市场机制在白色污染物回收处置中的应用探讨——以上海一次性塑料餐具废弃物为例

近10年来上海城市生活垃圾组分中,以塑料为代表的包装废物的组分份额上升趋势尤为显著;上海GDP持续高速增长,但单位GDP城市废弃物清运量的下降率却显著低于GDP的年均增长率,一定程度上说明环卫行业的投资渠道较为单一,缺乏竞争和优化配置的市场机制;上海各类废弃塑料主要流向江浙一带,进行小规模低技术层次的加工处理,容易形成隐蔽的废品交易暗流;造成“白色污染”屡禁不止的重要原因是忽视了基于生产者责任的市场调控机制,社会化的回收体系薄弱;上海从2000年10月起,对一次性塑料餐具的回收处置建立了基于生产者责任的市场机制,由于一次性塑料饭盒的区域回收网络建设滞后,实施的效果有效但仍有限.     

冬小麦中轻度水分胁迫的增产节水效应研究

利用大型水分试验场的防雨棚遮挡自然降水,采用人工定量补水进行冬小麦土壤含水量占田间持水量40%～50%、45%～50%、50%～55%、50%～60%、55%～60%、60%～70%持续时间分别为5、10、15天水分胁迫处理的控制试验。试验结果表明:50%～70%的中轻度水分胁迫处理,冬小麦具有显著的增产节水效果;2年平均,增产6.3%～7.4%,节水28.2%～34.1%。中轻度水分胁迫下,冬小麦增产节水作用机制的实现,主要是通过水分胁迫效应诱发增强:①冬小麦根系的找水功能;②产量构成因子的优化;③复水后光合速率的提高。冬小麦水分胁迫效应的最佳利用时间为返青-拔节期,此时进行水分胁迫效应利用最有利于冬小麦稳产增产。     

Chronic renal failure among farm families in cascade irrigation systems in Sri Lanka associated with elevated dietary cadmium levels in rice and freshwater fish (Tilapia)

Chronic renal failure (CRF), in the main agricultural region under reservoir based cascade irrigation in Sri Lanka has reached crisis proportion. Over 5,000 patients in the region are under treatment for CRF. The objective of this study is to establish the etiology of the CRF. Concentrations of nine heavy metals were determined in sediments, soils of reservoir peripheries, water and Nelumbo nucifera (lotus) grown in five major reservoirs that supply irrigation water. All five reservoirs carried higher levels of dissolved cadmium (Cd), iron (Fe) and lead (Pb). Dissolved Cd in reservoir water ranged from 0.03 to 0.06 mg/l. Sediment Cd concentration was 1.78-2.45 mg/kg. No arsenic (As) was detected. Cd content in lotus rhizomes was 253.82 mg/kg. The Provisional Tolerable Weekly Intake (PTWI) of Cd based on extreme exposure of rice is 8.702-15.927 mug/kg body weight (BW) for different age groups, 5-50 years. The PTWI of Cd due to extreme exposure of fish is 6.773-12.469 mug/kg BW. The PTWI on a rice staple with fish is 15.475-28.396 mug/kg BW. The mean urinary cadmium (UCd) concentration in CRF patients of age group 40-60 years was 7.58 mug Cd/g creatinine and in asymptomatic persons UCd was 11.62 mug Cd/g creatinine, indicating a chronic exposure to Cd. The possible source of Cd in reservoir sediments and water is Cd-contaminated agrochemicals. The CRF prevalent in north central Sri Lanka is a result of chronic dietary intake of Cd, supported by high natural levels of fluoride in drinking water, coupled with neglecting of routine de-silting of reservoirs for the past 20 years.     

复合生物滤池处理H2S和NH3的研究:生物相机理分析

采用天然斜发沸石和木屑作为复合生物滤池(生物滴滤池+生物过滤池)的填料,研究了该工艺处理含H₂S和NH₃混合恶臭气体的生物相机理.结果表明:生物滴滤池中形成了由细菌、藻类及原生动物组成的复杂生态系统,而生物过滤池中真菌为优势微生物.生物滴滤池的下层优势菌种主要为葡萄球菌属和球形芽孢杆菌等细菌,中层主要为梨形四膜虫属和肾形虫属,上层主要为钟虫和舟形藻属;生物过滤池优势菌种主要是聚多曲霉菌种.据对复合生物滤池的生物相机理探讨推论,生物滴滤池去除H₂S和NH₃机理主要是生物链的分级捕食和沸石的吸附-生物再生机理;生物过滤池去除H₂S和NH₃机理主要是真菌降解.因此,通过控制生物滴滤池和生物过滤池处于不同的环境条件,可使复合生物滤池能高效地同时处理H₂S和NH₃组成的混合恶臭气体.      

用复极固定床电解槽处理硝基苯废水

用复极固定床电解槽处理模拟硝基苯废水,考察了电解电压、N2SO4质量浓度、pH、硝基苯的初始质量浓度等条件对电解效果的影响。在Na2SO4质量浓度为1000mg／t、电解电压为40V、初始pH为10的条件下,复极固定床电解槽对硝基苯初始质量浓度为120mg／L的废水有较好的处理效果,硝基苯去除率可达到82．8％。探讨了复极固定床电解槽电化学降解硝基苯的机理。     

淹没式膜生物反应器中膜污染机理的研究

为减小微生物絮体对膜的污染,设计了一种具有沉降室的膜生物反应器,膜A与膜B分别淹没在上清液和污泥混合液中以相同的抽吸方式运行,与预期结果相反,膜A比膜B的污染速度还快．为探讨膜污染机理,考察了污泥混合液中不同组分对膜污染的影响,利用扫描电镜和原子力显微镜分析了膜面污染层的特征．结果发现,在污泥混合液与上清液中膜面污染层在微观结构上存在显差异,其方差平均粗糙度Rms分别为132．3nm和75．2nm．经膜污染机理分析认为：微生物絮体和大分子有机物会在膜面形成污染层,该污染层作为“二次膜”影响膜过滤性能．上清液中细小的微生物絮体和大分子有机物形成的污染层相对致密,会加剧膜污染．     

Mechanistic study of ozonation of p-nitrophenol in aqueous solution

Introduction p Nitrophenolhasbeenwidelyusedintheproductionof pesticides,herbicides,dyes,andotherindustrialchemicals.Asaresultofthesewidespreadapplications,wastewatersandwaterresources,includinggroundwaterandsurfacewaters,havebecomecontaminatedwiththiscomp…     

Comparative study of explosion processes controlled by homogeneous and heterogeneous combustion mechanisms

The dust explosion behaviors induced by two different combustion mechanisms (homogeneous and heterogeneous mechanisms) were comparatively investigated, based on the experiments under different dust concentrations, particle sizes and initial pressures in Siwek 20-L chamber. Based on the thermo-gravimetric analysis (TGA), sweet potato dust and magnesium dust were selected as the representative dusts with homogeneous and heterogeneous combustion mechanisms, respectively. Experiments find that these two dusts have different behaviors in the explosion kinetics due to different combustion mechanisms. For sweet potato dust, the explosion pressure p_max, the pressure rise rate (dp/dt)_max and the combustion fraction η exhibit similar variation trends as dust concentration increases and they all reach to the maximum values at the worst-case concentration; while for magnesium dust, the variation of (dp/dt)_max is somewhat different from that of p_max, that is, the (dp/dt)_max will achieve the maximum at the concentration higher than the worst-case and keep stabilized with further increase of dust concentration. As the particle size decreases, the (dp/dt)_max for sweet potato dust will increasingly rise and gradually approach to a stabilized value, but for magnesium dust, the increase of (dp/dt)_max becomes pronounced only in the range of smaller particle sizes. To account the effect of initial pressure on p_max under different combustion mechanisms, a dimensionless pressure P_R was introduced to denote the relative intensity of explosion. It is found that, for sweet potato dust, the increased initial pressure will promote the explosion process (or with high P_R) for the dust cloud with high concentration due to the augmented oxygen concentration, but for the dust cloud with low concentration, the increased initial pressure will suppress the explosion process due to the increased resistance in devolatilization. For magnesium dust, the rise of initial pressure will generally promote the explosion process even for the dust cloud with low concentration; however, in the case of small particle size, the promotion of increased initial pressure to the explosion process is not so pronounced.     

滇池流域生态承载力及系统耦合效应剖析

利用ENVI4.8和Arcgis9.3软件对2001~2010年的遥感影像数据进行处理和分析,计算得出各年份的生态承载力。结合相关年份的社会经济数据,同时根据滇池流域的实际情况提取18个分析指标,运用相关分析和回归分析方法,对滇池流域生态承载力以及其与生态环境系统、资源环境系统、社会经济系统3个子系统要素的耦合关系进行分析。结果表明:(1)2001~2010年滇池流域的总生态承载力和人均生态承载力呈快速下降趋势,降幅达37.3%;耕地生态承载力呈下降趋势最明显,下降幅度达52.61%,但建设用地的生态承载力上升幅度达27.08%。(2)滇池流域生态承载力与三大系统要素相关性较好,其耦合形态呈"J"、"L"型、"U"型和倒置的"S"型等。(3)对耦合形态的形成机理进行分析,其结果表明:城镇化、社会经济的发展以及流域内粗放型的经济增长方式对形成这种耦合形态的影响较大。     

黑土区城郊耕地重金属污染空间扩散机制

城郊复杂环境条件下的耕地土壤重金属污染空间扩散机制是落实土壤污染源头防控和保障黑土地质量安全的基础.针对以往溯源研究中污染源头难定位和扩散趋势不明确等问题,以长春市城郊地区为例,以耕地土壤As、Pb、Hg和Cd元素为研究对象,采用近邻传播（AP）算法和空间自回归的扩散格局-驱动因素组合分析法尝试揭示黑土区城郊耕地重金属污染空间扩散机制.结果表明,ω（As）和ω（Cd）均值分别为39.35mg ·kg^-1和0.183 mg ·kg^-1,累积水平较高.内梅罗指数显示研究区有52.38%的耕地已出现轻度污染.AP算法识别出As存在3个影响幅度相似的潜在污染源地,均位于远离城市的典型农耕区;Pb元素的2个潜在污染源地集中分布于范家屯镇附近的工业区;Hg和Cd元素的扩散格局复杂,尤其是Cd元素,呈现多地并发的污染扩散特征.空间滞后模型表明,As元素的空间扩散格局和农药施用强度有关;Cd元素主要受土壤类型和设施农业布局的制约;Pb元素受区域城镇化和工业化发展的影响;Hg元素和区域污染迁移条件相关.污染调蓄功能未对4种元素的空间扩散格局产生显著影响.研究丰富了耕地重金属污染的空间分析理论和方法,对落实城郊黑土地的污染源头防控具有科学意义.