Asger B. Hansen, 2007. NERI Technical Report No. 613, 71 pp.
One of the scopes of the national monitoring programmes for the aquatic environment, NOVA-2003, and for the aquatic environment and nature, NOVANA-2009, is to monitor and report the distribution and concentration of xenobiotics in the aquatic environment in <st1:country-region w:st="on"><st1:place w:st="on">Denmark</st1:place></st1:country-region> . The present report details studies of the content of a series of PAHs (Polycyclic Aromatic Hydrocarbons) in mussels (primarily blue mussels, Mytilus edulis) collected and analysed as part of these monitoring programs during 1998-2005 in order to assess the temporal trend. More specifically, the study included a compilation of existing data from 22 sampling stations covering nine geographically separate marine areas in <st1:place w:st="on"><st1:country-region w:st="on">Denmark</st1:country-region></st1:place> . The marine areas were divided into open sea coastal areas and more isolated areas like fiords and enclosed bays. From each station measured concentrations (based on wet weight) were first converted to a dry weight basis as this more representative of the true PAH burden of the mussels. Furthermore, geometric means of up to three individual samples from each station per year were calculated.
The dry weight converted concentrations were summed into five groups corresponding to the number of aromatic rings (i.e. 2 to 6) of the PAHs and plotted graphically as bar charts on a yearly basis. From these plots, the distribution and levels of each PAH group in mussels at each station can be easily assessed as can comparisons between stations from the same or different areas.
The next step included a summation of the dry weight converted concentrations into three different PAH groups covering alkylated 2-3 ringed-PAHs (PAH-petro), un-substituted 4-6 ringed-PAH (PAH-pyro) and perylene (PAH-bio). These summed concentrations were then log-trans-formed and tested by a non-parametric Mann-Kendal test to assess the significance of possible temporal trends. Similarly, slopes of observed trends were assessed by a non-parametric Sens’s slope estimates.
Eventually, possible sources of the observed PAH burden on the marine environment and on the mussels specifically were discussed on basis of a number of calculated PAH isomer ratios.
The study of the compiled PAD data has revealed that the concentrations in mussels generally are quite similar with levels ranging from 500 to 900 µg/kg dw (dry weight). There were no obvious differences between PAH concentrations in mussels from coastal stations at open sea and from stations at more enclosed areas like fiords and bays. At all stations the PAH content was dominated by smaller PAHs (2-4 rings) including their alkylated derivatives.
The study of temporal trends showed slight declines at almost all stations for both petrogenic and pyrogenic PAHs. However, for most stations the observed trends were not significant (?> 0.1) and must therefore be interpreted with great care.
The allocation of observed PAH burden of the marine environment to possible sources focused on PAHs of petrogenic and pyrogenic origin by employing specific isomer ratios. Generally, this showed that the measured PAHs were of pyrogenic origin.
The level of exposure of the marine environment with PAHs has been assessed using the OSPAR ecotoxicological assessment criteria (EAC). This shows that several stations exceeded the lower EAC level slightly for anthracene. Regarding the human exposure to PAHs by consumption of mussels from the exposed areas estimates of the total exposure expressed as the sum of benzo(a)pyrene toxic equivalents have been calculated. These estimates show that mussels from several stations in a few cases exceeded the acceptance criteria of 50 µg BaPyr-TE/kg dw (i.e. 10 µg BaPyr/kg ww) with a factor of up 2 to 3, but that there is decreasing trend. In no cases were the acceptance criteria for the toxicity of PAH in mussels exceeded in 2004/2005 irrespective of whether the estimates were based on the total of benzo(a)pyrene toxicity equivalents (BaPyr-TE) or on benzo(a)pyrene (BaPyr) alone.
Full report (in Danish) in pdf-format (2,297 kB).
