Evaluating Phosphorus Loss for Watershed Management: Integrating a Weighting Scheme of Watershed Heterogeneity into Export Coefficient Model

The identification of critical source areas (CSAs) and critical source periods (CSPs) are essential prerequisites for cost-effective practices of non-point source (NPS) pollution control. A simple empirical tool combining Export Coefficient Model (ECM) and a Geographic Information Systems (GIS)-based weighting scheme of watershed heterogeneity was proposed to estimate annual and monthly phosphorus loss, to identify critical source areas and periods, and to assess pollution control practices. The GIS-based weighting scheme was developed to represent the transport potential of runoff to move phosphorus from the land surfaces to waters, as a supplement to the source-based ECM. The empirical tool was applied to the Dianchi Lake watershed of China. The results showed that the total phosphorus loss from NPS in 2008 was 352.3 tons. The agricultural land was recognized as the largest and the most spatially various source type. The lakeside plain and the terraces of the watershed were identified as CSAs, which generated more than 90 % of non-point phosphorus. The early part of wet season (from May to August) was the CSPs, when about 70 % of non-point phosphorus was lost. The reduction of phosphorus fertilizers and the vegetated buffer strips (VBS) were effective in controlling phosphorus loss from NPS in the watershed. A reduction of 20 % in phosphorus fertilizer application combined with the set-up of VBS in both riparian area of the main watercourses and the lakeside areas would decrease 25 % of phosphorus loss.     

Effect of water current on the distribution of polycyclic aromatic hydrocarbons,heavy metals and benthic diatom community in sediments of Haihe estuary,China

The pollution loads continuously increased in Haihe estuary, of Tianjin, China, due to intensive human activities, especially the construction of the Haihe Gate and Lingang Industrial Area. In 2011, hydrological variability in Haihe estuary was investigated and sediments were collected. Total organic carbon (TOC), particle size, total polycyclic aromatic hydrocarbons (ΣPAHs), heavy metals (Cd, Cr, Cu, Ni, Pb, and Zn), and benthic diatom community were analyzed. The highest concentrations of ΣPAHs and heavy metals were found near the Haihe Gate. The Shannon diversity index and the relative abundance of Coscinodiscus perforatus (RC) indicated a decreasing trend seaward. Results of Pearson correlation analysis illustrated significant relations between water current velocity and ΣPAHs (p?p?p?相似文献   

气液混合脉冲放电体系中偶氮染料的脱色效果

为了深入探究水包气式气液混合脉冲放电体系中各参数对有机物降解效果的影响,建立了多针一板电极形式的气液混合脉冲放电等离子体体系,以典型的偶氮染料——酸性橙Ⅱ（A07）为目标物,考察该体系中影响染料脱色效果的关键因素。研究结果表明,气液混合脉冲放电体系中与脉冲电源输入功率有关的因素（脉冲电压峰值和脉冲频率）对A07脱色效果影响明显。随着脉冲电压峰值和脉冲频率的增加,A07溶液的脱色效率和相应的准一级降解动力学常数增加。在较高的脉冲电压峰值（30kV）和脉冲频率（75Hz）条件下,10mg／LA07溶液的脱色效率和准一级降解动力学常数分别达到r92．7％和3．50×10～／min。同时,研究证明酸性溶液条件较利于染料脱色。     

Life-cycle assessment of two sewage sludge-to-energy systems based on different sewage sludge characteristics: Energy balance and greenhouse gas-emission footprint analysis

Anaerobic digestion and incineration are widely used sewage sludge(SS) treatment and disposal approaches to recovering energy from SS, but it is difficult to select a suitable technical process from the various technologies. In this study, life-cycle assessments were adopted to compare the energy-and greenhouse gas-(GHG) emission footprints of two sludge-to-energy systems. One system uses a combination of AD with incineration(the AI system),whereas the other was simplified by direct incineration...     

沈阳市机械加工企业的环境风险排查与防控实践

以沈阳市某大型机械加工企业为对象,对企业环境风险排查与防控开展了实践研究,并进一步梳理了该行业存在的突出环境问题。结果表明:该企业在日常环境管理制度上,污水管网与处理设施、废气排放处治、固体废物及危险废物监管等方面存在一定环境风险。针对环境风险排查出的问题,从"第三方"视角提出了防控方案。     

南京市城区和郊区PM2.5中碳质组分特征差异及来源分析

为比较南京市城区和郊区细颗粒物（PM_2.5）中碳质组分特征及来源差异，利用碳组分在线监测仪器对2022年城区和郊区有机碳（OC）和元素碳（EC）进行连续监测。研究结果表明：（1）2022年南京市城区OC、EC质量浓度分别为（5.24±2.39），（1.27±0.62）μg/m³，郊区OC、EC质量浓度分别为（5.67±2.45），（1.32±0.70）μg/m³。2022年OC和EC质量浓度水平分别较2014—2018年均显著下降。城区和郊区的OC、EC质量浓度均呈现冬季高、夏季低的特点。从日变化特征看，城区和郊区OC和EC质量浓度均呈现白天低、夜间高的特点，并且具有明显的峰谷值。（2）城区和郊区OC、EC均在冬季呈现良好的相关性，显著高于春季和夏季。根据碳质组分与气态污染物的关系以及ρ（OC）/ρ（EC）分析结果，城区和郊区均存在二次污染，机动车和燃煤是城、郊区的主要污染源，机动车源对城区影响大于郊区，燃煤源对郊区影响大于城区。（3）污染源的直接排放对南京市OC的质量浓度水平影响较大，郊区二次有机碳（SOC）质量浓度高于城区。城区需要重点关注机动车排放，郊区需要与周边区域协同治理燃煤、生物质燃烧等方面的污染排放。     

人体温度的调节及冬季防寒服装穿着分析

为了研究在寒冷气候下人身体各部位应如何保持温暖,本文对人体的温度调节、产生热量、散发热量进行了介绍,对各部位的防寒服装进行了功能分析,并提出了各部位服装的穿着建议。     

空气湿度对自吸过滤式口罩过滤性能的影响研究

口罩是阻止颗粒物进入人体的有效防护用品,其性能优劣直接影响着佩戴人员的健康与安全。采用国标建议的呼吸阻力实验装置与自制的过滤效率实验装置,对自吸过滤式KN90,KN95系列口罩的呼吸阻力与不同相对湿度下的分级过滤效率进行实验研究。结果表明:所研究的6种口罩的呼气阻力与吸气阻力值不仅满足国标要求,而且满足佩戴舒适性的要求;在同一风速下,气流相对湿度的增加,使2种口罩对粒径为1 μm以下颗粒物的过滤效率降低,对1 μm以上颗粒物的过滤效率没有影响。     

在线固相萃取-液相色谱-串联质谱法直接测定水中15种全氟烷基化合物

通过优化样品保存、前处理、分析条件,建立了水中15种典型全氟烷基化合物(PFASs)在线固相萃取-液相色谱-串联质谱分析方法,并对饮用水水源地和末梢水中PFASs进行定量检测。水样过膜后,准确移取700 μL水样、300 μL甲醇至1.5 mL聚丙烯进样瓶,并加入同位素内标后直接进样800 μL至在线固相萃取流路,进行萃取富集,再通过十通阀切换将洗脱的PFASs转移至分析流路进行分离,质谱检测,内标法定量。方法分析总时长22 min,15种全氟烷基化合物的方法检出限为0.31~1.20 ng/L,纯水高、中、低浓度加标样品回收率为70%~115%,相对标准偏差为0.2%~14.0%(n=6)。经实际样品验证,该方法与传统手动固相萃取方法分析结果基本一致。结果表明,该方法操作简单、自动化程度高、有机试剂用量少、灵敏度高、方法稳定,可满足地表水和末梢水中PFASs的快速测定。     

基于结构方程模型的认知性VDT作业过程解析*

为实现通过过程控制和管理提高认知性视觉显示终端（VDT）作业人员可靠性和绩效的目标,应用结构方程模型（SEM）研究作业过程表征方法。构建认知性VDT作业的信息加工过程模型,抽取13个基本认知动素（CT）,提出CT概念结构模型假设,设计外显指标测试题项,运用问卷调查样本数据构建结构方程和测量方程;对测量数据与结构方程模型的拟合度进行分析,并训练BP神经网络模式识别模型对作业过程进行还原检验。结果表明:认知性VDT作业过程模型有效,元认知控制其他12个CT的结构关系成立,认知性VDT作业过程可由包括元认知在内的13个基本CT解析。