水中总氮测定方法存在问题的研究及改进

碱性过硫酸钾消解紫外分光光度法测定水中总氮采用的消解器皿是玻璃比色管,易造成空白偏高、结果偏低等问题。采用双圆柱状的消解杯对水样进行消解。结果表明,消解杯消解水中总氮,线性相关系数均大于0.999,检出限为0.05 mg/L,相对标准偏差小于5%,相对误差为0.88%~1.00%;改进后的消解器皿具有较好的精密度和准确度,能够更加准确测定水中总氮的含量。     

酸碱度对生活垃圾焚烧厂沥滤液蒸发处理效果的影响

采用蒸发法处理城市生活垃圾焚烧厂垃圾沥滤液,着重考察了不同沥滤液初始pH值对蒸发去除COD和氨氮效果的影响,并采用GC-MS对蒸发冷凝液中有机物成分进行了分析鉴定.结果表明,生活垃圾沥滤液的初始pH对冷凝液中COD、氨氮含量及有机污染物分布产生了决定性的影响.沥滤液在酸性条件下(pH≤6)蒸发,随着pH的增加,冷凝液中COD的含量线性降低,而氨氮的含量线性增加.当沥滤液的初始pH值从6增加到11,冷凝液中COD的含量呈对数函数降低,而氨氮的含量表现出显著增加趋势.从冷凝液中鉴定出38种有机污染物,多为沸点较低的醇、酸、酚和酯类.在酸性条件下(pH=3),冷凝液中挥发性有机酸和低碳醇的相对丰度接近90％.在近中性条件下(pH=6.2),冷凝液中的有机污染物以酚、酸和杂环类化合物为主.在碱性条件下(pH =11),冷凝液中酚和杂环类化合物占比较高,而酸的含量极少.     

淮河支流污染物综合降解系数动态测算

确定河流污染物综合降解系数动态变化规律对提高水环境容量测算精度和水环境管理具有重要意义。通过现场模拟法,采用一维稳态模型测算了淮河支流洪河五沟营-塔桥乡河段COD、氨氮和总磷在枯水期、平水期和丰水期的综合降解系数,COD、氨氮和总磷降解系数在各水期的关系为枯水期平水期丰水期,提出了建议值并利用实测浓度对计算结果进行了检验,结果表明,不同水期综合降解系数吻合情况较好。     

晋牛矿1303综放面采空区注氮方案研究及数值模拟

为了合理设计采空区注氮防灭火方案，以晋牛煤矿1303综放工作面为研究对象，通过在采空区进、回风侧布置束管监测系统，连续测定采空区气体浓度变化，划分采空区自燃“三带”分布区域,并基于采空区自燃“三带”划分标准和数值模拟的方法，利用流体力学COMSOL计算软件，研究不同注氮量、注氮位置下采空区氧化自燃带的分布规律。研究结果表明:注氮量和注氮位置参数的变化，对氧化自燃带上界限的影响并不显著，而对氧化自燃带的下界限影响比较显著；最合适的注氮位置应该在距离切顶线30 m左右，运用Origin软件得出注氮量与氧化自燃带宽度呈指数关系，由拟合式计算出最优注氮量为386 m3/h，此时氧化自燃带的宽度为31.5 m。     

水中藻类对连续流动法测定总氮结果的影响

以天津市河道、水库为研究对象,在藻类增殖期采用连续流动法与碱性过硫酸钾消解法对水体中总氮进行比对监测,同时分析水中藻类分类和藻细胞密度。试验表明:虽然两种方法测定总氮的结果精密度基本相同,但二者之间的系统误差存在显著差异,连续流动法较碱性过硫酸钾消解法的测定结果低5.4%。两种方法测定总氮结果的相对偏差与水体中藻细胞密度呈正相关性,当水体中藻细胞密度﹥2.41×108L-1时,对连续流动法测定总氮的结果产生显著影响,相对偏差超过标准规范要求。     

不同气源压缩气体泡沫灭石油醚火灾性能比较

采用实验室压缩气体泡沫系统,通过缩尺油盘火试验,分别考察基于不同气源的压缩气体泡沫对于石油醚火灾的灭火性能,分析探讨适用于低沸点的石油醚类燃料火灾扑救的气源类型和供气方案。结果表明,在泡沫溶液供给强度为2.5 L/(min·m2)的条件下,压缩氮气泡沫和压缩空气泡沫均可扑灭石油醚火灾,具有良好的抗烧性能;二者相比,压缩氮气泡沫比压缩空气泡沫的控灭火性能和抗烧性能均有一定提升;对于石油醚类的低沸点易燃液体火灾,建议采用以氮气作为气源的压缩氮气泡沫系统;该研究可为压缩气体泡沫系统在石油化工行业工程应用提供技术支撑。     

氨气敏电极法和纳氏试剂分光光度法对地表水中氨氮的比对测试

采用不同质量浓度的氨氮标准样品和实际样品,用氨气敏电极法和纳氏试剂分光光度法进行同步测试。结果表明,2种分析方法在水样氨氮质量浓度在0. 159～2. 81 mg/L范围内具有良好的可比性、精密性和准确性。氨气敏电极法的检出限为0. 03 mg/L,平行6次测定样品的相对标准偏差为0. 4%～4. 2%,加标回收率为85. 0%～110%;纳氏试剂分光光度法的检出限为0. 025 mg/L,平行6次测定样品的相对标准偏差为0. 5%～6. 4%,加标回收率为93. 0%～99. 8%。同时氨气敏电极法在样品预处理、试剂配制和分析时间上要优于纳氏试剂分光光度法。氨气敏电极法能够满足地表水自动监测在线比对实际工作的需求,该方法具有良好的适用性。     

Wetland Flowpaths Mediate Nitrogen and Phosphorus Concentrations across the Upper Mississippi River Basin

Eutrophication, harmful algal blooms, and human health impacts are critical environmental challenges resulting from excess nitrogen and phosphorus in surface waters. Yet we have limited information regarding how wetland characteristics mediate water quality across watershed scales. We developed a large, novel set of spatial variables characterizing hydrological flowpaths from wetlands to streams, that is, “wetland hydrological transport variables,” to explore how wetlands statistically explain the variability in total nitrogen (TN) and total phosphorus (TP) concentrations across the Upper Mississippi River Basin (UMRB) in the United States. We found that wetland flowpath variables improved landscape-to-aquatic nutrient multilinear regression models (from R² = 0.89 to 0.91 for TN; R² = 0.53 to 0.84 for TP) and provided insights into potential processes governing how wetlands influence watershed-scale TN and TP concentrations. Specifically, flowpath variables describing flow-attenuating environments, for example, subsurface transport compared to overland flowpaths, were related to lower TN and TP concentrations. Frequent hydrological connections from wetlands to streams were also linked to low TP concentrations, which likely suggests a nutrient source limitation in some areas of the UMRB. Consideration of wetland flowpaths could inform management and conservation activities designed to reduce nutrient export to downstream waters.     

Effect of particle size on CO adsorption and thermodynamic analysis

The liquid nitrogen adsorption method was used to characterize the pore structure of non-cohesive coal in the 061,404 working face of the Lingxin coal mine. The amount of specific surface area of micropores in the sample continuously rose as particle sizes reduced. The volumetric method was used to measure the CO isothermal adsorption curves of three samples (sample I, 0.425–0.25 mm, sample II, 0.18–0.25 mm, and sample III, 0.15–0.18 mm). The experimental results were fitted by the Langmuir model. According to the experimental results, it was conducive to CO adsorption with the conditions of high pressure and low-temperature. The decrease in grain diameter increased the number and volume of micropores in the sample, which improved the adsorption capacity of the sample. In addition, according to the adsorption data, the CO adsorption thermodynamics of three samples were analyzed, including surface potential (Ω), Gibbs free energy change (ΔG) and entropy change (ΔS). The results demonstrated that CO adsorption by coal was a spontaneous process. Sample III has the most substantial adsorption capacity, whereas the sample I has the weakest adsorption capacity.     

SBR法处理低C/N污水的工程应用——以某基地污水处理站改造工程为例

低C/N污水的生化处理过程中,由于碳源不足,不能满足硝化和反硝化的要求,造成出水NH3-N超标。采用SBR工艺对某基地污水处理站厌氧处理后的低C/N污水进行改造,处理后出水COD去除率达到97%以上,NH3-N去除率达到93%以上。