Chemistry on Board

Several classes of emerging organic contaminants including halogenic flame-retardants, fluorinated chemicals, pesticides and plasticizers will be investigated in this cruise. Aside from ocean currents, the atmosphere is considered to be the primary and most rapid pathway for organic contaminants transport to the marine and arctic environment. Two high-volume air samplers are set up on the monkey deck of Polarstern and continually running under headwind to collect oceanic air. Sometimes, the air samplers have to be turned off when the air is coming from the back of the ship to avoid sampling exhaust air from the chimney. Atmospheric particles are collected on a quartz fibre filter and the gaseous phase is retained using a polymer resin column. Along the track from Bremerhaven to AWI Hausgarten, the wind direction frequently varied between north, northeast, south and southwest. Therefore, we have changed the sampling columns according to the wind directions to ensure the air masses from different origins are sampled. The signals of new organic contaminants are expected in the air which crossed northern and western part of Europe, while classic POPs released from Arctic cryosphere might be recorded by the samples with air masses from high Arctic. Simultaneously, a high-volume water sampler is connected to the ship in-take system in the wet lab. Surface seawater from 12 m depth is sampled continuously while Polarstern steams towards the Arctic. Moreover, samples of each one-litre seawater are collected for the analysis of water-soluble substances (Figure 1).

Comparison of this data set with the contemporaneous atmospheric mixing ratios of each gas will allow a precise estimation of the sign of the fluxes (i.e. into or out of the ocean). On the other hand, experimental manipulations are done so as to simulate future climate change conditions in the Arctic and their relationship to the cycling of trace gases. Current predictions for climate change estimate ocean warming and increased acidification, as well as increased availability of light due to reduced ice coverage. To test the individual and combined effects of these stressors in the microbial communities responsible for the production and consumption of N₂O, CH₄, CO and DMS, the PETRA-team set up a series of incubation chambers which emulate current natural conditions and the predicted conditions for future climate change. A thorough comparison of these different conditions will provide essential insights on the potential trends on production and emissions of these trace gases in the future Arctic. To this end, the team has been collecting large amounts of water from the CTD/Rosette at selected locations and monitoring the changes in the physical and biogeochemical environments of these natural communities while contained in several enclosures (Figure 3). Despite a few technical issues at the beginning of the cruise, most measuring systems are performing well and lots of data points are being gathered, while a similarly large amount of frozen samples will be sent back to the labs of both institutes for further analysis.  

Now we are looking forward to seeing what the second half of our cruise brings, especially whether we also will be able to go west to Greenland or whether there is too much ice. We’ll let you know about that next week.  

With best greetings, Zhiyong Xie and Damian Arevalo-Martinez, and Wilken-Jon von Appen on behalf of the scientists on PS114