Concentration maxima of volatile organic iodine compounds in the bottomlayer water and the cold, dense water over the Chukchi Sea in the westernArctic Ocean: a possibility of production related to the degradation oforganic matter

[摘要] We conducted a shipboard observation over the Chukchi Sea and the Canada Basinin the western Arctic Ocean in September and October 2012 to obtain verticaldistributions of four volatile organic iodine compounds (VOIs) in seawater.The VOIs observed in this study were iodomethane (CH₃I), iodoethane(C₂H₅I), diiodomethane (CH₂I₂), and chloroiodomethane(CH₂ClI). Maximum concentrations of the four VOIs were found in thebottom layer water over the Chukchi Sea shelf, in which layer the maximumconcentration of ammonium (NH₄₊) also occurred. A significantcorrelation was observed between C₂H₅I and NH₄₊(correlation coefficient R = 0.93, P < 0.01, n = 64) andbetween CH₃I and NH₄₊ (R= 0.77, P < 0.01,n =  64), suggesting that the production of these VOIs increased with thedegradation of organic matter. Over the northern Chukchi Sea shelf–slopearea, concentration maxima of CH_I2, CH₂ClI, and CH3I werefound in the subsurface cold, dense water (CDW). A large nitrogen deficit (Ndeficit  =  NH₄₊+ NO₃₋+ NO₂₋−16PO₄₃₋)occurred simultaneously in this water, suggesting the production of the threeVOIs in the sediment or the bottom layer water over the shelf, probably inassociation with the degradation of organic matter. We conclude that VOIproduction over the Chukchi Sea shelf can be largely attributed to thedegradation of organic matter that is produced in the highly productive shelfwater. High concentrations of CH₂ClI were also found in the AlaskanCoastal Water (ACW) from the Bering Strait to the surface of the northernChukchi slope. The VOIs that originated at the Chukchi Sea shelf are expectedto be laterally transported to the Arctic Ocean basin through the CDW and thesurface ACW.

[学科分类] 地球化学与岩石