reported in this manner. Furthermore, only the glass fiber filters
associated with the four additional co-located air pumps were
analyzed for particulate iodine-131 by GEL.
Vegetation sampling consisted of grab samples taken from local
crops or annual grasses and plants collected from various locations.
The samples were collected, placed in plastic bags and shipped via
two-day delivery to GEL. Various types of vegetation were collected
depending on location and what was available at the time. Of the
five sample types of samples in this study, vegetation had the
widest distribution in terms of geographical area covered. Table 1
shows the sample matrix of available vegetation during the study
period.
Rainwater was collected as a supplemental sample as it is not
part of the normal REMP matrix. However, in the wake of the
Fukushima event it was deemed necessary. To accomplish this,
plastic paint trays were purchased from a local hardware store and
placed at four locations. Three of the sampling locations were near
DCPP and the fourth was located in San Luis Obispo. At each location
approximately 10 trays were laid out and each day after
experiencing rainfall in the area, the contents of the paint trays
were poured into 1 gallon bottles. The bottles were then shipped
via two-day delivery to GEL. The paint trays remained in the field at
their respective sampling locations throughout the study period.
2.2. Analysis methods
GEL conducted analysis on all sample types in this study.
Gamma analysis was performed with a high purity germanium
detector (HPGe) utilizing methods from the Department of Energy
(DOE) EML Procedures Manual, HASL-300, I-01. If necessary, iodine
was separated by absorption on AG 1 8 anion resin.3 For the
analysis of water samples, the methods followed were from EPA
600/4-80-032 Prescribed Procedures for Measurements of Radioactivity
in Drinking Water, Method 901.1. Minimum Detectable
Activity (MDA) for iodine-131 varied due to the short half-life and
the length of time between sample collection and counting. Relative
Percent Difference (RPD) was 20% or less or 100% or less if the
activity was less than five times the MDA. The criteria for the
assessment of method bias was ± 25% of true value on laboratory
control samples that were included with each batch (General
Engineering Labs, August 2013).
Analysis conducted by CDPH involved transferring the sampled
milk to 4 L Marinelli beakers and counting on a 50% relative efficiency
HPGe for 16 h. The method was in accordance with EPA
Method 901.1 Analysis for Gamma Emitting Radionuclides in
Drinking Water. If lower detection limits were desired, the inclusion
of the iodine carrier (KI) would provide an avenue for applying
Standard Methods 7500-I C, in which radioiodine is converted to
iodide and concentrated on an anion resin, then counted on a betagamma
coincidence system (Ruberu, May 2011 October 2013). In
this case, an HPGe was used for the milk samples. CDPH only