Source apportionment of polycyclic aromatic hydrocarbons and n-alkanes in the soil-sediment profile of Jianghan Oil Field, China

Abstract

Surface soil in oil exploration area always contains high contents of polycyclic aromatic hydrocarbons (PAHs) and n-alkanes. To investigate the migration possibility of PAHs and n-alkanes from surface through aquitard and aquiclude to aquifer, the distribution, together with the source apportionment using several indicators, such as composition pattern, fluoranthene/(fluoranthene+pyrene) (Flt/(Flt+Pyr)), anthracene/(anthracene+phenanthrene) (Ant/(Ant+PA)), and the carbon preference index (CPI) of n-alkanes, in a 30-m-deep soil-sediment profile were studied. Results showed that there were considerable PAHs and n-alkanes not only in surface soil but also in aquitard, aquiclude, and aquifer sediments. The PAHs and n-alkanes in surface soil strongly suggested petroleum pollution. The high molecular weight PAHs and the n-alkanes with both long and short chains could not migrate into deep sediments as their sources in surface soil and deep sediment were different. Whereas the aquitard and aquiclude had significant input of low molecular weight PAHs (LMWPAHs) from petroleum sources, the LMWPAHs in confined aquifer suggested pyrogenic sources. Therefore, LMWPAHs migrated from surface to aquitard and aquiclude, but did not cause aquifer pollution in Jianghan Oil Field. However, the high mobility of LMWPAHs from surface to aquitard and aquiclude suggested that the long-term risk of groundwater pollution from oil exploration should be concerned.

Gas chromatography‐mass spectrometry in assessment of road run‐off sediment quality parameters

“…In samples B and C, the calculated CPI values are above 2, which indicates a natural input of hydrocarbons [6, 30, 39]. On the other hand, based on a CPI value of around 1 as well as the dominance of n ‐alkanes with an odd number of C atoms, an anthropogenic source of pollution in all samples can be confirmed [17, 22, 23]. Based on previous findings, this leads to the conclusion that the samples contain an organic substance of native origin with intensive input from anthropogenic sources.…”

“…Odd C-number 1.00-4.80 [42] Pichavaram mangroves, India n-C11-n-C37 Various 0.75-8.63 [40] Central Alaska, USA n-C19-n-C35 Odd C-number 2.20-21.00 [38] Suez Gulf, Egypt n-C10-n-C40 Mainly even C-number 0.62-1.95 [43] Lake Middle Marviken, Sweden n-C15-n-C31 Odd C-number 3.60-8.00 [39] Banja Luka, Bosnia and Herzegovina n-C14-n-C39 Odd C-number 1.12-1.48 This study of C atoms, an anthropogenic source of pollution in all samples can be confirmed [17,22,23]. Based on previous findings, this leads to the conclusion that the samples contain an organic substance of native origin with intensive input from anthropogenic sources.…”

“…The dominance of n-alkanes with odd numbers of carbon atoms as well as the dominance of individual sterane and terpene homologs provide a specification of the anthropogenic source of pollution [21]. Based on the dominance of short-chain (C15, C17, and C19) and longchain (C27, C29, and C31) n-alkanes, it can be concluded whether it is an algal or sedimentary origin of hydrocarbons [17,20,22,23]. The biomarker group also includes steranes and terpenes, semi-volatile compounds that are formed during the biological decomposition of algae, bacteria, and vascular plants.…”

Occurrence, distribution and composition of aliphatic and polycyclic aromatic hydrocarbons in sediment cores from the Lower Fox River, Wisconsin, US

“…Fingerprint profiles of the suspected sources in the samples were examined graphically by reviewing PAH concentrations of parent and alkylation abundance to display their relative slope (decrease, increase, or bell-shaped). Diagnostic ratios were used to identify a probable match (Ma et al 2017; Ranjbar Jafarabadi et al 2017a). The diagnostic PAH ratios (Table SM-2) were used to determine petrogenic or pyrogenic sources and potential input sources (Short et al 1998 and Crane 2014).…”

Distribution, sources and transport of polycyclic aromatic hydrocarbons (PAHs) in karst spring systems from Western Hubei, Central China

“…It indicated that the strong permeable stratum is conducive to the rapid transport of organic pollutants, and the particulate matter may be the leading carriers of HMW-PAHs (Levy et al 2017). While in the weak permeable aquifer, HMW-PAHs are easily hindered and adsorbed by carbonate rock debris and deposited in karst conduit (Ma et al 2017). The MLRA results showed that the transport of PAHs from both the soil and spring water could explain 20.6% and 96.2% (R 2 =0.206, 0.962) of the PAHs in the spring sediments of MGQ and YQD spring systems, respectively.…”