Sulfur cycling is ubiquitous in marine sedimentary environments and is influenced by microbial and abiotic processes that alter both the abundance and isotopic composition of sulfur species that can ultimately be captured as sedimentary minerals. Microbial metabolisms that generate sulfur isotopic (δ³⁴S) signatures in hydrogen sulfide have a spatial distribution that varies on the micron scale, yet porewater hydrogen sulfide is most often measured in bulk samples representing much larger volumes. This mismatch of scales can lead to erroneous or non-unique interpretations of biogeochemical processes and environmental conditions. Recently, an in-situ film-based technique was described that captures dissolved sulfide (H₂S) in porewaters and which can be subsectioned to reconstruct the δ³⁴S_H2S profiles on the sub-cm scale within sediments. Here, we investigate the use of a Cameca 7f-GEO secondary ion mass spectrometer (SIMS) to analyze the δ³⁴S_H2S captured from porewaters on these films on even smaller spatial scales and particularly in films with low sulfide abundance that could not otherwise be processed with bulk extraction techniques. We present a best-practice method for film analysis that minimizes analytical artifacts from varying sulfide abundance and interactions with silver halide nanocrystals imbedded in the organic-based film amalgam. This method was tested on several films from field deployments, including examples with heterogeneities on small (~100 μm) scales, steep isotopic gradients, and very low sulfide abundance across the sediment-water interface. The results demonstrate that analysis using SIMS can accurately measure δ³⁴S of in-situ sulfide captured by film with high precision (1σ ~ 0.3‰) in both spot and image modes and that the film itself can accurately record δ³⁴S variability down to 25 μm spatial resolution, below which physical limitations of the film can create artifacts.

硫循环在海洋沉积环境中无处不在，并受到微生物和非生物过程的影响，这些过程会改变硫物种的丰度和同位素组成，这些硫物种最终可被捕获为沉积矿物。产生硫同位素微生物代谢（δ ³⁴ S）中的硫化氢的签名具有空间分布上的微米级而变化，但硫化物孔隙水氢是最经常代表大得多的体积批量样品中测量。比例尺的这种不匹配会导致对生物地球化学过程和环境条件的错误或非唯一解释。最近，有人描述了一种基于膜的原位技术，该技术可捕获孔隙水中的溶解硫化物（H ₂ S），并可细分以重建δ沉积物中亚厘米级的³⁴ S _H2S剖面。在这里，我们调查了使用Cameca公司7F-GEO二次离子质谱仪（SIMS）来分析δ ³⁴小号_H2S从这些膜上的孔隙中捕获的水甚至面积更小，尤其是在硫化物含量低的膜中，否则无法通过批量提取技术进行处理。我们提出了一种最佳实践的薄膜分析方法，该方法可最大程度地减少因变化的硫化物丰度以及与嵌入有机基薄膜汞齐中的卤化银纳米晶体之间的相互作用而引起的分析伪影。该方法已在野外部署的几张胶片上进行了测试，包括具有小范围（〜100μm）异质性，同位素梯度陡和沉积物-水界面上的硫化物丰度非常低的示例。结果证明使用SIMS可以精确测量δ该分析³⁴S的原位硫化物由具有高精度（1σ〜0.3‰）在两个点和图像模式膜和该膜本身可以准确记录δ捕获³⁴膜第变异性下降到25微米的空间分辨率，低于该物理限制会产生人工制品。