Retention time profiling of all 136 tetra- through octa- chlorinated dibenzo-p-dioxins and dibenzofurans on a variety of Si-Arylene gas chromatographic stationary phases

The applicability of three different Silphenylene Silicone co-polymer (Si-Arylene) GC stationary phases (J&W Scientific DB-5ms, Varian VF-5ms, and VF-Xms) has been evaluated for the separation of all 136 tetra- through the octa- chlorinated dibenzo-p-dioxins (PCDD) and chlorinated dibenzofurans (PCDF) from closely eluting isomers using gas chromatography/high resolution mass spectrometry (GC/HRMS). Their relative performance data are compared to the “conventional” 5% diphenyl 95% dimethylpolysiloxane GC column (Supelco Equity-5) and to each other based on absolute retention times, visualized mass chromatograms, and the separation of 2,3,7,8-substituted isomers. VF-Xms GC column was able to demonstrate a better performance towards separation of 2,3,7,8-substituted PCDD/PCDF compared to other Si-Arylene GC columns tested, where only 2,3,4,7,8-PnCDF can not be resolved from 1,2,3,6,9-PnCDF and 2,3,4,6,7,8-/1,2,3,6,8,9-HxCDF and 1,2,3,7,8,9-/1,2,3,4,8,9-HxCDF can be at least partially resolved. These data suggest that the development of a single GC column for the separation of all 17 2,3,7,8-substituted dioxins and furans is feasible, which therefore could be used as a standard tool for the PCDD/PCDF methods globally including USEPA methods 1613b, 8290A, 8280B, European Standard Method EN 1948, Canadian methods DFPCB-E3418, EPS 1/RM/19, Japanese methods JIS K0311 and JIS K0312. Having one specific GC column to separate all 2,3,7,8-substituted PCDD/PCDF will significantly improve the data quality, comparability by the various methods and assessment techniques while simultaneously leading to a more cost and time efficient operation.     

基于广义加权组合预测法的建设用地需求预测——以苏州市为例

对现行采用的多种常用建设用地需求量预测方法进行了比较,并以苏州市为例,采用5种预测模型进行了对比分析,利用近13年的统计数据进行了验证.结果表明,广义加权组合预测法得到的结果误差最小、精度最高.     

退田还湖对鄱阳湖洪水调控能力的影响

利用实测资料统计了鄱阳湖近50年来湖盆形态和洪水水情的变化,表明由于围垦的作用,1954~1992年鄱阳湖面积共减小1 300 km2,容积共减少81×108 m3,调节系数从17.3%下降到13.7%,调洪能力降低20.8%;20世纪90年代与50年代相比,年最高水位平均值抬高1.80 m。计算了退田还湖对近50年来两次特大洪水（1954年洪水和1998年洪水）最高水位的效应值,表明分别可使1954年洪水和1998年洪水的最高水位降低0.72 m和0.68 m。估算了退田还湖对鄱阳湖洪水位频率的影响,表明50年一遇和100年一遇的洪水位分别可降低0.63 m和0.68 m。计算还表明,高水还湖（单退）降低洪水位的作用与圩区还湖前夕的内涝程度密切相关,说明及时排除圩区的内涝对保障退田还湖的防洪减灾作用至关重要。分析了退田还湖面临的主要问题,分别是高水还湖圩区的内涝问题和平垸行洪（双退）圩区的血防问题;探讨解决这两个问题的具体对策,分别为单退圩堤采用“限高加固,排空待蓄”的运作方式,双退圩堤采用“敞开进洪,兼顾血防”的运用方式。     

安全工程专业英语课程教学探讨

当今社会不仅要求安全工作人员要有扎实的基本功,还要具备较强的专业英语阅读能力和翻译能力,这必然对安全工程专业英语的教学提出了新的要求。本文从目前安全工程专业发展和专业英语教学的特点和现状入手,挖掘出安全工程专业英语教学中存在的问题,从教学实践出发,探讨了安全工程专业英语教学中的教学目标、课程设置、教材选用、师资队伍的建设、教学方法、考核方式等问题,提出一些教学方法的改进措施,对提高安全工程专业英语教学质量和培养优秀全面的安全专业人才提供帮助。     

Shifting cultivation in peatlands

Transboundary haze pollution from smoke from land preparation fires has become a perennial problem in Indonesia, especially in the last 10 years during the dry season. Most of that smoke originates from illegal land preparation fires for oil palm and industrial forest plantation as well as from shifting cultivation, which is usually blamed for the smoke. In order to understand the role of fire in shifting cultivation areas dominated by peat soils, research was conducted during the dry season of 2001 on land belonging to the community of Pelalawan village, Pelalawan district, Riau province, Indonesia. The research showed that burning did not affect all peat areas equally. No peat was burned on a fibric site, while burning on a hemic site varied in depth from 6.0 cm to 12.6 cm, and on a sapric site from 15.4 cm to 31.9 cm. Further, on the fibric site only phosphorus increased significantly following burning, while on the hemic only the base saturation increased; on the sapric site, however, both base saturation and phosphorus increased compared to the condition before burning. These data show that if fire is continues to be used for land preparation in peat areas, peat becomes critically endangered.     

Subjective modeling choices and the robustness of impact evaluations in conservation science

Arbitrary modeling choices are inevitable in scientific studies. Yet, few empirical studies in conservation science report the effects these arbitrary choices have on estimated results. I explored the effects of subjective modeling choices in the context of counterfactual impact evaluations. Over 5000 candidate models based on reasonable changes in the choice of statistical matching algorithms (e.g., genetic and nearest distance mahalanobis matching), the parametrization of these algorithms (e.g., number of matches), and the inclusion of specific covariates (e.g., distance to nearest city, slope, or rainfall) were valid for studying the effect of Virunga National Park in Democratic Republic of the Congo on changes in tree cover loss and carbon storage over time. I randomly picked 2000 of the 5000 candidate models to determine how much and which subjective modeling choices affected the results the most. All valid models indicated that tree cover loss decreased and carbon storage increased in Virunga National Park from 2000 to 2019. Nonetheless, the order of magnitude of the estimates varied by a factor of 3 (from −4.78 to −13.12 percentage points decrease in tree cover loss and from 20 to 46 t Ce/ha for carbon storage). My results highlight that modeling choices, notably the choice of the matching algorithm, can have significant effects on point estimates and suggest that more structured robustness checks are a key step toward more credible findings in conservation science.     

四湖地区猕猴桃高效栽培模式与关键技术

针对地处四湖腹地的湖北省监利县果树资源利用率低及涝洼湿地的地理环境和生态条件 ,提出加快果树资源品种结构的调整 ,监北地势稍高 ,排灌方便的地方大力发展以猕猴桃为主的产业 ,同时利用架面下的行间土地套种蔬菜、瓜类作物、草莓、食用菌以及耐荫湿的中草药植物等立体生态农业的栽培模式 ,达到经济效益和生态效益的同步增长 ,与其相配套的栽培关键技术是采用地下通气排灌暗沟设施 ,重施有机质肥加磷肥 ;高畦壮苗定植 ;巧施追肥 ;适时排灌 ;树盘覆草保墒 ;人工辅助授粉和疏花疏果     

"立体互动教学法"在高职"应用写作"教学中的应用

进入新世纪，作为信息载体的应用写作越来越受到社会重视，然而目前高职院校中的应用写作教学现状却与这种重视不相适应。为此，本文试就目前高职教学中如何改革应用写作教学方法的问题，从“应用写作课与相关课程互动”、“写作理论和写作实践互动”、“应用写作文种之间互动”、“促使教学主体进行互动”四个方面提出了看法，以期对高职应用写作教学改革有所裨益。     

Evaluation of Three Watershed‐Scale Pesticide Environmental Transport and Fate Models1

Abstract: The U.S. Environmental Protection Agency (USEPA) Office of Pesticide Programs (OPP) has completed an evaluation of three watershed‐scale simulation models for potential use in Food Quality Protection Act pesticide drinking water exposure assessments. The evaluation may also guide OPP in identifying computer simulation tools that can be used in performing aquatic ecological exposure assessments. Models selected for evaluation were the Soil Water Assessment Tool (SWAT), the Nonpoint Source Model (NPSM), a modified version of the Hydrologic Simulation Program‐Fortran (HSPF), and the Pesticide Root Zone Model‐Riverine Water Quality (PRZM‐RIVWQ) model. Simulated concentrations of the pesticides atrazine, metolachlor, and trifluralin in surface water were compared with field data monitored in the Sugar Creek watershed of Indiana’s White River basin by the National Water Quality Assessment (NAWQA) program. The evaluation not only provided USEPA with experience in using watershed models for estimating pesticide concentration in flowing water but also led to the development of improved statistical techniques for assessing model accuracy. Further, it demonstrated the difficulty of representing spatially and temporally variable soil, weather, and pesticide applications with relatively infrequent, spatially fixed, point estimates. It also demonstrated the value of using monitoring and modeling as mutually supporting tools and pointed to the need to design monitoring programs that support modeling.     

纳米碳酸钙碳化法生产方法研究

简要介绍了碳化法生产纳米碳酸钙工艺流程。重点探讨了其中的碳化方法，获知目前我国主要有鼓泡碳化、喷雾碳化和超重力碳化等的碳化工艺。同时着重探讨了碳化反应的机理，并以此为依据讨论和比较了鼓泡碳化、喷雾碳化和超重力碳化3种碳化工艺。