Results* from March are now available from 10/12 of the current InFORM sampling locations. Recent samples from Sandspit and Bella Bella are still being processed and data shown are from February. After the positive measurement of Fukushima-derived 134Cs radiation in February at Ucluelet, we expected this signal to spread in samples collected in March. Instead, there is no detectable 134Cs (detection limit ~0.2 Bq m-3) in any of the March samples. To understand this, we investigated the coastal conditions that were present along Vancouver Island during February and March.
After examining satellite measurements of sea surface temperature, we find that the days leading up to the February sampling in Ucluelet had particularly warm water, as indicated by yellow-red colors above left, pushed up against the coast. In the days following sampling, that warm water retreated offshore, as indicated by dark blues and purple colors above right. The Fukushima signature, 134Cs, is likely tied to that warm water mass that was brushing the coast for a few days in mid February. This sampling period highlights the dynamic nature of the coastal system and the necessity for regular measurements to understand the complete story.
All coastal samples continue to have measureable levels of 137Cs (half life ~30 years), that is present because of atmospheric nuclear weapons testing that happened in the 1950s and 1960s and the 1986 Chernobyl nuclear disaster.
*Note: Results are preliminary and may be slightly adjusted pending results from further chemical analysis.