1 Cesium radioisotope content of wild edible fungi, mineral soil, and surface litter in western
2 North America after the Fukushima nuclear accident.
3
4 Matthew J. Trappea, Leah D. Mincb, Kimberly S. Kittredgec, Jeremias W. Pinkd
5
6 a Department of Forest Ecosystems and Society, 321 Richardson Hall, Oregon State University,
7 Corvallis, Oregon, USA, 97331, [email protected], corresponding author, Tel. 01-
8 541-737-6072
9
10 b Radiation Center, 100 Radiation Center, Oregon State University, Corvallis, Oregon, USA,
11 97331, [email protected]
12
13 c Northwest Mycological Consultants, 702 NW 4th Street, Corvallis, Oregon, USA, 97330,
15
16 d Department of Anthropology, 238 Waldo Hall, Oregon State University, Corvallis, Oregon,
17 USA, 97331, [email protected]
1
18 ABSTRACT
19 We measured activity levels of cesium radioisotopes 134Cs and 137Cs in wild edible fungi,
20 mineral soil, and surface litter of the west coast of North America from southern California to
21 northern Vancouver Island after the Fukushima nuclear accident. All activity measurements
22 were below governmental limits for human health. 137Cs activity increased to the north in
23 mineral soils and fungal samples, while 134Cs activity increased to the south in surface litter
24 samples. Chanterelles did not significantly bioconcentrate either radioisotope, but chanterelle
25 activity levels were correlated with those of mineral soil. Activity levels demonstrated a high
26 degree of variability, even in samples from the same site. In most cases the level of 137Cs
27 activity was substantially higher than that of 134Cs, suggesting that 137Cs was present in the
28 environment prior to the Fukushima release.
29
30 Keywords: bioaccumulation, cesium, chanterelle, Fukushima, fungi, mushroom, radiation
31
32 INTRODUCTION
33 The disaster at the Fukushima Daiichi nuclear power plant after the March 11, 2011 earthquake
34 and tsunami released an estimated 35.8 (±16.5) PBq (3.66 x 1016 Bq) each of the radioisotopes
35 cesium–137 (137Cs) and cesium–134 (134Cs) between March 11 and April 18, 2011. About 19%
36 of the airborne radioactive particles were deposited on Japan, 79% in the Pacific Ocean, and 2%
37 on land areas other than Japan (Stohl et al. 2012).
38
39 The purpose of this study was to measure and report the levels of cesium radionuclides in wild
40 edible fungi and their substrates on the North American west coast after the Fukushima accident.
2
41 Fungi are of particular interest because they can bioaccumulate heavy metals (Campos et al.
42 2009) including radionuclides (Vinichuk et al. 2010) and are consumed by humans (Pilz and
43 Molina 2002). This bioaccumulation is often referred to as a “Transfer Factor” (Ehlken and
44 Kirchner 2002); the radioisotope level detected in the mushroom tissue divided by that of its
45 substrate. A Transfer Factor of 1 indicates that activity levels in fungal tissue are the same as
46 their substrate, above 1 indicates bioaccumulation above substrate levels, and below 1 indicates
47 that activity levels in fungal tissue are below those of their substrate.
48
49 We analyzed samples of edible fungi and associated surface litter and mineral soil on a
50 latitudinal gradient from northern Vancouver Island, British Columbia to Los Angeles,
51 California for activity of 134Cs and 137Cs radioisotopes. The cesium isotopes were selected
52 because the relatively short half-life of 134Cs (2.1 yr) makes it a good indicator of recent events,
53 and the longer half-life of 137Cs (30.2 yr) makes it a persistent environmental contaminant.
54
55 Different taxa of fungi have been shown to bioaccumulate radionuclides at different rates
56 (Vinichuk and Dolhilevyech 2005). One factor that may affect fungal bioaccumulation is their
57 trophic status (Gillett and Crout 2000). Mycorrhizal fungi form symbioses with roots of plants,
58 and are efficient at absorption and transport of minerals and nutrients from soil to roots (Leake et
59 al. 2004). Saprobic fungi enzymatically decompose organic material, absorbing not only the
60 resultant carbohydrates but also other compounds present in the substrate (Bazala et al. 2008).
61 The hyphae of saprobic fungi dominate the surface litter layer, while the hyphae of mycorrhizal
62 fungi dominate deeper soil horizons (Lindahl et al. 2007). Some fungi contain pigments that
63 chelate and retain cesium (Garaudée et al. 2002). Many abiotic site factors including clay
3
64 content (Staunton and Levacic 1999), soil pH (Kruyts and Delvaux 2002), precipitation and
65 runoff (Parsons and Foster 2011), and microsite conditions (Bunzl et al. 1997) can also affect
66 bioaccumulation.
67
68 Although we welcomed all samples of wild edible fungi, for consistency in data analysis we
69 focused on obtaining chanterelles (Cantharellus spp.) across a latitudinal gradient. Cantharellus
70 species are among the more widely distributed and frequently consumed edible taxa (Pilz et al.
71 2003). No single species of Cantharellus extends throughout the range of this project; in the
72 Pacific Northwest (PNW) we sampled Cantharellus cascadensis, C. formosus, and C. subalbidus
73 (associated with conifers), and in California, Cantharellus californicus (associated with oaks).
74
75 Our first hypothesis was that activity levels of cesium isotopes in wild edible mushrooms are
76 below the FDA Derived Intervention Limits (FDA 1998) of 1200 Bq/kg. Many studies have
77 documented radioisotope uptake by mushrooms in Europe after the Chernobyl accident of 1986,
78 but we found little quantitative data on the safety of edible wild mushrooms in western North
79 America. Given the relatively small proportion of the release that reached North America, we
80 expected that activity levels would be less than 1200 kg/Bq.
81
82 Our second hypothesis was that cesium activity would be higher in samples farther north due to
83 jet stream influenced precipitation patterns. Most deposition of radioisotopes occurs during rain
84 events (Clark and Smith 1988) and typical jet stream behavior brings more winter precipitation
85 to the PNW than California.
86
4
87 Our third hypothesis was that chanterelles would bioaccumulate cesium isotopes at levels above
88 those of their substrates (Transfer Factor > 1.0). Bioaccumulation of radioisotope and Transfer
89 Factors are well documented in closely related European fungal species, but we know of no such
90 studies in North America. The last known survey of radiation levels in Pacific Northwest forest
91 ecosystems was performed by Eberhardt et al. (1969).
92
93 MATERIALS AND METHODS
94 Samples of wild edible fungi, mineral soil, and surface litter were collected by a network of
95 volunteers on the west coast of North America from Los Angeles, California, to northern
96 Vancouver Island, British Columbia in the fall/winter season of 2011-2012, ca 6-10 mo after the
97 Fukushima accident. From each location we requested samples of 100 g dry weight of each
98 material type, however some samples were smaller. Because our priority was to include a large
99 sampling area, many samples were unreplicated from a given location. “Surface litter” was
100 undecomposed material from the O horizon collected from ca 1 m around a fungal sporocarp
101 sample. “Mineral soil” was blended humic-mineral A horizon material collected beneath the
102 stem of the sampled mushroom ca 5-10 cm deep. We also analyzed 8 fungal and 2 substrate
103 samples that had been collected and preserved (dried) before the Fukushima accident.
104
105 Fungal samples were cleaned of most adhering soil and debris, air dried at 60°C for 12–24 h, and
106 ground to a uniform powder with a Wiley mill. Each sample was then weighed, placed in a
107 polyethylene container (either 120 cc “urine cups” for smaller samples and 450 cc “cottage
108 cheese” containers for larger samples), and the volume determined to the nearest 10 ml. Each
109 sample was analyzed at the Oregon State University Radiation Center for ~24 h, and gamma
5
110 activity recorded at the 795 keV line for Cs-134 and at 662 keV for Cs-137 on one of three high
111 purity germanium detectors. All detectors utilized are ORTEC coaxial HPGe with certified
112 relative efficiencies of 28%, 32% and 34%, and resolutions of 1.72, 1.70, and 1.74 (FWHM at
113 1333 keV), respectively. The detectors are oriented in a vertical configuration within graded
114 shielding (Pb-Al-Cu) and located within a low-background counting facility.
115
116 In order to accurately quantify activity for the diversity of sample volumes represented,
117 calibration curves were developed for each detector for a range of sample geometries in both
118 container types using a mixed isotope certified calibration source (Analytics 69477-717). The
119 liquid source was first transferred to a urine cup containing 40 ml of lab-grade cellulose powder
120 and allowed to dry; loss of activity due to transfer was determined by counting the original
121 source container immediately before and after transfer on the same detector. Additional
122 cellulose powder was added to the urine cup and mixed with the source to simulate the various
123 volumes of fungal samples (40, 60, 90, and 130 ml), and the detector efficiency determined for
124 each volume with the urine cup placed on the detector face. The cellulose power was then
125 transferred to a cottage-cheese container, and additional powder was added to simulate sample
126 volumes of 200, 300, 350, 400, 450, and 500 ml. Results for the final (500 ml) cellulose powder
127 source were compared against a certified 500 cc calibration source (Eckert and Ziegler 1555-12-
128 2), and measured activities found to be within 6% of certified activities for the 662 and 1333 keV
129 peaks at the same geometry.
130
131 For each geometry, detector efficiency was measured directly at 662 keV based on Cs-137
132 activity, and at 1173 and 1333 keV based on Co-60 activity; efficiency for the 795 keV peak was
6
133 then interpolated using a quadratic fit of efficiency vs. energy by the GammaVision® gamma
134 spectroscopy software package. For the urine cup containers, measurement efficiencies were in
135 the range of 1.6 - 3.1% at 662 keV and 1.4 - 2.2% at 795 keV, depending on the volume of
136 material present and detector utilized (Fig. 1). For the larger cottage-cheese containers,
137 measurement efficiencies in the range of 0.8 – 1.9% were observed at the 662 keV peak, and 0.7
138 – 1.6% for the 795 keV peak, again depending on sample volume and detector. Finally, in order
139 to estimate detector efficiency across a range of intervening sample volumes not measured
140 directly, a log-log regression model of efficiency vs. volume was developed separately for the
141 662 keV and 795 keV lines for both container types (Fig. 2); sample decay counts were then fit
142 to the volume-appropriate efficiency calibration curve to determine absolute activity for a
143 specific volume. All activities were decay-corrected to April 1, 2011 and are reported as Bq/kg
144 of sample material, with associated errors representing 1-σ uncertainly in peak areas.
145
146 Due to the potential for wide variances in bioaccumulation between fungal taxa, we focused our
147 statistical analyses on chanterelle species. For regression analyses, all cesium activity data
148 (Bq/kg) were natural log transformed to remediate exponential distributions.
149
150 Mineral soil pH was measured by mixing 1 g of soil in 5 mL of deionized water and allowing it
151 to equilibrate for 1h. Measurements were taken with a Hanna 99104 pH tester calibrated in 3.0
152 pH and 7.0 pH buffer solutions before measurements and again afterward to confirm stability.
153
154 RESULTS
7
155 Table 1 presents site locality and all measurement data. In all cases, levels of 134Cs+137Cs were
156 well below the 1200 Bq/kg DIL (FDA 1998), and many samples had barely detectable activity
157 levels after 24 h of measurement. Transfer Factors are calculated for fungi that were collected
158 with a directly proximate substrate, most often mineral soil but in some cases (C. tubaeformis, H.
159 erinaceus, and P. ostreatus) decaying wood. Across all sample types, activity levels were
160 significantly higher (two-tailed t-test, p< 0.001) for 137Cs ( =15.63 Bq/kg) than 134Cs ( =0.97
161 Bq/kg).
162
163 Figure 3 presents the mean activity levels for 134Cs and 137Cs in chanterelle mushrooms, mineral
164 soil, deciduous (mostly oak) litter, and needle litter samples. Deciduous litter is associated with
165 samples from California, while needle litter is associated with PNW samples. Table 2 presents
166 mean values for each material type overall and also by latitudinal groups.
167
168 Figures 4-9 present relationships between cesium isotopes in mineral soil, surface litter, and
169 chanterelles relative to latitude. In regression analyses, two geographically separated groups of
170 data are apparent; a smaller grouping from latitudes 34º-39º (California) and larger grouping
171 from latitudes 41º-51º in the Pacific Northwest (PNW). The division is a consequence of the
172 lack of samples between latitudes 39 and 41, but also reflects differences in ecosystems, such as
173 chanterelle species and surface litter. Each regression figure depicts the overall fit and the fits
174 within each geographic group. The sample size of the California subgroup was too small for in-
175 group patterns to reach statistical significance.
176
8
177 Activity levels of 134Cs across all mineral soil samples (Fig. 4) showed no correlation with
178 latitude (p=0.14, adj. R2=0.05). In contrast, activity of 137Cs in mineral soils (Fig. 5) is
179 significantly correlated with latitude (p<0.01, adj. R2=0.27), and although within-group sample
180 size precluded significance at α=0.05, both the PNW and California groups closely followed the
181 overall fit.
182
183 Activity levels of 134Cs across all litter samples (Fig. 6) were negatively correlated with latitude
184 (p=0.006, adj. R2=0.22). Within the California or PNW groups there was no significant
185 correlation between 134Cs and surface litter (Fig. 6). The regional clustering effect is particularly
186 pronounced in these data, and as a group the California sample activities were significantly
187 higher than of the PNW group (two-tailed t-test, p = 0.006). Activity of 137Cs in surface litter
188 (Fig. 7) had no significant correlation with latitude (p=0.69), and within-group trends closely
189 followed the overall fit.
190
191 Accumulations of 134Cs in chanterelles (Fig. 8) were quite low (<3Bq/kg). No significant overall
192 latitudinal patterns (p=0.42) were apparent, nor was there a significant trend within the PNW
193 group (p=0.93). The downward trend with increasing latitude in the California group was
194 strongly influenced by outliers and not statistically significant.
195
196 Accumulations of 137Cs in chanterelles (Fig. 9) were markedly higher than of 134Cs, but only one
197 sample exceeded 50 Bq/kg (Bamfield). There was a significant trend across all samples for
198 higher levels of 137Cs to the north (p<0.01, adj. R2=0.39), a pattern reflected in both in the PNW
199 group (p=0.06, adj. R2=0.11) and the California samples. This relationship remains significant
9
200 (p<0.01, adj. R2=0.36) even when the Bamfield chanterelle is removed from analysis. In contrast
201 with the 134Cs surface litter data, the PNW cluster was significantly higher than the California
202 cluster (two-tailed t-test, p = 0.004).
203
204 Given that 137Cs activity in mineral soil and chanterelles are both correlated with latitude, it is no
205 surprise that 137Cs activity in mineral soil is strongly correlated (p<0.0001, adj. R2=0.51) with
206 levels in chanterelles (Fig. 10). However, cesium isotopes are more mobile at lower soil pH, and
207 soil pH is also negatively correlated with latitude (as a function of precipitation) as depicted in
208 Fig. 11 (p=0.015, adj. R2=0.16). Figure 12 shows the relationship between mineral soil pH and
209 137Cs activity in chanterelles (p=0.004, adj. R2=0.22), and Fig. 13 the relationship between
210 mineral soil pH and chanterelle Transfer Factors (p=0.007, adj. R2=0.31).
211
212 To deconvolve these interrelationships, Table 3 shows respective significances with all
213 combinations of these interaction terms. These data suggest that 137Cs activity in chanterelles is
214 more strongly influenced by mineral soil activity than other factors. Latitude increased goodness
215 of fit over mineral soil activity alone, but latitude is surrogate for geographic deposition (rainfall)
216 patterns and not directly involved with bioaccumulation. The addition of soil pH into the model
217 actually reduced the coefficient of determination.
218
219 Figure 14 shows the relationship between chanterelle Transfer Factors relative to mineral soil
220 137Cs activity. The solid line is the regression fit for the data, and the dashed line indicates the
221 1:1 ratio of fungal tissue activity to mineral soil substrate activity. The chanterelle regression
222 consists of fungal samples specifically paired with soil samples immediately proximate to the
10
223 fungal collection. We lacked such pairings for most non-chanterelle fungi and therefore could
224 not construct a meaningful regression, although some individual datapoints are available (Table
225 1).
226
227 There is little evidence in this study that chanterelles are bioaccumulating either cesium isotope
228 at levels greater than in the surrounding mineral soil. The mean Transfer Factor for 137Cs in
229 chanterelles was 1.0, however the median was 0.4. For 134Cs in chanterelles the mean Transfer
230 Factor was 1.4, and the median 0.7. For both isotopes, a few chanterelle samples with somewhat
231 high Transfer Factors (6.0-6.5) raised the average, but most individuals were below 1.0.
232
233 One category of non-chanterelle fungi that did have relatively high Transfer Factors was those
234 that inhabited decaying wood. This group included the mycorrhizal Craterellus tubaeformis
235 (mean 137Cs Transfer Factor 4.5, n=5), and the saprobic Hericium erinaceus (137Cs Transfer
236 Factor 105.3, n=1) and Pleurotus ostreatus (137Cs mean Transfer Factor 11.7, n=2). This may be
237 a function of increased enzymatic activity by fungi adapted to woody substrates, possibly
238 enhancing their ability to mobilize and take up cesium isotopes.
239
240 Regressions of 134Cs and 137Cs activity levels in non-chanterelle fungi with latitude are presented
241 in Figs. 15 and 16. Conclusions about latitudinal effects could be confounded by differing
242 bioaccumulation profiles between species, however the analyses show that the pattern of 137Cs in
243 fungal tissue across all taxa is similar to that of chanterelles, increasing significantly with latitude
244 (p<0.01, adj. R2=0.24). No such pattern was detected for 134Cs (p=0.19) in the same sample set.
245 When the samples are separated by trophic status (mycorrhizal fungi, n=90; saprobic fungi,
11
246 n=12), the latitudinal correlation with fungal 137Cs is enhanced for mycorrhizal fungi (p<0.01,
247 adj. R2=0.32) and no significant correlations are found for saprobic fungi (p=0.4).
248
249 We acquired 8 fungal and 2 substrate samples from prior to the Fukushima accident. Their
250 activity levels are presented in Table 4, and compared with those of analogous post-Fukushima
251 materials from nearby sites. Of the five pre–Fukushima Cantharellus collections, the one with
252 the highest 137Cs measurements was again the most northerly (Vancouver, WA). Only one
253 sample exceeded 5 Bq/kg of 134Cs, and it was collected before the Fukushima accident. That
254 same sample also had the highest 137Cs activity. Among chanterelles (C. formosus), the mean
255 137Cs activity level for pre-Fukushima collections was 11.6 Bq/kg, and for post-Fukushima
256 collections, 10.9 Bq/kg. These data suggest that much of the detected activity predated the
257 Fukushima accident.
258
259 DISCUSSION
260 We did not expect the substantially higher activity levels of 137Cs over 134Cs that we found in
261 most of our samples. 134Cs and 137Cs were released from Fukushima in approximately equal
262 proportions; 134Cs:137Cs ratios ranged from .06 to 1.5 ( =0.78) in Seattle air samples (Leon et al.
263 2011), 0.6 to 2.5 ( =1.0) in San Francisco Bay area rainwater (Norman et al. 2011), 0.2 to 6.7
264 ( =1.0) at multiple National Atmospheric Deposition Program (NADP) sites in the United
265 States (Wetherbee et al. 2012), 0.9 to 1.7 ( =1.2) in Japanese river water sampled March 31,
266 2011 (Oura and Ebihara 2012), and 0.71 to 1.3 ( =0.87) in Russian precipitation (Bolsunovsky
267 and Dementyev 2011). The greater activity levels of 137Cs reported here can be ascribed to
268 historic deposition and were likely present in the environment prior to the Fukushima accident.
12
269 Our pre-Fukushima sample data (Table 4), historic soil and sedimentary data (McHenry et al.
270 1973), and soil measurements of 137Cs before and after the Fukushima accident in northern
271 Canada (Blagoeva and Zikovsky 1995) and eastern Russia (Ramzaev et al. 2013) are consistent
272 with this conclusion.
273
274 Our first hypothesis that activity levels of cesium isotopes in wild edible mushrooms are below
275 the FDA Derived Intervention Limits (1200 Bq/kg) is affirmed (Table 1). Of the 107 fungal
276 samples assayed, only 11 had 134Cs+137Cs activity levels above 50 Bq/kg. Excepting the sample
277 from Bamfield, all chanterelle activities were below 50 Bq/kg, and 58% of all fungal samples
278 had activity levels below 10 Bq/kg.
279
280 Of the nine fungal samples exceeding 100 Bq/kg of 137Cs, four were in the family Gomphaceae
281 (the genera Gomphus, Ramaria, and Turbinellus). The Gomphus clavatus from Umpqua River
282 was the only sample south of 43° latitude to exceed 100 Bq/kg. Because the FDA DIL is applied
283 to foods as prepared for consumption and many edible mushrooms are 67-90% water (Manzi et
284 al. 2004), our dry weight measurements may be three- to tenfold higher by weight than fresh
285 material.
286
287 Figure 3 illustrates the differences in activity levels between cesium isotopes and sample
288 material. Three things are immediately apparent: 137Cs is generally quite higher than 134Cs
289 activity, 137Cs levels in chanterelles and mineral soil are very similar, and the only material in
290 which 134Cs and 137Cs levels are similar is deciduous litter. The correlation between chanterelle
291 and mineral soil activity is not surprising given the mycorrhizal trophism of chanterelles (also
13
292 see Fig. 10). While mycorrhizal fungi receive the bulk of their carbon from host plants by way
293 of root symbiosis, they also are effective foragers for inorganic nutrients in mineral soil horizons.
294
295 If 134Cs and 137Cs arrived from Fukushima in equal proportions, and recent deposition is better
296 reflected in surface litter than mineral soil (Bunzl et al. 1992), we would expect to see
297 comparable levels of 134Cs and 137Cs in surface litter, and surface levels should exceed those of
298 mineral soil. The similarity of 134Cs and 137Cs activity levels in deciduous litter may be the most
299 informative data about deposition patterns originating from Fukushima, as the 134Cs:137Cs ratio is
300 closest to the parity measured in other studies summarized above.
301
302 One possible explanation for the difference in 134Cs levels between deciduous and needle litter
303 levels are their different morphologies: conifer needles tend to have a waxy, hydrophobic
304 exterior and a low surface:volume ratio, while deciduous leaves readily absorb radioisotopes
305 through their cuticles (Ertel et al. 1992). If this were the case we would expect to see 137Cs
306 activity in deciduous litter to be higher than needle litter as well, however this is not the case:
307 137Cs is actually higher in needle litter and higher still in mineral soil. Given the elevated levels
308 of 137Cs in PNW mineral soil, it is possible that the 137Cs activity in PNW needle litter is a result
309 of uptake from mineral soil by the tree before the needles were shed (Tuovinen et al. 2011).
310
311 Table 2 summarizes the data underlying Fig. 3. The difference in 137Cs content between saprobic
312 and mycorrhizal fungi in the PNW is much greater than that in California or of 134Cs. This
313 reflects not only the higher levels of 137Cs in PNW mineral soils, but also the difference in
314 substrates. The 137Cs numbers for chanterelles are higher than those of mineral soil in general,
14
315 but this relationship is weaker when analyzing only paired chanterelle-soil samples (Fig. 14).
316 The aggregation of all other mycorrhizal fun gi has much higher 137Cs activity levels than do
317 chanterelles, but this is strongly influenced by a small number of non-chanterelle fungi with very
318 high activity levels.
319
320 Our second hypothesis, that levels of cesium isotopes would be higher at northern latitudes, was
321 true for 137Cs in mineral soils and fungal tissue but false for 137Cs in surface litter and 134Cs in all
322 materials. In fact, 134Cs activity levels in surface litter were higher to the south. The patterns
323 observed for 137Cs are consistent with legacy deposition prior to the Fukushima accident. The
324 134Cs data may be explained by specific weather patterns shortly after the main releases from
325 Fukushima between March 12-15, 2011.
326
327 Some of the released radioisotopes reached sufficient altitude to be entrained by the polar jet
328 stream (Hsu et al. 2012). The polar jet stream ordinarily makes landfall on the west coast of
329 North America north of 40º latitude. However, when the front of the Fukushima plume arrived
330 at the North American west coast between March 17-20, the jet stream had dipped south
331 (California Regional Weather Server 2013), bringing 4.4 cm of rain to San Francisco. During
332 that period, Corvallis, OR reported 1.9 cm and Victoria, BC 1.2 cm of precipitation. The atypical
333 path of the jet stream during those critical days is consistent with the observation that 134Cs levels
334 were slightly higher in California than the PNW, while the normal jet stream pattern is consistent
335 with higher historic levels of 137Cs in the PNW and in mineral soils.
336
15
337 Our third hypothesis, that chanterelles would bioaccumulate cesium isotopes at levels above
338 those of their substrates (Transfer Factor > 1.0) was not well supported. While some samples
339 had 137Cs Transfer Factors as high as 6.5 the majority were below 1.0. Although there was not
340 strong evidence for bioaccumulation in chanterelles, variability among 137Cs activity levels of
341 fungi was generally higher than that of mineral soil and surface litter samples. Fungal samples of
342 differing species often had pronounced within-site differences; 137Cs in samples from Marys
343 Peak ranged from 0.7 to 595 Bq/kg while mineral soils ranged from 2.4 to 10.1. Although we
344 were reluctant to quantify Transfer Factors for fungal samples that lacked paired proximate
345 mineral soil samples, such contrasts between and fungal and averaged site soil activity levels
346 indicate that bioaccumulation is occurring with many species.
347
348 CONCLUSIONS
349 Activity levels in all fungal samples were below the FDA DIL of 1200 Bq/kg of 134Cs+137Cs, and
350 in most cases less than 50 Bq/kg. Levels of 137Cs were higher at northern latitudes in
351 mycorrhizal fungi and mineral soils but not in saprobic fungi, probably a consequence of
352 mycorrhizal mycelia foraging in deeper soil horizons than those of saprobic fungi. 137Cs activity
353 increased to the north in mineral soils and fungal samples, while 134Cs activity increased to the
354 south in surface litter samples. Chanterelles did not significantly bioconcentrate either
355 radioisotope, but chanterelle activity levels were correlated with those of mineral soil. Activity
356 levels in fungi demonstrated a high degree of variability, even in samples from the same site. In
357 most cases the level of 137Cs activity was substantially higher than that of 134Cs, suggesting that
358 137Cs was present in the environment prior to the Fukushima release. Historic sources of 137Cs
16
359 may have been Chernobyl or weapons testing, and it is likely the higher levels found at more
360 northern latitudes is a result of higher overall precipitation rates.
361
362 ACKNOWLEDGEMENTS
363 The authors wish to thank the individuals and organizations who donated their time, postage, and
364 dinner to this project: Dennis Albert, Jennifer Barnett, Shannon Berch, Mike Beug, Paul Bishop,
365 Bob Cantor, Mark Carnessale, Phil Carpenter, Georgette Castor, Kent Davis, Sejon Ding, Jean–
366 Louis Excoffier, Jonathan Frank, Richard Gaines, Terry Giddens, Ron Hamill, Kathryn Higley,
367 Susie Holmes, Wren Hudgins, Jake and Laura Hurlbert, Jadwiga Jaworowska, Jim Jones, Everett
368 Kittredge, Kathy Kittredge, Augustine Lehecka, Hanna Lewandowski, Igor and Donna
369 Malcevski, Lisa McCarthy–Smith, Doni McKay, Marian McMeekin, Chris Melotti,
370 MycoLogical Natural Products, Ikuko Okuyama, Dwayne Paige, Mike and Michelle Parish,
371 Alisha Quandt, Dustin Quandt, Steve Reese, Owen Rice, Kathleen and Jerry Sand, Chris
372 Schoenstein, Seattle Public Utilities, Jane Smith, Starker Forests, Sherwood Stolt, Evelyn Tay,
373 James Trappe, Mysti Weber, and Norene Wedam. This project was implemented without
374 external funding, and the authors gratefully acknowledge the Oregon State University Radiation
375 Center for donating analyzer time. We also thank two anonymous reviewers for their helpful
376 suggestions to improve this manuscript.
377
378
379
380
381
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506 Table 1. Cesium isotope measurements in wild edible mushrooms, mineral soil, and surface litter, Bq/kg dry weight. Activity reported 507 with measurement uncertainty. M=Mycorrhizal, S=Saprobic, P=Parasitic. TF=Transfer Factor, calculated for those fungi with paired 508 mineral soil samples. 509 134Cs 137Cs 134Cs 137Cs Site Name Latitude Longitude Material Trophic pH Bq/kg Bq/kg TF TF San Josef Beach, BC 50° 40.6' -128° 16.7' Cantharellus formosus M 0.7 ± 0.9 29.7 ± 0.8 0.6 2.8 Mineral soil 6.6 1.2 ± 0.5 10.6 ± 0.3 Needle litter 0.8 ± 0.3 3.7 ± 0.1 Quatse Lake, BC 50° 37.7' -127° 33.2' Cantharellus formosus M 0.6 ± 0.4 10.6 ± 0.4 0.5 2.2 Mineral soil 6.1 1.3 ± 0.3 4.9 ± 0.2 Needle litter 0.7 ± 0.2 1.9 ± 0.1 Alice Lake, BC 50° 29.9' -127° 22.4' Cantharellus formosus M 0.7 ± 0.3 6.2 ± 0.3 0.7 0.3 Mineral soil 6.4 1.0 ± 0.4 21.3 ± 0.4 Needle litter 0.7 ± 0.3 4.6 ± 0.2 Quathiaksi Cove, BC 50° 02.4' -125° 13.1' Cantharellus formosus M 0.1 ± 0.7 19.4 ± 0.6 0.1 6.5 Lactarius deterrimus M 0.5 ± 1.3 47.7 ± 1.9 Mineral soil 6.4 1.4 ± 0.4 3.0 ± 0.2 Needle litter 2.4 ± 0.5 1.3 ± 0.2 Bamfield, BC 48° 49.2' -125° 04.0' Cantharellus formosus M 1.3 ± 1.9 157.0 ± 4.6
Cantharellus formosus M 0.2 ± 1.0 46.6 ± 2.9
Laetiporus coniferarum S 0.6 ± 0.6 1.0 ± 0.3 Needle litter 0.7 ± 0.5 8.7 ± 0.4 Needle litter 1.6 ± 0.4 8.8 ± 0.5 Wallace Falls, WA 47° 53.8' -121° 40.5' Cantharellus formosus M 0.7 ± 1.1 10.5 ± 1.1 0.4 0.6 Mineral soil 6.4 1.9 ± 0.7 18.8 ± 0.6 Needle litter 1.7 ± 1 16.5 ± 0.8 Wenatchee, WA 47° 50.4' -120° 38.8' Cantharellus formosus M 0.9 ± 0.9 7.6 ± 0.7
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Needle litter 0.6 ± 0.2 3.3 ± 0.2 Tanner, WA 47° 31.3' -121° 44.3' Cantharellus formosus M 0.8 ± 0.5 15.6 ± 0.5 2.7 1.4 Mineral soil 6.1 0.3 ± 0.2 11.0 ± 0.7 Mineral soil 6.3 1.5 ± 0.7 16.6 ± 0.5 Needle litter 0.4 ± 0.2 6.9 ± 0.2 Cedar River, WA #1 47° 25.5' -121° 45.4' Cantharellus formosus M 1.5 ± 1.2 43.2 ± 2.9 5.0 3.6 Craterellus tubaeformis M 2.9 ± 2.2 191.9 ± 5.3 Mineral soil 6.1 0.3 ± 0.2 12.1 ± 0.7 Mineral soil 6.5 0.8 ± 0.4 14.3 ± 0.7 Needle litter 0.2 ± 0.3 5.5 ± 0.3 Needle litter 0.8 ± 0.4 11.2 ± 0.5 Russula sp. with Cedar River, WA #2 47° 25.4' -121° 44.2' M 0.6 ± 1.2 57.0 ± 2.1 2.0 2.6 Hypomyces Turbinellus floccosus M 0.0 ± 1.9 121.9 ± 5.6 0.0 5.5 Mineral soil 6.1 1.7 ± 0.7 8.4 ± 0.4 Mineral soil 6.2 0.3 ± 0.4 22.0 ± 0.9 Needle litter 1.3 ± 0.4 2.7 ± 0.2 Needle litter 0.3 ± 0.5 3.0 ± 0.3 Cedar River, WA #3 47° 24.9' -121° 47.6' Lactarius subviscidus M 0.2 ± 1.0 15.3 ± 0.9 0.1 1.5 Mineral soil 6.3 1.5 ± 0.6 10.1 ± 0.5 Needle litter 3.7 ± 0.8 4.0 ± 0.5 Cedar River, WA #4 47° 22.7' -121° 57.4' Cantharellus formosus M 2.0 ± 1.1 21.4 ± 1.1 6.7 2.4 Mineral soil 6.5 0.3 ± 0.3 8.9 ± 0.3 Needle litter 1.4 ± 0.6 2.2 ± 0.3 Cedar River, WA #5 47° 22.4' -121° 41.8' Clavulina cinerea M 1.1 ± 1.8 170.4 ± 3.5 Craterellus tubaeformis M 1.8 ± 1.9 58.1 ± 2.5 Mineral soil 6.1 0.6 ± 0.5 12.6 ± 0.6 Needle litter 1.3 ± 0.4 5.4 ± 0.3 Olympic Penninsula, 47° 22.3' -122° 58.6' Cantharellus formosus M 0.4 ± 0.3 6.5 ± 0.3 WA
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Cantharellus subalbidus M 0.1 ± 0.4 19.6 ± 0.5 1.0 1.6 Leccinum ponderosum M 0.3 ± 0.2 5.8 ± 0.3 Mineral soil 6.0 0.1 ± 0.4 12.3 ± 0.4 Needle litter 0.5 ± 0.2 4.1 ± 0.2 Long Beach, WA 46° 36.5' -124° 03.3' Cantharellus formosus M 0.6 ± 0.3 5.5 ± 0.3
Tricholoma magnivelare M 1.6 ± 0.9 8.8 ± 0.6 Needle litter 0.3 ± 0.2 2.6 ± 0.2 Klickitat, WA 45° 49.1' -121° 28.8' Cantharellus subalbidus M 1.6 ± 0.5 1.1 ± 0.4 5.3 1.1 Mineral soil 6.8 0.3 ± 0.1 1.0 ± 0 Mineral soil 6.7 0.6 ± 0.3 8.9 ± 0.3 Needle litter 0.7 ± 0.2 0.6 ± 0.1 Needle litter 1.1 ± 0.3 4.1 ± 0.3 Spring Creek, WA 45° 48.9' -121° 30.8' Cantharellus cascadensis M 0.3 ± 0.7 0.0 ± 0.1 0.8 0.1 Mineral soil 6.7 0.4 ± 0.1 0.5 ± 0 Needle litter 0.7 ± 0.2 0.4 ± 0.1 Indian Cemetary, WA 45° 48.3' -121° 28.4' Cantharellus formosus M 0.3 ± 0.2 0.3 ± 0.1 0.3 0.1 Mineral soil 6.1 1.0 ± 0.2 3.3 ± 0.1 Needle litter 0.4 ± 0.2 0.7 ± 0.1 Lake Oswego, OR 45° 22.6' -122° 40.7' Cantharellus formosus M 0.6 ± 1.1 36.3 ± 1.2
Russula xerampelina M 0.6 ± 1.9 131.3 ± 3.8 Needle litter 0.8 ± 0.3 7.2 ± 0.3 Estacada, OR 45° 08.0' -122° 08.8' Cantharellus formosus M 0.5 ± 0.4 6.5 ± 0.3
Detroit, OR #1 44° 46.3' -122° 12.4' Cantharellus formosus 0.3 ± 0.2 5.6 ± 0.5 0.4 0.2
Russula xerampelina M 0.3 ± 0.5 8.7 ± 0.4 0.8 2.9 Mineral soil 6.0 0.7 ± 0.3 23.3 ± 0.9 Mineral soil 6.4 0.4 ± 0.2 8 ± 0.4 Needle litter 0.4 ± 0.2 3.1 ± 0.1 Needle litter 1.2 ± 0.2 7.9 ± 0.4 Detroit, OR #2 44° 45.7' -122° 06.4' Cantharellus formosus M 0.3 ± 0.4 11.9 ± 0.4 0.6 0.9
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Sparassis crispa S/P 2.7 ± 1.6 10.6 ± 1.1 Gomphidius oregonense M 0.1 ± 0.4 4.3 ± 0.3 Ramaria botrytis M 1.3 ± 1.9 100.4 ± 3.2 Mineral soil 6.3 0.5 ± 0.5 13.9 ± 0.4 Needle litter 0.3 ± 0.2 6.6 ± 0.3 Blodgett, OR 44° 36.0' -123° 34.1' Tuber oregonense M 1.6 ± 0.3 1.0 ± 0.2 1.5 0.2 Mineral soil 6.6 1.1 ± 0.3 5.0 ± 0.1 Corvallis, OR 44° 34.2' -123° 15.6' Armillarea solidipes P 3.1 ± 1.0 2.5 ± 0.6 Philomath, OR #1 44° 29.6' -123° 24.8' Craterellus tubaeformis M 7.0 ± 1.7 8.5 ± 1.1 8.8 7.7 Gomphidius oregonense M 1.1 ± 0.9 1.0 ± 0.6 Helvella maculata M 0.4 ± 0.1 0.7 ± 0.1 Lactarius deterrimus M 0.4 ± 0.3 1.3 ± 0.2 Suillus lakeii M 0.1 ± 0.4 1.2 ± 0.2 Decayed wood 0.8 ± 0.3 1.1 ± 0.2 Mineral soil 6.6 0.9 ± 0.2 0.8 ± 0 Mineral soil 6.4 0.7 ± 0.1 1 ± 0.1 Mineral soil 6.6 0.7 ± 0.2 1.3 ± 0 Needle litter 0.8 ± 0.1 0.4 ± 0 Needle litter 0.9 ± 0.2 0.7 ± 0 Needle litter 0.5 ± 0.1 1 ± 0.1 Marys Peak, OR 44° 28.1' -123° 30.3' Boletus aereus M 0.1 ± 0.4 10.3 ± 0.3 Boletus aereus M 1.0 ± 0.5 2.1 ± 0.4 Craterellus tubaeformis M 0.5 ± 1.0 22.4 ± 0.8 1.3 7.0 Hydnum repandum M 2.9 ± 1.6 17.2 ± 1.2 Lactarius deterrimus M 1.1 ± 0.5 5.8 ± 0.4 Lyophyllum decastes S 1.6 ± 0.8 8.4 ± 0.6 595.3 ± Ramaria botrytis M 1.8 ± 4.7 20.7 Russula xerampelina M 0.1± 0.6 1.2 ± 0.4
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Suillus caerulescens M 0.2 ± 0.3 0.7 ± 0.2 Decayed wood 0.4 ± 0.2 3.2 ± 0.2 Mineral soil 6.3 0.2 ± 0.1 2.4 ± 0.1
Mineral soil 6.3 0.2 ± 0.2 8.9 ± 0.5 Mineral soil 6.4 0.9 ± 0.3 10.1 ± 0.2 Needle litter 0.8 ± 0.1 1.2 ± 0.1 Needle litter 0.7 ± 0.2 2.6 ± 0.1 Needle litter 0.7 ± 0.2 8.2 ± 0.4 Philomath, OR #2 44° 27.0' -123° 27.7' Cantharellus formosus M 0.2 ± 0.2 0.8 ± 0.1 0.3 0.4 Craterellus tubaeformis M 3.2 ± 0.9 7.4 ± 0.6 4.6 1.9 Russula xerampelina M 0.1 ± 0.3 0.7 ± 0.2 Sparassis crispa S/P 0.2 ± 0.1 0.6 ± 0.1 Decayed wood 0.7 ± 0.2 3.9 ± 0.2 Mineral soil 6.3 0.6 ± 0.1 2.1 ± 0.1 Mineral soil 6.5 0.8 ± 0.2 6.6 ± 0.3 Needle litter 0.9 ± 0.2 1.7 ± 0.1 Needle litter 1.1 ± 0.2 1.9 ± 0.1 Philomath, OR #3 44° 26.2' -123° 26.7' Cantharellus formosus M 0.1 ± 0.2 1.3 ± 0.1 0.2 0.1 Cantharellus subalbidus M 0.5 ± 0.4 2.0 ± 0.2 0.6 0.6 Craterellus tubaeformis M 1.6 ± 0.5 14.7 ± 0.4 5.3 3.3 Helvella maculata M 0.4 ± 0.3 2.7 ± 0.2 Hydnum repandum M 0.9 ± 1.1 20.8 ± 0.8 Lactarius deterrimus M 3.4 ± 0.9 4.0 ± 0.6 Russula sp. with M 0.7 ± 0.6 8.0 ± 0.5 Hypomyces Decayed wood 0.3 ± 0.3 4.4 ± 0.3 Mineral soil 6.5 0.7 ± 0.2 2.3 ± 0.1 Mineral soil 6.5 0.9 ± 0.2 3.2 ± 0.1 Mineral soil 7.0 0.5 ± 0.3 14.5 ± 0.6
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Needle litter 0.7 ± 0.2 1.1 ± 0.1 Needle litter 0.8 ± 0.2 1.6 ± 0.1 Needle litter 1.0 ± 0.2 3.1 ± 0.1 Sisters, OR 44° 25.7' -121° 42.3' Morchella spp. M 0.4 ± 0.3 3.9 ± 0.2 Mineral soil 6.8 0.9 ± 0.4 16.2 ± 0.5 Needle litter 1.0 ± 0.3 0.7 ± 0.1 Lane Co., OR 44° 25.7' -122° 28.4' Agaricus subrutilescens S 0.4 ± 0.3 3.9 ± 0.2 Laetiporus coniferarum S 0.1 ± 1.2 1.7 ± 0.8 Mineral soil 6.7 0.9 ± 0.4 16.2 ± 0.4 Soda Fork, OR 44° 24.6' -122° 16.8' Cantharellus formosus M 0.4 ± 0.4 8.0 ± 0.3 1.0 0.4 Craterellus tubaeformis M 0.4 ± 1.2 35.0 ± 1.2 0.2 2.7 Hydnum umbilicatum M 0.3 ± 0.4 19.9 ± 1.0 Tricholoma equestre M 4.2 ± 3.5 244.4 ± 8 Decayed wood 2.3 ± 0.6 13.0 ± 0.5 Mineral soil 5.9 0.4 ± 0.3 20.5 ± 0.8 Mineral soil 6.5 1.5 ± 0.6 26.7 ± 0.6 Needle litter 1.1 ± 0.3 2.4 ± 0.1 Needle litter 1.3 ± 0.3 5.0 ± 0.3 Needle litter 1.3 ± 0.3 6.1 ± 0.3 Yachats, OR 44° 19.6' -124° 05.8' Cantharellus formosus M 0.5 ± 0.3 2.9 ± 0.3 2.5 0.2 Cantharellus formosus M 1.2 ± 0.8 14.1 ± 0.8 1.5 0.7 Boletus edulis M 0.8 ± 1.0 31.6 ± 1.2 Hericium erinaceus S 0.2 ± 0.8 19.5 ± 0.8 Leccinum manzanitae M 0.2 ± 0.6 3.5 ± 0.5 Mineral soil 6.5 0.2 ± 0.3 14.9 ± 0.5 Mineral soil 6.2 0.8 ± 0.5 20.8 ± 0.6 Needle litter 1.9 ± 0.9 8.3 ± 0.6 Needle litter 0.5 ± 0.2 4.7 ± 0.3 Lobster Valley, OR 44° 19.2' -122° 47.2' Cantharellus formosus M 1.2 ± 0.3 3.4 ± 0.2 1.2 1.0
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Agaricus subrutilescens S 3.0 ± 1.0 4.1 ± 0.6 Mineral soil 6.1 1.0 ± 0.2 3.5 ± 0.1 Needle litter 0.8 ± 0.1 2.0 ± 0.1 Monroe, OR 44° 17.7' -123° 20.4' Hydnum repandum M 0.2 ± 0.9 37.7 ± 1 Russula xerampelina M 0.1 ± 0.1 0.2 ± 0.1 Mineral soil 6.6 0.9 ± 0.2 1.7 ± 0.1 Needle litter 0.5 ± 0.2 0.8 ± 0.1 Deadwood, OR 44° 10.6' -123° 40.9' Cantharellus formosus M 1.0 ± 0.3 1.9 ± 0.2 0.9 0.2 Mineral soil 6.7 1.1 ± 0.4 10.4 ± 0.3 Needle litter 1.1 ± 0.2 3.3 ± 0.1 Oakridge, OR 43° 40.8' -122° 12.5' Cantharellus formosus M 0.6 ± 0.3 1.9 ± 0.2 6.0 0.3 Mineral soil 6.8 0.1 ± 0.5 7.6 ± 0.3 Needle litter 1.0 ± 0.3 5.2 ± 0.3 Sutherlin, OR 43° 34.4' -122° 57.7' Cantharellus formosus M 0.3 ± 0.3 0.6 ± 0.2 0.3 0.3 Mineral soil 6.6 0.9 ± 0.2 2.0 ± 0.1 Needle litter 0.5 ± 0.2 0.9 ± 0.1 Umpqua River, OR 43° 19.1' -122° 58.9' Cantharellus formosus M 0.8 ± 0.3 2.9 ± 0.2 0.9 0.4 309.9 ± Gomphus clavatus M 0.4 ± 1.2 10.8 Mineral soil 6.6 0.9 ± 0.3 7.8 ± 0.2 Needle litter 0.9 ± 0.5 22.0 ± 0.8 Azalea, OR 42° 51.3' -123° 00.4' Cantharellus formosus M 1.3 ± 0.5 10.3 ± 0.4
Needle litter 0.3 ± 0.3 9.9 ± 0.3 Williams, OR 42° 08.9' -123° 16.7' Cantharellus formosus M 0.3 ± 0.3 3.6 ± 0.3 0.3 3.3 Mineral soil 6.7 0.9 ± 0.2 1.1 ± 0.1 Needle litter 1.3 ± 0.3 2.2 ± 0.1 Craterellus Gualala, CA 38° 50.1' -123° 36.2' M 0.1 ± 0.1 0.1 ± 0.1 cornucopioides Craterellus tubaeformis M 1.1 ± 0.4 1.9 ± 0.2 Mineral soil 6.3 1.4 ± 0.3 10.1 ± 0.3
30
Deciduous litter 1.7 ± 0.3 8.6 ± 0.4 Santa Rosa, CA 38° 31.1' -122° 35.2' Cantharellus californicus M 0.1 ± 0.4 1.0 ± 0.3
Tomales Bay, CA 38° 07.9' -122° 53.6' Lepista nuda M 1.4 ± 0.3 2.2 ± 0.2 Mineral soil 6.3 1.0 ± 0.1 1.0 ± 0.1 Deciduous litter 1.3 ± 0.2 1.5 ± 0.1 El Sobrante, CA 37° 57.6' -122° 15.2' Cantharellus californicus M 0.4 ± 0.1 0.3 ± 0.1 0.2 0.1 Cantharellus californicus M 0.1 ± 0.1 0.4 ± 0.1 0.2 0.2 Pleurotus ostreatus S 1.0 ± 0.2 1.7 ± 0.1 5.0 8.5 Russula eccentrica M 0.3 ± 0.2 0.8 ± 0.1 Decayed wood 0.2 ± 0.1 0.2 ± 0.1 Mineral soil 6.8 0.6 ± 0.1 2.2 ± 0.1 Mineral soil 6.6 0.5 ± 0.2 2.8 ± 0.1 Deciduous litter 0.9 ± 0.2 1.8 ± 0.1
Deciduous litter 2.1 ± 0.3 3.2 ± 0.2 Woodside, CA 37° 24.5' -122° 15.6' Pleurotus ostreatus S 0.5 ± 0.2 1.5 ± 0.1 Mineral soil 6.7 1.5 ± 0.3 1.0 ± 0.1 Mineral soil 6.5 0.9 ± 0.2 1.8 ± 0.1 Deciduous litter 1.2 ± 0.2 0.8 ± 0.1 Deciduous litter 2.0 ± 0.2 2.3 ± 0.1 Cupertino, CA 37° 11.0' -121° 50.5' Cantharellus californicus M 0.6 ± 0.2 1.2 ± 0.2 1.2 0.5 Mineral soil 6.4 0.5 ± 0.1 2.4 ± 0.1 Deciduous litter 6.3 ± 0.3 7.0 ± 0.2 Almaden, CA 37° 09.9' -121° 47.7' Cantharellus californicus M 0.6 ± 0.2 0.3 ± 0.1 0.5 0.1 Calvatia booniana M 0.1 ± 0.2 0.4 ± 0.1 Mineral soil 6.8 1.1 ± 0.2 1.4 ± 0.1 Mineral soil 6.8 1.2 ± 0.2 2.5 ± 0.1 Deciduous litter 6.0 ± 0.3 6.0 ± 0.2 San Jose, CA 37° 09.3' -121° 49.7' Pleurotus ostreatus S 1.5 ± 1.0 10.4 ± 0.8 1.7 14.9 Decayed wood 0.9 ± 0.2 0.7 ± 0.1
31
Aptos, CA 36° 58.9' -121° 51.7' Cantharellus californicus M 0.4 ± 0.1 0.4 ± 0.1 1.3 0.3 Deciduous litter 2.2 ± 0.2 2.7 ± 0.1 Mineral soil 6.4 0.3 ± 0.1 1.2 ± 0.1 Calabasas, CA 34° 05.8' -118° 43.1' Boletus dryophilus M 0.1 ± 0.4 0.6 ± 0.2 0.0 0.7 Mineral soil 6.8 1.3 ± 0.2 0.9 ± 0.1 Deciduous litter 3.5 ± 0.2 3.3 ± 0.1 Topanga, CA 34° 05.7 -118° 39.2 Cantharellus californicus M 0.5 ± 0.1 0.1 ± 0.1 0.7 0.1 Hericium erinaceus S 0.7 ± 0.9 42.1 ± 1.6 1.4 105.3 Decayed wood 0.5 ± 0.1 0.4 ± 0.1 Mineral soil 6.8 0.7 ± 0.1 0.9 ± 0.1
Deciduous litter 1.4 ± 0.2 1.6 ± 0.1
Santa Monica Mtns., 34° 04.9' -118° 43.0' Cantharellus californicus M 1.8 ± 0.3 0.6 ± 0.2 0.6 0.1 CA Mineral soil 6.9 2.9 ± 0.4 4.3 ± 0.2 Deciduous litter 5.6 ± 0.9 3.7 ± 0.4 510 511
32
512 Table 2. Summary of data by material type, geographic province, and cesium isotope. Differences in group means between California 513 and PNW regions significant at α<0.05 are bolded. This data includes the Bamfield chanterelle outlier (157 Bq/kg), without which the 514 PNW mean is 10.8 (12.3) Bq/kg and the overall mean 8.8 (11.8) Bq/kg. 515 Material 134Cs 137Cs
California PNW All California PNW All
Mineral Soil n 13 44 57 13 44 57 x (sd) 1.1 (0.7) 0.7 (0.4) 0.8 (0.5) 2.5 (2.5) 9.5 (7.3) 7.9 (7.1) ̅ min 0.3 0.05 0.1 0.9 0.5 0.5
max 2.9 1.9 2.9 10.1 26.7 26.7
Surface Litter n 12 52 64 12 52 64 x (sd) 2.9 (2.0) 0.9 (0.6) 1.3 (1.2) 3.6 (2.4) 4.3 (4.1) 4.2 (3.9) ̅ min 0.9 0.2 0.2 0.8 0.4 0.4
max 6.3 3.6 6.3 8.6 22.0 22.0
Chanterelles n 8 34 42 8 34 42 x (sd) 0.6 (0.5) 0.7 (0.5) 0.7 (0.5) 0.4 (0.4) 15.1 (27.8) 12.3 (25.7) ̅ min 0.1 0.1 0.1 0.0 0.0 0.0
max 1.8 1.9 1.9 1.2 157.0 157.0
Other n 4 45 49 4 45 49 Mycorrhizal Fungi x̅ (sd) 1.0 (1.0) 1.0 (1.4) 1 (1.3) 2.8 (3.5) 52.5 (107.7) 48.5 (104.0) min 0.1 0.0 0.0 0.6 0.2 0.2
max 2.4 7 2.4 8.0 595.3 595.3
Saprobic n 6 9 15 6 9 15 Fungi x̅ (sd) 1.1 (1.1) 1.1 (1.1) 1.1 (1.1) 8.4 (16.5) 6.7 (6.2) 7.4 (11.0) min 0 0 0.0 0.4 0.7 0.4
max 3.1 2.7 3.1 42.1 19.5 42.1
516 517 33
518 Table 3. Coefficients of determination (R2) for regression interactions of latitude, mineral soil activity, mineral soil pH, and Transfer 519 Factors on chanterelle activity levels. 520 Regressed against Chanterelle 137Cs activity adj. R2 Latitude + 137Cs Mineral Soil 0.560 Latitude + 137Cs Mineral Soil + pH 0.539 137Cs Mineral Soil 0.511 137Cs Mineral Soil + Transfer Factor 0.511 137Cs Mineral Soil + pH + Transfer Factor 0.509 Latitude + 137Cs Mineral Soil + Transfer Factor 0.499 Latitude + 137Cs Mineral Soil + pH + Transfer Factor 0.497 137Cs Mineral Soil + pH 0.486 Latitude 0.359 Latitude + Transfer Factor 0.312 Transfer Factor 0.311 Latitude + pH + Transfer Factor 0.303 pH + Transfer Factor 0.301 pH 0.223 Latitude + pH 0.170 521 522
34
523 Table 4. Cesium isotope measurements in comparable samples collected before and after the Fukushima accident, Bq/kg dry weight. 524 Pre-Fukushima Post-Fukushima Year Year Material Site 134Cs 137Cs Site 134Cs 137Cs collected collected Cantharellus formosus Vancouver, WA 2010 5.1 ± 3.2 46.5 ± 4.6 Lake Oswego, OR 2011 0.6 ± 1.1 36.3 ± 1.2 Cantharellus formosus Florence, OR 2008 0.5 ± 0.3 2.9 ± 0.2 Yachats, OR 2011 0.5 ± 0.3 2.9 ± 0.3 Cantharellus formosus Yachats, OR 2011 1.2 ± 0.8 14.1 ± 0.8
Cantharellus formosus Junction City, OR 2010 0.2 ± 0.2 2.0 ± 0.1 Lobster Valley, OR 2012 1.2 ± 0.3 3.4 ± 0.2 Cantharellus formosus Blue River, OR 2010 1.8 ± 0.5 5.4 ± 0.3 Soda Fork, OR 2011 0.4 ± 0.4 8.0 ± 0.3 Cantharellus formosus Sutherlin, OR 2010 0.4 ± 0.2 1.2 ± 0.1 Sutherlin, OR 2012 0.3 ± 0.3 0.6 ± 0.2 Morchella spp. Western Oregon 2010 0.1 ± 0.4 9.1 ± 0.4 Sisters, OR 2011 0.4 ± 0.3 3.9 ± 0.2 Tuber gibbosum Molalla, OR 2010 0.7 ± 0.3 0.1 ± 0.2 Blodgett, OR 2012 1.6 ± 0.3 1.0 ± 0.2 Mineral soil Sisters, OR 2010 0.3 ± 0.2 2.0 ± 0.1 Sisters, OR 2012 0.9 ± 0.4 16.2 ± 0.5 Needle litter Sisters, OR 2003 0.5 ± 0.2 0.5 ± 0.1 Sisters, OR 2012 1.0 ± 0.3 0.7 ± 0.1
35
525 FIGURE CAPTIONS
526 Figure 1. Detector efficiency as a function of gamma energy for four different sample volumes in urine
527 cup container. Separate calibration curves were developed for the cottage-cheese container.
528
529 Figure 2. Detector efficiency at the 795 keV peak as a function of sample volume in the urine cup
530 container. Separate efficiency curves were developed for the 662 keV line, as well as for different
531 volumes within the cottage-cheese container.
532
533 Fig. 3. Mean activity levels for sampled materials. This chart omits the 157 Bq/kg chanterelle collection
534 from Bamfield due to its outlier influence on the Y axis. Letters indicate mean values not significantly
535 different at α<0.05.
536
537 Fig. 4. Regression of 134Cs in mineral soil samples (Bq/kg) with latitude (ºN) of collection site.
538
539 Fig. 5. Regression of 137Cs in mineral soil samples (Bq/kg) with latitude (ºN) of collection site.
540
541 Fig. 6. Regression of 134Cs in surface litter samples (Bq/kg) with latitude (ºN) of collection site.
542
543 Fig. 7. Regression of 137Cs in surface litter samples (Bq/kg) with latitude (ºN) of collection site.
544
545 Fig. 8. Regression of 134Cs in chanterelle mushroom samples (Bq/kg) with latitude (ºN) of collection
546 site.
547
548 Fig. 9. Regression of 137Cs in chanterelle mushroom samples (Bq/kg) with latitude (ºN) of collection
549 site.
36
550 Fig. 10. Regression of 137Cs in chanterelle mushroom samples with 137Cs in proximate mineral soil
551 samples (Bq/kg). Footnote: The most active chanterelle (Bamfield) is not included in this data because
552 it did not have an accompanying mineral soil sample.
553
554 Fig. 11. Regression of mineral soil pH with latitude (ºN) of collection site.
555
556 Fig. 12 . Regression of mineral soil pH with 137Cs in chanterelle mushroom samples (Bq/kg).
557
558 Figure 13. Regression of mineral soil pH with Transfer Factors of 137Cs in chanterelle mushrooms.
559
560 Figure 14. Transfer factors for chanterelles. Note that the Bamfield chanterelle sample is not included in
561 this analysis because it did not come with a paired mineral soil sample.
562
563 Figure 15. Regression of 134Cs activity in non-chanterelle fungi with latitude (ºN).
564
565 Figure 16. Regression of 137Cs activity in non-chanterelle fungi with latitude (ºN).
37
Measurement Efficiency for Different Urine Cup Volumes, Detector V1 0.030
0.025
0.020 40 ml 0.015 60 ml 0.010 90 ml
Detector Efficiency 130 ml 0.005
0.000 600 700 800 900 1000 1100 1200 1300 1400 Energy (keV) 566 567 Figure 1. Detector efficiency as a function of gamma energy for four different sample volumes in urine 568 cup container. Separate calibration curves were developed for the cottage-cheese container. 569
Log(795 keV) = -2.38- 0.38*Log(Volume)
570 571 572 Figure 2. Detector efficiency at the 795 keV peak as a function of sample volume in the urine cup 573 container. Separate efficiency curves were developed for the 662 keV line, as well as for different 574 volumes within the cottage-cheese container. 575 38
21
18
15
12 Chanterelles Mineral Soil
9 Deciduous Litter Activity, Bq/kg Needle Litter 6
3
0 137 Cs 134 Cs 576 577 578 Fig. 3. Mean activity levels for sampled materials. This chart omits the 157 Bq/kg chanterelle collection 579 from Bamfield due to its outlier influence on the Y axis. Letters indicate mean values not significantly 580 different at α<0.05. 581 582
583 584 585 Fig. 4. Regression of 134Cs in mineral soil samples (Bq/kg) with latitude (ºN) of collection site. 39
586 587 588 Fig. 5. Regression of 137Cs in mineral soil samples (Bq/kg) with latitude (ºN) of collection site. 589 590
591 592 593 Fig. 6. Regression of 134Cs in surface litter samples (Bq/kg) with latitude (ºN) of collection site. 594
40
595 596 597 Fig. 7. Regression of 137Cs in surface litter samples (Bq/kg) with latitude (ºN) of collection site. 598 599
600 601 602 Fig. 8. Regression of 134Cs in chanterelle mushroom samples (Bq/kg) with latitude (ºN) of collection 603 site.
41
604 605 606 Fig. 9. Regression of 137Cs in chanterelle mushroom samples (Bq/kg) with latitude (ºN) of collection 607 site. 608 545
2.29
0.41.5 Cs, Bq/kg Cs, 137
-1.40.2 Chanterelle Chanterelle
-3.20.1
-50 -1.00 0.4 -0.50 0.6 0.001.0 0.501.6 1.00 2.7 1.50 4.5 2.007.4 12.22.50 3.0020.1 3.5033.1 Mineral Soil 137Cs, Bq/kg 609 610 611 Fig. 10. Regression of 137Cs in chanterelle mushroom samples with 137Cs in proximate mineral soil 612 samples (Bq/kg). Footnote: The most active chanterelle (Bamfield) is not included in this data because 613 it did not have an accompanying mineral soil sample. 42
614 615 616 Fig. 11. Regression of mineral soil pH with latitude (ºN) of collection site. 617
618 619 620 Fig. 12 . Regression of mineral soil pH with 137Cs in chanterelle mushroom samples (Bq/kg). 621
43
7.2
7
6.8
6.6
6.4 Mineral Soil pH
6.2
6
5.8 -2.5 -1.5 -0.5 0.5 1.5 137Cs Transfer Factor 622 623 624 Figure 13. Regression of mineral soil pH with Transfer Factors of 137Cs in chanterelle mushrooms. 625 626
627 628 629 Figure 14. Transfer factors for chanterelles. Note that the Bamfield chanterelle sample is not included in 630 this analysis because it did not come with a paired mineral soil sample. 631 44
2.00
1.25
Cs, Bq/kg Cs, 0.50 134
-0.25
-1.00 chanterelle fungi, fungi, chanterelle - Non -1.75
-2.50 33 35 37 39 41 43 45 47 49 51 Latitude 632 633 634 Figure 15. Regression of 134Cs activity in non-chanterelle fungi with latitude (ºN).
635
6.50665
5.50245
4.5090
Cs, Bq/kg Cs, 3.5033 137 2.5012
1.504.5
0.501.6 chanterelle fungi, fungi, chanterelle - -0.500.6 Non
-1.500.2
-2.500.1 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 Latitude 636 637
638 Figure 16. Regression of 137Cs activity in non-chanterelle fungi with latitude (ºN). 45