On June 15, the first GEOTRACES-China expedition (KK1903), which was carried out along the GEOTRACES GP09 section in the west Pacific, was completed onboard R/V TKK. Thirsty-six scientists from six domestic and four foreign research institutes participated in the cruise, and a total of 16 stations were occupied to collect Trace- Metal-Clean (TMC) seawater and particle samples., including 12 Clean Stations, 2 Mega Stations and 2 Normal Stations. For the very first time, a large-scale comprehensive survey of trace elements and isotopes was carried out initiatively by Chinese researchers, onboard a Chinese research vessel, in compliance with the scientific goals and technical standards of the international GEOTRACES Science Programme.
A group photo of all KK1903 cruise participants. Photo: Liping Ye
About GEOTRACES
GEOTRACES is an international programme which aims to improve the understanding of biogeochemical cycles and large-scale distribution of trace elements and their isotopes in the marine environment. Scientists from approximately 35 nations have been involved in the programme, which is designed to study all major ocean basins over the next decade. (©️ GEOTRACES website)
Map legend: GEOTRACES Sections. In red: Planned sections. In Yellow: Completed Sections. In black: Sections completed as GEOTRACES contribution to the IPY (International Polar Year). Photo: GEOTRACES website
R/V TKK is equipped with three sets of seawater sampling systems, including two for conventional sampling and one for Trace-Metal-Clean sampling, which is the first set of Trace Elements and Isotopes Sampling System (TEISS) in China, provided reliable support for the GEOTRACES-China expedition.
The in-situ pumps, modified by the XMU team, were deployed 14 times during the cruise to collect particles in the water column, totally filtered 157,530 L seawater within 105 hours. It was the first time that TEIs adsorbed onto suspended particles were collected onboard a Chinese research vessel.
The in-situ pumps were recovered to the deck. Photo: Na Qian
What are trace elements?
Elements with a concentration of 0.05 to 50 nmol·L-1 or less in seawater are referred to as trace elements. To study trace elements, scientists must collect and analyze the seawater samples in an ultra-clean environment.
TMC CTD was recovered to the deck. Photo: Na Qian
Prior to officially conducting the cruise onboard R/V TKK, the GEOTRACES team from State Key Laboratory of Marine Environmental Science (XMU) had arranged two sea trials to ensure the optimal function of TMC CTD, according to Prof. Yihua Cai, Chief Scientist of this cruise.
“Different from conventional CTD, the TMC CTD rosette of Niskin bottles must be soaked and cleaned repeatedly with high-purity hydrochloric acid. Afterward, rinsing and cleaning procedures constantly conducted in situ are essential before the system is officially put into service,” said Liping Ye, one of the cruise participants. Scientists had to prepare for this 50-day cruise at least 100 days in advance, which was an enormous amount of unseen effort.
Once the TMC package is recovered to the deck, the water sampling bottles must be transferred to the lab vans immediately for filtration and preservation. The two class 1,000 clean vans are loaded onto the deck near the CTD sampling system. Scientists working in these vans must wear clean suits, masks, and PE gloves to avoid contaminating the samples.
This was the first effort led by Chinese scientists and contributed to this internationally renowned scientific programme. It’s only the first step for them to involve in this field campaign, a leap will follow up in the future.
TMC CTD was deployed underwater. Photo: Liping Ye
