Results from First Sampling Period

The table below shows the radioactive isotopes measured in each of the kelp samples, corrected to time of collection during the first sampling period (February to March 2014). Some samples were taken beyond this period due to logistical issues. To date, all 45 samples have been analyzed and are shown in the table. All data is based on a single sample size (n=1) of 6.5 kg fresh weight of blade tissue. Several sample locations were in close proximity.

The kelp samples were dried and milled into a powder and then sent to LBNL to be measured with a high-purity germanium detector. As expected, all kelp samples contained significant amounts of naturally occurring radioactivity, primarily due to potassium-40 (K-40) since dried kelp has a high potassium content. Also found were smaller amounts of other naturally occurring radioactive isotopes, including Beryllium-7 which is a cosmogenic nuclide present in air and rain, and portions of the Uranium-238 and Thorium-232 radioactive decay chains.

Cesium-137 was detected in all West Coast samples at very low levels. This isotope is still detectable in the marine environment due to above-ground nuclear weapons testing that took place mostly in the 1950s and 1960s. The very low limits set on the shorter-lived Cesium-134 mean that the Cs-137 cannot be directly tied to the Fukushima releases and is more likely due to these "legacy" sources. For more information on radiocesium, please visit the FAQ: Why Cesium?.

For a sense of scale, the K-40 activities ranged from 2500 to 4500 Becquerels per kilogram dry weight (Bq/kg dwt), where one Becquerel is one nuclear decay per second, while the Cs-137 was detected in all samples at levels ranging from 0.08 to 0.44 Bq/kg, or about 10,000 times lower than K-40. The upper limits set for Cs-134 are approximately 0.04 Bq/kg, or 100,000 times lower than some of the K-40 levels.

Two kelp samples obtained from the Chilean coast had very low to undetectable levels of Cs-137. This is consistent with the lower levels of Cs-137 known to be in the southern oceans. Because kelps are not found in the tropics, related brown seaweeds, Sargassum sps. were sampled from Hawaii and Guam. The samples from Hawaii and Guam were consistent with the North American samples, showing no signs of Fukushima radioactivity.

Iodine-131 was seen in kelp from southern California, primarily Los Angeles and Orange Counties. This most likely comes from water treatment plants processing medical waste: please see Iodine-131 From Local Inputs.


Sample ID Location
KSMSC-1
Kodiak Island, AK
Sitka-1
Sitka, AK
RES-1
Tofino, BC
RES-2
Tofino, BC
DC-1
Bamfield, BC
DC-2
Bamfield, BC
RRU-1
Sooke, BC
OLYM-1
Olympic National Park, WA
HSU-1
Humboldt County, CA
BML-1
Van Damme State Park, CA
VD-1
Van Damme State Park, CA
SHAV-1
Mendocino, CA
NPS-1
Tomales Point, Marin County, CA
CDFW-1
Tomales Bay, CA
MLMLDAV-1
Davenport Landing, Santa Cruz County, CA
UCSCTER-1
Santa Cruz, CA
HMS-1
Pacific Grove, CA
MLMLSWC-1
Stillwater Cove, Carmel, CA
BC-1
Big Creek Cove, Monterey County, CA
BC-2
Big Creek Cove, Monterey County, CA
CAM-1a
Cambria, San Luis Obispo County, CA
CAM-1b
Cambria, San Luis Obispo County, CA
CP-1
San Luis Obispo, CA
REED-1c
Santa Barbara, CA
REED-1b
Santa Barbara, CA
REED-1a
Santa Barbara, CA
SBCK-1
Santa Barbara, CA
UCSB-1a
Santa Cruz Island (Channel Islands)
NPS(CI)-1
East Anacapa Island (Channel Islands)
UCSB-1b
Santa Cruz Island (Channel Islands)
Oxy-1
Rancho Palos Verdes, Los Angeles County, CA
LAW-1
Los Angeles, CA
LB-1
Long Beach, Los Angeles County, CA
CSC-1
San Pedro, Los Angeles County, CA
KML-1
Orange County, CA
CCA-1
Orange County, CA
GI-1a
Orange County, CA
USC-1
Catalina Island, CA
OI-1
San Clemente, Orange County, CA
PTL-1
Point Loma (San Diego)
UABC-1
Baja California, Mexico
UH-1
Hawaii
UOGML-1
Guam
UCN-1
Chile
UDLL-1
Chile
Anthropogenic Natural
Collection Date Cs-137 Cs-134 I-131 K-40 U-238 series (early) U-238 series (late) Th-232 series (early) Th-232 series (late) Be-7
03/05/2014
0.18 ± 0.04
nondetect (< 0.05)
nondetect (< 1.5)
4512 ± 10
56.0 ± 3.8
3.14 ± 0.07
1.35 ± 0.15
0.22 ± 0.03
2.68 ± 0.55
03/02/2014
0.19 ± 0.04
nondetect (< 0.05)
nondetect (< 0.16)
3944 ± 7
58.8 ± 2.0
2.30 ± 0.07
nondetect (< 0.17)
0.05 ± 0.01
nondetect (< 0.47)
03/03/2014
0.32 ± 0.04
nondetect (< 0.04)
nondetect (< 0.18)
3099 ± 8
59.2 ± 1.7
0.75 ± 0.05
0.84 ± 0.13
0.12 ± 0.02
7.25 ± 0.41
05/30/2014
0.35 ± 0.06
nondetect (< 0.04)
nondetect (< 13)
3794 ± 5
100.5 ± 8.5
2.83 ± 0.06
1.24 ± 0.23
0.17 ± 0.02
nondetect (< 0.84)
04/19/2014
0.26 ± 0.04
nondetect (< 0.05)
nondetect (< 6.7)
3950 ± 6
152.6 ± 7.4
4.1 ± 0.1
1.67 ± 0.14
0.36 ± 0.04
45.1 ± 1.1
05/20/2014
0.44 ± 0.04
nondetect (< 0.04)
nondetect (< 0.51)
3061 ± 7
87 ± 3
0.37 ± 0.03
nondetect (< 0.12)
0.16 ± 0.02
6.52 ± 0.64
04/13/2014
0.14 ± 0.04
nondetect (< 0.04)
nondetect (< 0.10)
3751 ± 6
38.9 ± 1.6
1.45 ± 0.05
0.53 ± 0.17
0.22 ± 0.03
4.46 ± 0.42
03/27/2014
0.18 ± 0.03
nondetect (< 0.04)
nondetect (< 0.6)
3464 ± 6
38.2 ± 2.6
2.80 ± 0.06
1.06 ± 0.12
0.19 ± 0.02
2.81 ± 0.43
02/28/2014
0.23 ± 0.04
nondetect (< 0.04)
nondetect (< 1.8)
3968 ± 9
20.1 ± 3.5
2.15 ± 0.07
1.05 ± 0.18
0.18 ± 0.02
1.96 ± 0.79
02/04/2014
0.22 ± 0.03
nondetect (< 0.04)
nondetect (< 28.9)
3649 ± 11
93.1 ± 8.0
2.32 ± 0.05
1.07 ± 0.14
0.52 ± 0.04
4.19 ± 0.86
02/25/2014
0.16 ± 0.05
nondetect (< 0.04)
nondetect (< 16)
3131 ± 8
85.6 ± 8.1
2.11 ± 0.06
0.82 ± 0.17
0.44 ± 0.05
3.99 ± 0.97
02/23/2014
0.19 ± 0.05
nondetect (< 0.04)
nondetect (< 13)
4170 ± 5
106 ± 8
1.72 ± 0.06
0.49 ± 0.13
0.22 ± 0.03
2.55 ± 0.84
03/03/2014
0.25 ± 0.05
nondetect (< 0.05)
nondetect (< 1.6)
3959 ± 5
21.2 ± 3.6
1.92 ± 0.06
1.17 ± 0.16
0.21 ± 0.03
2.06 ± 0.56
02/25/2014
0.35 ± 0.05
nondetect (< 0.05)
nondetect (< 13)
3810 ± 8
74.5 ± 10.2
2.99 ± 0.07
4.96 ± 0.20
1.20 ± 0.07
9.60 ± 0.88
02/27/2014
0.31 ± 0.05
nondetect (< 0.05)
nondetect (< 6.9)
3640 ± 8
50.8 ± 6.1
2.49 ± 0.08
1.20 ± 0.14
0.19 ± 0.03
2.59 ± 0.80
02/26/2014
0.24 ± 0.04
nondetect (< 0.04)
nondetect (< 16)
3093 ± 6
283 ± 9
2.84 ± 0.06
0.61 ± 0.14
0.36 ± 0.04
1.00 ± 0.67
03/05/2014
0.28 ± 0.05
nondetect (< 0.04)
nondetect (< 6.9)
3748 ± 9
254 ± 7
2.16 ± 0.06
0.37 ± 0.10
0.40 ± 0.03
6.51 ± 0.73
03/05/2014
0.29 ± 0.04
nondetect (< 0.04)
nondetect (< 3.2)
3729 ± 5
49.7 ± 4.1
2.18 ± 0.05
1.01 ± 0.16
0.23 ± 0.02
3.82 ± 0.87
02/24/2014
0.12 ± 0.04
nondetect (< 0.05)
nondetect (< 10.1)
3138 ± 15
141 ± 6
1.31 ± 0.06
0.57 ± 0.14
0.26 ± 0.04
nondetect (< 0.88)
02/27/2014
0.21 ± 0.04
nondetect (< 0.04)
nondetect (< 6.9)
3374 ± 5
78.5 ± 4.9
1.71 ± 0.05
1.26 ± 0.13
0.27 ± 0.03
nondetect (< 0.71)
02/24/2014
0.14 ± 0.04
nondetect (< 0.04)
nondetect (< 4.8)
3354 ± 6
158 ± 6
1.90 ± 0.06
0.69 ± 0.14
0.21 ± 0.03
1.38 ± 0.54
02/24/2014
0.21 ± 0.05
nondetect (< 0.04)
nondetect (< 11.3)
4406 ± 6
108 ± 7
1.83 ± 0.06
1.44 ± 0.32
0.26 ± 0.03
1.84 ± 0.84
02/24/2014
0.24 ± 0.04
nondetect (< 0.04)
nondetect (< 0.48)
3987 ± 9
50.8 ± 2.7
1.77 ± 0.07
0.79 ± 0.12
0.20 ± 0.02
2.08 ± 0.39
03/13/2014
0.29 ± 0.05
nondetect (< 0.04)
25.1 ± 5.8
4171 ± 6
76.8 ± 6.9
1.96 ± 0.06
1.17 ± 0.18
0.35 ± 0.04
1.23 ± 0.73
03/04/2014
0.27 ± 0.06
nondetect (< 0.04)
nondetect (< 11.6)
3305 ± 5
58.2 ± 7.5
1.77 ± 0.06
1.16 ± 0.14
0.42 ± 0.04
1.63 ± 0.71
02/25/2014
0.23 ± 0.04
nondetect (< 0.04)
nondetect (< 21.5)
3988 ± 6
121 ± 10
1.85 ± 0.05
1.58 ± 0.15
0.25 ± 0.03
1.52 ± 0.69
03/03/2014
0.16 ± 0.03
nondetect (< 0.04)
26.6 ± 0.3
3856 ± 8
70.3 ± 1.7
2.16 ± 0.04
2.02 ± 0.12
0.43 ± 0.03
4.02 ± 0.39
02/24/2014
0.16 ± 0.04
nondetect (< 0.04)
nondetect (< 32)
3515 ± 6
271 ± 12
0.94 ± 0.04
0.15 ± 0.12
0.19 ± 0.03
nondetect (< 0.93)
02/26/2014
0.33 ± 0.06
nondetect (< 0.05)
nondetect (< 19)
3545 ± 6
342 ± 10
0.76 ± 0.06
0.41 ± 0.16
0.39 ± 0.05
1.60 ± 0.81
02/24/2014
0.28 ± 0.03
nondetect (< 0.05)
nondetect (< 36)
3707 ± 5
762 ± 12
0.91 ± 0.04
0.39 ± 0.13
0.39 ± 0.03
2.57 ± 0.82
02/26/2014
0.29 ± 0.03
nondetect (< 0.04)
8.1 ± 0.2
3267 ± 6
153 ± 2
1.54 ± 0.05
0.69 ± 0.14
0.15 ± 0.02
nondetect (< 0.41)
03/06/2014
0.34 ± 0.04
nondetect (< 0.04)
23.0 ± 7.3
3958 ± 5
128 ± 7
2.46 ± 0.05
1.06 ± 0.14
0.27 ± 0.03
2.56 ± 0.69
03/06/2014
0.30 ± 0.03
nondetect (< 0.04)
152 ± 1
3903 ± 11
47.0 ± 1.9
1.61 ± 0.05
1.18 ± 0.11
0.22 ± 0.02
nondetect (< 0.44)
02/26/2014
0.23 ± 0.03
nondetect (< 0.04)
24.7 ± 0.2
3303 ± 9
79.9 ± 1.9
1.46 ± 0.05
0.64 ± 0.22
0.14 ± 0.02
1.40 ± 0.38
03/14/2014
0.23 ± 0.06
nondetect (< 0.03)
20.9 ± 2.8
3011 ± 12
47.0 ± 2.6
1.90 ± 0.05
1.36 ± 0.15
0.20 ± 0.02
2.39 ± 0.44
03/04/2014
0.36 ± 0.03
nondetect (< 0.03)
10.1 ± 0.3
2938 ± 9
306 ± 3
1.48 ± 0.04
0.81 ± 0.15
0.23 ± 0.00
2.50 ± 0.44
02/26/2014
0.42 ± 0.04
nondetect (< 0.03)
15.2 ± 0.3
2747 ± 6
109 ± 2
1.66 ± 0.04
0.49 ± 0.10
0.23 ± 0.02
1.75 ± 0.73
03/05/2014
0.32 ± 0.04
nondetect (< 0.04)
1.1 ± 0.2
3776 ± 10
718 ± 3
1.41 ± 0.04
0.19 ± 0.11
0.41 ± 0.03
2.61 ± 0.43
03/06/2014
0.44 ± 0.04
nondetect (< 0.03)
10.9 ± 0.4
3039 ± 5
161 ± 2
1.26 ± 0.04
1.19 ± 0.13
0.31 ± 0.03
1.38 ± 0.34
02/26/2014
0.26 ± 0.04
nondetect (< 0.04)
nondetect (< 29)
2625 ± 4
489 ± 11
0.86 ± 0.04
0.33 ± 0.14
0.30 ± 0.03
nondetect (< 0.81)
03/12/2014
0.20 ± 0.06
nondetect (< 0.06)
nondetect (< 0.21)
3113 ± 15
98.6 ± 2.6
0.78 ± 0.06
0.47 ± 0.19
0.24 ± 0.05
nondetect (< 0.54)
03/06/2014
0.20 ± 0.04
nondetect (< 0.04)
nondetect (< 0.87)
2656 ± 7
30.6 ± 2.9
2.22 ± 0.06
nondetect (< 0.13)
0.16 ± 0.02
8.43 ± 0.65
02/02/2014
0.08 ± 0.03
nondetect (< 0.03)
nondetect (< 1.8)
3418 ± 6
153 ± 4
2.14 ± 0.04
0.39 ± 0.11
0.15 ± 0.02
4.19 ± 0.61
03/31/2014
nondetect (< 0.03)
nondetect (< 0.04)
nondetect (< 0.29)
3533 ± 7
55.5 ± 2.0
2.78 ± 0.05
0.88 ± 0.12
0.16 ± 0.02
nondetect (< 0.41)
03/30/2014
0.06 ± 0.02
nondetect (< 0.03)
nondetect (< 2.9)
3321 ± 6
208 ± 4
2.29 ± 0.04
0.62 ± 0.08
0.22 ± 0.02
5.35 ± 0.43


Table Notes:

  • All uncertainties quoted are "one-sigma," meaning that they represent a 68% confidence range for the quantity measured. Detection limits are also "one-sigma" in that they give the 68% confidence upper limit.
  • Radioactive isotopes are measured in units of Becquerels per kilogram dry weight (Bq/kg dwt). One Becquerel is one nuclear decay per second.
  • Data are decay-corrected to the date the sample was collected.


Update Log:

  • 5/7/2014 10:15 - initial data posted
  • 6/10/2014 13:00 - remainder of sample data posted
  • 10/10/2014 16:00 - updated the table format, final British Columbia samples posted
  • 11/07/2014 16:30 - updated table format