Fractal analysis of polyferric chloride-humic acid （PFC-HA） flocs in different topological spaces

The fractal dimensions in different topological spaces of polyferric chloride-humic acid (PFC-HA) flocs, formed in flocculating different kinds of humic acids (HA) water with different initial pH (9.00, 7.00, 5.00) and PFC dosages, were calculated by effective density-maximum diameter, image analysis, and N2 absorption-desorption methods, respectively. The mass fractal dimensions (Df) of PFC-HA flocs, being more than 2.0, calculated by bi-logarithm relation of effective density-maximum diameter and Logan empirical formula at initial pH of 7.00 had 11-13 percentage greater than those at pH 9.00 and 5.00, indicating the most compact flocs formed in flocculated HA water at initial pH of 7.00. The image analysis for those flocs indicates that after flocculating the HA water at initial pH greater than 7.00 with PFC flocculant, the fractal dimensions of D2 (logA vs. logdL) and D3 (logVsphere vs. logdL) of PFC-HA flocs decreased with the increase of PFC dosages, and PFC-HA flocs showed a gradually looser structure. At the optimum dosage of PFC, the D2 (logA vs. logdL) values of the flocs show 14%--43% difference with their corresponding Df, and they even had different tendency as the change of initial pH values. However, the D2 values of the flocs formed at three different initial pH in HA solution, calculated from the horizontal projected images with magnification about 9, had a same tendency with the corresponding Df. Based on fractal Frenkel-Halsey-Hill (FHH) adsorption and desorption equations, the pore surface fractal dimensions (Ds) for dried powders of PFC-HA flocs formed in HA water with initial pH 9.00 and 7.00 were all close to 2.9421, and the Ds values of flocs formed at initial pH 5.00 were less than 2.3746. It indicated that the pore surface fractal dimensions of PFC-HA flocs dried powder mainly show the irregularity from the mesopore-size distribution and some marcopore-size distribution.     

单室型微生物燃料电池处理黄姜废水的性能研究

以黄姜废水为底物,采用单室型微生物燃料电池,验证了MFC处理黄姜废水的可行性,研究了进水COD和SO42-浓度对产电性能的影响.控制电导率和COD等条件一致,黄姜废水最大功率密度为葡萄糖配水的80.3%.低COD浓度条件下MFC产电稳定,功率密度随COD浓度上升而提高,最高为322 mW/m2;当COD提高至2766 mg/L以上时,MFC稳定产电的时长缩短且更新基质后无法恢复最佳产电水平,表明过高的COD负荷会抑制产电微生物活性.COD最终去除率在68.2%~84.8%之间,且随着初始浓度的提高去除率有所下降.进水SO42-浓度的提高使MFC输出功率密度增大,但当SO42-浓度>7 716 mg/L(电导率>8.19 mS/cm)时,继续提高SO42-浓度无法使功率密度增大.与沉淀SO42-后的废水比较,含硫原水的最大功率密度平均下降14.5%,其库仑效率也随SO42-浓度提高明显下降,表明存在SO42-作为电子受体被还原,降低了MFC的效率.     

沉淀池的数值模拟

运用计算流体力学软件FLUENT模拟了平流式沉淀池在不同进水口高度,进水挡板位置,颗粒密度和圆弧形扰流板位置下的流场、悬浮物的浓度场。从模拟结果的分析比较可以看出,在一定范围内改变沉淀池的进水口高度,对沉淀池的去除效果没有影响。挡板的淹没深度和颗粒的密度则对悬浮物的去除效率影响较大。挡板的水平位置只在一定范围内变化才能使沉淀池保持较为理想的去除效率。圆弧形扰流板的加设可以改变沉淀池内流态不均的现象,从而提高沉淀池的运行效率。     

辽东湾北部海域大型底栖动物研究:Ⅰ.种类组成与数量分布

于2007年7月下旬在辽东湾进行了29个站位的大型底栖动物调查,共发现大型底栖生物79种;其中包括多毛类18科24种,甲壳动物15科19种,软体动物13科24种,棘皮动物4科6种,其他类群5种.整个调查区内大型底栖动物的优势现象不明显,优势度指数大于1%的物种仅有5种,分别为光滑河篮蛤、日本倍棘蛇尾、日本浪漂水虱、纽虫和西格织纹螺.调查区内底栖动物种类数、栖息密度以及生物量的高值区与低值区呈斑块状互相嵌套.大型底柄动物的平均栖息密度为68.28 m-2,平均生物量为22.75 g/m2;其中软体动物的平均栖息密度为30.52 m-2,生物量为6.92 g/m2;多毛类的平均栖息密度为14.48m-2,生物量为4.15g/m2;甲壳类的平均栖息密度为12.76 m-2,生物量为1.86g/m2;棘皮动物平均栖息密度为6.38 m-2,生物量为8.64 g/m2.1959年渤海各分区大型底栖动物的平均牛物量为10.29～12.83 g/m2.与其相比,除莱州湾外,目前各分区的平均生物量(16.45～22.75 g/m2)均显著升高,变化幅度有所增大.     

电絮凝-微滤技术应用于给水处理的实验研究

利用电絮凝-微滤法进行了给水处理的实验研究,探讨了电流密度、电解时间和pH值等因素,对源水中的TOC、氨氮、油类的去除的影响。结果表明,增大电流密度有利于上述污染物的去除,TOC和氨氮的去除率随pH升高而增加,pH变化对油类的去除率影响较小。     

SCR脱硝系统中液氨环境风险性评价

从危害度和危险度两个方面对脱硝系统中的液氨环境风险事故进行分析,并提出风险防范措施和应急预案,为同类项目的液氨环境风险评价提供参考。     

微生物燃料电池中底物的研究进展

微生物燃料电池是一种利用可溶性有机废物和可再生生物质等原料萃取电能的装置,而底物作为能量转化的能源物质,是影响 微生物燃料电池产电能力的重要因素之一.能够充当底物的有机质种类十分丰富,如多种低浓度有机废水和纤维素等,底物的种类不同,电池的产电能力也会存在差异.因此,有必要对这一系统中底物对电池产电性能及其他方面的影响进...     

Elevated atmospheric CO2 and drought effects on leaf gas exchange properties of barley

Atmospheric CO₂ concentration (C_a) is rising, predicted to cause global warming, and alter precipitation patterns. During 1994, spring barley (Hordeum vulgare L. cv. Alexis) was grown in a strip-split-plot experimental design to determine the effects that the main plot C_a treatments [A: Ambient at 370 μmol (CO₂) mol⁻¹; E: Enriched with free-air CO₂ enrichment (FACE) at ∼550 μmol (CO₂) mol⁻¹] had on several gas exchange properties of fully expanded sunlit primary leaves. The interacting strip-split-plot irrigation treatments were Dry or Wet [50% (D) or 100% (W) replacement of potential evapotranspiration] at ample nitrogen (261 kg N ha⁻¹) and phosphorous (29 kg P ha⁻¹) fertility. Elevated C_a facilitated drought avoidance by reducing stomatal conductance (g_s) by 34% that conserved water and enabled stomata to remain open for a longer period into a drought. This resulted in a 28% reduction in drought-induced midafternoon depression in net assimilation rate (A). Elevated C_a increased A by 37% under Dry and 23% under Wet. Any reduction in A under Wet conditions occurred because of nonstomatal limitations, whereas under Dry it occurred because of stomatal limitations. Elevated C_a increased the diurnal integral of A (A′) that resulted in an increase in the seasonal-long integral of A′ (A″) for barley leaves by 12% (P = 0.14) under both Dry and Wet - 650, 730, 905 and 1020 ± 65 g (C) m⁻² y⁻¹ for AD, ED, AW and EW treatments, respectively. Elevated C_a increased season-long average dry weight (DW_S; crown, shoots) by 14% (P = 0.02), whereas deficit irrigation reduced DW_S by 7% (P = 0.06), although these values may have been affected by a short but severe pea aphid [Acyrthosiphon pisum (Harris)] infestation. Hence, an elevated-C_a-based improvement in gas exchange properties enhanced growth of a barley crop.     

中国工业污染物排放密度的影响因素分析——基于污染供需分析框架的实证研究

本文在污染供需分析框架下,选取中国2001-2006年34个工业产业的面板数据,分析影响工业废水、工业二氧化硫和工业烟尘等三种污染物排放密度的主要因素。实证研究结果显示：污染密度均与能源消耗密度、相对工资水平和国有资本比重正相关,与企业规模、环境管制指标和外资比重负相关。要解决环境污染的问题,建立政府引导、企业为主和社会参与的节能减排机制才是根本出路。为此需要做到：（1）鼓励节能型技术的研发和应用;（2）强化对地方政府的环境管制政策执行力度的监督;（3）加强对中小企业的监管力度;（4）理顺政府对环保信息的披露机制;（5）充分发挥社会公众和非政府组织的监督作用;（6）提高外资进入的环境标准。     

基于空间自相关模型的农村居民点时空演变格局与特征研究

农村居民点作为农村人口重要空间聚集区,其空间布局、演变特征受历史、自然、社会、经济、传统文化等多重因素的影响。科学识别农村居民点的时空分布形态,并揭示其内在的变化规律和驱动因素,对促进农村居民点科学规划、提高农村土地资源空间布局优化均具有重要意义。利用都江堰市2005和2012年两期遥感影像提取农村居民点、城镇、道路、河流等矢量数据,借助RS、GIS空间分析技术,定量研究都江堰市农村居民点时空变化过程、格局和特征,并引入空间自回归模型深入分析不同环境因素对农村居民点空间布局的影响程度。研究结果表明:(1)都江堰市农村居民点的空间分布密度存在显著的空间正相关性,即密度值较高或较低的地区在空间上呈现显著的聚集状态,但局部的空间异质性在增强;(2)密度的高值集群主要集中分布在都江堰市东南部沙西线沿线以及南部成青快速通道一线,并且有进一步沿道路延线纵深扩张的趋势,而密度的低值集群由于受地形的影响,在空间分布上变化不大,主要位于龙门山沿线的乡镇;(3)2005~2012年,地形位指数每增加1%,农村居民点的空间密度减少0.505%,而距城镇、河流和道路的距离每增加1%,农村居民点的空间密度分别增加0.124%、0.144%、0.006%;(4)不同环境因素对农村居民点空间分布的影响程度大小为:地形影响城镇辐射影响河流影响道路影响,并且随着时间的推移,各环境因素的影响程度都在不断地增强。该研究以期为今后同类研究提供一定的方法借鉴,为农村居民点动态变化监测、农村土地节约集约利用、新农村规划等提供理论方法和技术应用支撑。