CONA - Community Observation Networks for Air

Winter 2020 may be different to previous winters. During level-4 lockdown, many more people were at home for more hours of the day. This was probably little changed in level-3. It is plausible to assume not only does this mean more people spending extended time in places where they are likely to be inhaling woodsmoke, it also means fireplaces are on for longer, more wood being burned and more smoke in the air. Home heating emissions usually start to impact air quality from around mid-April, with each cold snap being a little colder and PM10 levels a little higher. At the time of writing, PM10 levels across communities with well-known woodsmoke issues “appear” (at first glance) to be about normal for the time of year, or maybe very slightly down. However, deducing what is happening with emissions (the amount of smoke being released from chimneys into the air) from air quality data (how concentrated that smoke is after its been diluted, transported and reaches a monitor, or someo...

As we start heading into winter a source of airborne particles emerges and rapidly comes to dominate PM levels across much of the country. Until relatively recently, wood was the natural choice for a home heating fuel in a country with plenty of trees. But it is also a relatively inefficient fuel. It is very hard to burn it completely, especially when it’s in the form of logs. The result is lots and lots of by-products, many of which are toxic or carcinogenic, and which collectively form the thick, pungent smoke that rises from thousands of New Zealand homes, mainly starting in April. In Auckland, less than a quarter of homes still use wood, yet there are enough for average levels of PM10 rise by a third between April and June every year. In central North Island, and most of South Island wood-heating is more prevalent. Where it is colder, and traffic levels lower, the effect is most dramatic. In Timaru, for instance, woodsmoke can cause PM 10  to double between April an...

You may have heard the news that the air around us has been sparklingly clean during lockdown – or level-4 at least. Dramatic images have been circling the world showing empty highways coinciding with clear views of distant mountains. Levels of PM2.5 – the tiny particulates that penetrate deep into our lungs with every breath, and have been linked to not just respiratory illnesses, but also heart disease, strokes and premature death – have fallen 50 – 60 % in Delhi, Los Angeles and Wuhan. And in New Zealand? Somewhere between 10 % and zero. This has surprised some. Traffic volumes plummeted all over New Zealand almost immediately when level-4 was declared and pretty much stayed that way, despite a slight up-creep as level-3 approached. For example, data released by the NZ Transport Agency shows that, averaged over the whole of level-4, volumes of light vehicles measured at 6 sites in 4 cities fell by 73 - 81 %  and heavy duty vehicles fell by 64 – 84 %. Yet, PM2.5 fell by on...