Fine-particle Mn and other metals linked to the introduction of MMT into gasoline in Sydney, Australia： Results of a natural experiment

PM2.5 particulates were analyzed using accelerator-based ion beam methods for a suite of 21 species （H, C, Na, Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Br, Pb） to evaluate the contribution to Sydney air associated with the introduction of MMT as a replacement for Pb. MMT was discontinued in 2004. Teflon filters continuously sampled for 7 years from 1998 to 2004 were analyzed from two sites： a suburb （Mascot） close to the Central Business District [CBD （n=718）] and a high trafficked area, and a relatively rural （background） setting, ～20 km west of the CBD （n=730）. Mean Mn concentrations in air at the background site increased from 1.5- 1.6 ng/m^3 to 〈2 ng/m^3 at the time of the greatest MMT use whereas those at Mascot increased from about 2 to 5 ng/m^3. From the maximum values, the Mn showed a steady decrease at both sites concomitant with the decreasing use of MMT. Lead concentrations in air at both sites decreased from 1998 onwards, concomitant with the phase out of leaded gasoline in 2002. A high correlation was obtained for the relationship between Mn in air and lead replacement gasoline （LRG） use （R2 0.83） and an improved correlation for Mn/Al＋Si＋K and LRG use （R2 0.93）. With Mn concentrations normalized to background values of Al＋Si＋K to account for the lithogenically-derived Mn, the proportion of anthropogenic Mn was -70%. Changes for Mn and Pb in the particulates are attributed to the before-during-after use of MMT and decreasing use of Pb in gasoline.     

Normalized residual displacement spectra for post-mains

Residual displacement,as a significant measure of structural inelasticity,is effectively used in post-earthquake seismic assessment of structures.This demand can be considered for seismic evaluation of structures under multiple earthquakes.This study introduces a simple and novel index to predict the residual displacement of mainshock-damaged structures against subsequent aftershock.The proposed index is defined as a ratio between residual displacement of damaged structures against aftershock and peak inelastic displacement of intact structures under mainshock.In this study,constantstrength spectra based on the index are developed considering the effects of important structural characteristics and also significant seismic parameters.Moreover,analytical equations are presented to predict the proposed index for bi-linear single-degree-of-freedom(SDOF)systems considering both the effects of positive and negative polarities of aftershock.Furthermore,an equation is suggested to estimate the peak inelastic displacement of intact systems under mainshock,which is required to compute the index.     

An ensemble forecast of the South China Sea monsoon

1.IntroductionThispaperexploresanensembleforecaststrategyforthelarge--scaletropicalpredictionproblem.Thisisgeneralizedfromarecentstudyontheuseofempiricalorthogonalfunction(EOF)--basedperturbationsforhurricanetrackensembleforecasts,(ZhangandKrishnamur...     

全球离散格网:回顾与展望

全球离散格网是数字球体表达的基本数据模型,它提供了一种栅格化表达地球弯曲表面的方法,催生了数字地球.该文回顾全球离散格网与数字地球的发展史,评析了以谷歌地球为代表的第一代数字地球的技术实现.在为科学界及社会公众提供地表与近地表信息交流方面,数字地球的有效性面临挑战,第一代数字地球在很多方面存在不足,其中最显著的缺陷是不能基于社会与环境过程模型模拟地球的将来状态.展望未来,简要分析了下一代数字地球应具有的基本特征.     

5 我们预测地震能达到怎样的程度?

我们的地震预测能达到怎样的程度呢?正如Ian Main在辩论导论中所提出的那样,我们能容易地预测地震活动总体的特性,而且显然我们不能完全地预测单个地震的特性.但是,哪里是容易与不可能的界限呢?为了寻找这一界限,我们来看一下Ian Main的地震预测的4个等级.首先应略述一下与此问题有关的主要观测,以及地震发生与可预测性的两个标准模型,然后再简要评论一下这些模型,并说明一种较普通的方法如何能导致对地震可预测性的更好理解.     

CIPP最佳实践

本文简要介绍了CIPP施工中4个关键性施工工序中应注意的问题。     

Discriminating sources of PCB contamination in fish on the coastal shelf off San Diego, California (USA)

Management of coastal ecosystems necessitates the evaluation of pollutant loading based on adequate source discrimination. Monitoring of sediments and fish on the shelf off San Diego has shown that some areas on the shelf are contaminated with polychlorinated biphenyls (PCBs). Here, we present an analysis of PCB contamination in fish on the shelf off San Diego designed to discriminate possible sources. The analysis was complicated by the variability of species available for analysis across the shelf, variable affinities of PCBs among species, and non-detects in the data. We utilized survival regression analysis to account for these complications. We also examined spatial patterns of PCBs in bay and offshore sediments and reviewed more than 20 years of influent and effluent data for local wastewater treatment facilities. We conclude that most PCB contamination in shelf sediments and fish is due to the ongoing practice of dumping contaminated sediments dredged from San Diego Bay.