Use of amendments to reduce leaching loss of phosphorus and other nutrients from a sandy soil in Florida

Goal, Scope and Background Transport of P from agricultural land contributes to the eutrophication of surface waters. Soil amendment is considered one of the best management practices (BMPs) to reduce P loss from sandy soils. Laboratory column leaching experiments were conducted to evaluate the effectiveness of different soil amendments in reducing P leaching from a typical sandy soil in Florida. Methods The tested amendments were CaCl₂, CaCO₃, Al(OH)₃, cellulose, and mill mud, and applied at the rate of 15 g/kg for a single amendment and each 7.5 g/kg if two amendments were combined. Leaching was conducted every four days for 32 days, 250 mL of deionized water being leached for each column per leaching event. Leachates were collected from each leaching event and analyzed for reactive P, PO₄-P, and macro and micro-elements. Results and Discussion Except for the soils amended with CaCl₂, or CaCl₂+CaCO₃, reactive P and PO₄-P leaching losses mainly occurred in the first three leaching events. Phosphorus leaching from the soils amended with CaCl₂ or CaCl₂+CaCO₃ was less but more persistent than that of other amendments. Reactive Pleaching loss was reduced by 36.0% and 40.4% for the amendments of CaCl₂, and CaCl₂+CaCO₃, respectively, as compared with chemical fertilizer alone, and the corresponding values for PO₄-P were 70.8% and 71.9%. The concentrations of K, Mg, Cu, and Fe in leachate were also decreased by CaCl₂ or CaCl₂+CaCO₃ amendment. Among the seven amendments, CaCl₂, CaCO₃, or their combination were most effective in reducing P leaching from the sandy soil, followed by cellulose and Al(OH)₃, the effects of mill mud and mill mud + Al(OH)₃ were marginal. Conclusions These results indicate that the use of CaCl₂, CaCO₃, or their combination can significantly reduce P leaching from sandy soil, and should be considered in the development of BMPs for the sandy soil regions. Recommendations and Outlook Most agricultural soils in south Florida are very sandy with minimal holding capacities for moisture and nutrients. Repeated application of fertilizer is necessary to sustain desired yield of crops on these soils. However, eutrophication of fresh water systems in this area has been increasingly concerned by the public. Losses of P from agricultural fields by means of leaching and surface runoff are suspected as one of the important non-point contamination sources. The benefits and effectiveness of soil amendment in reducing P losses from cropping production systems while sustaining desired crop yield need to be demonstrated. Calcium chloride, CaCO₃, or their combination significantly reduce Pleaching from sandy soil, and should be considered in the development of BMPs for the sandy soil regions.     

微波活化对Ca(OH)2孔隙结构及脱氯性能的影响

采用微波炉对一定质量的氢氧化钙样品进行活化,利用压汞仪考察了不同微波活化时间及脱氯反应前后的Ca(OH)2总比孔表面积、分段比表面积和孔径分布的变化,并在脱氯实验台上对脱氯效率进行实际测试.结果表明,微波活化存在一个最佳时间,在此时间内样品比孔表面积增大50%左右,而超过这一时间样品比表面积回复性减小;微波活化主要通过增加3～20 nm孔径段的微孔为样品提供更大比表面积;这些新增加的微孔在脱氯反应过程中被完全利用或消耗;最佳活化时间下的微波活化使Ca(OH)2在较低Ca/Cl摩尔比下获得更大脱氯效率,Ca/Cl摩尔比=4.1时,脱氯效率增加了20%.     

民族地区农村突发事件区域应急联动机制研究

民族地区农村公共危机形态复杂多样,危机承受能力弱,政府对民族地区农村突发事件的管理往往"远水解不了近渴"。利用民族地区农村合作组织的快速发展机遇,将其纳入农村应急管理体系,构建农村区域应急联动机制,使其成为农村应急服务的基层主体与应急资源的储备基地,不但可以提高农村突发事件的自救互救能力,而且完善了政府的应急管理体系。     

Hepatitis E Virus Genotype 4 Sequences Detected in Sewage from Treatment Plants of China

The aim of this study was to investigate the occurrence of hepatitis E virus (HEV) in sewage samples in Shen Zhen, China. Sewage samples were collected from 152 sewage plants including livestock sewage, domestic sewage and treated sewage from May to July of 2015. Two of 152 samples were HEV positive (1.32%) from the livestock sewage plants. Partial ORF2 fragments of HEV were sequenced and a phylogenetic tree was constructed using MEGA5.1. Blast and phylogenetic analyses showed that both of these two sequences belonged to HEV Genotype 4. To the best of our knowledge, this is the first study on the molecular characterization of HEV in wastewater in China and the first time to detect Genotype 4 in the sewage. Results from this study indicate that the possibilities of sporadic infections of HEV should be emphasized because virus still has the possibility to be circulating in the sewage in China.     

陶瓷质微孔管过滤式除尘器的研究

陶瓷质微孔管过滤式除尘器是一种新型耐高温除尘器。在此介绍了该除尘器的组成、特点、结构和陶瓷质微孔管过滤原理。通过实验室及工业实验,证明该除尘器具有耐高温、耐腐蚀、耐磨损、使用寿命长、除尘效率高等优点,值得推广借鉴。     

ICP-MS同时测定饮用水中25种元素的研究

采用电感耦合等离子体质谱(ICP-MS)对饮用水中25种元素进行同时测定,并对其方法进行了研究.结果表明用ICP-MS同时测定饮用水中25种元素,其最低检出限为Th 1.238 E-5μg/L;其RSD%均小于5%;加标回收率介于98.94～100.4%之间,具有较高的灵敏度、精密度和准确,特别是对一些浓度低达ng/L级,但对人体健康却产生重要影响的超痕量组分,如Tl、Th、U等的测定,本法具有其它传统分析难以满足的优势.应用于直接测定元素浓度范围从ng/L-mg/L级的实际样品,具有快速、简便、准确等优点.     

浅析绿色社区创建措施——以长沙市芙蓉区国家级绿色社区为例

随着我国经济建设的发展，生态环境受到了一定程度的破坏，环境污染成为制约城市发展的重要问题。国家颁布文件要求全国环境保护重点城市要逐步开展创建“绿色社区”活动，培养公众良好的环境伦理道德规范，促进良好社会风尚的形成。生态学在城市社区规划和建设中的应用为社区研究提供了指导思想和理论依据。绿色社区的创建工作在全国已经蔚然成风，关于绿色社区的研究在国内外逐渐兴起，成为建筑界、城市生态学研究的热点，由于它平衡了环境保护和人类社会经济发展之间的关系．被认为是可持续发展理论在城市发展中有效可行的具体应用。本文分析了绿色社区的基本内涵，指出绿色社区以可持续发展思想为指导，体现“人与自然和谐共生”的思想，具有整体性、长期性和地域性的特点，进而阐明长沙市芙蓉区绿色社区的创建情况，最后探讨了绿色社区的创建措施和途径。     

酸性多糖微生物絮凝剂的提取、纯化与分析

对一株链球菌发酵获得的絮凝活性物质进行了分离和提取,并应用DEAE-Sephadex A25,Sephdarose 4B凝胶色谱柱从发酵液中提取活性物质并纯化.通过薄层色谱、气相色谱、紫外光谱、红外光谱、元素分析等表征,初步推测了其主要成分为酸性多糖,其中多糖含量(73%)、糖醛酸含量(20.6%)、多糖分子量为4.3×105,可能还有少量氨基或短肽结构.     

鞘细菌FC9901氧化铁生化机制的研究

本文对分离到的鞘细菌菌株FC990 1氧化铁的生化机制进行了初步研究。结果表明 ,该菌株的营养类型为化能有机营养型 ,其能源主要来自有机碳源的氧化 ,并不能从Fe2 + 氧化过程中获取能量。活性定位研究和 pH、温度、抑制剂试验结果表明 ,该铁氧化活性物质是酶 ,而且是一种胞外酶。铁的生物学氧化属于酶学催化过程 ,并遵守酶的动力学。     

长江口潮滩芦苇根表铁膜磁性特征及其环境意义

湿地植物根表铁膜对包括重金属在内的物质迁移转化具有重要作用,其氧化铁组成研究备受重视,但利用环境磁学方法进行表征的研究还未见报道.本文对长江口潮滩植物芦苇根系及周边沉积物进行了磁学分析,并结合沉积物粒度、漫反射光谱等测试,对芦苇根表铁膜的磁性矿物组成进行了系统研究.结果表明,芦苇根表铁膜磁性矿物主要包括磁铁矿和赤铁矿.由于沉积物不同深度氧化还原环境的不同,铁膜磁性矿物组成存在垂向差异.研究柱样24 cm深度以上,由于相对氧化的环境,铁膜磁性矿物除磁铁矿外,还有较多的赤铁矿贡献;24 cm深度以下,因根系处于相对还原的环境,磁性矿物以磁铁矿为主.与沉积物相比,24 cm以上深度铁膜中亚铁磁性矿物含量较低,24 cm深度以下则相反,反映铁膜和沉积物磁性矿物来源不同.本项研究表明,磁性测量方法有助于认识湿地植物根表铁膜的矿物组成,对湿地生物地球化学过程研究具有重要价值.