The Science of the total environment
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Sci. Total Environ. · Feb 2014
Spatio-temporal analysis of remotely-sensed forest mortality associated with road de-icing salts.
Forest mortality along highways has long been a concern in areas where de-icing compounds are applied during winter. This study combined the spatial advantage of high-resolution remote sensing imagery and the temporal advantage of long-term archival imagery to quantify forest mortality and to detect the subtle and chronic effects of road de-icing salts for a large mountain watershed in the Sierra Nevada Mountains, USA. IKONOS-derived mortality was used in a fine-scale spatial analysis to assess road proximity and roadside topography effects on forest mortality and to compare two potential mechanisms of de-icing salt damage, i.e. aerial deposition and soil uptake. ⋯ Immediate effects of de-icing salt were only distinct in wet years when salt application and spray generation by passing traffic and snow plowing were likely high and other damaging factors, such as bark beetles or drought mortality, were likely weak. A strong and consistent one-year lag in the effect of salt application on incidence of mortality suggested that longer-term impacts of de-icing salt on forest health likely involved more complex pathways than simply aerial deposition. Our multi-scale remote sensing approach provided convincing evidence that de-icing salt was a significant factor for roadside forest mortality and allows for efficient future monitoring at the large-watershed scale.
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Sci. Total Environ. · Feb 2014
Oxidative potential and chemical speciation of size-resolved particulate matter (PM) at near-freeway and urban background sites in the greater Beirut area.
To assess particle oxidative potential in the greater Beirut area, size-resolved PM10-2.5, PM2.5-0.25 and PM0.25 samples were collected at near-freeway and urban background sites. Metals and trace elements, including Mn, Cr, Cu, Ba, Mo and Sb, displayed increased levels and crustal enrichment factors at the roadway, indicating their vehicular origin. These elements in addition to Co, V, Ni and Zn were mostly distributed in PM2.5-0.25 and PM0.25 at both sites, with moderate-to-high water-solubility (>30%). ⋯ Relative to other urban settings, while the intrinsic redox activity of PM10-2.5 in Beirut is comparable to that measured at an urban site in Los Angeles (LA), its PM0.25-induced ROS-activity is ~2.3-fold greater. Moreover, the intrinsic ROS-activity of ambient PM2.5 in Beirut is comparable to that reported in Milan-Italy, but 3.1-times PM2.5 activity in the heavily-polluted Lahore-Pakistan. Lastly, findings suggest a dominant role of transition metals in generating ROS compared to organic carbon in the LA area.
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Sci. Total Environ. · Feb 2014
Effective drinking water collaborations are not accidental: interagency relationships in the international water utility sector.
The role that deficient institutional relationships have played in aggravating drinking water incidents over the last 30 years has been identified in several inquiries of high profile drinking water safety events, peer-reviewed articles and media reports. These indicate that collaboration between water utilities and public health agencies (PHAs) during normal operations, and in emergencies, needs improvement. ⋯ Core determinants of effective interagency relationships are discussed. Intentionally maintained functional relationships represent a key ingredient in assuring the delivery of safe, high quality drinking water.