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首页> 外文期刊>Marine Chemistry >Resolving micron-scale heterogeneity in porewater δ~(34)S_(H2S) by combining films for in-situ sulfide capture and secondary ion mass spectrometry
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Resolving micron-scale heterogeneity in porewater δ~(34)S_(H2S) by combining films for in-situ sulfide capture and secondary ion mass spectrometry

机译：通过组合用于原位硫化物捕获和二次离子质谱法的薄膜分辨于孔水δ〜（34）S_（H2S）中的微米级异质性

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摘要

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 (delta S-34) 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 delta S-34(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 delta S-34(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 (similar to 100 mu m) scales, steep isotopic gradients, and very low sulfide abundance across the sediment-water interface. The results demonstrate that analysis using SIMS can accurately measure delta S-34 of in-situ sulfide captured by film with high precision (1 sigma similar to 0.3 parts per thousand) in both spot and image modes and that the film itself can accurately record delta S-34 variability down to 25 mu m spatial resolution, below which physical limitations of the film can create artifacts.
机译：硫循环在海洋沉积环境中普遍存在，受微生物和非生物过程的影响，可改变最终捕获为沉积矿物质的硫种类的丰度和同位素组成。在硫化氢中产生硫同位素（Delta S-34）签名的微生物代谢具有在微米级上变化的空间分布，但硫化水硫化氢最常在散装样品中测量，所述散装样本表示更大的体积。这种鳞片失配会导致错误或非独特的生物地球化学过程和环境条件的解释。最近，描述了一种原位薄膜的技术，其在胎儿中捕获溶解的硫化物（H2S），并且可以被逐渐逐渐缩放以在沉积物内的亚厘米级上重建ΔS-34（H2S）曲线。在此，我们研究了CMECA 7F-Geo二次离子质谱仪（SIMS）来分析在这些薄膜上捕获的ΔS-34（H2S）在这些薄膜上捕获的甚至更小的空间尺度，特别是在可能的低硫化物丰度的薄膜中否则没有用批量提取技术处理。我们提出了一种最佳实践方法，用于薄膜分析方法，使分析伪像从不同硫化物丰度和与嵌入的有机基膜氨基汞合金中嵌入的卤化银纳米晶体相互作用。该方法在来自场部署的几件膜上测试，包括小（类似于100μm）的异质性的实例，沉积物界面上的小（类似100μm），陡峭的同位素梯度和非常低的硫化物丰度。结果表明，使用SIMS的分析可以在点和图像模式下准确地测量由具有高精度（1 sigma类似于0.3份同样的0.3份）的薄膜的原位硫化物的ΔS34，并且胶片本身可以准确地记录Delta S-34可变性降至25亩空间分辨率，低于胶片的物理限制可以产生伪影。

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