Not only does the advisory continue, it seems to be getting worse.
The PM-10 reading over the past 24 hours, according to the Ministry of Environment, is at 83.8 micrograms per cubic metre, which is up from the 60s yesterday.
The Provincial Ambient Air Quality Objective is 50.
Ralph Adams, an Air Quality Meteorologist, says the situation isn’t expected to change anytime soon…
“There is some wind forecast for this afternoon, but then its right back to stagnant conditions over the next few days into the weekend, so it looks like this period of haze and high dust and also high smoke levels now, is likely to continue with some minor breaks over the next few days.”
Adams says it is a very unique situation this year…
“Normally we tend to get periods of high smoke due to poor dispersion in winter. So in the middle of winter when its very cold, very poor dispersion, we tend to get pollution built up under the inversions in the valleys and that’s when we get our high PM 2.5 Then in spring, when the snow melts and it warms up, we get the dust from the road traction material. What’s a little bit unusual this time is that we’ve essentially got both of them happening at the same time.”
As for how high the concentration of PM-10 can go, Adams says it’s really impossible to say…
“There is no real way to tell because it depends on how much traction material was put down last winter, how much traffic there is, how fast the traffic is, where the traction material is built up ? All of these factors effect what the concentrations are. The other thing to remember though is that the advisories are based on a 24 hour rolling average. In other words the average of the last 24 hours into the previous day, but the hourly values actually go up and down much more rapidly and they’ll fluctuate. For instance I believe over the last 24 hours I remember seeing values go well over one hundred in Quesnel, and then it will drop”
Adams says there are higher values when traffic increases and because Quesnel has a large highway running through it, it has traffic sort of continuously, and particularly heavy traffic…
“Because the heavier the vehicle is the wider the vehicle usually is, so it creates more turbulence behind it which tends to kick up more dust. So depending on what kind of traffic you’ve got and what the density of traffic is during the day, you can get these rapid changes in dust during the day. And the other thing you’ll find is if it rains, within a few minutes of it raining, the values can drop very quickly.”
Williams Lake is also above the provincial objective for PM-10 at 50.4 but Adams says an advisory hasn’t been issued because the levels have been going down over the past few hours.