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XRF is an acronym for x-ray fluorescence, a process whereby electrons are displaced from their atomic orbital positions, releasing a burst of energy that is characteristic of a specific element. This release of energy is then registered by the detector in then XRF instrument, which in turn categorizes the energies by element.
The relatively poor air quality over the past week or two is mostly due to recent meteorology conditions. The persistent high pressure over California right now leads to cooler temperatures, a low inversion layer, light winds (no storms), and poor vertical mixing. This meteorology pattern traps our area’s emissions within the area and closer to the ground, leading to higher measured concentrations. Hopefully this will ease up a bit later this week.
I have passed along the information that the AirNow site is listing “Fairfield” on the Current AQI and AQI Loop of the “NowCast” values (as in the screenshot below). However, even though the header says Fairfield, the measured AQI listed on the AirNow page is not specific to any given monitor. The map and current AQI listed is the highest AQI measured for that hour at any site in the reporting zone for the zip code that is entered. There are five reporting zones in the Bay Area – and they are shown on the map here: http://www.baaqmd.gov/about-air-quality/current-air-quality and described here http://www.sparetheair.org/stay-informed/todays-air-quality/reporting-zones. Vallejo is in the Northern Zone, so for our AQI forecasts and AirNow current AQI, it is reflecting the maximum AQI in that whole area for a given day or hour.
I think a better site to track real-time measured concentrations at a specific Air District-operated monitor is the query page for the CARB AQMIS database located at https://www.arb.ca.gov/
A new global alliance promoting the voluntary adoption of an independent on-road vehicle emissions test and rating system.
Urban particulate air pollution is a serious health issue. Trees within cities can remove ﬁne particles from the atmosphere and consequently improve air quality and human health. Tree effects on PM2.5 concentrations and human health are modeled for 10 U.S. cities. The total amount of PM2.5 removed annually by trees varied from 4.7 tonnes in Syracuse to 64.5 tonnes in Atlanta, with annual values varying from $1.1 million in Syracuse to $60.1 million in New York City. Most of these values were from the effects of reducing human mortality. Mortality reductions were typically around 1 person yr-1 per city, but were as high as 7.6 people yr-1 in New York City. Average annual percent air quality improvement ranged be- tween 0.05% in San Francisco and 0.24% in Atlanta. Understanding the impact of urban trees on air quality can lead to improved urban forest management strategies to sustain human health in cities.
See here https://www.nrs.fs.fed.us/pubs/43676
see this link:
C.A.R.E. communities – Areas with cumulative Impact from air pollution in the San Francisco Bay area