From Tepco’s report released on 9/4/2015, the density of Strontium-90 increased to 155% of the previous highest reading in the seaside of Reactor 2.
It was measured in groundwater gathered to pump up. The sampling by DNSUnlocker”> date was 8/3/2015, Sr-90 density was 2,800,000 Bq/m3. The previous highest reading was 1,800,000 Bq/m3, which was analyzed on 7/2/2015.
From the report of 9/15/2015 about the same area, the density of Mn-54, which has 310 days of a half-life, reached the highest reading of 680 Bq/m3 on 9/10/2015. 4 days later, it rose up to 970 Bq/m3 again.
Source: Fukushima Diary