地下水硝态氮污染研究进展

随着人口的增加及城市化进程的加快,地下水硝态氮污染日益严重,硝态氮污染治理已经成为近些年来国内外学者研究的热点.通过对地下水硝态氮污染来源、硝态氮迁移及转化机理的研究,探讨硝态氮污染的源头,并结合我国不同地区硝态氮污染实例,总结了国内地下水硝态氮污染的现状,并对硝态氮污染修复技术进行简要概述.     

溶解氧在IVCW系统变化及与氮去除的相关性研究

试验模拟复合垂直流人工湿地系统的运行,研究系统内部溶解氧的变化趋势及溶解氧与氮去除效果的相关性.结果表明:复合垂直流人工湿地中,氨态氮、亚硝态氮和溶解氧沿水流方向逐渐减小；硝态氮沿流程先上升后下降；由于上行池因溶解氧低,总氮的去除过程主要发生在下行池.     

太湖流域旱地农业区氮素流失特征研究

了解水文过程对研究径流污染物的输出规律及控制农业非点源污染有重要意义。以张家港海芸枇杷林试验区为依托,监测自然降雨条件下研究区出口径流和地下水中的氮素浓度,研究了太湖流域典型旱地总氮(TN)、硝态氮(NO-3-N)、铵态氮(NH+4-N)流失的特征。结果表明,硝态氮是氮素流失的主要形式,占氮流失总量的90.1%;径流初期氮素浓度迅速升高,之后随径流增大逐渐降低,径流退水阶段壤中流携带土壤中硝态氮补给地表流,氮素浓度回升;氮素输出浓度随降雨强度的增强而升高。     

不同菹草密度对上覆水可交换态氮迁移转化的影响

为了探索不同沉水植物密度对上覆水中可交换态氮迁移转化的影响,采用SPSS17.0统计软件,选择菹草为例进行模拟试验,试验设置了空白组、150g菹草组和300g菹草组三个不同密度组,分析了菹草生长对上覆水中氨氮、硝氮迁移转化的影响。结果表明,在一定的菹草密度范围内,菹草的密度越大,上覆水体中叶绿素a含量及蓝藻、绿藻和硅藻的生物量减小量越大;在与浮游藻类营养竞争中,高密度菹草组具有优势,并在较短的时间内稳定,且高密度菹草显著降低了上覆水体中的氨氮浓度(p0.01)。     

青海湖湖水中氮的时空变化

为揭示氮素在青海湖的分布情况,分析了青海湖湖水9个采样点135个水样的总氮、硝酸盐氮、亚硝酸盐氮和氨氮的浓度。结果表明,湖水总氮、硝酸盐氮、亚硝酸盐氮、氨氮平均浓度分别为4.334、2.160、0.007、0.843mg/L;不同测点氮素浓度变化较大,其中黑马河、布哈河、沙柳河浓度均较高,总氮、硝酸盐氮、亚硝酸盐氮、氨氮浓度范围分别为6.071~9.245、3.259~6.192、0.008~0.027、1.148~1.321mg/L,其余测点总氮、亚硝酸盐氮浓度较低,而硝酸盐氮、氨氮浓度较高。8月各测点水样中氮素浓度最高,6月氮素浓度最低。分析表明,青海湖湖水中氮的分布与转化受湖水理化性质及雨季氮的外源输入影响较大。     

生物质挥发分燃烧NO生成规律研究

生物质燃料在燃烧过程中燃料氮会转化为NO释放,而生物质中绝大部分的燃料氮在热解过程中以挥发分氮的形式释放,因此挥发分氮对于NO的生成极为重要。为探究生物质挥发分燃烧生成NO的规律,在水平管式炉反应器及Chemkin仿真模拟上研究了不同生物质、不同温度、不同氧浓度对挥发分NO生成的影响。试验结果表明:生物质含氮量越高,挥发分NO的转化率越低;挥发分NO的转化率随温度上升先增加,在800℃达到峰值后略微减小;氧浓度越高,挥发分NO的转化率越高。该结论有助于理解生物质挥发分燃烧生成NO的规律,对采取合理措施降低NO排放有积极意义。     

脱氮技术的发展

氮以有机氮和无机氮两种形态存在于水体中.前者有蛋白质、复肽、氨基酸和尿素等,它们来源于生活污水、农业废弃物和羊毛加工、制革、印染、食品加工等工业废水.这些有机氮经微生物分解后将转化为无机氮,水中的无机氮指氨氮、亚硝态氮和硝态氮(这三种无机氮统称为氮化合物).     

生物质湿解过程中C和N的迁移行为研究

以麦秆、梧桐叶和草坪草为原料,采用小型湿解实验系统,考察不同温度(160、180、200、220、240℃)、60 min停留时间下3种湿解产物中C和N元素的分布形态及其迁移行为。研究发现:温度对生物质湿解产物分布有重要影响,高温有利于湿解液相产物的生成,湿解固体富碳产物产量降低;随反应温度的升高,C以可溶性糖和有机可溶物形式进入液相中的比例明显增加,N和C的迁移特性稍有差异,当达到较高温度(220℃)后,以可溶性氨态氮或硝态氮进入液相的比例急剧增加;3种生物质样品因其化学结构和组分的不同,其湿解过程中的产物分布及C和N的迁移对温度升高的响应依次增加。     

镇江丘陵区农业流域土地利用对氮素输移的影响

为研究镇江丘陵区句容水库流域土地利用对氮素输移的影响,构建了句容水库流域SWAT模型,分别采用2005～2007年的径流数据对径流模型进行率定和验证、2007年的氮浓度监测数据对氮负荷模型进行验证,并计算了流域不同土地利用类型上有机氮及硝态氮的输出、模拟了有机氮和硝态氮流失在年内的分布。结果发现有机氮输出量强度、硝态氮随径流输出强度及流失年内逐月分布规律;居住地面积比例、地表径流和氮负荷都随着林地面积的减少而增大。     

无烟煤粉循环流化床预热过程中的煤氮转化特性

在基于循环流化床预热的无烟煤粉燃烧实验台上,在循环流化床空气当量比低于0.3的条件下对无烟煤粉在预热过程中煤氮的迁移和转化特性进行了研究.结果表明,煤氮的主要转化产物为NH3和N2;随着煤中挥发分含量的升高和煤阶的降低,煤氮的转化率和煤氮向N2的转化率增加;随着预热温度的升高,煤氮的转化率和煤氮向N2的转化率增加,预热生成的NH3质量浓度降低;随着循环流化床空气当量比的增加,煤氮的转化率和煤氮向N2的转化率增加,预热生成的NH3的质量浓度降低.煤氮向NH3和N2的转化反应以及NH3和N2之间的转换反应是决定无烟煤预热过程中煤氮迁移转化的主要热化学反应.     

Biochar and plant growth promoting rhizobacteria effects on switchgrass (Panicum virgatum cv. Cave-in-Rock) for biomass production in southern Québec depend on soil type and location

Switchgrass (Panicum virgatum L.) is a fast growing native C₄ perennial and a lignocellulosic biomass crop for North America. In combination with biochar, an active plant growth promoting rhizobacterial (PGPR) community can contribute to the long-term sequestration of carbon in soil, fix nitrogen, and enhance the availability of other nutrients to plants. Biochar and PGPR have the potential to improve grass biomass production, but they have not been tested together under high-latitude temperate zone field conditions. Therefore, the objective of this three-year field study was to determine whether there were effects on biomass yield and yield components of switchgrass (cv. Cave-in-Rock) due to a rhizobacterium that was able to mobilize soil phosphorus (Pseudomonas rhodesiae), a bacterial consortium that was able to supply nitrogen (Paenibacillus polymyxa, Rahnella sp., and Serrati sp.), and pine wood chip biochar applied as a soil amendment at 20 Mg ha⁻¹. The incorporation of biochar, or inoculation with the N-fixing consortium, and the combined inoculation of the experimental bacteria had positive effects on switchgrass height. At a loam soil site in Sainte-Anne-de-Bellevue, Québec, when nitrogen fertilizer was not applied, the addition of biochar had a positive effect on stand count (tillers m⁻¹ row). On the sandy soil in Sainte-Anne-de-Bellevue, when biochar was applied with 100 kg N ha⁻¹, biomass yield increased over the control but did not provide additional benefits over plots receiving only 50 kg N ha⁻¹. It remains unclear whether or not the increased C sequestration of this management system justifies increased N fertilizer usage.     

坡度与降雨强度对坡面侵蚀产沙过程影响的试验研究

鉴于坡度和降雨强度的变化对坡面侵蚀产沙过程影响明显,通过设计室内大型试验土槽,采用室内人工模拟降雨的方法,对不同坡度和降雨强度下坡面侵蚀输沙动态过程进行试验研究。结果表明,在降雨强度不变的条件下,累计产沙量、输沙率随坡面坡度增大而增大;同一坡度下累计产沙量、输沙率随降雨强度的增加而增加;输沙率与降雨强度呈线性关系,与坡度呈幂函数关系。进而基于试验结果,通过二元非线性回归,建立了输沙率、单位面积单位时间产沙量、坡度及降雨强度之间的经验公式。     

坡面氮素流失模型的建立与应用

根据农田土壤氮素流失过程建立了基于次降雨事件的坡面氮素迁移模型,采用G-A方程、运动波方程计算了下渗与坡面流,运用欧洲土壤侵蚀模型模拟了土壤侵蚀,并综合考虑了水-土界面与土壤中的对流扩散过程及氮素迁移过程.以野外实验为例,对该模型进行率定及验证,结果表明该模型结构简单、参数易获取、物理意义明确、模拟地表径流中各形态氮素浓度过程效果较好.     

Change in carbon footprint of canola production in the Canadian Prairies from 1986 to 2006

Accounting for greenhouse gas (GHG) emissions at the production stage of a bioenergy crop is essential for evaluating its eco-efficiency. The objective of this study was to calculate the change in GHG emissions for canola (Brassica napus L.) production on the Canadian Prairies from 1986 to 2006. Net GHG emissions in the sub-humid and semi-arid climatic zones were estimated for fallow-seeded and stubble-seeded canola in intensive-, reduced- and no-tillage systems, with consideration given to emissions associated with synthetic nitrogen (N) fertilizer input, mineralized N from crop residues, N leaching and volatilization, farm operations, the manufacturing and transportation of fertilizer, agrochemicals and farm machinery, and emission and removal of CO₂ associated with changes in land use (LUC) and land management (LMC). The GHG emissions on an area basis were higher in stubble-seeded canola than in fallow-seeded canola but, the opposite was true on a grain dry matter (DM) basis. Nitrous oxide emissions associated with canola production, CO₂ emissions associated with farm energy use and the manufacturing of synthetic N fertilizer and its transportation contributed 49% of the GHG emissions in 1986 which increased to 66% in 2006. Average CO₂ emissions due to LUC decreased from 27% of total GHG emissions in 1986 to 8% in 2006 and soil C sequestration due to LMC increased from 8% to 37%, respectively. These changes caused a reduction in net GHG emission intensities of 40% on an area basis and of 65% on a grain DM basis. Despite the reduction in GHG emission intensities, GHG emissions associated with canola in the Prairies increased from 3.4 Tg CO₂ equiv in 1986 to 3.8 Tg CO₂ equiv in 2006 because of the more than doubling of canola production.     

昆明市盘龙区山洪灾害分析评价方法

山洪灾害分析评价是山洪灾害群防群治的基础,以昆明市盘龙区为例,选择沿河村落所在小流域为分析对象,推求设计暴雨与设计洪水、评估现状防洪能力、采用试算法推求了三种不同土壤湿度条件下的预警雨量,在此基础上分析了产汇流模型模拟误差与预警雨量误差的对应关系,获得盘龙区重点山洪村防洪能力评价及预警雨量。分析结果表明,推求的预警雨量可以满足当地山洪预警雨量发布的需求,研究成果可为当地山洪监测预警系统提供参考。     

Land application of organic waste – Effects on the soil ecosystem

Growing populations and the increasing use of existing resources has led to growth in organic waste emissions. Therefore, a sustainable approach to managing this waste has become a major concern in densely populated areas. Biological treatment is an efficient method for reducing the amount of organic waste, and for producing energy. A large number of biogas plants and compost facilities that use organic waste as a substrate for electricity and fuel production are being built around the world. The biological treatment process in these plants produces large amounts of organic waste, and there is therefore a growing need to find a sustainable use for this material. Organic waste, such as biogas residues and compost can be a valuable fertilizer for agricultural soils. They can serve as a source of plant nutrients and can also improve soil structure and water holding capacity. However, as organic residues are known to contain both heavy metals and organic contaminants there is a need for long term field experiments to ensure that soil and plant quality is maintained. In order to investigate the potential risks and benefits of using organic waste in agriculture, an 8 year field experiment was established in central Sweden. Under realistic conditions, compost and biogas residues from source-separated household waste were compared with traditional mineral fertilizer. We examined crop yield and soil chemical and microbiological properties. The main conclusion from the field experiment was that biogas residues resulted in crop yields almost as high as the mineral fertilizer NPS. In addition, several important soil microbiological properties, such as substrate induced respiration, potential ammonium oxidation and nitrogen mineralization were improved after application of both biogas residues and compost. Moreover, no negative effects could be detected from using either of the organic wastes. In particular the genetic structure of the soil bacterial community appeared to resist changes caused by addition of organic waste.     

某大学校园及周边不同下垫面降雨径流污染过程研究

以大学校园及其周边区域降雨、径流和径流水质3年观测试验数据为依据,分析不同下垫面降雨过程、径流过程及污染物运移过程的规律及特征,计算出不同下垫面污染物输出系数。结果表明,雨水中氨氮浓度高于Ⅳ类水质标准,悬浮物、硝酸盐氮和COD浓度均低于最高水质标准;产流时间与产流前平均降雨强度呈幂函数关系,不同下垫面径流过程与降雨过程呈正相关关系;径流强度是径流携带污染物运移的重要影响因素,径流强度增加,径流携带污染物质量随之上升。污染物输出系数计算结果表明,屋面主要污染物为含氮污染物,餐饮街道主要为有机污染,不同下垫面悬浮物、硝酸盐氮、氨氮和COD输出系数均值分别为2294.91、7.21、14.86、430.34kg/hm2/a。     

沼肥对保护地番茄生长发育及其产量的影响

采用二裂式区组设计的方法,以番茄为供试作物,以沼肥（沼液、沼渣）、猪粪和化肥为肥料,研究了不同施肥措施对番茄生长发育及其产量的影响。结果表明：与施用化肥相比,施用沼液的番茄植株平均株高及根系体积有所增加,番茄产量略有降低;与施用猪粪相比,施用沼渣可促进植株茎秆的健壮生长及根系发育,番茄产量提高20．8％;与沼渣和化肥配合施用相比,沼渣与沼液配合施用促进了番茄植株的生长发育,其植株生长稳健,根系发达,而且番茄产量增加;与猪粪和化肥配合施用相比,猪粪与沼液配合施用促进了番茄植株的生长发育,其株高较高、茎秆粗壮、根系发达,但番茄产量下降。     

降雨对类土质滑坡微观结构及稳定性的影响分析

以福建省永泰滑坡为例,利用电镜试验分析了类土质滑坡土体的微观结构,掌握了降雨对类土质土体微观结构的影响,并基于数值模拟方法从宏观上研究了不同降雨模型对类土质滑坡稳定性的影响。结果表明,含水率及干湿循环对土体微观结构的影响较为显著,表现为土体含水率越高,干湿循环的次数越多,土颗粒之间的连接减弱、定向性变差及排列趋于无序,进而造成其微观结构的破坏;另外,在总降雨量保持不变的情况下,不同降雨模型对滑坡稳定性的影响也较为显著,表现为高强度降雨工况对滑坡稳定性的影响低于低强度降雨工况对滑坡的影响,前期降雨对滑坡稳定性影响最大,后期次之,中期对滑坡稳定性影响最小。