基于IFS-动态加权的地下综合体深基坑施工风险评价

为控制地下综合体深基坑施工风险,提出了一种基于直觉模糊集(IFS)-动态加权的风险评价方法.从地质条件、建筑环境、岩土设计、施工方案和偶然风险5个方面分析地下综合体深基坑施工风险因素,构建了综合风险评价指标体系.采取施工风险5级划分方法,利用IFS理论确定指标风险;以偏大型正态加权函数确定指标权重,得到系统综合风险.以西安市某地下综合体深基坑施工实际为背景,进行方法应用.结果表明,该西安市地下综合体深基坑施工系统风险等级为显著风险.其中,指标"邻近建筑""地下管网"的风险等级为高度风险,"道路交通""基坑边坡稳定性""降排水实施"为显著风险,对此提出了相应的安全措施.     

Use of historical and contemporary distribution of mammals in China to inform conservation

A systematic understanding of dynamic animal extinction trajectories for different regions in a nation like China is critically important to developing practical conservation strategies. We explored historical and contemporary changes in terrestrial mammalian diversity to determine how diversity in each of the 5 regions in China has changed over time and to examine the conservation potential of these regions. We used records from databases on Pleistocene mammalian fossils and historical distribution records (1175–2020) for Primates (as a case study) to reconstruct evolutionary and historical distribution trajectories of the 11 orders of terrestrial mammals and to predict their prospective survival based on the national conservation strategy applied. The results indicated that since the Pleistocene, 4–5 mammalian orders have been lost in the northeast, 3 in central China, 2 along the coast, and 1 in the northwest. In the southwest, all 11 orders were maintained. Contemporarily, the coast and southwest had the highest and second-highest species densities. The southwest region and southeastern sections of the northwest region were the most historically and contemporarily diverse areas, which suggests that they should be the first priority for protected area (PA) designation. The central and coastal areas should be secondarily prioritized. In these 2 regions, conservation should focus on human coexistence with nature. Less attention should be paid to the PA in the northeast and western northwest because in these areas ecosystems are depauperate and the climate is harsh. Conservation in these areas should focus principally on avoiding further human encroachment on natural areas. Article impact statement: Historical and contemporary patterns of extinction can be a basis for mammalian conservation strategies.     

Microplastic pollution in freshwater systems in Southeast Asia: contamination levels,sources, and ecological impacts

Environmental Science and Pollution Research - Plastics are synthetic polymers known for their outstanding durability and versatility, and have replaced traditional materials in many applications....     

基于PFC对含断续节理岩质边坡静力荷载下破坏形式的研究

在含断续节理岩质边坡的破坏中,阶梯状破坏尤其显著,是一种常见的失稳破坏形式。借助二维颗粒流软件(PFC2D5.0)进行简单地质结构模型下的边坡数值模拟,通过采用PFC软件中的人工合成岩体技术,研究了7种不同组合形式下含断续节理岩质边坡的破坏形式及其内部微观接触力场的演变规律。首先对PFC软件中采用的微观力学性质参数进行了验证模拟,通过对完整岩块进行双轴压缩试验和巴西劈裂试验的模拟,得出其应力-应变曲线和强度包络线,从而计算出完整岩块的内聚力、内摩擦角等宏观力学参数;然后通过对含裂隙的颗粒集合体进行直剪试验的模拟,得出其剪应力-剪切位移曲线以及峰值强度和残余强度与正应力的关系曲线,从而计算出裂隙的内聚力和内摩擦角;最后对含上述微观力学性质参数的边坡进行静力荷载下破坏形式的模拟,得出裂隙萌生前应力集中、裂隙萌生后应力释放,以及可将潜在滑动面上方的坡体位移分成4个区,即坡脚处最大位移区、坡肩处较大位移区、坡体内部较小位移区、坡体后缘最小位移区,并验证了萌生的裂隙一般会近垂直于岩桥向坡体表面扩展,切割潜在滑动面以上坡体。     

近代我国海潮灾害的时空特征与等级

本文根据相关历史资料,对近代我国海潮灾害的时空特征、灾害等级等进行了初步研究。据不完全统计,近代我国共发生海潮灾害147次,平均每年发生1.34次,以一般海潮灾害为主,在前期记载较多,后期较少;多在秋季爆发,且月份集中在6、7、8月,具有明显的季节性、普遍性、连续性和集中性等特征;我国的东海是海潮灾害的频发区。     

论灾害风险研究中的空间尺度耦合

作为人地关系中"地"对"人"负面作用的核心学科——灾害风险学存在着显著的地理空间尺度差异与尺度效应。本文提出灾害风险尺度耦合的概念与类型,从数据、方法和区划三个方面提出灾害风险研究中的空间降尺度和空间升尺度耦合思路,供同行学者参考。     

Predicting the transfer of 137Cs to rice plants by a dynamic compartment model with a consideration of the soil properties

The factors governing chlorine transfer from Phaeozem and Greyzem soils to various important crop species (foodstuff and forage) were determined in natural conditions in the Kiev region of Ukraine. The stable chlorine concentration ratio (CR) values were the lowest in apple (0.5+/-0.3) and strawberry (2+/-1), higher in vegetables (5+/-3), seeds (15+/-7) and reached a maximum in straw (187+/-90). The average CR values of 36Cl were estimated for the most important crops using all experimental data on 36Cl and stable chlorine transfer into plants from various soils. It was experimentally shown that boiling potatoes in water leads to an equilibrium between 36Cl specific content in the water and moisture in the cooked potato. The 36Cl processing factor (PF) for boiling various foodstuffs is equal to the ratio of water mass in the cooked foodstuff to the total water mass (in the food and the decoction). 36Cl PF for cereal flour can be estimated as 1. The 36Cl processing factor for dairy products is equal to the ratio of residual water mass in the product to initial water mass in milk. At a 36Cl specific activity in soil of 1 Bq kg-1, the estimated annual dietary 36Cl intake into human organism (adult man) is about 10 kBq. Sixty to seventy percent of the above amount will be taken in via milk and dairy products, 7-16% via meat, 14-16% via bread and bakery items and 8-12% via vegetables. The highest annual 36Cl intake, 10.7 kBq, is predicted for 1-year-old children. The expected effective doses from annual 36Cl intake are higher for younger age groups, increasing from 0.008 mSv in adults to 0.12 mSv in 1-year-old children.     

Evaluation of accuracy of linear regression models in predicting urban stormwater discharge characteristics

Stormwater runoff has been identified as a source of pollution for the environment, especially for receiving waters. In order to quantify and manage the impacts of stormwater runoff on the environment, predictive models and mathematical models have been developed. Predictive tools such as regression models have been widely used to predict stormwater discharge characteristics. Storm event characteristics, such as antecedent dry days （ADD）, have been related to response variables, such as pollutant loads and concentrations. However it has been a controversial issue among many studies to consider ADD as an important variable in predicting stormwater discharge characteristics. In this study, we examined the accuracy of general linear regression models in predicting discharge characteristics of roadway runoff. A total of 17 storm events were monitored in two highway segments, located in Gwangju, Korea. Data from the monitoring were used to calibrate United States Environmental Protection Agency＇s Storm Water Management Model （SWMM）. The calibrated SWMM was simulated for 55 storm events, and the results of total suspended solid （TSS） discharge loads and event mean concentrations （EMC） were extracted. From these data, linear regression models were developed. R2 and p-values of the regression of ADD for both TSS loads and EMCs were investigated. Results showed that pollutant loads were better predicted than pollutant EMC in the multiple regression models. Regression may not provide the true effect of site-specific characteristics, due to uncertainty in the data.     

Bi-PbO2电极电化学氧化去除模拟废水中氨氮的研究

本实验采用钛网作为基体,利用电沉积方法制备了纯PbO2电极和Bi-PbO2电极,通过SEM、XRD、XPS对电极的表面形态进行了表征,利用循环伏安法对Bi-PbO2电极电化学特性进行了研究.同时,以氨氮模拟废水作为研究对象,考察了Bi-PbO2电极的电催化活性,探讨了氨氮电化学氧化降解机理.结果表明,Bi-PbO2电极的形态表征、电催化活性明显高于纯PbO2电极,氨氮的去除效率随电流密度的增加而提高,碱性条件下氨氮的去除效果明显好于酸性条件,适量浓度的Cl-的引入在碱性条件下提高了氨氮的去除效果.当氨氮初始浓度为50 mg·L-1、电流密度为40 mA·cm-2、pH=12、Cl-浓度为600 mg·L-1时,电解120 min后,氨氮100%去除.氨氮的降解机理为:体系中无添加氯离子,酸性条件下氨氮主要是通过间接氧化去除,碱性条件下通过直接电氧化和间接氧化共同完成;体系中添加氯离子,氨氮的去除主要是通过溶液中生成的有效氯间接氧化去除.     

钙钛矿型催化剂催化湿式氧化处理煤气化废水纳滤浓缩液

采用溶胶-凝胶法制备了Mn掺杂钙钛矿型催化剂LaFexMn1-xO3,并以其为催化剂催化湿式双氧水氧化处理煤气化废水纳滤浓缩液。采用XRD,SEM,FTIR技术对催化剂进行了表征。表征结果显示：制备的催化剂均具有标准的钙钛矿型结构,其中,LaFe0.9Mn0.1O3的结构稳定,比表面积大。实验结果表明：制备的催化剂中LaFe0.9Mn0.1O3的催化活性最高,且稳定性好,连续使用5次后催化活性未见明显减弱;在H2O2投加量3.0 g/L、n（H2O2）∶n（LaFe0.9Mn0.1O3）=12∶1、反应温度160 ℃、反应压力1 MPa、浓缩液pH 3、反应时间60 min的最优条件下,COD、UV254和TOC的去除率分别达到80.9%、95.2%和68.0%,BOD5/COD由0.02提升至0.40,可生化性大幅提高。