Compact autonomous voltammetric sensor for sulfide monitoring in deep sea vent habitats

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• 作者：Leonardo Contreira-Pereira ; Mustafa Y¨¹cel ; Dario Omanovic ; Jean-Pierre Brulport ; Nadine Le Bris
• 关键词：Deep sea ; Hydrothermal ; Chemosynthetic fauna ; Sulfide ; Voltammetry ; Habitat ; EPR
• 刊名：Deep Sea Research Part I: Oceanographic Research Papers
• 出版年：2013
• 出版时间：October, 2013
• 年：2013
• 卷：80
• 期：Complete
• 页码：47-57
• 全文大小：1986 K

文摘

In situ chemical monitoring at deep-sea hydrothermal vents remains a challenge. Particularly, tools are still scarce for assessing the ranges and temporal variability of sulfide in these harsh environmental conditions. There is a particular need for compact and relatively simple devices to enlarge the capacity of in situ measurements of this major energy source in chemosynthetic ecosystems. With this objective, a voltammetric sensor based on a bare-silver working electrode was developed and tested in real conditions. In the laboratory, the sensor presented a linear response from 10 to 1000 ¦ÌM sulfide, together with a low pH sensitivity and moderate temperature dependence. The device was operated at 850 and 2500 m depth during 3 cruises over two different vent fields. The autonomous potentiostat (290 mm length, ? 35 mm) equipped with laboratory-made electrodes was mounted on a wand, for manipulation from a submersible, or on a holder for unattended deployments. The system was applied in mussel, tubeworm and annelid worm habitats, characterized by different ranges of sulfide concentration, pH and temperature. Calibrations performed before and after each deployment confirmed the stability of the sensor response over a few hours to 11 days, with a maximum drift of 11.4 % during this period. Short-term measurements in the vicinity of Riftia pachyptila and Alvinella pompejana were consistent with previous results on these habitats, with concentrations ranging from 20 to 140 ¦ÌM and 100 to 450 ¦ÌM and sulfide versus temperature ratio of 14 ¦ÌM ¡ãC^?1 and 20 ¦ÌM ¡ãC^?1, respectively. A continuous 4-day record on a bed of Bathymodiolus Thermophilus mussels furthermore illustrated the capacity of the sensor to capture fluctuating sulfide concentration between 0 and 70 ¦ÌM, in combination to temperature, and to investigate the changes in the sulfide versus temperature ratio over time. The method has a higher detection limit (<10 ¦ÌM) than previous in situ sulfide measurement methods, but has the advantage of selectivity to free sulfide (compared to colorimetry), low pH sensitivity (compared to amperometry) and lower reconditioning requirement for electrode surface (with respect to gold-amalgam voltammetry). This sensor is therefore a valuable complementary tool for discrete and continuous measurements within the moderate temperature environment of fauna at deep-sea vents.