The most common HIMs are (Wilson et al. 2014): thickness or mass loading (tephra fall, PDC deposits, lahar deposits), dynamic pressure (PDC, lahar), flow height (lava flow, lahar), presence or absence (lava flow, gas emissions), density per unit area (ballistics), impact energy (ballistics) and concentration (gas emissions, tephra fall).
Population density and PM2.5 emissions density from point sources were no longer predictive of AMI.
Also, we evaluate the potential for improved model prediction resulting from the use of geographic covariates with higher spatial resolution than those used previously for traffic density, population density, and point-source emissions density.
Based on some limited variable selection, the covariates w k, s, t (some of which do not vary with time) are population density, elevation, area emissions, point emissions, density of A3 roads, wind speed, and temperature.
Increasing county-level population density was positively associated with measured PM2.5 levels, as was increasing point-source emissions density within 7.5 km (Additional file 1: Figure S1 panels A6 and A7, respectively).
Also, the 1999 2007 PM2.5 and 1988–2007 Pmodelsdels both included county population density, point-source emissions density (for the corresponding PM size fraction), distance to nearest road for road classes A1-A3, and urban land use within 1 km.
