Monitoring 14C contamination in Chinese research vessels with swipe tests

Abstract

Since 14C-tracer is widely used in determining oceanic primary production, most research vessels have a history of using 14C labeled sodium bicarbonate solutions for culture experiments. A contamination monitor test (swipe test) prior to each cruise can help to detect and prevent possible 14C contamination before sampling for 14C studies at natural abundance. Here we report 14C measurements of more than 100 swipe samples collected onboard workplaces of seven Chinese research vessels over a four-year period (2012–2016). Five out of seven ships showed no obvious 14C contamination with F14C values lower than 0.2. Two spots of R/V Dongfanghong 2 showed elevated 14C contamination (F14C were as high as 0.831 and 0.573) during 2012–2014. However, the laboratory surface was cleaned by renovation before the next monitoring operation in May to June 2016. R/V Kexue Yihao was found to have elevated 14C on swipe samples, with an F14C up to 0.331 from November to December 2012. During the same cruise, seawater samples for a natural-level DI14C study were also found to be contaminated. Our results highlight the need for stringent screening and protection procedures on research vessels regarding 14C contamination if the cruise involves sampling for natural-level 14C studies. We recommend the undertaking of swipe tests before and after each cruise.