生态工程背景下黄土高原植被变化时空特征及其驱动力

[目的]分析1990—2015年黄土高原植被的时空演变规律,并从气候变化和人类活动两个方面分析该地区植被变化的驱动力,以期为生态环境保护相关政策的制定和区域可持续发展提供理论依据。[方法]基于GIMMS NDVI和MODIS NDVI建立长时间序列NDVI数据集,采用线性趋势分析、多元线性回归和改进的人类残差等分析方法,以NDVI为指标,辅助土地利用数据,对黄土高原地区1990—2015年期间植被时空变化特征及其影响因素进行了定量分析。[结果]①在1990到2015年期间,黄土高原地区植被的NDVI总体表现为上升趋势,且变化趋势较明显的分为两个时期,其中2000年以后NDVI上升速率较快;②2000年以后,黄土高原植被NDVI迅速上升,上升区域面积达到总面积的91.90%,其中NDVI显著上升面积比为65.78%;③黄土高原地区植被面积总体表现为增加,且主要来自于耕地的转入;④人类活动促使的植被恢复区域占黄土高原总面积的21.74%,主要分布在内蒙古的东部和北部、甘肃和宁夏的南部,以及陕西和山西的中部地区。[结论]随着退耕还林还草政策的实施,黄土高原地区植被面积持续增加,且植被生长状况持续变好,黄土高原植被恢复的原因主要是气候和人类共同影响,其中人类影响的程度较大。     

10 kV浇注支柱式电流互感器电场有限元分析及结构优化设计

浇注支柱式电流互感器是电力系统中用于测量、控制和保护的重要设备.以LZZBJ9-10B型浇注支柱式电流互感器为例,通过ANSOFT Maxwell软件对互感器内部进行三维电场仿真分析.研究结果表明,互感器内部电场集中分布区域在一次绕组的4个端角和二次绕组的左右两端,对一、二次绕组电场进行局部二维分析,得到绕组电场强度最大值和最小值的分布点的位置,提出通过改变绝缘挡板的厚度避免主绝缘材料因电场分布不均匀而发生局部放电的有效措施,并运用ANSOFT Maxwell软件进行电场分析得到验证.研究结果为10 kV浇注支柱式电流互感器的结构优化设计和安全运行提供了依据.     

重庆市霾天气下大气能见度与颗粒污染物的关系

利用重庆沙坪坝站2013-2015年逐时环境气象资料,对大气能见度与相对湿度和PM_(2.5)之间的关系进行分析研究,结果表明:重庆市区霾都是在相对湿度大于65%的条件下产生的,重度霾时相对湿度达到86%左右,重庆粗细粒子质量比PM_(2.5)/PM_(10)在霾发生时大于65%,重度霾情况下粗细粒子质量比达82%,说明伴随着细粒子比例的增加, PM_(2.5)细颗粒对能见度的影响作用明显,重庆霾进一步加重, PM_(2.5)相对PM_(10)来说对霾影响作用更大.不同相对湿度条件下,能见度与PM_(2.5)颗粒物关系不同,在70%≤RH80%湿度条件下PM_(2.5)与大气能见度相关性最大,非霾天气下PM_(2.5)阈值仅为30μg/m~3.相对湿度在40%～90%之间,随着相对湿度的增加,颗粒物逐渐吸湿增长,其产生消光效应逐渐加剧,导致能见度不断降低,在PM_(2.5)质量浓度大于85μg/m~3情形下,不论相对湿度大小,都极易形成霾天气,而PM_(2.5)质量浓度小于85μg/m~3情形下,如果相对湿度较高,随着湿度变化颗粒物吸湿增长,也极易形成霾天气.     

高压/酶解/闪式高速提取对金华火腿骨呈味物质的影响

以金华火腿骨为研究对象,研究不同提取方法对其呈味物质释放的影响。通过感官评价及可溶性糖、有机酸、5′-核苷酸和游离氨基酸的测定分析不同处理组间样品的差异,同时采用偏最小二乘回归法（partial least squares regression,PLSR）对提取物感官和呈味物质间进行相关性分析。感官评价发现,高压蒸煮的样品的鲜味、咸味和可接受度最高,其协同滋味的综合评分最佳;呈味物质分析发现,原液中所有呈味物质含量都最低,高压-复配酶解处理的样品中可溶性糖总量最高,高达132.68 mg/100 g;经过酶解处理样品有机酸含量显著增加（P<0.05）,达到3 733.32 mg/100 g;样品经不同处理后,5′-核苷酸含量呈现显著性增加（P<0.05）,总含量最高的是经过高压蒸煮处理的样品,质量分数高达1.24 mg/100 g,是原液和其他处理组样品的2.38～12.4倍;与样品原液相比,游离氨基酸总量都显著增加（P<0.05）,高压蒸煮处理的样品中含量最高,总质量分数为642.44 mg/100 g。借助偏最小二乘回归方法对样品的感官属性及呈味成分进行相关性分析,发现样品间具有显著性差异（P<0.05）,不同的处理方式所释放的呈味物质分布规律显著不同,高压蒸煮的样品与咸味和鲜味具有显著相关性（P<0.05）;酶解处理的样品与酸味和甜味有较强相关性,其他组样品与感官与呈味属性相关性不强。结论：不同处理方式的金华火腿骨具有不同的风味,其风味特征与多种物质有关,该研究结果为火腿骨的深度开发提供了理论指导,提高金华火腿骨的附加值。     

早稻秸秆还田对次年早稻土微生物及酶的影响

为了探明翻耕条件下秸秆还田量对土壤生物学特性的影响,制定合理的秸秆还田量,减少环境的污染和保障农业的可持续性发展,通过定位试验进行了0%、33%、67%、100%早稻秸秆覆盖翻耕对次年早稻土壤微生物数量、微生物活度、稻草腐解酶活性、氨化作用强度及硝化作用强度的影响研究.结果表明:在次年早稻生长期内,土壤好气性和嫌气性细菌数量呈现前期迅速提高,中后期快速下降的趋势,真菌和放线菌数量呈现前期迅速下降,中后期缓慢上升的趋势.土壤微生物活度则呈前期上升,中期达到最高点后开始下降,后期又有所回升的趋势.土壤木聚糖酶和纤维素酶活性以分蘖盛期为界点,表现出前期增加、后期下降的特点;土壤脲酶呈现先缓慢下降,再迅速下降,最后再缓慢上升的趋势;而土壤蛋白酶和过氧化氢酶的活性在早稻各个生育期的变化不大.土壤氨化作用强度的变化特点是先下降后上升,在齐穗期达到高峰后又迅速下降;而土壤硝化作用强度则呈现前期快速下降、中期缓慢增加、后期再急剧下降的趋势.土壤微生物数量及活性分析评价发现,在双季稻栽培时,配合水稻专用复混肥一次性施用,以早稻秸秆2 500～5 000 kg·hm-2翻耕还田较为适宜.     

Influence of daily collection and culture medium recycling on the growth and beta-carotene yield of Dunaliella salina

The halophilic green alga Dunaliella salina has the potential to be cultivated for beta-carotene-rich biomass, however, open-air systems need to be further improved in order to become more competitive and more economical, rather than leave the major beta-carotene consuming market derived from artificially synthesis. A set of daily collection ratios was designed and scaled up with the aim to harvest cell biomass and beta-carotene from D. salina at logarithmic phase; the yields were comparable to the normal culture without daily removal of culture. Daily collection of 1/7.5 volume of algal culture was found to be appropriate to keep the balance between the cell biomass and beta-carotene accumulation. Light intensity as one of the important factors would affect both cell growth and beta-carotene content synchronously. Further, the method of recycling 1/7.5 volume of culture after removal of algae cells was developed in order to decrease input cost for the effective production of beta-carotene, and both the resulting yields of the cell biomass and beta-carotene gained an advantage over those from the normal D. salina culture.     

Antioxidant effects of phlorotannins isolated from Ishige okamurae in free radical mediated oxidative systems

Three phlorotannins, including phloroglucinol, diphlorethohydroxycarmalol, and 6,6'-bieckol, were isolated from Ishige okamurae by column chromatography. The structures of the phlorotannins were determined on the basis of spectroscopic analysis, including NMR and mass spectrometry (MS) techniques. Antioxidant effects of phlorotannins were measured by direct free radical scavenging activities using the electron spin resonance spectrometry (ESR) technique and cellular systems in vitro. The results indicated that diphlorethohydroxycarmalol and 6,6'-bieckol showed potential radical scavenging activities against the 2,2-diphenyl-1-picrylhydrazyl (DPPH), hydroxyl, alkyl, and superoxide radicals. Moreover, no cytotoxicities of the phlorotannins on human fetal lung fibroblasts cell line (MRC-5), mouse macrophages cell line (RAW264.7), and human leukemic cell line (HL-60) were observed. In addition, diphlorethohydroxycarmalol and 6,6'-bieckol significantly reduced the intracellular reactive oxygen species level assessed by 2',7'-dichlorofluorescein diacetate (DCFH-DA) assay in RAW264.7 cells, and myeloperoxide (MPO) activity in HL-60 cells and radical-mediated oxidation of cell membrane proteins in RAW264.7 cells were dose-dependently inhibited in the presence of diphlorethohydroxycarmalol and 6,6'-bieckol. In conclusion, these results suggested that phlorotannins could be used as novel functional foodstuffs or antioxidants in the cosmetic and drug industries.     

江西红壤地区农田生态系统大气氮沉降通量的研究

2004年12月至2005年11月在江西鹰潭中国科学院红壤生态实验站进行了为期1a的大气氮沉降的外场观测试验。本文对观测得到的数据资料进行分析,定量给出了农田生态系统大气氮化物浓度和氮沉降通量。结果表明,鹰潭地区农田下垫面大气中NH3、NOx和ON(有机氮)的平均浓度分别为24.6、3.54、7.2μgm-3。气溶胶中铵盐、硝酸盐、ON的平均浓度分别为4.16、4.64、0.92μgm-3。降水中NH4+离子、NO3-离子、ON的平均浓度分别为0.89、0.73、0.26mgL-1。全年大气氮沉降总量为N6.26gm-2,其中干沉降为N3.19gm-2,占总沉降量的51%;湿沉降为N3.07gm-2,占总沉降量的49%。无机氮沉降为N5.47gm-2,占总沉降量的87.4%;有机氮沉降为N0.79gm-2,占总沉降量的12.6%。与草地、森林、湖泊等其他下垫面相比,江西红壤地区农田下垫面大气氮沉降量相对较大,对农田生态系统氮素平衡将产生重要影响。     

长期施肥黑土微生物区系及功能多样性的变化

Black soil （Mollisol） is one of the main soil types in northeastern China. Biolog and polymerase chain reactiondenaturing gradient gel electrophoresis （PCR-DGGE） methods were used to examine the influence of various fertilizer combinations on the structure and function of the bacterial community in a black soil collected from Harbin, Heilongjiang Province. Biolog results showed that substrate richness and catabolic diversity of the soil bacterial community were the greatest in the chemical fertilizer and chemical fertilizer＋manure treatments. The metabolic ability of the bacterial community in the manure treatment was similar to the control. DGGE fingerprinting indicated similarity in the distribution of most 16S rDNA bands among all treatments, suggesting that microorganisms with those bands were stable and not influenced by fertilization. However, chemical fertilizer increased the diversity of soil bacterial community. Principal com- ponent analysis of Biolog and DGGE data revealed that the structure and function of the bacterial community were similar in the control and manure treatments, suggesting that the application of manure increased the soil microbial population, but had no effect on the bacterial community structure. Catabolic function was similar in the chemical fertilizer and chemical fertilizer＋manure treatments, but the composition structure of the soil microbes differed between them. The use of chemical fertilizers could result in a decline in the catabolic activity of fast-growing or eutrophic bacteria.