Occurrence and mass loadings of n‐Alkanes in riverine runoff of the Pearl River Delta, South China: Global implications for levels and inputs

Abstract

Riverine runoff samples were collected monthly from March 2005 to February 2006 from the eight major outlets of the Pearl River Delta (PRD), South China, and analyzed to obtain the concentrations of n-alkanes in both the filtrate and particulate phases. The average concentrations of Sigma(C15-C34) (i.e., sum of C15 to C34 normal alkanes) ranged from 0.06 to 2.97 microg/L (mean, 0.64 microg/L) in filtrate samples and from 1.00 to 98.8 microg/g (average, 19.8 microg/g dry weight) in particulate samples. Compared to results from around the world, the levels of hydrocarbon compounds in the PRD were at the high end of the global range. Evaluation of compositional indices of n-alkanes indicated that petroleum-related sources are the main contributor of n-alkanes found in the PRD, with minor contributions from high plant wax. Regression analyses appeared to suggest that n-alkanes are transported into the aquatic environment of the PRD via various pathways, and the transport mechanisms also are considerably influenced by the complex hydrologic conditions in the PRD. The annual riverine input of Sigma(C15-C34) from the PRD to the coastal ocean was 360 tons/year, or the equivalent of approximately 8,800 tons/year of petroleum hydrocarbons. The emission of Sigma(C15-C34) from all sources in the PRD was estimated at 39,000 tons/year, or 2.4 g/day per capita. Overall, the PRD contributes approximately 0.2% of the annual global input of n-alkanes to the coastal oceans, similar to the contributions of polycyclic aromatic hydrocarbons, further indicating that the PRD has been a significant source of hydrocarbon contamination to the global coastal marine environment.

Application of multiple geochemical markers to investigate organic pollution in a dynamic coastal zone

“…Chem. 32,2013in the present study were also higher than those in riverine runoff samples of the PRD (1.10 AE 0.34) [10], and urban aerosols of Guangzhou (1.03-1.16) [22], which were attributed to anthropogenic vehicular emissions. The compositional profiles of resolved n-alkanes (Fig.…”

“…The difference between the measured and prepared concentrations of the target analytes must be less than 20% before sample analysis. For field samples, the recoveries of the n-alkane and LAB surrogate standards, tetracosane-d 50 and 1-phenyldodecane-d 30 , were 70 AE 4% and 61 AE 12%, respectively, whereas those of the PAH surrogate standards, naphthalene-d 8 , acenaphthene-d 10 , phenanthrene-d 10 , and chrysene-d 12 , were 50 AE 15%, 65 AE 18%, 100 AE 21%, and 99 AE 15%, respectively. The recoveries of the same surrogate standards in quality assurance and quality control samples were 61 AE 5%, 75 AE 20%, 41 AE 5%, 53 AE 6%, 74 AE 12%, and 130 AE 9%, respectively.…”

“…A total of 23 n-alkanes (pristane [Pr], phytane [Ph], and n-C 15 to n-C 35 , where the subscript indicates the carbon number), 19 LABs (i-C j LAB, where i represents the position of phenyl substitution and the subscript j indicates the carbon number [10][11][12][13] of the alkyl chain), and 28 PAH congeners, including 16 priority PAHs, were selected as target analytes (Supplemental Data, Table S1). A Shimadzu GCMS-QP2010 Plus gas chromatograph/mass spectrometer equipped with an AOC20i auto injector was utilized to determine the concentrations of n-alkanes and PAHs.…”

“…Consequently, intensive anthropogenic activities may induce large amounts of terrestrial organic materials to deposit in coastal marine systems through riverine runoff [8], or atmospheric deposition [9], or both. For example, the annual riverine inputs of n-alkanes, LABs, and S 15 PAH (sum of the U.S. Environmental Protection Agency's 16 PAH priority pollutants minus naphthalene) from the Pearl River Delta (PRD) to the northern South China Sea (NSCS) were estimated to be 360 tons [10], 14 tons [11], and 33.9 tons [12], respectively. Because estuarine and coastal sediments are known to serve as both sinks and secondary sources of terrestrial organic materials [13], coastal marine systems are therefore dynamic areas connecting lands and oceans.…”

Polycyclic aromatic hydrocarbons in upstream riverine runoff of the Pearl River Delta, China: An assessment of regional input sources

“…Similar correlations have been reported in our previous studies on riverine fluxes through the eight major outlets of the PRD (Fig. 1) for S 27 PAH , organochlorine pesticides and polychlorinated biphenyls (Guan et al, 2009), polybrominated diphenyl ethers , linear alkylbenzene (Ni et al, 2008), and n-alkanes (Wang et al, 2008b), which was attributed to the attainment of a steady state for these chemicals within the aquatic system of the PRD (Guan et al, 2009). Based on this result, a steady state was not reached for S 15 PAH in upstream Pearl River, but attained for S 12 PAH.…”