还原稳定化法修复六价铬污染土壤的中试研究

为探索还原稳定化法修复六价铬污染土壤的工程可行性,以某化工厂铬渣堆存场内六价铬污染土壤为研究对象,开展还原稳定化法修复六价铬污染土壤的中试研究。结果表明,DARAMEND-M、硫酸亚铁(Fe SO4)和多硫化钙(CPS)3种药剂对土壤中Cr(Ⅵ)的还原率超过了99%,糖蜜对Cr(Ⅵ)的还原率达93.9%。经糖蜜和DARAMEND-M处理的下层土壤,水溶态铬+交换态铬由原来的21.77%分别下降至6.26%和2.95%;经Fe SO4和CPS处理的渣土混合物,水溶态铬+交换态铬由22.12%分别下降至4.58%和2.94%,铬的稳定性明显增强。采用糖蜜、DARAMEND-M和Fe SO4处理后可以降低土壤p H值,而CPS处理则提高土壤p H值;糖蜜和DARAMEND-M有助于提高土壤微生物量碳含量。总体而言,糖蜜和DARAMEND-M适合修复低Cr(Ⅵ)污染土壤,在还原稳定化效果和长效性方面,DARAMEND-M药剂优于糖蜜;Fe SO4和CPS在修复高Cr(Ⅵ)污染土壤方面具显著效果。     

中国旅游扶贫地空间分布格局及成因

旅游扶贫试点村是中国实施旅游扶贫的重要载体,是精准扶贫理念的集中体现。本研究以全国560个旅游扶贫试点村为研究样本,综合运用空间分析、相关性分析等方法探究了中国旅游扶贫地的空间分布格局和成因。研究表明:1试点村在地理空间上呈现凝聚型分布状态,地带间分布差异较小,西部分布稍多于东部,中部相对最少,与传统认知上的贫困村分布格局存在错位现象。2试点村系统分形特征明显,存在局部围绕贫困山区集聚的情况,空间分布上呈现不等概率分布状态,分形结构较为复杂。3试点村分布密度最大区域为燕山-太行山、罗霄山、沂蒙山和武夷山-南岭山区,其次为六盘山、秦巴山、武陵山、大别山和滇桂黔等山区,且大都高密度分布在各省区边缘和交界地带,呈现"大集聚、小分散"的空间分布格局。4中国旅游扶贫地的空间格局的形成主要原因有旅游资源禀赋、地形海拔高度、交通因素及政府政策导向四个方面。5优质的旅游资源禀赋、较高的地形海拔高度、落后的交通条件以及强有力的地方政策支持可以作为试点村的评选标准;并从空间上建议增加中西部试点村布点;对空间上集聚在贫困山区的试点村其旅游扶贫应注意保护性开发利用原生态的自然环境,深挖地域文化符号;各省区边缘和交界地带试点村应加强区域旅游合作。最后结合试点村的分布和致贫的原因,把试点村划分为资源利用不足型、山地环境制约型、交通区位非优型、政策支持欠缺型四种类型,从而提出针对不同类型试点村旅游扶贫路径。     

好氧堆肥反应器对人粪便堆肥中温降解的中试研究

控制温度为（35±2）℃,以新鲜锯末为空白载体,在控制含水率为55%~60%和强制通风的好氧条件下,进行为期15 d的实验,进行了人粪便好氧堆肥的中试研究,重点分析了在堆肥过程中有机物的降解、氮素的迁移转化规律及生物量的变化。结果表明,粪便中有机物含量在前2天稍微上升,然后迅速下降,最终去除率为71.82%;随着NH₃-N释放量的增加,堆料中N_tot含量从第4天开始减少,最终损失 22.61%,其中N_org损失占74.35%,NH₃-N占23.52%;所损失的氮素有91.66%以氨氮的形式释放。粪便中的有机物和氮的含量能在8~10 d后达到稳定,且堆体无臭味;粪便中溶解性有机物为微生物的生长提供营养物质,因此生物量变化的过程与有机物降解的有着紧密的联系;病原菌在堆肥过程中得到有效去除,表明该反应器堆肥的无害化。     

工作场所手传振动测量

在职业卫生领域中,振动加速度有效值是最常用的测量值,振动加速度级的运用方便了运算和表述。给出频率计权和时间加权的计算公式和方法、加速度与加速度级间的换算。测量中强调了传感器定位和紧固方法会影响测量结果。     

Evaluation of Monte Carlo-based calibrations of HPGe detectors for in situ gamma-ray spectrometry

The aim of this work was to evaluate the use of Monte Carlo-based calibrations for in situ gamma-ray spectrometry. We have performed in situ measurements at five different sites in Sweden using HPGe detectors to determine ground deposition activity levels of ¹³⁷Cs from the 1986 Chernobyl accident. Monte Carlo-calculated efficiency calibration factors were compared with corresponding values calculated using a more traditional semi-empirical method. In addition, results for the activity ground deposition were also compared with activity densities found in soil samples. In order to facilitate meaningful comparisons between the different types of results, the combined standard uncertainty of in situ measurements was assessed for both calibration methods. Good agreement, both between the two calibration methods, and between in situ measurements and soil samples, was found at all five sites. Uncertainties in in situ measurements for the given measurement conditions, about 20 years after the fallout occurred, were found to be in the range 15–20% (with a coverage factor k = 1, i.e. with a confidence interval of about 68%).     

Characterization of phosphogypsum wastes associated with phosphoric acid and fertilizers production

The present work is directed to characterize the phosphogypsum (PG) wastes associated with phosphoric acid produced by the wet process in industrial facility for the production of fertilizers and chemicals in Egypt. The PG waste samples were characterized in terms of spectroscopic analysis (X-ray diffraction, X-ray fluorescence, IR spectra) and radiometric analysis (γ- and α-measurements). The γ-ray measurements showed that the average activity concentrations are 140 ± 12.6, 459 ± 36.7, 323 ± 28.4, 8.3 ± 0.76 and 64.3 ± 4.1 Bq/kg for U-238, Ra-226, Pb-210, Th-232 and K-40, respectively. The α-particle measurements of uranium isotopes showed that the average activity concentrations of U-238, U-235 and U-234 were 153 ± 9.8, 7 ± 0.38, 152 ± 10.4 Bq/kg, respectively. The average radiochemical recovery (%) of the destructive α-particle measurements is ∼70% with a resolution (FWHM) of ∼30 keV. Activity ratios of U-238/Ra-226 and U-238/Pb-210 were less than unity (i.e., <1) and equal to 0.31 ± 0.02 and 0.47 ± 0.16, respectively. The isotopic ratios of U-238/U-235 and U-238/U-234 (in PG and PR samples) were close to the normal values of ∼21.7 and ∼1, respectively and are not affected by the wet processing of phosphate rock (PR). The obtained results of PG waste samples were compared with phosphate rock (PR) samples. The radiation hazard indices are namely, radium activity index (Ra-Eq > 370 Bq/kg), total absorbed gamma dose rate (D_γr > 5 nGy/h) and radon emanation fraction (Rn-EF > 20%). Uncertainty of the sample counting was 95% confidence level of σ. The results indicated the necessity to find suitable routes to decrease and/or redistribute the radionuclide of environmental interest (i.e., Ra-226) in PG wastes, consequently to reduce its radiation impacts in the surrounding environment.     

碳排放权交易试点是否促进了对外直接投资?

环境规制与跨国投资之间的关系一直是学术界关注的焦点。作为重要的环境规制手段,碳排放权交易试点的推进标志着我国环境规制强度的增强。对外直接投资(OFDI)作为最典型的跨国经济活动之一,是中国"走出去"战略的重要组成部分。近年来,中国对外直接投资存量与净额都呈现稳定的上升趋势,与此同时,环境规制强度也在不断提升。中国对外直接投资是否受到国内环境规制加强的影响值得探讨,而2013年正式启动碳排放权交易试点为解决此问题提供了一个准自然实验场景。基于此,文章使用中国30个省级行政单位2010—2019年的面板数据,以北京、上海、广东、天津、湖北、重庆和福建开展的碳排放权交易试点作为准自然实验,运用双重差分法(DID)研究碳排放权交易试点的开展是否提升了对外直接投资水平。研究结论表明,碳排放权交易试点能够显著提升我国对外直接投资水平。且该结论在平行趋势检验、合成控制法(SCM)、安慰剂检验等检验后依旧稳健。此外,潜在机制的研究发现碳排放权交易试点满足"污染避难所假说"和"波特假说",进而促进了对外直接投资水平的提升。通过净效应的初步讨论,文章发现"污染避难所假说"仍旧在目前占据主导地位。研究结论意味着:(1)未来要继续推进全国统一的碳排放权交易市场建设;(2)持续探索激发碳排放权交易试点对创新产生的激励效应;(3)完善投资便利化的制度与措施,搭建国际技术交易或信息平台等。一方面促进我国生态环境的改善,另一方面促进对外投资水平的增质提量。