Evaluation of the ERC virtual impactor

Measurements have been made on a dichotomous virtual impactor developed by the Environmental Research Corporation. The object was to study the feasibility of employing the virtual impaction scheme in air samplers to collect size fractionated particle samples for subsequent x-ray fluorescence analysis. The size separation characteristics and losses as a function of particle size at specific locations within the apparatus were determined. It was found that except for the intrinsic losses near the size cut point, most of the losses can be significantiy reduced with improved design. The prospect of large scale deployment of virtual impactors for continuous air monitoring is favorable. (auth

Nature’s nations: the shared conservation history of Canada and the USA

Historians often study the history of conservation within the confines of national borders, concentrating on the bureaucratic and political manifestations of policy within individual governments. Even studies of the popular expression of conservationist ideas are generally limited to the national or sub-national (province, state, etc.) scale. This paper suggests that conservationist discourse, policy and practice in Canada and the USA were the products of a significant cross-border movement of ideas and initiatives derived from common European sources. In addition, the historical development of common approaches to conservation in North America suggests, contrary to common assumptions, that Canada did not always lag behind the USA in terms of policy innovation. The basic tenets of conservation (i.e. state control over resource, class-based disdain for subsistence hunters and utilitarian approaches to resource management) have instead developed at similar time periods and along parallel ideological paths in Canada and the USA

Grooved impactor and inertial trap for sampling inhalable particulate matter. [Patents]

An inertial trap and grooved impactor for providing a sharp cutoff for particles over 15 microns from entering an inhalable particulate sampler is disclosed. The impactor head has a tapered surface and is provided with V-shaped grooves. The tapered surface functions for reducing particle blow-off or reentrainment while the grooves prevent particle bounce. Water droplets and any resuspended material over the 15 micron size are collected by the inertial trap and deposited in a reservoir associated with the impactor