Guy J. Graening, P.E.

Brown and Caldwell

10540 White Rock Road, Suite 180

Rancho Cordova, CA 95670

Mr. Graening,

Here is the information you requested in your email of May 10, 2007
regarding the first batch of Yerington Teflon filters.

# Teflon Filter Handling and Filter Pack Preparation

Filter packs are assembled and disassembled in accordance with DRI SOP
2-112.2, Filter Pack Assembly.

All samples received at DRI for analysis are logged on the day that they
are received following the procedure described in the DRI Shipping and
Receiving SOP, 2-113.2.

Any unusual deposits or filter conditions should be noted on the sample
list. These conditions include, but are not limited to:

• scratches or smudges

• holes

• wet spots

• foreign particles (e.g., insects, metal shavings, hair, etc.)

Damage to the filters after receipt at DRI must be noted as such. The
conditions of the samples must be documented so that an accurate
assessment of analytical quality can be made.

# Filter Analysis

### Gravimetric Analysis

Gravimetric analysis is performed in accordance with DRI SOP 2-114.2, as
summarized below:

Unexposed and exposed Teflon-membrane filters are equilibrated at a
temperature of 21.5 ± 1.5 °C and a relative humidity of 35 ± 5% for a
minimum of 24 hours prior to weighing. Weighing is performed on a
Mettler MT-5 electro microbalance with ±0.001 mg sensitivity. The charge
on each filter is neutralized by exposure to a polonium source for 30
seconds before the filter is placed on the balance pan. The balance is
calibrated with a 200 mg Class S weight and the tare is set prior to
weighing each batch of filters. After every 10 filters are weighed, the
calibration and tare are re-checked. If the results of these performance
tests deviate from specifications by more than ±5 mg, the balance is
re-calibrated.

All initial filter weights are checked by an independent technician.
Samples are re-weighed if these check-weights do not agree with the
original weights within ±0.010 mg. At least 30% of the exposed filter
weights are checked by an independent technician. Samples are re-weighed
if these check-weights do not agree with the original weights within
±0.015 mg. Pre- and post-weights, check weights, and re-weights (if
required) are recorded on data sheets and are directly entered into a
data base via an RS232 connection. All weights are entered by filter
number into the DRI aerosol data base.

### Elements by XRF

Elemental analysis by energy dispersive x-ray fluorescence is performed
in accordance with DRI SOP 2-209.2 as summarized below:

After gravimetric analysis, samples collected on the Teflon-membrane
filters were analyzed by energy dispersive X-ray fluorescence (ED-XRF,
PanAlytical Epsilon 5) for the following 53 elements: sodium (Na),
magnesium (Mg), aluminum (Al), silicon (Si), phosphorus (P), sulfur (S),
chlorine (Cl), potassium (K), calcium (Ca), scandium (Sc) titanium (Ti),
vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co),
nickel (Ni), copper (Cu), zinc (Zn), gallium (Ga), arsenic (As),
selenium (Se), bromine (Br), rubidium (Rb), strontium (Sr), yttrium (Y),
zirconium (Zr), niobium (Nb), molybdenum (Mo), palladium (Pd), silver
(Ag), cadmium (Cd), indium (In), tin (Sn), antimony (Sb), cesium (Cs),
barium (Ba), lanthanum (La), Cerium (Ce), samarium (Sm), europium (Eu),
terbium (Tb), hafnium (Hf), tantalum (Ta), wolfram (W), iridium (Ir),
gold (Au), mercury (Hg), thallium (Tl), lead (Pb), radium (Ra), thorium
(Th), and uranium (U).

Calibration is performed using thin film standards from Micromatter Inc.
A multielement thin film standard is analyzed with each run to monitor
for calibration drift and is used as the indicator for routine
calibrations.

### Inorganic Ion Analyses 

Water soluble ions are obtained by extraction and analysis following DRI
SOPs 2-109.5 and 2-203.5 as summarized below:

Water-soluble sulfate, is obtained by wetting the filter with 200 µl of
ethanol and then extracting the filter in 10 ml of distilled-deionized
water (DDW). The extraction vials are capped and sonicated for 60
minutes, shaken for 60 minutes, then aged overnight to assure complete
extraction of the deposited material in the solvent. The ultrasonic bath
water is monitored to prevent temperature increases from the dissipation
of ultrasonic energy in the water. After extraction, these solutions are
stored under refrigeration prior to analysis.

### Ion Chromatographic Analysis for Chloride, Nitrate, and Sulfate

Water-soluble sulfate (SO~4~^=^) is measured with the Dionex 2020i
(Sunnyvale, CA) ion chromatograph (IC). In IC, an ion-exchange column
separates the sample ions in time for individual quantification by a
conductivity detector. Prior to detection, the column effluent enters a
suppressor column where the chemical composition of the component is
altered, resulting in a matrix of low conductivity. The ions are
identified by their elution/retention times and are quantified by the
conductivity peak area. Approximately 2 ml of the filter extract are
injected into the ion chromatograph. The resulting peaks are integrated
and the peak integrals are converted to concentrations using calibration
curves derived from solution standards. The Dionex system for the
analysis of Cl^-^, NO~3~^-^, and SO~4~^=^ contains a guard column (AG4a
column, Cat. No. #37042), an anion separator column (AS4a column, Cat.
No. #37041) with a strong basic anion exchange resin, and an anion micro
membrane suppressor column (250 ´ 6 mm ID) with a strong acid ion
exchange resin. The anion eluent consists of sodium carbonate
(Na~2~CO~3~) and sodium bicarbonate (NaHCO~3~) prepared in DDW. The DDW
is verified to have a conductivity of less than 1.8 ´ 10-5 ohm/cm prior
to preparation of the eluent. For quantitative determinations, the ion
chromatograph is operated at a flow rate of 2.0 ml/min.

The primary standard solution containing NaCl, NaNO~3~, and (Na)~2~SO~4~
is prepared with reagent grade salts dried in an oven at 105 °C for one
hour and then brought to room temperature in a desiccator. These
anhydrous salts are weighed to the nearest 0.10 mg on a routinely
calibrated analytical balance under controlled temperature (\~20 °C) and
relative humidity (±30%) conditions. These salts are diluted in precise
volumes of DDW. Calibration standards are prepared at least once each
month by diluting the primary standard solution to concentrations
covering the range expected in the filter extracts. These standards are
then stored in a refrigerator. The calibration concentrations prepared
are at 0.1, 0.2, 0.5, 1.0, and 2.0 mg/ml for each of the analysis
species.

Calibration curves are performed weekly. Chemical compounds are
identified by matching the retention time of each peak in the unknown
sample with the retention times of peaks in the chromatograms of the
standards. A DDW blank is analyzed after every 20 samples and a
calibration standard is analyzed after every 10 samples. These quality
control checks verify the baseline and the calibration, respectively.
Environmental Research Associates (ERA, Arvada, CO) standards are used
daily as an independent quality assurance (QA) check. These standards
(ERA Wastewater Nutrient and ERA Mineral WW) are traceable to NIST
simulated rainwater standards. If the values obtained for these
standards do not coincide within a pre-specified uncertainty level
(typically three standard deviations of the baseline level or ±5%), the
samples between that standard and the previous calibration standards are
re-analyzed.

After analysis, the printout for each sample in the batch is reviewed
for the following: 1) proper operational settings, 2) correct peak
shapes and integration windows, 3) peak overlaps, 4) correct background
subtraction, and 5) quality control sample comparisons. When values for
replicates differ by more than ±10% or values for standards differ by
more than ±5%, samples before and after these quality control checks are
designated for re-analysis in a subsequent batch. Individual samples
with unusual peak shapes, background subtractions, or deviations from
standard operating parameters are also designated for re-analysis.

# Batch 01 Specific Results

Three Teflon filters (TEOM001,002 and 003) were received on 4/10/2007,
these filters had DRI IDs, BCTT004, 010 and 011 respectively. After
final gravimetric and XRF analysis of these three filters it was
determined that filters 004 and 010 were actually filters 001 and 002.
The initial weights for filters 001 and 002 were used in the
determination of the mass concentrations for these two exposed filters.
Microscopic examination of the filters under an optical microscope
confirmed the apparent switching of these filters. All three filters
were very lightly loaded, with filters 010 and 011 (TEOM 002 and 003)
having loadings typical of a field blank. The heaviest filter 004
(TEOM001) had only 68 micrograms of deposit, and during the login
procedure this filter was flagged for having part of the Teflon membrane
separated from the support ring.

XRF analysis of the three filters confirmed the gravimetric results with
filters 011 and 010 showing essentially no elements above detection
limits. Filter 004 did have a few of the typical crustal elements above
detection limits. Wet chemical analysis also showed filter 004 with
sulfate above detection limits.

Please let me know if I may be of further assistance.

Regards,

Steven D. Kohl

Associate Research Scientist

Desert Research Institute