Suburban home in upstate NY.
Yesterday morning I noticed the town street sweeper on our street. I have a pet with asthma and she was not doing so well later that day. I happened to check my air quality monitor and saw this HUGE spike in PM 2.5 just as the street sweeping was taking place (the red line on the chart).
Has anyone else noticed this effect? The town sprays very little water as they sweep. Town Street Sweeper
Thanks for sharing this. It could be the dust from the road but it could also be from the exhaust of the sweeper. If the vehicle runs slowly and potentially the wind direction is towards the sensor this could very well be.
How far is the monitor from the road?
Do you see any spike in CO2 at the same time? This could indicate an emission source.
Is the monitor indoors or outdoors?
I am involved in academic research with non-exhaust emissions from road vehicles. In the US and in the European Union, particulate matter from tailpipe has significantly dropped in the past decades due to strict regulations. Tailpipes of light-duty vehicles in the US and in Europe are allowed to emit a maximum of 1.9 and 4.5 mg/km, respectively. Many cars emit significantly less tailpipe PM than allowed (by mass). Let’s assume the sweeper emitted exhaust PM of 5 mg while driving past you and all PM has diluted in a cube of 10m x 10m x 10m (= 1000 m3) with your monitor being inside that cube, then we would expect a PM2.5 increase of only 5 ug/m3. Given that your spike was visible for more than 1 hour, we can assume that the aerosol was well-mixed. In other words, my estimate of 5 ug/m3 is very conservative and probably overestimates by one order of magnitude or more, depending on where your monitor was located and how the wind conditions were (asuming the sweeper follows the US EPA exhaust regulations).
To me, it seems more likely that the PM2.5 spike was caused by resuspension of road dust that accumulated at the kerbside. I believe this emission mechanism is the major source of road-associated PM in the US. Many people claim that tyre wear is the major emission source of airborne PM, but there is actually very little evidence in primary literature to back this up, as tyre wear particles tend to be around 100 microns or more (too big to stay airborne). I hypothesise that the big tyre wear particles accumulate on the road (along particles from road/brake wear etc.): the big tyre particles undergo chemical changes during wear, which causes accelerated degradation => the big particles fall apart and turn into fine dust, which can be resuspended by other vehicles or wind. Kerbside dust may be more relevant for air quality than currently anticipated.
Thank you for sharing your observation! I am thrilled to see this.
Good questions.
All the PMs spiked. CO2 did not. The monitor is indoors, about 105 ft from the center of the road. According to the personal weather station at the end of the street, wind was dead calm.
The soil here is almost all sand, very erodable. We are actually organizing around severe erosion and flooding from the creek that runs through many of our properties.
This neighborhood has lawns mowed some by services and some by homeowners. Mostly with riding and zero turn mowers which kick up a lot of very fine dust, with some use of leaf blowers as well. Dust gets deposited everywhere - on my home the outside windowsills have to be cleaned every year; the aluminum trim and vinyl siding under soffits where there is less air movement, collects it as well.
If you watch the video that I linked to in the first post, this is just three months prior. The town uses diesel mechanical broom sweepers.
My understanding of these charts is that the spike on each is an hour or less. This corresponds to the sweeper traveling past my home and three more, turning around at the corner and traveling past again. Maybe 15 minutes at the most.
Your comment re tire dust is interesting. I wonder how much of it is washed into the stream, vs suspended in the air. Unfortunately your bot is not allowing the link to USGS re 6PPD, a rubber additive that reacts with ozone and harms fish.
I have screenshots showing all PM spikes, CO2 and calm wind but can only post one image.
