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Abstract: Early studies of plant response to ozone (O3) utilized concentration-based metrics, primarily by summarizing the commonly monitored hourly average data sets. Research with the O3 concentration parameter led to the recognition that both peak concentrations and cumulative effects are important when relating plant response to O3. The US and Canada currently use O3 concentration-based (exposure-based) parameters for ambient air quality standards for protecting vegetation; the European countries use exposure-based critical levels to relate O3 to vegetation response. Because plant response is thought to be more closely related to O3 absorbed into leaf tissue, recent research has been focused on flux-based O3 parameters. Even though flux-based indices may appear to be more biologically relevant than concentration-based indices, there are limitations associated with their use. The current set of flux-based indices assumes that the plant has no defense mechanism to detoxify O3. This is a serious limitation. In this paper, we review the literature on exposure- and flux-based indices for predicting plant response. Both exposure- and flux-based metrics may overestimate plant response. At this time, flux-based models that take into consideration detoxification mechanisms (referred to as effective flux) provide the best approach to relate O3 to plant response. However, because there is considerable uncertainty in quantifying the various defense mechanisms, effective flux at this time is difficult to quantify. Without adequate effective-flux based models, exposure-based O3 metrics appear to be the only practical measure for use in relating ambient air quality standards to vegetation response. [Copyright &y& Elsevier]

The building sector is a significant source of GHG emissions and has great potential for emission reductions. The effectiveness of building energy codes on energy savings and emission mitigation is of a primary concern to policy makers, but uncertainty in cost and benefit in different regions complicates code selection and implementation. The impacts of a specific building energy standard vary depending on the heating system's thermal efficiency and the heating fuel's carbon intensity. This paper examines the GHG emissions due to space heating for new construction single-detached households in Canada under different building energy codes and enforcement scenarios. The two codes considered are the BC step code and Passive House criteria. Three scenarios are examined reflecting different levels of stringency of standards between 2020 and 2032. The results show both BC step code and passive house criteria can help mitigate the space heating GHG emissions. There is no significant difference between the BC step code and the passive house criteria from the perspective of GHG emission reduction in the province of British Columbia; however, when implemented nationwide, the passive house criteria is 12% more effective in abating space heating GHG emissions than the most stringent level (i.e. Step 5) of BC step code. • Passive House criteria are more effective in reducing the space heating GHG emissions than BC Step Code does in Canada. • BC Step Code and Passive House criteria can save space heating GHG emissions of new single-houses by 77% and 89%, respectively. • Building performance standards are less impactful in regions where fuel carbon intensity is low. • No notable difference is found between BC Step Code and Passive House criteria in GHG emission reduction per unit area in BC. [ABSTRACT FROM AUTHOR]