Removal of trace Cr(VI) from aqueous solution by porous activated carbon balls supported by nanoscale zero-valent iron composites

Environmental Science and Pollution Research - In this study, porous activated carbon balls supported by nanoscale zero-valent iron composites (Fe@PACB-700) were used for the first time for the...     

火灾发生率空间分异及影响因素研究

为了探究我国火灾空间聚集特征与影响因素的空间异质性,采用全局莫兰指数、局部莫兰指数、逐步回归模型、地理加权回归模型、地理探测器方法对我国地级市单元进行研究。研究结果表明:我国火灾发生率具有显著的聚集性;我国火灾发生率较低的“冷点”区域有1个,火灾发生率较高的“热点”区域有4个;人均GDP、城镇居民人均可支配收入、人口密度、年平均气温4 个因素的影响效应具有空间异质性。人均GDP与火灾发生率为正相关,另外3影响因素对火灾发生率的作用表现出正负2种相关关系;2因素交互作用要比单因素作用于火灾发生率时影响力更显著,各影响因素的交互作用类型有非线性增强型和双因子增强型2种。     

Prediction of the adsorption capability onto activated carbon of a large data set of chemicals by local lazy regression method

Accurate quantitative structure–property relationship (QSPR) models based on a large data set containing a total of 3483 organic compounds were developed to predict chemicals’ adsorption capability onto activated carbon in gas phrase. Both global multiple linear regression (MLR) method and local lazy regression (LLR) method were used to develop QSPR models. The results proved that LLR has prediction accuracy 10% higher than that of MLR model. By applying LLR method we can predict the test set (787 compounds) with Q²_ext of 0.900 and root mean square error (RMSE) of 0.129. The accurate model based on this large data set could be useful to predict adsorption property of new compounds since such model covers a highly diverse structural space.     

Analysis of 3-year observations of CFC-11, CFC-12 and CFC-113 from a semi-rural site in China

In-situ measurements of atmospheric chlorofluorocarbons (CFCs) can be used to the assess their global and regional emissions and to check for compliance with phase-out schedules under Montreal protocol and its amendments. The atmospheric mixing ratios of CFC-11 (CCl₃F), CFC-12 (CCl₂F₂) and CFC-113 (CCl₂F–CClF₂) have been measured by an automated in-situ GC-ECDs system at the regional Chinese Global Atmosphere Watch (GAW) station Shangdianzi (SDZ), from November 2006 to October 2009. The time series for these three principal CFCs showed large episodic events and background conditions occurred for approximately 30% (CFC-11), 52% (CFC-12) and 56% (CFC-113) of the measurements. The mean background mixing ratios for CFC-11, CFC-12 and CFC-113 were 244.8 ppt (parts per trillion, 10^?12, molar) 539.6 ppt and 76.8 ppt, respectively, for 2006–2009. The enhanced CFC mixing ratios compared to AGAGE sites such as Trinidad Head (THD), US and Mace Head (MHD), Ireland suggest regional influences even during background conditions at SDZ, which is much closer to highly-populated areas. Between 2006 and 2009 background CFCs exhibited downward trends at rates of ?2.0 ppt yr^?1 for CFC-11, ?2.5 ppt yr^?1 for CFC-12 and ?0.7 ppt yr^?1 for CFC-113. De-trended 3-year average background seasonal cycles displayed small fluctuations with peak-to-trough amplitudes of 1.0 ± 0.02 ppt (0.4%) for background CFC-11, 1.3 ± 2.1 ppt (0.3%) for CFC-12 and 0.2 ± 0.4 ppt (0.3%) for CFC-113. On the other hand, during pollution periods these CFCs showed much larger seasonal cycles of 11.2 ± 10.7 ppt (5%) for CFC-11, 7.5 ± 6.5 ppt (2%) for CFC-12 and 1.0 ± 1.2 ppt (1.2%) for CFC-113, with apparent winter minima and early summer maxima. This enhancement was attributed to prevailing wind directions from urban regions in summer and to enhanced anthropogenic sources during the warm season. In general, horizontal winds from northeast showed negative contribution to atmospheric CFCs loading, whereas South Western advection (urban sector: Beijing) had positive contributions.     

ASBBR-二级SBBR-化学除磷组合工艺处理榨菜腌制废水

针对榨菜腌制废水高盐高氮磷高有机物浓度的特征,提出"厌氧序批式生物膜反应器(ASBBR)-二级序批式生物膜反应器(SBBR)-化学除磷"组合处理工艺,在前期对组合工艺中单元工艺的关键工况参数研究的基础上,考察组合工艺的处理效能。实验结果表明,采用该组合工艺,可使进水COD、NH4+-N、TN及PO43--P分别为10 000、345、550和38.5mg/L的榨菜腌制废水,处理出水COD、NH4+-N、TN及PO43--P分别达到93.6、12.3、18和0.1 mg/L,去除率分别为99.1%、96.4%、96.7%和99.9%,出水达到污水综合排放一级标准。     

Effects of landforms on the erosion rate in a small watershed by the Cs tracing method

It's very important to analyze and evaluate quantitatively the effects of landforms on soil erosion for the prevention and treatment of soil loss in a small watershed. The objective of this study was to evaluate the effects of landform factors on erosion rate by the ¹³⁷Cs tracing method in a small watershed in the Purple Hilly Area of China. The erosion rates under different slope lengths, slope gradients and slope aspects were estimated in Xiangshuitan watershed in the Purple Hilly Area in Sichuan Basin by the ¹³⁷Cs tracing method. The results showed that the erosion rate decreased exponentially with downslope distance, and it increased with increasing slope gradient during the scope of 5°-16°. The slope aspect had great impact on the erosion rate, and the hillside on the sunny slope had larger erosion rate than that on the shady slope, particularly for the farmland.     

溶剂热法合成SnWO_4及其可见光催化活性

采用溶剂热法合成了新型的可见光催化剂SnWO4,以甲基橙为目标污染物,考察了合成温度、合成时间和煅烧工艺对催化剂可见光催化活性的影响。实验结果表明:煅烧工艺会明显降低催化剂的光催化活性;在合成温度为180℃、合成时间为8h、未煅烧的条件下,合成的催化剂的光催化效果最好,光照90min后,对甲基橙的降解率可达99.93%。     

Estimates of synthetic fertilizer N-induced direct nitrous oxide emission from Chinese croplands during 1980-2000

There is increasing concern that agricultural intensification in China has greatly increased N₂O emissions due to rapidly increased fertilizer use. By linking a spatial database of precipitation, synthetic fertilizer N input, cropping rotation and area via GIS, a precipitation-rectified emission factor of N₂O for upland croplands and water regime-specific emission factors for irrigated rice paddies were adopted to estimate annual synthetic fertilizer N-induced direct N₂O emissions (FIE-N₂O) from Chinese croplands during 1980-2000. Annual FIE-N₂O was estimated to be 115.7 Gg N₂O-N year⁻¹ in the 1980s and 210.5 Gg N₂O-N year⁻¹ in the 1990s, with an annual increasing rate of 9.14 Gg N₂O-N year⁻¹ over the period 1980-2000. Upland croplands contributed most to the national total of FIE-N₂O, accounting for 79% in 1980 and 92% in 2000. Approximately 65% of the FIE-N₂O emitted in eastern and southern central China.     

Agricultural Productivity Changes Induced by the Sloping Land Conversion Program: An Analysis of Wuqi County in the Loess Plateau Region

This paper examines the agricultural productivity change induced by the Sloping Land Conversion Program (SLCP) using the Malmquist index method and household data collected from Wuqi. We find that during the period of 1998–2004, the total factor productivity (TFP) grew by 15.8%. While numerous households suffered a TFP decline, the majority of them experienced a large gain. By decomposing the TFP, we further show that its increase is due exclusively to the improvement of technical efficiency rather than to technological change. To validate these findings and put them in perspective, we also estimated the TFP change with county-level aggregate data. It is revealed that driven by technological change and scale efficiency, the TFP grew slightly during the period of 1992–1998. Because of the tremendous cropland reduction and production mode shift caused by implementing the SLCP, the TFP declined substantially during the first three years of the program; due to continued improvement of technical efficiency; however, its growth accelerated later. Altogether, our evidence consistently suggests that implementing the SLCP has contributed to the agricultural TFP growth in the longer term and that the efficiency improvement has resulted mainly from the increased public expenditures for extension services and diffusion of technical knowledge. Wuqi’s experience proves that it is possible to achieve environmental conservation and increase productivity simultaneously, even when facing a cropland reduction and production mode alternation.     

小型燃油锅炉NOx的排放特征与管理控制

以68台燃油锅炉（≤10～MW）NOx排放实测数据为基础,通过统计分析方法,研究了NOx的排放特征;通过对比分析,探讨了我国燃油锅炉NOx排放控制与管理现状,讨论了进一步加强我国燃油锅炉NOx排放管理控制的可能性与可行性,并提出了相应的管理控制建议。结果表明,NOx平均排放浓度为318．2mg／m^3,基于燃料消耗量的平均排放因子为4．4kg／t,基于燃料发热量的平均排放因子为102．8ng／J,基于燃料氮含量的平均排放因子为2．1mg／mg;建议采取分阶段控制的方式,逐步提高NOx排放限制,从而实现控源减排目标。