耕地质量地球化学评价及应用研究——以重庆市荣昌区为例

基于Arcgis平台,以耕地图斑为评价单元,对重庆市荣昌区耕地质量进行了地球化学评价及其应用研究。结果表明,研究区耕地土壤质量较好,地球化学等级以中等为主,占耕地总面积的74.44%,优质和良好等级占24%。土壤养分综合等级以中等为主,有机质、氧化钙和磷元素较缺乏,钾、硫、锌等多种元素较丰富。土壤环境质量总体较好,清洁和轻微污染区面积较大,轻度至重度污染区不足1%,土壤污染主要由Cd元素引起。耕地质量地球化学评价可广泛应用于耕地分等定级、基本农田划定、土地整治和农业生产活动中。     

Theoretical study on the formation mechanism of polychlorinated dibenzothiophenes/thianthrenes from 2-chlorothiophenol molecules

Homogeneous formation of polychlorinated dibenzothiophenes/thianthrenes(PCDT/TAs),sulfurated compounds analogous to polychlorinated dibenzo-p-dioxin/dibenzofurans(PCDD/Fs), has been well-documented to occur via radical–radical coupling reactions from chlorinated thiophenol precursors. However, the current understanding of the formation mechanism of PCDT/TAs is exclusively limited to the inherent point of view that chlorothiophenoxy radicals act as the only required intermediates for PCDT/TAs. This study investigates reaction pathways for the formation of PCDT/TAs involving two new types of radical species, i.e., substituted phenyl radicals and substituted thiophenoxyl diradicals. Taking 2-chlorothiophenol(2-CTP) as a model compound for chlorothiophenols,we found that apart from the mostly discussed chlorothiophenoxy radicals, substituted phenyl radicals and substituted thiophenoxyl diradicals could also be readily formed via the reaction of 2-CTP with H radicals. Furthermore, direct self-and cross-coupling of these radicals can result in the formation of PCDT/TAs, including 1-monochlorothianthrene(1-MCTA), 1,6-dichlorothianthrene(1,6-DCTA), 4,6-dichlorodibenzothiophene(4,6-DCDT)and 1,6-dichlorodibenzothiophene(1,6-DCDT). The pathways proposed in this work are proven to be both thermodynamically and kinetically favorable. Particularly, comparisons were made between the formation mechanisms of sulfurated and oxygenated dioxin systems from an energetic point view, showing that replacing oxygen with sulfur atoms greatly reduces the activation barriers of the rate-controlling steps involved in the PCDT/TA formation processes compared with those involved for PCDD/Fs. The calculated results in this work may improve our understanding of the formation mechanism of PCDT/TAs from chlorothiophenol precursors and should be informative to environmental scientists.     

安全疏散中ICT技术应用研究脉络与热点分析

为了研究ICT技术在安全疏散领域的应用现状、演进和热点,以Web of Science核心数据库中有关ICT技术对安全疏散应用研究的科技文献为研究对象,运用CiteSpace软件对文献研究主题和时空分布、研究演进和科研网络以及研究热点和前沿态势进行分析。研究结果表明:ICT技术对安全疏散应用研究可以划分为低潮期、发展期和爆发期3个阶段,形成了3大科研网络版块;随着ICT技术的发展,刊发相关研究的期刊从综合类向专业类拓展,并从火灾科学、交通科学和心理科学等多学科进行了交叉研究;在不同的发展时期,研究侧重点不尽相同,当前以无线传感网络、建筑疏散和导航系统等领域为研究热点,基于研究成果,提出相关研究热点和前沿等建议。     

High-resolution inventory of NO emissions from agricultural soils over the Ile-de-France region

Arable soils are a significant source of nitric oxide (NO), a precursor of tropospheric ozone, and thereby contribute to ozone pollution. However, their actual impact on ozone formation is strongly related to their spatial and temporal emission patterns, which warrant high-resolution estimates.Here, we combined an agro-ecosystem model and geo-referenced databases to map these sources over the 12 000 km² administrative region surrounding Paris, France, with a kilometric level resolution. The six most frequent arable crop species were simulated, with emission rates ranging from 1.4 kg N-NO ha⁻¹ yr⁻¹ to 11.1 kg N-NO ha⁻¹ yr⁻¹. The overall emission factor for fertilizer-derived NO emissions was 1.7%, while background emissions contributed half of the total NO efflux. Emissions were strongly seasonal, being highest in spring due to fertilizer inputs. They were mostly sensitive to soil type, crops' growing season and fertilizer N rates.     

Decomposition of Al13 promoted by salicylic acid under acidic condition: Mechanism study by differential mass spectrometry method and DFT calculation

Decomposition of the polycation Al₁₃O₄(OH)₂₄(H₂O)₁₂⁷⁺ (Al₁₃) promoted by ligand is a vital subject to advance our understanding of natural and artificial occurrence and evolution of aluminum ions, especially in the case of acidic condition that dissolved Al³⁺ species can be released from the Al-bearing substances. However, the microscopic pathway of synchronous proton-promoted and ligand-promoted decomposition process for Al₁₃ is still in the status of ambiguity. Herein, we applied differential mass spectrometry method and DFT calculation to study the initial detailed process of Al₁₃ decomposition under the presence of proton and salicylic acid (H₂Sal). Mass results showed that the mononuclear Al³⁺-H₂Sal complexes dominated the resulting Al species, whereas the monodentate complex Al₁₃HSal⁶⁺ was not observed in the spectra. The difference of decomposition levels between the ligand/Al ratio 0.2 and 0.5 cases revealed that proton and ligand performed synergistic effect in initial Al₁₃ decomposition process, and the proton transfer determined the ring closure efficiency. The ring closure reaction is the prerequisite for the collapse of Al₁₃ structure and detachment of the mononuclear complex. DFT calculations reveal that hydrogen bond plays an important role in inducing the formation of chelated complex accompanying proton transfer. Attachment of protons at the bridging OH⁻ can elongate and weaken the critical bond between targeted Al³⁺ and µ₄-O^2- resulting from delocalization of electron pairs in the oxygen atom. These results demonstrate the detailed mechanism of Al₁₃ composition promoted by ligand and proton, and provide significant understanding for further application and control of Al₁₃.     

基于CiteSpace中国生态补偿研究的知识图谱分析

生态补偿已成为生态环境管理领域的热点问题。本文基于CiteSpace可视化文献分析工具,以CSSCI数据库中1998—2018年的期刊论文作为数据源,以"生态补偿"为关键词进行文献检索,通过共被引、关键词共现分析以及聚类分析等,探讨生态补偿研究领域的知识基础以及研究热点与前沿。结果表明:①生态补偿研究的发文数量经历了缓慢上升、快速增长、平稳增加三个阶段;②生态补偿研究作者集中度较高,发行期刊涵盖经济学、地理学、生态学、制度经济学等多个学科,反映出生态补偿是一个多学科交叉的研究主题,生态补偿研究的综合性不断增强;③依据关键词知识图谱,"国家重点生态功能区""生态环境""可持续发展"等成为最新研究热点;④新时期生态文明建设下,"草原生态补偿""支付意愿""转移支付""退耕还林"等成为生态补偿研究的最新前沿话题。     

Marine Eutrophication: A Proposed Data Analysis Procedure For Assessing Spatial Trends

A methodology for the discrimination of the different trophic levels at a spatial scale in the marine environment is proposedusing spatial analysis methods and non-parametric statistics. Phytoplankton cell number, being a representative parameter to express trophic trends in the marine ecosystem is selected forthe methodology development; Saronicos Gulf, Greece is used for the case study. The proposed stepwise methodology includes interpolation for assessing the spatial distribution of phytoplankton cell number, division of the Gulf into a number of quadrates, development of a scale characterising trophic levels and finally characterisation of the trophic state ofeach quadrate using non-parametric statistics. The advantages of this methodology and the potential applications in coastal management studies are also discussed.     

时序逻辑电路分析方法的改进

本文采用次态卡诺图法对时序逻辑电路的功能进行分析,力图改进传统异步时序电路的分析方法,在保证分析结果正确无误的前提下,简化了常规分析方法中繁琐的步骤,更具有实用性。以一个8421BCD码表示的十进制异步减法计数器为例,给出各触发器状态方程的表达式,并用状态表、状态图分析其逻辑功能。     

辽宁省地质灾害遥感调查电子地图的制作

通过辽宁省地质构造解译图和辽宁省地质灾害遥感解译图这两个电子地图的制作，说明了电子地图制作的工具选择、制作方法、关键技术以及地图应用等。体现了地理信息系统这一现代化科技手段在防灾、减灾和地质环境的整治与保护方面的价值。     

交通事故发生规律与城市道路系统的规划设计研究

笔者分析了城市交通事故发生率与道路等级、道路断面形式、路网密度、交叉口形式、道路车速的关系及交通事故人群的分布规律,认为道路宽而稀、支路缺乏、街道功能不清是我国城市道路网与用地微观布局的基本特点。大量数据分析表明,这种路网体系与我国的城市交通事故率偏高有着密切关系。路网规划是城市路网建设的基本依据,笔者认为,应当将降低城市交通事故率作为路网规划的考虑内容之一,同时指出,应在路网规划中合理选择道路断面形式、交叉口形式,建议适度加密路网、健全支路体系、理清街道功能,并考虑城市道路的车速控制与驾驶心态调整。