Air quality in the Canterbury region of New Zealand has been of concern for many years. Environment Canterbury (ECan) works within local government in New Zealand to provide environmental management and information to the Canterbury region. As part of the agency’s vision and purpose, ECan is committed to studying the drivers of air pollution in the region and applying source-specific mitigation strategies to drive the pollutant concentrations down.
In recent years, many towns in the region have observed elevated levels of coarse particulate matter (coarse PM). ECan wanted to understand the meteorological and seasonal/diurnal influences on coarse PM data collected at their monitoring site in Timaru over the past eight years and a preliminary analysis to identify the primary drivers of elevated concentrations in recent years.
Golder’s air team was engaged by ECan to identify any strong relationships between elevated levels of coarse PM with ambient conditions and weather scenarios. Coarse PM does not have a standard threshold concentration against which to identify ‘elevated’ levels. With that in mind, the team presented an approach to categorise the coarse PM distribution into normal background, moderately elevated and highly elevated concentrations and evaluate the trends in each of these categories.
Drawing on the specialist skills in air quality research, data analysis and visualisation, the team assessed diurnal, seasonal and meteorological factors to determine whether wind, temperature, humidity or rainfall affected coarse PM concentrations. Leveraging analytical and programming skills, the team evaluated the data and were able to derive variations in coarse PM concentrations at annual, monthly, weekly, daily and hourly resolution. This analysis identified long-term as well as short-term temporal trends in the region.
Driven by Golder’s in-depth understanding of the influences of various land uses and as well as the anthropogenic and biogenic sources in the region, our team was able to carry out scenario-based analysis to investigate impacts of multiple variables (e.g. changing wind speeds during an elongated dry period and in daytime hours) on elevated coarse PM concentrations.
Our client was interested in further investigating the data themselves, so we facilitated this request by developing a web app that enables them to filter the data to various levels, create visualisations instantaneously, and generate reports. Our initial work provides a steppingstone towards deeper investigation into coarse PM in the region.
Our client was pleased with our high-quality, reproducible and rapid output that identified key drivers of background coarse PM as well as elevated coarse PM levels, including highlighting some relationships of coarse PM with ambient conditions that had not been considered previously. With greater insights into the drivers of trends in coarse PM levels, Canterbury will be better able to consider mechanisms for improving air quality for a cleaner, healthier future for its communities.