Reaction mechanism of arsenic capture by a calcium-based sorbent during the combustion of arsenic-contaminated biomass: A pilot-scale experience

Pilot-scale combustion is required to treat arsenic-enriched biomass in China. CaO addition to arsenic-enriched biomass reduces arsenic emission. CaO captures arsenic via chemical adsorption to form Ca₃(AsO₄)₂. Large quantities of contaminated biomass due to phytoremediation were disposed through combustion in low-income rural regions of China. This process provided a solution to reduce waste volume and disposal cost. Pilot-scale combustion trials were conducted for in site disposal at phytoremediation sites. The reaction mechanism of arsenic capture during pilot-scale combustion should be determined to control the arsenic emission in flue gas. This study investigated three Pteris vittata L. biomass with a disposal capacity of 600 kg/d and different arsenic concentrations from three sites in China. The arsenic concentration in flue gas was greater than that of the national standard in the trial with no emission control, and the arsenic concentration in biomass was 486 mg/kg. CaO addition notably reduced arsenic emission in flue gas, and absorption was efficient when CaO was mixed with biomass at 10% of the total weight. For the trial with 10% CaO addition, arsenic recovery from ash reached 76%, which is an ~8-fold increase compared with the control. Synchrotron radiation analysis confirmed that calcium arsenate is the dominant reaction product.     

Temporal trends in agricultural water use and the relationships to hydroclimatic factors in the High Plains aquifer region

The High Plains aquifer (HPA) is the primary water source for agricultural irrigation in the US Great Plains. The water levels in many locations of the aquifer have declined steadily over the past several decades because the rate of water withdrawals exceeds recharge, which has been a serious concern to the water resources management in the region. We evaluated temporal trends and variations in agricultural water use and hydroclimatic variables including precipitation, air temperature, reference evapotranspiration, runoff, groundwater level, and terrestrial water storage across the HPA region for different periods from 1985 to 2020 at the grid, county, or region scale. The results showed that water withdrawals decreased from 21.3 km³/year in 1985 to 18.2 km³/year in 2015, while irrigated croplands increased from 71,928 km² in 1985 to 78,464 km² in 2015 in the entire HPA. The hydroclimatic time-series showed wetting trends in most of the northern HPA, but drying and warming trends in the southern region from 1985 to 2020. The groundwater level time-series indicated flat trends in the north, but significant declining in the central and southern HPA. Trends in irrigation water withdrawals and irrigation area across the HPA were controlled by the advancement of irrigation systems and technologies and the management of sustainable water use, but also were affected by dynamical changes in the hydroclimatic conditions.     

高瓦斯工作面隅角柔性气囊安全封堵研究

为解决高瓦斯工作面隅角封堵工人劳动强度大、效率低,封堵效果不佳易造成隅角瓦斯浓度超限等安全问题,研发设计了矿用阻燃内外胆组合结构的轻型柔性隅角封堵气囊,并相应提出了单体液压支柱配合轻型柔性气囊的隅角封堵新方法。通过实验室测试实验和现场工业性试验表明:选用PVC材料和双抗涂覆布材料的气囊质量小、轻便实用,大幅降低了工人的劳动强度,提高了工作效率,减小了传统封堵方式编织袋装碎煤造成的遗煤浪费;该气囊可适应大变形(变形率可达42.5%)、耐冲击(2×104J的冲击能量不破坏),抗撕扯能力强,且具有阻燃特性,重复使用率高,大大节约了隅角封堵的成本;使用气囊封堵后,采空区内瓦斯浓度显著增大,说明气囊封堵的密闭性增加,安全封堵效果十分明显。     

基于不同强度等级混凝土的动力学特性研究

基于TAW-2000D电液伺服岩石三轴仪和直径75 mm的霍普金森压杆试验装置,得到了C25,C35和C45混凝土在静、动载荷作用下的应力-应变曲线,探讨了混凝土强度等级、动态峰值强度、峰值应变和应变率之间的变化规律。结果表明:混凝土准静态应力-应变曲线和动态应力-应变曲线在形态上存在明显差异,动态应力-应变曲线的峰值点随应变率的增大向右上方移动,线弹性阶段各曲线斜率变化不明显;动态峰值应力、动态弹性模量和峰值应变均存在不同程度的率相关性,并且混凝土材料的应变率敏感性随其强度等级的提高而增强;混凝土C45的各力学指标对应变率的敏感性最强,C35次之,C25的应变率敏感性最弱;推导了应变率与强度等级和冲击速率之间的经验公式,三者之间存在非线性变化规律。     

Teams as boundaries: How intra‐team and inter‐team brokerage influence network changes in knowledge‐seeking networks

What role does an ego's brokerage location—within a team (intra‐team) or outside the team (inter‐team)—play in the evolution of an instrumental knowledge‐seeking network in terms of both proximal (i.e., within the team) and distal (i.e., outside the team) tie formation and tie decay? We address this question by drawing on literature about social networks, brokerage, and teams. We use temporally separated data from 302 students embedded in 97 teams to test our hypotheses about the impacts of intra‐team and inter‐team brokerage on proximal and distal network evolution, specifically on four network changes in knowledge‐seeking networks: proximal tie formation, proximal tie decay, distal tie formation, and distal tie decay. We find that these four changes depend on individual network brokerage location even after controlling for personality and task characteristics. Specifically, inter‐team brokers change their networks both within and outside their teams, whereas intra‐team brokers curtail their network changes. We argue that these opposite effects occur because inter‐team brokers have greater autonomy than intra‐team brokers. This study adds to the ongoing dialog about network evolution in social network literature and to the conversations about brokerage and its location in the context of team‐based work.     

On the subjective experience and correlates of downtime at work: A mixed‐method examination

In the current paper, we studied downtime at work. Downtime represents a unique aspect of work time, as employees have low workload and more discretion about their activities but are still paid to be at work. Despite its prevalence and potentially significant implications for productivity and well‐being, the experience of downtime has not been a focus in the literature. To study this phenomenon, we first used a qualitative method involving 15 focus groups. Results from 95 employees showed that downtime is distinct from formal breaks and withdrawal behavior and is generally a negative subjective experience. Categories of antecedents of experience and downtime activities were classified. Next, to further explore the phenomenon, and based on Study 1 and relevant literature, we proposed several hypotheses and tested them using an experience sampling method. Results from 86 employees (across 5 workdays and 689 data points) indicated that the amount of downtime was negatively related to day level job satisfaction, job performance, and subjective health. The duration of relaxation activities during downtime mitigated the negative effects of downtime on fatigue. The effects of enjoyment level of the activities, job autonomy, work engagement, and boredom proneness were also examined. Implications, limitations, and future research are discussed.     

水体颗粒物以及土壤对有机物吸附常数的测定

本文介绍了用批量平衡测定水体悬浮颗粒物以及土壤对有机物吸附常数的测定方法，并给出实例和方法的注意事项。     

多氯苯生产中有机氯化物的分析

在气相色谱和色谱-质谱分析的基础上,对以六六六为原料生产多氯苯的两种工艺的产品及废渣进行了分析。结果表明:伴随多氯苯的生成,尚有多种氯化物产生。在水解生产工艺中,产品和废渣中有微量PCDDs和PCDFs,但产品中还有少量PCBs。在热解工艺中,废渣内发现大量的PCBs,PCDDs和PCDFs,最毒的异构体,2,3,7,8-TCDD含量高达24ppm。     

水体表面微层的环境化学研究

水体表面微层是大气和水体间的界面，其物理、化学和生物特性可影响水体中各种物质的存在形式及最终归缩。本文总结了近几十年的参考文献，对表面微层的采样及各类物质的表面微层的行为做了系统的论述，指出了研究的难点和今后的发展方向。     

除草剂乙草胺对非洲爪蟾性腺发育的影响

使用性腺发育对内分泌干扰作用敏感的两栖动物非洲爪蟾作为模型动物,通过考察性别比、性腺整体形态和组织学形态来揭示乙草胺对其性腺发育的影响,从而确定乙草胺是否具有内分泌干扰活性.46/47期蝌蚪经不同浓度(5μg·L-1、10μg·L-1、20μg·L-1)的乙草胺暴露处理至变态后1个月,在变态结束后3个月时,解剖性腺、鉴别雌雄并固定性腺做组织切片.实验中对照组所有性腺都为典型的卵巢或睾丸,雌性百分率为48.78%(20/41).而乙草胺暴露组却出现了明显的异常睾丸,其总体上是睾丸,但又带有部分卵巢的特征,在统计性别时将具有异常睾丸的爪蟾归为雄性.5μg·L-1、10μg·L-1、20μg·L-1暴露组的雌性百分率分别为:57.14%(24/42)、66.67%(22/36)、55.26%(21/38).虽经统计分析无显著性差异,但乙草胺暴露组中雌性多于雄性的趋势和出现带有雌性特征的雄性的现象,一定程度上却暗示了乙草胺可能对非洲爪蟾的性腺发育有雌性化作用.正常睾丸的组织学结构应有发育成熟的生精小管,其内有各个时期的精子囊和生精细胞及精子.但经乙草胺处理的爪蟾睾丸却表现出几种明显的异常:没有生精小管,相反却像发育早期的睾丸一样,充满大量的精原细胞,完全没有生精细胞和精子;有生精小管结构,但其内精子囊结构不明显,生精细胞少并且排列混乱,其间有很大的空隙;睾丸出现腔隙,并有大量体细胞存在,这种结构与57期的卵巢相似;睾丸中出现异常的生精细胞,与58期卵巢的卵细胞相似;睾丸组织中有明显的卵细胞散布.组织学研究发现的乙草胺导致的睾丸结构证明了乙草胺对非洲爪蟾的睾丸发育有抑制雄性化作用和雌性化作用,即乙草胺对非洲爪蟾的性腺发育有内分泌干扰作用.