Variability of present and past PAH (polyaromatic hydro carbons) concentrations in sediments of the SW Barents Sea

Abstract

The concentration and distribution of polyaromatic hydrocarbons (PAHs) in surface and subsurface sediment samples from Tromsøflaket and Ingøydjupet, southwestern Barents Sea, were investigated in order to provide insight into the levels and origins of PAHs in a region with petroleum activities. PAH profiles in sediments were evaluated in context with sediment grain size and total organic carbon in order to assess the influence of ocean currents on the transportation and deposition of PAHs. The PAH concentrations are of background (Level I) to good level (Level II) based on the Water Framework Directive classification system. SUM PAH (SUM of 26 PAH compounds) ranged from 39 to 2197 µg/kg (average 225 µg/kg), and NPD (naphthalene, phenanthrene and dibenzothiophene, including their C1-C3 alkyl homologues) in surface samples ranged from 14 to 2045 µg/kg (average 157 µg/kg). However, the average values presented here are higher than have been reported in previous studies. The observed changes in PAH contents in surface and subsurface sediments vary in accordance with changes in grain size (clay and silt 17-99%) and total organic carbon content (0.37-0.98%). In turn, these sedimentary parameters are controlled by the inflow of Atlantic Water and the strength of the two predominating current systems in this region: the North Atlantic Current and Norwegian Coastal Current. Source-allocation modeling suggests that PAHs in surface samples are mainly of pyrogenic or mixed pyrogenic and petrogenic origin. Taken together, these patterns of PAH levels and sources reflect natural variability, indicating that the derived dataset establishes a pre-impacted baseline of the present state of the seafloor.

Concentration, sources and risk assessment of PAHs in bottom sediments

“…The important point sources of PAHs in the catchment area of the Rybnik reservoir are also sewage treatment plants. Moreover, high content of organic matter (Rybnik reservoir) and clay fraction (Rzeszów reservoir) of the soil and sediment system is the most important factor in the sorption of polycyclic aromatic hydrocarbons and thus their accumulation in the environment (Lahlou and Ortega-Calvo 1999 ; Müller et al 2007 ; Crampon et al 2014 ; Junttila et al 2015 ; Abdel-Shafy and Mansour 2016 ). Sediments from the Chechło, Brzóza Stadnicka and Brzóza Królewska reservoirs also had relatively a high C OM content and high C/N ratio values (Table 2 ).…”

“…high molecular weight PAHs have high affinity to BC (Klimkowicz-Pawlas et al 2016 ). Other important parameters that affect the retention and release of hydrophobic organic chemicals are temperature, conductivity, pH and clay content (Hiller et al 2009 ; Junttila et al 2015 ). Smectite, illites and kaolinite are the three common clay minerals which have the greatest impact on sorption/desorption because of their high surface area and CEC as well as their surface reactivity (Junttila et al 2015 ).…”

“…Other important parameters that affect the retention and release of hydrophobic organic chemicals are temperature, conductivity, pH and clay content (Hiller et al 2009 ; Junttila et al 2015 ). Smectite, illites and kaolinite are the three common clay minerals which have the greatest impact on sorption/desorption because of their high surface area and CEC as well as their surface reactivity (Junttila et al 2015 ). Small-sized particles have large specific areas and high adsorption capacity of organic compounds (Dahle et al 2003 ; Wu et al 2016 ).…”

“…Many authors observed that organic carbon and sediment grain size are positively or negatively correlated with organic compounds, especially if the absorbents and adsorbents are of the same source (Lubecki and Kowalewska 2010 ; Ali et al 2014 ). McElroy et al ( 1989 ) and Junttila et al ( 2015 ) found that PAHs have a strong affinity for organic matter and therefore tend to accumulate in fine-grained sediments. The correlation between PAH and clay content implies that PAHs are trapped in the fine-grained sediments (Junttila et al 2015 ).…”

“…McElroy et al ( 1989 ) and Junttila et al ( 2015 ) found that PAHs have a strong affinity for organic matter and therefore tend to accumulate in fine-grained sediments. The correlation between PAH and clay content implies that PAHs are trapped in the fine-grained sediments (Junttila et al 2015 ). The nonlinear correlation between organic carbon and PAH concentrations in sediments suggests that the PAHs were recently generated and therefore were yet to fully partition into organic matter in sediments (Sojinu et al 2010 ).…”