Measuring PM2.5 around the world

If you want an amazingly well-funded study, you'd be hard pressed to outdo sponsorship from the US department of defence (DOD). In that spirit I present the DODs Enhanced Particulate Matter Surveillance Program (EPMSP), which in their words collected

Aerosol and bulk soil samples ... during a period of approximately one year at 15 military sites—including Djibouti, Afghanistan (Bagram, Khowst), Qatar, United Arab Emirates, Iraq (Balad, Baghdad, Tallil, Tikrit, Taji, Al Asad), and Kuwait (Northern, Central, Coastal, and Southern regions). 

That's what SPARTAN equals in terms of proposed site counts: up to 20 depending on future funding.

The DOD sampled each site for 24 hours at 6-day intervals from 2006 to 2007. Each site was measured for PM10, PM2.5, and total suspended particulates (TSP).

Their sampling equipment came from Airmetrics, which certainly give great credit to the company's instrument reliability (SPARTAN's sampling instruments are still in the early stages of design, but we should (or ought to) have something comparable in the near future. The hard deadline to start field testing is March 2013. My focus is to avoid having things come down to the wire).

EPMSP collected samples on Teflon, Quartz, and Nuclepore filters (I keep wanting to spell it Nucleopore!) in the three size frames. The most impressive statistic is the following account of their total assembled data:

The number of laboratory analyses performed in the course of the EPMSP is summarized in Table 2-2, and includes 66,462 analyses on Teflon® membrane, 23,807 on quartz fiber, and several million single particle analyses on Nuclepore®  

Several million samples! I cannot imagine how long that would take SPARTAN to measure, but not certainly not within my stay at Dal. To be fair most of these were samplings of the Nuclepore filters for scanning electron microscopy (SEM) analysis. The Teflon and quartz filters consisted of 'only' a few tenns of thousands of chemical analyses.

The data itself is very useful for our network, such as the PM2.5 levels we might expect to encounter. In Baghdad and Tikrit, Iraq annual levels exceed 100 ug/m3; Recall that acceptably 'clean' air must have fewer than 10 ug/m3 PM2.5 particulates. The TSP in all 15 sites exceeded 100 ug/m3, while up to 600 ug/m3 in Tikrit. Considering trace metal levels, "The USACHPPM 1-year interim Air-MEG of 3.42 μg/m3 for aluminum (Al) was on average exceeded at all 15 sites". These are not a healthy places to breathe.

The study points out that PM2.5/PM10 ratios vary considerably from place to place. In the middle east they apparently lie between 0.21 and 0.60. More anthropogenic combustion usually means the ratio is higher. This large variance supports the need for separate PM2.5 monitoring; PM10 is clearly only weakly related with fine aerosols.

In terms of sand-based composition, the middle east contains similar amounts of aluminosilicates as compared to the United States' more arid desert regions.

The EPMSP study used Nuclepore filters specifically for SEM analysis, as this surface type is good for very size-selective trapping of particulates on a smooth surface. Background signals are small, and the particulates look 'cleaned', like rock species isolated in a museum case. Their methodology has convinced me we should probably be using only Teflon for chemical analysis and gravimmetric weighing.

---

Aside: I really admire the openness of the data presented here. As a typical example, they write: "Gravimetric results from both Teflon® and quartz fiber filters were processed and are available on the DOEHRS Portal". Compare this to Canada's NAPS raw data access. Military-funded science is surprisingly more open than some other types. Food for thought.