On-site and high-resolution spectrophotometric measurement of total dissolved sulfide in natural waters

Peng Li; Songtao Li; Dongxing Yuan; Kunde Lin

doi:10.1016/j.scitotenv.2022.160919

On-site and high-resolution spectrophotometric measurement of total dissolved sulfide in natural waters

Sci Total Environ. 2023 Mar 10:863:160919. doi: 10.1016/j.scitotenv.2022.160919. Epub 2022 Dec 15.

Authors

Peng Li¹, Songtao Li¹, Dongxing Yuan¹, Kunde Lin²

Affiliations

¹ Fujian Provincial Key Laboratory for Coastal Ecology and Environmental Studies, Xiamen 361102, PR China; College of the Environment and Ecology, Xiamen University, Xiamen 361102, PR China.
² Fujian Provincial Key Laboratory for Coastal Ecology and Environmental Studies, Xiamen 361102, PR China; College of the Environment and Ecology, Xiamen University, Xiamen 361102, PR China. Electronic address: link@xmu.edu.cn.

PMID: 36529398
DOI: 10.1016/j.scitotenv.2022.160919

Abstract

Reliable high-resolution data is essential for understanding the aquatic sulfur biogeochemical processes. However, the accurate quantification of total dissolved sulfide (TDS) remains challenging due to its low concentration and vulnerability to oxidation. Furthermore, the frequency and the spatial coverage of TDS measurements are constrained by the cost of the laboratory analysis. In this study, an automated portable system was developed for on-site real-time measurement of trace TDS in natural waters. This system was based on the classic methylene blue (MB) spectrophotometric assay combined with on-line solid phase extraction (SPE) and flow injection analysis (FIA). A commercially available weak-cation-exchange cartridge was used as the SPE sorbent. Experimental parameters affecting the performance of the proposed system were optimized. Under the optimized conditions, linear calibration range of 0.02-2.50 μmol L^-1 was obtained with a sample loading volume of 5.0 mL and a sample throughput of 12 h^-1. The limit of detection could be lowered to 0.003 μmol L^-1 by pre-concentrating 10.0 mL sample. The precision, determined as the relative standard deviation (RSD), was <2.75 % (n = 11) and the recoveries from spiked samples ranged from 54.4 % to 97.5 % with RSDs of 1.1-2.3 % (n = 3). Furthermore, the FIA-SPE-MB system was successfully deployed in the Taihu Lake for continuous 48 h monitoring of variations in TDS, demonstrating the applicability of this system for on-site TDS measurement in natural waters.

Keywords: Flow injection analysis; Methylene blue assay; On-line solid phase extraction; On-site measurement; Total dissolved sulfide.