再采用Fluent计算旋翼流场,从而分析旋翼结冰对直升机悬停性能的影响。结果 通过改变结冰条件,分析了不同结冰条件对直升机悬停效率的影响,表明旋翼结冰会显著降低直升机的悬停效率,且随着结冰时间、水滴平均直径(MVD)和液态水含量(LWC)的增大,直升机的悬停效率逐渐降低。结论 不同结冰条件对直升机悬停效率下降趋势的影响不同,随着结冰时间的增大,悬停效率基本呈线性下降,而随着MVD和LWC的增大,悬停效率的下降趋势逐渐变缓,下降幅度逐渐减小。