Atmospheric sources and soil filtering of PAH content in karst seepage waters

A framework for the extraction and interpretation of organic molecules in speleothem carbonate

“…Two possible mechanisms of FA incorporation may lead to this concentration profile: (1) Migration of exterior contaminants towards the interior of the speleothem calcite, exceeding laboratory background contamination levels; or (2) two end member sources of FAs including an outer source of contamination which migrates through permeable speleothem calcite, and an interior source which is approximately one order of magnitude above the level of the blank and incorporated at the time of speleothem growth. If these interior FAs are indeed indigenous to speleothem growth, their carbon number characteristics (range C 8 –C 18 ; even number predominance; C max = C 16 –C 18 ) have typically been assigned as representative of multiple sources including microbial and vascular plant origins, leached and filtered through soil profiles during drip water percolation through the epikarst to the site of speleothem growth . However, having previously classified speleothem calcite as permeable to the movement of alkanes and FAs, it is difficult to confidently assign an indigenous origin to these interior molecules without further evidence such as compound specific isotopes.…”

“…Organic matter is transported into a cave environment predominantly via four main pathways; transport by air, drip water and fauna, or autochthonous production . The flux of organic matter along drip water flow pathways is largely controlled by the physical and chemical characteristics of the overlying soil, karst and hydrological flow routes . Autochthonous production is enabled through cave microbiological communities, and air/fauna transport is capable of moving pollen/spores into the cave system where particulates and volatile organic components may adhere to speleothem deposits .…”

Organic characterisation of cave drip water by LC-OCD and fluorescence analysis

“…There has been increasing interest in dissolved organic matter (DOM) in cave drip water and the potential use of organic markers in speleothems as paleoclimate proxies (Blyth et al, 2008;Fairchild and Baker, 2012). While initial studies focussed on bulk organic matter (Baker et al, 1997), subsequent investigations have focussed on the potential of lipid biomarkers (Xie et al, 2003;Blyth et al, 2007;Rushdi et al, 2011), polycyclic aromatic hydrocarbons (PAHs) (Perrette et al, 2013), δ 13 C of organic matter (Blyth et al, 2013a, b) and trace elements associated with organic colloids (Hartland et al, 2012;. Lipids such as n-alkanes have been shown to record vegetation and land-use change (Blyth et al, 2007; and glycerol dialkyl glycerol tetraethers have shown potential as a paleotemperature proxy (Blyth and Schouten, 2013;Blyth et al, 2014).…”

“…This combined with relatively small water sample volumes that can be obtained from stalagmite drip water means that unfeasibly large water sample volumes are required for most biomolecular characterisation techniques. Apart from one study on drip water PAHs (Perrette et al 2013) and one on LMW fatty acids (Bosle et al 2014), published drip water organic matter monitoring has focussed on the measurement of the fluorescent organic matter fraction (fDOM), as this requires about 4 mL of water sample, no pretreatment and has low detection limits (Baker et al, 1997;Baker and Genty, 1999), however, this technique can only provide information about the fluorescent fraction of the organic matter.…”

Ecological Risk Assessment of PAHs in a Karst Underground River System

“…For the Guozhuang karst water system in northern China, total PAH concentrations ranged from 2137 to 9037 ng/L in groundwater [34]. PAHs also were detected in karst seepage waters in caves and groundwater, and soils can effectively retain PAHs -particularly medium to high molecular weight PAHs [30,36]. But increasing PAH concentrations were found at the outlet of the catchment during high discharge events (like snow melt or rainfall events) [30,37].…”