Aperçu de la méthode de mesure des sulfures dans les échantillons de sédiments marins par électrode à ions spécifiques (EIS) et variantes de sa mise en oeuvre

Abstract

This document is part of a Canadian Science Advisory Secretariat (CSAS) process to give Fisheries and Oceans Canada (DFO) science advice pertaining to the sulfide ion selective electrode (ISE) method. This method is currently the only approved regulatory tool within Canada used to determine the oxic state of the benthos as a result of organic loading from finfish aquaculture activities. ISE is an easily operated and highly cost-effective technique compared to other high level instrumental methods. However, due to its manual nature, methodological steps can be prone to subjective interpretation by the analyst resulting in inconsistent execution by different individuals and/or laboratories. In terms of sulfide monitoring, this can potentially lead to the generation of variable, and inaccurate data with ramifications to regulatory decision making. The sulfide ISE method was initially evaluated by Wildish et al. (1999) and subsequently adopted for use by New Brunswick, Nova Scotia, and nationally as part of the Aquaculture Activities Regulations (DFO 2018a), which British Columbia follows as part of Annex 8 of the Aquaculture Activities Regulations guidance document. In their environmental monitoring standard operating procedures (SOPs), New Brunswick (NB DELG 2018), Nova Scotia (NS DFA 2021), and British Columbia (DFO 2018b) all refer to Wildish et al. (1999) for measurement of sulfide in collected sediment samples. However, they deviate in certain aspects from Wildish et al. (1999), and also amongst themselves, e.g., the number of standards used to calibrate the ISE, the time from sample collection to analysis, etc. In this paper, we list the necessary steps required for the determination of sulfide in sediment samples, and also document deviations from Wildish et al. (1999) by the aforementioned regulators, along with procedural differences between one another. A proposed methodological procedure for determination of sulfide in sediment samples is also presented, which could lead the way for development of a revised and more prescriptive SOP that can be adopted nationally.