A proposal for a diet-based local PCDD/F deposition limit

This study proposes a method to estimate the maximal tolerable value for the atmospheric deposition of dioxins (PCDD/Fs) to soil. The case study for the application of this methodology is an Alpine valley where a steel production plant is present. In order to estimate the limit value for the PCDD/F deposition, consolidated food chain models were applied, but were adapted to be run backwards with respect to their original formulation, by starting from the diet of people living in the region and from the PCDD/F Tolerable Daily Intake value proposed by the World Health Organization. For this case study, the estimated limit value was 2.30 pg WHO-TEQ m⁻² d⁻¹ when only local diary products were taken into account and 1.91 pg WHO-TEQ m⁻² d⁻¹ when also the role of local cereals and vegetables was considered. The average PCDD/F deposition measured in the same region during a monitoring campaign was lower than the above limit values (1.40 pg WHO-TEQ m⁻² d⁻¹). Indications on how to consider the contribution of meat and fish are provided too. The approach proposed in this paper represents a useful tool to assess the acceptable overall deposition for a specific region.     

建筑物可靠性评价

探讨了现存建筑物可靠性评价的极限状态方法,提出荷载水平方法,建立了结构构件可靠性评价的极限状态准则。基于结构失效的机构理论,提出结构体系可靠性评价的“破损机构”方法,以使结构成为“破损机构”或“局部破损机构”的“破损截面”的最高等级作为结构体系可靠性评级。     

Assessment of natural components of PM10 at UK urban and rural sites

Proposals from the European Commission have raised the possibility that Member States may be able to subtract the concentrations of natural components of airborne particulate matter from measured concentrations when evaluating compliance with EU Limit Values. By applying the pragmatic mass closure model [Harrison et al., 2003. A pragmatic mass closure model for airborne particulate matter at urban background and roadside sites. Atmospheric Environment 37, 4927–4933] to chemical composition data for PM₁₀, it has been possible to estimate the concentrations of natural sea salt, strongly bound water and secondary organic carbon (which is assumed wholly biogenic) to the measured mass of PM₁₀. Because of the difficulty in distinguishing between natural and anthropogenic crustal dusts, the contribution of natural windblown dust and soil has not been accounted for. When the natural components are estimated for two urban and one rural site in the UK, the long-term mean PM₁₀ concentration is reduced by between 5.2 and 7.3 μg m⁻³. The number of exceedences of the 50 μg m⁻³ 24-h limit value falls dramatically from 54 to 21 (from a total of 291 days) at an urban street canyon site, 7 to 3 (n=292 days) at an urban background site and from 8 to 0 (n=241 days) at a rural site when using gravimetric PM₁₀ concentrations. The calculations have also been performed using PM₁₀ concentrations measured by TEOM increased by a factor of 1.3 as recommended by the European Commission as an interim means of estimating gravimetric equivalency, and the number of exceedences of the 24-h limit value fell from 92 to 47 (from a total of 291 days) at the urban street canyon site, from 11 to 3 (n=292 days) at the urban background site and from 6 to 3 (n=241) at the rural site. Clearly, therefore, application of this proposed measure would make a very major difference to the likelihood of compliance or otherwise with the 24-h limit value for PM₁₀.     

直读光谱仪碳元素检出限不确定度分析

依据JJG1059-1999对直读光谱仪碳元素检出限的不确定度进行了评估,分析了影响测量不确定度的各个因素,计算得出直读光谱仪碳元素检出限的扩展不确定度为:U=0.11%,k=2。     

2007—2015年长江流域四川段主要江河放射性水平分析

对2007—2015年长江流域四川段主要12条江河水体放射性核素活度浓度的监测结果进行了分析。结果表明，四川段主要江河放射性核素水平远低于我国规定的露天水源的限制浓度。与1995年中国环境天然放射性（四川省部分）、1988年长江水系天然放射性活度浓度参考范围相比，U、Th、²²⁶Ra、⁴⁰K、¹³⁷C_s均有上升趋势，其他核素活度浓度涨落不明显均在本底范围内。总 α、总 β放射性活度浓度测值均符合《生活饮用水卫生标准》（GB 5749—2006）的限值要求。