Estimating the impact of seawater on the production of soil water-extractable organic carbon during coastal erosion

The production of water-extractable organic carbon (WEOC) during arctic coastal erosion and permafrost degradation may contribute significantly to C fluxes under warming conditions, but it remains difficult to quantify. A tundra soil collected near Barrow, AK, was selected to evaluate the effects of soil pretreatments (oven drying vs. freeze drying) as well as extraction solutions (pure water vs. seawater) on WEOC yields. Both oven drying and freeze drying significantly increased WEOC release compared with the original moist soil samples; dried samples released, on average, 18% more WEOC than did original moist samples. Similar results were observed for the production of low-molecular-weight dissolved organic C. However, extractable OC released from different soil horizons exhibited differences in specific UV absorption, suggesting differences in WEOC quality. Furthermore, extractable OC yields were significantly less in samples extracted with seawater compared with those extracted with pure water, likely due to the effects of major ions on extractable OC flocculation. Compared with samples from the active horizons, upper permafrost samples released more WEOC, suggesting that continuously frozen samples were more sensitive than samples that had experienced more drying-wetting cycles in nature. Specific UV absorption of seawater-extracted OC was significantly lower than that of OC extracted using pure water, suggesting more aromatic or humic substances were flocculated during seawater extraction. Our results suggest that overestimation of total terrestrial WEOC input to the Arctic Ocean during coastal erosion could occur if estimations were based on WEOC extracted from dried soil samples using pure water.     

中国城市建设用地集聚对利用效率的影响:机理、空间效应与分群差异

为探究城市建设用地集聚对城市建设用地利用效率的作用机理,文章基于2003—2017年中国278个地级及以上城市面板数据,通过构建多产出随机前沿生产函数模型测度城市建设用地利用效率,采用时间-空间双固定的空间杜宾模型探讨了不同程度的城市建设用地集聚对利用效率的影响机理与差异。结果表明:(1)从时空特征上来看,样本考察期内中国城市建设用地利用效率总体上呈稳步提升趋势,东部城市建设用地效率最高,西部次之,中部最低。(2)从全国维度的空间计量模型回归结果来看,城市建设用地集聚所带来的规模效应和外溢效应对城市建设用地利用效率具有改进作用,有利于利用效率进一步提升。(3)从不同城市建设用地集聚度分群回归结果来看,高集聚城市(东部发达地区)的直接效应显示随着城市建设用地集聚度的提高,利用效率也不断提高;间接效应中,建设用地集聚度的提高对周边城市的利用效率产生先带动后抑制的"倒U"形作用。低集聚城市(中西部欠发达地区)的直接效应和间接效应均显示,随着城市建设用地集聚的提高,其利用效率存在"先降后升"的"U"形曲线特征。可见,在城市发展的不同阶段,城市建设用地集聚对城市土地利用效率存在差异化影响。因此,中国城市发展应立足当前发展阶段特征,制定差别化的供地政策,促进城市建设用地集聚,针对性地提升区域要素利用效率,支撑经济社会进一步发展。     

《废气治理环保项目劳动安全卫生设计专篇》编写要求

强调了劳动安全卫生设计的重要性，就《废气治理环保项目劳动安全卫生设计专篇》的编写方法进行了说明。指出了环保项目中常见的危险危害因素，并提出相应的防范技术措施。     

农用地资源修正法定级之技术路线探讨——以佛山市高明区为例

目前我国农用地资源定级很少运用修正法,少数学者对修正法定级做过尝试性的实证研究工作,以期探讨修正法定级技术路线的科学性与可行性.在前人研究的基础上,以佛山高明区为例,探讨了修正法定级之修正基础的确定、修正因素的选择、修正系数的计算、定级指数的确定等几个关键技术步骤,提出了以农用地自然质量等指数作为修正基础,采用标准化方法对修正因素分值进行订正,用连乘法计算农用地质量定级指数来划分农用地级别的修正法定级的技术路线,并与因素法定级的成果进行对比分析与验证.     

电能表自动化检定系统监控功能的完善

针对电能表自动化检定系统工作过程中的异常现象,通过对其产生原因和影响因素的分析,提出了采用增加触点检测、温度监测、各工位信息实时集中监控的方法对监控功能进行完善。应用结果表明:改进方法实现了对各检定工位的实时监控,系统异常现象减少,合格率得到了提升,保证了检定系统的高效稳定运行。     

Wall losses of oxygenated volatile organic compounds from oxidation of toluene: Effects of chamber volume and relative humidity

Vapor wall losses can affect the yields of secondary organic aerosol. The effects of surface-to-volume (S/V) ratio and relative humidity (RH) on the vapor-wall interactions were investigated in this study. The oxygenated volatile organic compounds (OVOCs) were generated from toluene-H₂O₂ irradiations. The average gas to wall loss rate constant (k_gw) of OVOCs in a 400 L reactor (S/V = 7.5 m⁻¹) is 2.47 (2.41 under humid conditions) times higher than that in a 5000 L reactor (S/V = 3.6 m⁻¹) under dry conditions. In contrast, the average desorption rate constant (k_wg) of OVOCs in 400 L reactor is only 1.37 (1.20 under humid conditions) times higher than that in 5000 L reactor under dry conditions. It shows that increasing the S/V ratio can promote the wall losses of OVOCs. By contrast, the RH effect on k_gw is not prominent. The average k_gw value under humid conditions is almost the same as under dry conditions in the 400 L (5000 L) reactor. However, increasing RH can decrease the desorption rates. The average k_wg value under dry conditions is 1.45 (1.27) times higher than that under humid conditions in the 400 L (5000 L) reactor. The high RH can increase the partitioning equilibrium timescales and enhance the wall losses of OVOCs.     

多层频率选择表面复合吸波结构的研究

文中采用一种快速求解方法——半解析半数值法计算多层频率选择表面(Frequency Selective Surface,简称FSS)复合结构的反射系数,然后结合具体两层复合结构的实例通过测试验证了半解析半数值法的正确性,并基于复合结构吸波材料吸波频带窄的缺点,在此基础上,设计出一种新的圆形FSS复合结构吸波材料。计算和测试结果都表明,这种新的复合结构在较宽带宽内具有低反射系数。     

大功率中短波广播天线电磁辐射的预测与防护

随着城镇密集度越来越高,大功率电磁辐射设备如大功率中短波天线不可避免的与建筑越来越近,因而对室内的电磁环境污染逐步加剧。电磁辐射造成的危害通常包括对人体健康的危害(健康效应)和干扰其他电磁设备而造成严重后果(电磁干扰)。针对大功率中短波天线造成的电磁环境污染问题,提出一套远场条件下电磁辐射的预测方法并成功预测了一个典型大功率中短波天线群附近的拟建项目区域的电磁环境,在此基础上,提出有效的针对拟建项目的电磁防护方案。     

基于边际机会成本理论的农地价格矫正研究——以江都市为例

当前我国农地非农化进程的加快使农地资源价值显化问题凸现出来，但在现行的政策与制度框架内，农地价格严重扭曲，不能完全表达农地的真正价值。社会经济的不断发展要求农地资源能合理配置并达到可持续利用，因此要实现这一目标，就必须建立一套完整的农地价值核算体系与农地价格体系，并对现行扭曲的农地价格进行矫正。本文通过理论与实证分析，利用边际成本定价的方法探讨体现农地真正价值的农地完全价格，并通过这一价格将农地的资源价值纳入整个绿色GDP核算体系中，这也是本文提出的政策性建议之一。