粮食生产的投入产出影响因素分析--基于江苏省粮食生产的实证研究

在对江苏省13个市的粮食生产数据搜集整理的基础上,运用面板数据模型进行了投入产出的影响因素分析。结果显示,土地是影响目前江苏省粮食生产的最主要因素,因此随着城市化进程的不断加快,耕地面积的缩减,粮食产量有下降的趋势;此外,由于技术效率和劳动生产率的提高,出现了在劳动力投入不断下降条件下的粮食产量上升,但是二者表面上的反向关系不应当被简单理解为劳动力对产出弹性的负作用;在农资投入方面,化肥与农业机械动力的投入对于江苏省粮食生产有积极影响。     

大城市边缘区土地利用时空格局模拟--以武汉市洪山区为例

大城市边缘区的土地利用变化复杂而迅速,采用定量模型对此地域的时空格局进行模拟,在土地规划领域有重大意义。以武汉市洪山区为例,首先采用DPSIR模型对大城市边缘区的工业用地、居住用地、服务设施用地、绿地等进行驱动力机制的定性分析,得出每种用地相应的驱动力、压力和状态;进而采用CLUE S模型,通过用地变化驱动力因子作用权重系数的求解,模拟时段内各类用地的需求分析与用地变化的动态分配过程,对边缘区的用地演变进行模拟;最后通过用地现状图对模拟用地进行验证,模拟结果基本拟合。在模拟的基础之上,设定了两种大城市边缘区空间发展的情景模式,即不作任何空间约束的用地演变和进行可持续发展约束的用地演变,有针对性地提出该区域的发展需要重点保护水体和自然风景区。其方法及成果可为大城市边缘区制定发展管理政策提供科学参考。     

管流电氧化杀藻及其影响要素

对藻种类、电流密度、电极材料、细胞密度和流量对电化学氧化杀藻的影响进行了研究.实验结果显示,铜绿微囊藻比水华鱼腥藻对电化学氧化更为敏感,藻的种类和形状对杀藻效果存在影响.使用普通镀锌水管、铜水管和钛管作为阴极进行实验,发现阴极材料对结果影响不大,而阳极对杀藻效果影响较大,钌钛电极效果明显好于钛电极.电流密度对杀藻效果影响很大,电流密度为1mA.cm^-2时,杀藻效果不明显,当电流密度大于2.5mA.cm^-2时,杀藻效果开始非常显著.细胞密度是影响杀藻效果的重要因素,在5mA.cm^-2下,低密度(6×10⁸个/L)水样的光密度值下降明显比高密度(6×10⁹个/L)水样快.水样在反应器中的流量对结果影响不大.     

Can Nutrient Spiralling be Used to Detect Seasonal Nutrient Uptake in a Forested Stream?

Nutrient spiralling measurements were conducted in Lyrebird Creek, a forested stream in the Dandenong Ranges, Victoria, Australia. Spiralling indices from several nutrient (, ) enrichment experiments were correlated with seasonal variation in factors thought to control nutrient uptake, i.e., temperature, light and algal biomass. It was hypothesized that nutrient uptake would be higher in summer as increased temperatures would promote both biotic and abiotic processes and higher light levels in summer would stimulate photosynthesis. However, results did not support this hypothesis. Uptake length for and and uptake velocity were not correlated with chlorophyll-a, light or temperature (r ² < 0.30, P > 0.1) despite the seasonality of these biophysical factors (r ² > 0.42, P < 0.02). Lyrebird Creek might had no seasonal trend in nutrient uptake and/or nutrient spiraling measurements only appears suitable for contrasting streams with large differences in biophysical factors that supports biotic and abiotic nutrient processing. In addition, small errors in measuring a nutrient concentration can result in a large range in the estimated S _w and increased difficulty in determining significant differences in nutrient spiralling indices.     

Removal of a type of endocrine disruptors-di-n-butyl phthalate from water by ozonation

Ozonation of synthetic water containing a type of endocrine disruptor-di-n-butyl phthalate （DBP） was examined. Key impact factors such as pH, temperature, ionic strength, ozone dosage and initial DBP concentration were investigated. In addition, the activities of radicals on uncatalysed and catalysed ozonation were studied. The degradation intermediate products were followed and the kinetic of the ozonation were assessed as well. Results revealed that ozonation of DBP followed two mechanisms. Firstly, the reaction rate of direct ozonation was slower at lower pH, temperature, and ionic strength. Secondly, when these factors were increased for indirect radical reaction, higher percentage of DBP was removed with the increase of the initial ozone dosage and the decrease of the initial DBP concentration. In addition, tea-butanol, humic substances and Fe（Ⅱ） affected DBP ozonation through the radical pathway. It was determined that ozonation was restrained by adding tea-butanol for its radical inhibition effect. Furthermore, humic substances enhanced the reaction to some extent, but a slight negative effect would be encountered if the optimum dosage was exceeded. As a matter of fact, Mn（Ⅱ） affected the ozonation by ＂active sites＂ mechanism. In the experiment, three different kinds of intermediate products were produced during ozonation, but the amount of products for each one of them decreased as pH, temperature, ionic strength and initial ozone dosage increased. A kinetic equation of the reaction between ozone and DBP was obtained.     

盐结皮对艾比湖湿地土壤特性的影响及其自然要素分析

为探讨艾比湖湿地内土壤盐结皮(SSC)与土壤特性的相互作用关系,以及影响SSC厚度的 自然要素.采用野外调查与室内试验相结合的方法,在湿地内选取30个具有代表性的样点,并在其周围选取无SSC的样点(30个)作对比,对研究区内有SSC和无SSC覆盖的土壤特性(有机质、容重、质量含水量、总盐、全氮、全磷和pH)进行对比分析...     

环保管家服务模式的分析与探讨

通过分析环保管家发展现状,对环保管家的推广意义、行业发展制约因素进行分析探讨,并针对环保管家的发展趋势提出意见和建议.     

环丙沙星在亚高山草甸不同深度土壤上的吸附及其影响因素

兽用抗菌药物环丙沙星(CIP,ciprofloxacin)的大量使用引发了人们的广泛关注.文章研究了CIP在亚高山草甸土剖面土壤上的吸附动力学、吸附热力学和pH、有机质含量、阳离子交换量等因素对吸附的影响,以揭示CIP在亚高山草甸土上的吸附机制,为CIP的生态风险评价提供一定的依据.结果表明,CIP在亚高山草甸土上的吸...     

武汉市城区空气质量特征及控制对策分析

以武汉市近6年空气污染物浓度数据为基础,分析了城区空气质量特征.武汉市近6年空气污染指数年均值均小于100;年优良天气频率介于60%-75%,逐月天气优良频率以秋、冬两季较低,春、夏两季较高;SO2、NO2均符合国家空气质量二级标准,空气质量总体状况良好.但可吸入颗粒物年年超标,SO2浓度和酸雨检出率有逐年增高的趋势.同时针对空气污染特征,分析了其影响因素,提出了进一步改善空气质量的基本对策.     

典型喀斯特地区土壤-作物系统镉的富集特征与污染评价

为了研究喀斯特地区Cd在表层土壤和农作物中的富集特征及影响因素,为土地安全利用提供理论依据,选择在重庆市黔江区中部采集表层土壤样品360件、深层土壤样品7件、85件水稻样品和73件玉米样品(配套采集根系土样),分析了土壤及农作物中Cd的含量、土壤中TFe2O3、Mn、有机质(Corg)、Se等含量和土壤pH.基于地统计...