Biomass production and carbon sequestration potential in poplar plantations with different management patterns

Biomass production and carbon storage in short-rotation poplar plantations over 10 years were evaluated at the Hanyuan Forestry Farm, Baoying County, China. Experimental treatments applied in a split-plot design included four planting densities (1111, 833, 625 and 500 stems ha(-1)) and three poplar clones (NL-80351, I-69 and I-72). Based on the model of total biomass production developed, total plantation biomass production was significantly different in the plantations. The ranking of the plantation biomass production by planting density was 1111>833 more more than 625>500 stems ha(-1), and by components was stem>root>or=branch>leaf for all plantations. At 10 years, the highest total biomass in the plantation of 1111 stems ha(-1) reached about 146 t ha(-1), which was 5.3%, 11.6% and 24.2% higher than the plantations of 833, 625 and 500 stems ha(-1), respectively. The annual increment of biomass production over 10 years differed significantly among initial planting densities and stand ages (p<0.01), but no significant difference was observed from age 7 to 10. Mean carbon concentration among all biomass components ranged from 42-50%, with the highest carbon concentrations in stems and the lowest in leaves. Over the study period, the dynamic pattern of total plantation carbon storage by planting density was similar to that of total biomass production. At age 10, the highest total plantation carbon storage in the plantation of 1111 stems ha(-1) reached about 72.0 t ha(-1), which was 5.4%, 11.9% and 24.8% higher than in the plantations of 833, 625 and 500 stems ha(-1), respectively. The annual carbon storage increment over 10 years differed significantly among initial planting densities and stand ages (p<0.01), and it showed a pattern similar to the annual biomass production increment of the plantations. The results suggest that biomass production and carbon storage potential were highest for planting densities of 1111 and 833 stems ha(-1) grown over 5- and 6-year cutting cycles, respectively. If 3- or 4-year cutting cycles are used, the planting density should be higher than 1111 stems ha(-1) (e.g., 1667 or 2500 stems ha(-1)). Based on the mean annual carbon storage for the plantation of 625 stems ha(-1), as an estimation, the mean carbon storage in the biomass of poplar plantations (excluding leaves) amounts to 3.75x10(7) t ha(-1)yr(-1) in China.     

Mechanism for the destruction of carbon tetrachloride and chloroform DNAPLs by modified Fenton's reagent

The destruction of a carbon tetrachloride DNAPL and a chloroform DNAPL was investigated in reactions containing 0.5 mL of DNAPL and a solution of modified Fenton's reagent (2M H2O2 and 5mM iron(III)-chelate). Carbon tetrachloride and chloroform masses were followed in the DNAPLs, the aqueous phases, and the off gasses. In addition, the rate of DNAPL destruction was compared to the rate of gas-purge dissolution. Carbon tetrachloride DNAPLs were rapidly destroyed by modified Fenton's reagent at 6.5 times the rate of gas purge dissolution, with 74% of the DNAPL destroyed within 24h. Use of reactions in which a single reactive oxygen species (hydroxyl radical, hydroperoxide anion, or superoxide radical anion) was generated showed that superoxide is the reactive species in modified Fenton's reagent responsible for carbon tetrachloride DNAPL destruction. Chloroform DNAPLs were also destroyed by modified Fenton's reagent, but at a rate slower than the rate of gas purge dissolution. Reactions generating a single reactive oxygen species demonstrated that chloroform destruction was the result of both superoxide and hydroxyl radical activity. Such a mechanism of chloroform DNAPL destruction is in agreement with the slow but relatively equal reactivity of chloroform with both superoxide and hydroxyl radical. The results of this research demonstrate that modified Fenton's reagent can rapidly and effectively destroy DNAPLs of contaminants characterized by minimal reactivity with hydroxyl radical, and should receive more consideration as a DNAPL cleanup technology.     

混凝土徐变对碳纤维布加固钢筋混凝土梁的挠度影响

根据混凝土徐变规律,推导CFRP加固钢筋混凝土梁的徐变计算公式,分析混凝土徐变对CFRP加固钢筋混凝土梁中和轴的影响,建立CFRP加固钢筋混凝土梁的挠度计算模型;通过实例分析、验证计算模型的有效性,研究成果可供碳纤维布加固钢筋混凝土结构设计参考。     

麦草低污染制浆新技术

麦草低污染制浆新工艺采用亚硫酸钠-甲醛-蒽醌（加入少量催化剂）制浆（SFP-AQ法）,生产吨浆的COD排放总量下降30％,色度下降60％,悬浮物总量下降50％,制浆黑液的pH值下降至7～8。采用该新工艺同时还可产生表面活性好、便于利用的木素磺酸钠和其他产品,使纤维资源得到综合利用,为解决中小型草浆造纸厂的污染问题提供一条有效途径。j     

不同酸对造纸黑液酸析效果的研究

采用酸析法从造纸黑液中分离木质素,同时去除部分COD和色度,从而完成对黑液的初步处理。实验研究了酸析的最佳pH值,并将硫酸、硝酸、盐酸、磷酸、甲酸和草酸作为酸析剂,分析其分别对黑液色度、COD的去除效果及对木质素提取的影响。介绍了通过快速消解分光光度法来测定COD值,和用分光光度法测定色度值,分别建立COD值和色度对吸光度的工作曲线,使测量更加方便高效快捷,其精确度和准确度都能符合分析方法要求。实验结果表明,酸析效果较好的pH取值范围为2～4,考虑用酸的经济性和处理效果,选择pH=3作为最佳酸析条件;经过对酸析过程规律和原因的分析可得,硫酸、硝酸和磷酸对黑液处理效果较为理想,其中硫酸因其经济性被选为最佳,其色度、COD去除率分别为97.9%和66.1%,木质素的析出量为8.65 g/L。     

湖泊碳循环及碳通量的估算方法

湖泊由于其特殊的地理位置,较高的生产力,在碳循环中具有重要作用。作为湖泊营养元素的碳在湖泊水体中的赋存形态主要包括:碳酸盐系统(CO2,CO32-,HCO3-,H2CO3)、溶解态有机碳、生物死亡残体颗粒碳及生物体有机碳等。研究表明包括有机碳和溶解态无机碳在内的全世界湖泊总碳汇为0.077Gt/a,其中对大气的汇达到0.0532Gt/a。湖泊除从地表径流、地下水获得碳以外,还可从空气物质中获得碳。估算及测定水气界面CO2通量的方法主要有:①赖利估算法;②单侧扩散法;③同位素估算法;④涡度相关法;⑤静态箱式法。     

中心城区河道基本消除黑臭的可行性措施和对策

概述了上海浦东新区水环境的现状,并对新区黑臭河道的数量、分布和污染程度作了详细的分析,探讨了新区河道黑臭的成因,针对新区已基本消除黑臭的骨干河道和黑臭的中心城区镇(街道)、村级河道分别提出了不同的污染防治可行性措施和对策。     

Influences of influent carbon source on extracellular polymeric substances (EPS) and physicochemical properties of activated sludge

It is necessary to understand the bioflocculation, settling and dewatering characteristics in the activated sludge process in order to establish more efficient operational strategies. The influences of carbon source on the extracellular polymeric substances (EPS) and flocculation, settling and dewatering properties of the activated sludge were investigated. Laboratory-scale completely mixed activated sludge processes were used to grow the activated sludge with different carbon sources of starch, glucose and sodium acetate. The sludge fed with acetate had highest loosely bound EPS (LB-EPS) and that fed with starch lowest. The amount of tightly bound EPS (TB-EPS), protein content in LB-EPS, polysaccharide content and protein contents in TB-EPS, were independent of the influent carbon source. The polysaccharide content in LB-EPS of the activated sludge fed with sodium acetate was lower slightly than those of starch and glucose. The sludge also had a nearly consistent flocs size and the sludge volume index (SVI) value. ESS content of the sludge fed with sodium acetate was higher initially, although it was similar to those fed with glucose and starch finally. However, the specific resistance to filtration and normalized capillary suction time fluctuated first, but finally were stable at around 5.0 × 10⁸ m kg⁻¹ and 3.5 s L g⁻¹ SS, respectively. Only the protein content in LB-EPS weakly correlated with the flocs size and SVI of the activated sludge. But there was no correlation between any other EPS contents or components and the physicochemical properties of the activated sludge.     

GC-C-IRMS测定污染场地土壤中苯系物单体碳同位素比值

选取苯系物中的代表性组分苯、甲苯和二甲苯等化合物,通过热脱附、气相色谱质谱条件的优化及方法学考察,建立了热脱附进样-气相色谱-同位素比值质谱(GC-C-IRMS)测定苯系物单体碳同位素比值的方法。结果表明,单体化合物进样量在0.3μg以上均能满足测定要求;与直接进样方式相比,热脱附进样对单体碳同位素比值测定无分馏影响;标准溶液和苯系物土壤样品测定结果的RSD分别为1.0%~1.7%和0.3%~2.6%。     

Preparation of nZVI embedded modified mesoporous carbon for catalytic persulfate to degradation of reactive black 5

• The MCNZVI is prepared as an interesting material for PS activation. • Graphitized carbon shells facilitate electron transfer from Fe⁰. • The MCNZVI exhibits excellent performance to degrade RB5 by ¹O₂. • The MCNZVI has high stability and reusability in the oxidation system. High-efficiency and cost-effective catalysts with available strategies for persulfate (PS) activation are critical for the complete mineralization of organic contaminants in the environmental remediation and protection fields. A nanoscale zero-valent iron-embedded modified mesoporous carbon (MCNZVI) with a core-shell structure is synthesized using the hydrothermal synthesis method and high-temperature pyrolysis. The results showed that nZVI could be impregnated within mesoporous carbon frameworks with a comparatively high graphitization degree, rich nitrogen doping content, and a large surface area and pore volume. This material was used as a persulfate activator for the oxidation removal of Reactive Black 5 (RB5). The effects of the material dosage, PS concentration, pH, and some inorganic anions (i.e., Cl⁻, SO₄²⁻) on RB5 degradation were then investigated. The highest degradation efficiency (97.3%) of RB5 was achieved via PS (20 mmol/L) activation by the MCNZVI (0.5 g/L). The pseudo-first-order kinetics (k = 2.11 × 10⁻² min⁻¹) in the MCNZVI/PS (0.5 g/L, 20 mmol/L) was greater than 100 times than that in the MCNZVI and PS. The reactive oxygen species (ROS), including ¹O₂, SO₄^·−, HO^·, and ·O₂⁻, were generated by PS activation with the MCNZVI. Singlet oxygen was demonstrated to be the primary ROS responsible for the RB5 degradation. The MCNZVI could be reused and regenerated for recycling. This work provides new insights into PS activation to remove organic contamination.