Comment Log Display

Thank you.  

I speak to endorse Appendix H (August 13, 2007 revision) of the
Ozone SIP.

All organic gasses react photochemically, however they do not
react equally.

The relative reactivities of many VOCs have been determined
rigorously by Carter’s lab at UCRiverside providing the MIR scale
as a benchmark.

Although differing background air conditions and meteorological
dynamics affect actual ozone formation, we find similar rankings
in our recent field and lab work, with perhaps even stronger
differences among compounds.

Using a scale, we can strive to reduce ozone most cost effectively
by reducing the more reactive VOCs where more feasible.  [Also
importantly, we can strive to ensure we avoid making ozone worse
by reducing a low reactivity VOC in place of a smaller amount of a
more reactive VOC.]

Although MeBr should certainly be handled carefully for health
reasons, and its emissions minimized for stratospheric benefits,
MeBr has such a very, very low reactivity that it would be
reasonable to exclude it from regulation as a ground-level ozone
precursor.

Under the MIR scale, 1 entire ton of MeBr released out of the soil
produces only as much ozone as a mere 10 pounds of average VOC; it
is 200 times less reactive.

Of the other 3 fumigants commonly used in Ventura, two have
relatively mid-range MIRs, and the third, metam sodium (or
potassium), can release a gas by-product, but it has a fairly low
reactivity.

To quote the DPR News Release from November 15th 2006: “The number
of pounds applied is not as significant as the chemicals that
contribute to that total.”  The director was referring to less
toxic pesticides moving us in the right direction, but I suggest
less ozone-forming also points in the right direction.  […said
Warmerdam. “Increased use of less toxic materials shows that we
are moving in the right direction.”]

Furthermore, ozone production is strongly dependent on nitrogen
oxides, NOx, which must also continue to be reduced.  This is
especially true in air basins under conditions where NOx is the
limiting reagent, and where natural background VOCs limit our
ability to reduce total VOCs.  The ARB emissions inventory for
2006 in Ventura lists 55 tons/day anthropogenic but 33 tons/day
natural – nearly 40% of VOCs.

NOx reductions are definitely another area where agricultural
activities can help improve ozone.  For Ventura (according to the
ARB emissions inventory), only 5 source categories rank greater
than ‘Farm Equipment’.  And unlike VOCs, only a tiny amount of
NOx, roughly 2% comes from natural sources.  We can reduce it much
further than VOCs, and I am certain the agricultural community can
do their share.

Lastly, I wish to acknowledge my colleagues at UCDavis and our
cooperators around the state.

Thank you.