Effects of precipitation and temperature on rain-use efficiency of China's forests北大核心CSCD

Water plays an important role in the growth of plants. It is important to investigate the responses of different ecosystems to precipitation patterns, especially in terms of global changes involving extreme precipitation or drought. However, little is known about the rain-use efficiency (RUE) in China's forests and the correlation of the RUE with the precipitation and other environmental factors. Furthermore, it is unclear whether differences in the forest types or functional groups result in divergent RUE patterns. To investigate the RUE in China's forests, we analyzed the data from 1 266 sampling plots from 17 forest types. The results indicated that: (1) the mean RUE of China's forests is 1.21 g m-2 mm-1. The RUE and precipitation are negatively correlated in all the 17 forest types; (2) the average RUE of broadleaved forests (mainly angiosperms) is higher than that of coniferous forests (mainly gymnosperms), and the angiosperms are more adaptable to changes in the precipitation than gymnosperms; (3) the average RUE of deciduous forests is higher than that of the evergreen forests. The RUE of deciduous forests declines with increasing precipitation to a threshold value. However, the RUE of evergreen forests are unaffected by changes in the precipitation; and (4) the latitude and mean annual temperature are the major factors constraining the RUE under comprehensive environmental factors. We conclude that the mean RUE declines with increasing precipitation to a threshold value, and that the temperature is a crucial factor for RUE. © 2018 Science Press. All rights reserved.     

Enhancement of photocatalytic performance in sonochemical synthesized ZnO–rGO nanocomposites owing to effective interfacial interaction

Nanocomposites composed of two or more components with desirable performance have attracted tremendous attention, mainly due to the synergic effect between the components. The effective combination of ZnO and reduced graphene oxide would lead to ameliorate the photocatalytic performance. To enhance applicability of semiconductor photocatalytic, the composites used should be good interfacial contact governed by suitable particle size distribution. Herein we aim to fabricate the different crystallize size of ZnO nanoparticles (NPs) in ZnO–reduced graphene oxide (ZnO–rGO) nanocomposites by sonochemical synthesis and subsequent facile drying treatment method. The Zn precursor, Zn(Ac)₂, with a plenty of functional groups, was used as a starting source for both reduction of graphene oxide and formation of ZnO on rGO sheets through chemical bonds without the addition of hazardous reducing agents. LiOH was chosen as an assistive reagent to enhance the complete reaction between Zn(Ac)₂ and GO in the formation of ZnO–rGO nanocomposites. More remarkably, drying condition has the great influence on the crystallize size of ZnO NPs in as-prepared ZnO–rGO nanocomposites. It is found that ZnO–rGO nanocomposites dried at ?50 °C (freeze drying) show the highest photocatalytic efficiency in the degradation of rhodamine B (RhB) as compared to ZnO–rGO nanocomposites by other drying conditions under visible-light irradiation. Correlating the crystallize size obtained by different drying temperatures with the photocatalytic activity, it is probed that the smaller crystallize size in ZnO–rGO nanocomposites enhances the interfacial contact and a chemical bonding between rGO and ZnO NPs leading to the effective separation of electrons and holes. In addition, the O ₂ ^·? anion was determined to be the main active oxidant by free radicals trapping experiment and a photodegradation mechanism of ZnO–rGO nanocomposites over rhodamine B (RhB) was proposed based on our observations.     

农药类化合物对大型溞的毒性作用模式:与基线毒性化合物比较研究

农药在控制有害生物的同时,对水生生态系统产生较大的毒性效应。本文通过实验获得了25种基线化合物对大型溞的急性毒性数据,并与57种农药类化合物对大型溞的急性毒性数据进行比较研究,同时根据体外浓度LC_(50)、生物富集因子BCF和体内临界浓度CBR的关系,计算了这些化合物在大型溞体内的临界浓度,研究了农药类化合物对大型溞的毒性作用机理。结果表明,基线化合物在大型溞体内的临界浓度log1/CBR值在一个很窄的范围波动,而农药类化合物在大型溞体内的临界浓度log1/CBR值范围广且较高。这说明多数农药类化合物对大型溞为反应性毒性作用模式。其中,除草剂对大型溞的毒性显著低于杀菌剂和杀虫剂对大型溞的毒性。这可能是因为除草剂主要通过干扰植物光合作用、植物激素或植物分子合成发挥毒性效应,从而导致其对大型溞的生理系统难以发生反应性毒性效应。而杀虫剂和杀菌剂主要通过干扰生物神经系统、生殖系统、呼吸作用或大分子合成发挥毒性效应,因此易与大型溞生理系统发生生物化学反应,从而具有较高的毒性效应。本文分别建立了除草剂、杀菌剂和杀虫剂对大型溞的急性毒性QSAR模型。除草剂对大型溞的急性毒性机理较简单,其毒性与化合物疏水性程度和离子化程度有关;而杀菌剂对大型溞的急性毒性主要与化合物的标准生成热和极性表面积有关;杀虫剂对大型溞的急性毒性作用机理较复杂,它们对大型溞的毒性效应与其和生物分子之间的氢键和范德华力有关。     

氟啶胺对斑马鱼胚胎线粒体氧化磷酸化和多巴胺系统基因表达的干扰效应

杀菌剂氟啶胺是哺乳动物细胞中一种典型的线粒体氧化磷酸化解偶联试剂,极易在鱼体内富集,且对鱼类具有极高的毒性。本文测定了氟啶胺对斑马鱼(Danio rerio)胚胎的96 h半数致死浓度LC50值,并研究了该浓度下氟啶胺对斑马鱼胚胎线粒体呼吸耗氧速率和多巴胺神经通路中关键基因表达的干扰效应。氟啶胺对斑马鱼胚胎的96 h-LC50值为0.5μmol·L~(-1),该浓度下氟啶胺能够导致胚胎发生中轴骨骼发育不全和心脏水肿等畸形现象,这说明该杀菌剂对斑马鱼胚胎具有极高的毒性。在该浓度下,胚胎的基础呼吸速率和ATP产量均受到了显著抑制,这说明氟啶胺在斑马鱼细胞内同样具有解偶联活性,该杀菌剂能够干扰斑马鱼的线粒体氧化磷酸化过程。另外,LC50浓度氟啶胺还能够激活线粒体内锰超氧化物歧化酶基因(sod2)的表达,这说明氟啶胺能够引发线粒体内氧化自由基的产生,从而导致线粒体功能异常。由于多巴胺系统对线粒体能量产生和氧气消耗具有较高的敏感性,因此本文检测了斑马鱼体内多巴胺系统关键基因的转录水平。LC50浓度的氟啶胺能够显著抑制与多巴胺合成有关的酪氨酸羟化酶基因(th)和与多巴胺接收有关的多巴胺受体基因(drd2a)的转录水平,这说明斑马鱼在发育中多巴胺系统是氟啶胺引发神经疾病的有效靶位。一直以来氟啶胺在水环境中的残留是备受关注的环境问题,因此研究氟啶胺对斑马鱼胚胎的毒性作用机制具有重要意义。     

土石坝溃决机理模型试验研究进展

大坝溃决将给人类社会带来巨大的灾难,因此国内外都很关注溃坝问题的研究。由于多数大坝均为土石坝,且土石坝是逐渐溃决的过程,而混凝土坝一般表现为瞬时溃决,因此土石坝溃决机理与溃决过程的研究对于溃坝过程数学模型的建立和致灾后果的评价具有重要的指导意义。自20世纪90年代以来,国内外学者围绕土石坝溃决机理开展了广泛深入的模型试验研究,取得了一系列重要的研究成果。分别从土石坝溃决原因、土石坝溃决机理研究进展、土石坝漫顶溃决模型试验、土石坝管涌溃决模型试验等方面介绍国内外的研究进展。重点针对土石坝坝型(均质坝、黏性心墙坝、面板堆石坝)和主要破坏模式(漫顶溃坝与管涌溃坝),介绍国内外开展的不同尺度的溃坝模型试验,分析研究了土石坝的溃决机理,并对今后的研究工作重点提出了相关建议。     

Using loose nanofiltration membrane for lake water treatment: A pilot study

• A pilot study was conducted for drinking water treatment using loose NF membranes. • The membranes had very high rejection of NOM and medium rejection of Ca²⁺/Mg²⁺. • Organic fouling was dominant and contribution of inorganic fouling was substantial. • Both organic and inorganic fouling had spatial non-uniformity on membrane surface. • Applying EDTA at basic conditions was effective in removing membrane fouling. Nanofiltration (NF) using loose membranes has a high application potential for advanced treatment of drinking water by selectively removing contaminants from the water, while membrane fouling remains one of the biggest problems of the process. This paper reported a seven-month pilot study of using a loose NF membrane to treat a sand filtration effluent which had a relatively high turbidity (~0.4 NTU) and high concentrations of organic matter (up to 5 mg/L as TOC), hardness and sulfate. Results showed that the membrane demonstrated a high rejection of TOC (by>90%) and a moderately high rejection of two pesticides (54%–82%) while a moderate rejection of both calcium and magnesium (~45%) and a low rejection of total dissolved solids (~27%). The membrane elements suffered from severe membrane fouling, with the membrane permeance decreased by 70% after 85 days operation. The membrane fouling was dominated by organic fouling, while biological fouling was moderate. Inorganic fouling was mainly caused by deposition of aluminum-bearing substances. Though inorganic foulants were minor contents on membrane, their contribution to overall membrane fouling was substantial. Membrane fouling was not uniform on membrane. While contents of organic and inorganic foulants were the highest at the inlet and outlet region, respectively, the severity of membrane fouling increased from the inlet to the outlet region of membrane element with a difference higher than 30%. While alkaline cleaning was not effective in removing the membrane foulants, the use of ethylenediamine tetraacetate (EDTA) at alkaline conditions could effectively restore the membrane permeance.     

古树名木保护地方立法评析与建议

对我国出台的15部古树名木保护地方性法规和规章出台时间、主要内容进行了归纳分析。结果发现:法规和规章中存在着管理体制不顺、权责利不对等、处罚标准不合理等问题。在研究基础上,提出完善古树名木保护立法的建议:加快推进古树名木保护国家立法,逐步完善地方立法,进一步理顺保护管理体制,建立古树名木保护补偿制度,加强科学研究与技术推广等。     

利用"三废"制轻型保温隔热建筑材料

塑料的问世给人们的日常生活带来了极大方便的同时,也给人类居住环境造成很大破坏。人们使用后的聚苯乙烯泡沫包装盒(板)和塑料袋随处可见,形成了难以消除的“白色污染”。还有工业废渣到处堆积如山,没有得到充分利用。针对这种情况．笔者为了开发这些“三废”材料的新用途．利用泡沫塑料和炉渣表观密度小、空隙率大、保温隔热性能好等特性,研制了一种轻型保温隔热建筑材料,经过实验取得了良好效果。     

Biochar addition to soil highly increases P retention and decreases the risk of phosphate contamination of waters

Environmental Chemistry Letters - Phosphorus loss from agricultural soils is an important cause of eutrophication. The diversity of soil conditions and biochar feedstocks induces...     

Properties of mortars made by uncalcined FGD gypsum-fly ash-ground granulated blast furnace slag composite binder

A series of novel mortars were developed from composite binder of uncalcined FGD gypsum, fly ash (FA) and ground granulated blast furnace slag (GGBFS) for the good utilization of flue gas desulphurization (FGD) gypsum. At a fixed ratio (20%) of GGBFS to the composite binder, keeping consistency of the mortar between 9.5 and 10.0 cm, the properties of the composite mortar were studied. The results show that higher water/binder (W/B) is required to keep the consistency when increasing the percentage of FGD gypsum. No obvious influences of the W/B and content of FGD gypsum on the bleeding of paste were observed which keeps lower than 2% under all experimental conditions tried. The highest compressive and flexural strengths (ratio is 20% FGD gypsum, 20% GGBFS and 60% FA) are 22.6 and 4.3 MPa at 28 days, respectively. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) results indicate that massive ettringite crystals and C-S-H gels exist in the hydration products. At 90 days the mortars with FGD gypsum is dramatically smaller drying shrinkage (563-938 micro strain) than that without FGD gypsum (about 2250 micro strain). The release of the SO(4)(2-) from the mortar was analyzed, indicating that the dissolution of sulfate increases with FGD gypsum. The concentration of SO(4)(2-) releasing from the mortar with 10% FGD gypsum is almost equal to that obtained from the mortar without FGD gypsum. The release of SO(4)(2-) from the mortar with 20% FGD gypsum is 9200 mg·m(-2), which is lower than that from the mortar with 95% cement clinker and 5% FGD gypsum.