Publikationsdatum:
2019
Beschreibung:
Abstract
Determining the biogeochemical pathways utilized by microbes living in groundwater is essential for understanding the subsurface C cycle and the fate of organic compounds, including pollutants. The radiocarbon signature (Δ14C) of fatty acid methyl esters derived from microbial phospholipids (PLFA) provides useful information for differentiating microbial C sources and infering microbial metabolism. However, in subsurface environments those analyses remain challenging. Here, we present a method combining large volume groundwater filtration (up to 10’000 L) and PLFA purification for subsequent compound specific radiocarbon analyses. The analytical method involves conventional chemical extraction of PLFA followed by purification of individual compounds by semi‐preparative‐high performance liquid chromatography (prep‐HPLC). Different saturated PLFA in amounts of up to 10 μg each can be simultaneously separated on a C18‐high load column using a mixture of MeOH/water and acetonitrile as mobile phase. Our procedure introduced dead‐Cext contaminations of 0.57 ± 0.29 μg and of 0.35 ± 0.18 μg for the HPLC and combustion/graphitization steps of sample preparation, respectively. However, tests on different HPLC C18‐columns revealed a large difference in dead‐Cext associated with column bleed. Modern‐Cext in the amount of 0.40 ± 0.20 μg was introduced by the combustion/graphitization step of sample preparation but others steps did not add modern‐Cext. The entire method recovered ∼50% of the purified compounds on average but this did not affect their 14C‐content. This method will allow routine analysis of the Δ14C of PLFA isolated from groundwaters or others sample types, revealing the relationships between microbial and soil‐derived C, sedimentary or dissolved C sources.
Print ISSN:
0043-1397
Digitale ISSN:
1944-7973
Thema:
Architektur, Bauingenieurwesen, Vermessung
,
Geographie
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