The aim of the study was to determine if gold-mining activities could impact the mercury (Hg) concentrations and isotopic signatures in freshwater fish consumed by riparian people in French Guiana. Total Hg, MeHg concentrations, and Hg stable isotopes ratios were analyzed in fish muscles from different species belonging to three feeding patterns (herbivorous, periphytophagous, and piscivorous). We compared tributaries impacted by gold-mining activities (Camopi, CR) with a pristine area upstream (Trois-Sauts, TS), along the Oyapock River. We measured δ¹⁵N and δ ¹³C to examine whether Hg patterns are due to differences in trophic level. Differences in δ ¹⁵N and δ ¹³C values between both studied sites were only observed for periphytophagous fish, due to difference of CN baselines, with enriched values at TS. Total Hg concentrations and Hg stable isotope signatures showed that Hg accumulated in fish from both areas has undergone different biogeochemical processes. Δ¹⁹⁹Hg variation in fish (−0.5 to 0.2‰) was higher than the ecosystem baseline defined by a Δ¹⁹⁹Hg of −0.66‰ in sediments, and suggested limited aqueous photochemical MeHg degradation. Photochemistry-corrected δ²⁰²Hg in fish was 0.7‰ higher than the baseline, consistent with biophysical and chemical isotope fractionation in the aquatic environment. While THg concentrations in periphytophagous fish were higher in the gold-mining area, disturbed by inputs of suspended particles, than in TS, the ensemble of Hg isotope shifts in fish is affected by the difference of biotic (methylation/demethylation) and abiotic (photochemistry) processes between both areas and did therefore not allow to resolve the contribution of gold-mining-related liquid Hg(0) in fish tissues. Mercury isotopes of MeHg in fish and lower trophic level organisms can be complementary to light stable isotope tracers.

该研究的目的是确定金矿开采活动是否会影响法属圭亚那沿岸居民食用的淡水鱼中的汞 (Hg) 浓度和同位素特征。在属于三种摄食模式（草食性、食肉性和食鱼性）的不同物种的鱼肌肉中分析了总汞、甲基汞浓度和汞稳定同位素比率。我们将受金矿开采活动影响的支流（Camopi，CR）与沿 Oyapock 河上游的原始区域（Trois-Sauts，TS）进行了比较。我们测量了 δ ¹⁵ N 和 δ ¹³ C 以检查 Hg 模式是否是由于营养水平的差异造成的。δ ¹⁵ N 和δ ^{13 的}差异由于 CN 基线的差异，两个研究地点之间的 C 值仅在周围食性鱼类中观察到，在 TS 处具有丰富的值。总汞浓度和汞稳定同位素特征表明，这两个地区的鱼体内积累的汞经历了不同的生物地球化学过程。鱼类中的Δ ¹⁹⁹ Hg 变化（-0.5 至 0.2‰）高于由沉积物中的 Δ ¹⁹⁹ Hg 为 -0.66‰定义的生态系统基线，并表明水相光化学甲基汞降解有限。光化学校正δ ²⁰²鱼类中的 Hg 比基线高 0.7‰，与水生环境中的生物物理和化学同位素分馏一致。虽然受悬浮颗粒输入的干扰，金矿区周围食性鱼类的 THg 浓度高于 TS，但鱼类中 Hg 同位素变化的整体受到生物（甲基化/去甲基化）和非生物（光化学）差异的影响。 ) 两个区域之间的过程，因此无法解决与金矿开采相关的液态 Hg(0) 在鱼类组织中的贡献。鱼类和低营养级生物体中甲基汞的汞同位素可以与光稳定同位素示踪剂互补。