IMW Initial Phase Report 



in bivalve samples collected for the IMW Program that were previously analyzed for chlorinated 

 hydrocarbons. The following is a brief overview of the PAH data provided by GERG. These 

 preliminary data provide information on the PAH concentrations in Central and South America, 

 including Mexico, and the Caribbean region. 



The preliminary total concentrations found in samples from 56 locations in the Caribbean 

 region, Central and South America, including Mexico, is summarized in Table 16. Total 

 concentrations are presented as the uncensored sum of 18 specific PAHs measured for NOAA's 

 Status and Trends Mussel Watch Program in the U.S.A. (S&T PAHs) and as the uncensored sum 

 of all the PAHs listed in Table 15 (tPAHs). The geographical distribution for total S&T PAHs and 

 tPAHs are provided in Figures 27 and 28, respectively. In these figures the concentrations are 

 shown in a north-to-south geographical sequence from the U.S.A.-Mexico border down along the 

 east and west coasts to the most southern sites in Chile and Argentina, respectively. Examples of 

 S&T PAH profile distribution encountered in samples from different locations are shown in Figure 

 29. 



Total concentrations of S&T PAHs and tPAHs ranged from 20 to 1,670 ng/g dry weight 

 and from 28 to 13,800 ng/g dry weight, respectively. In general the highest concentrations in both 

 groups were encountered in sites located near Navy/commercial ports and/or large urban centers. 

 The high concentrations encountered in samples from stations ARHU and ARAP in Argentina, 

 BRRE and BRGB in Brazil, CHPA and CHCO in Chile and MEEM in Mexico are examples of the 

 influence of these sources of PAHs. The lowest concentrations were in contrast, found in areas 

 with low population and/or minimal transportation activities using fossil fuel. 



The different molecular distribution for individual S&T PAHs shown in Figure 29 

 illustrates the differences in hydrocarbon sources encountered during this study. In most samples, 

 the ratios of 4+5-ring to 2+3-ring PAHs were lower than 1. The predominance of the methyl and 

 dimethyl naphthalenes is indicative of petroleum inputs. This is consistent with the dominance of 

 substituted homologs over their unsubstituted parent compounds observed in most of the samples 

 analyzed and roughly indicated by the methyl phenanthrene-to-phenanthrene ratios in Figure 29 

 (Sericano, personal communication). Petroleum, however, is not the only source of PAHs in the 

 samples as indicated by some of the diagnostic ratios useful in determining PAH sources. For 

 example the ratios of phenanthrene to anthracene (range =<1.0 to 29) indicate the contribution of 

 combustion products to total PAH concentrations in some of the samples. 



These data show a wide range of concentrations of PAHs in the bivalve tissue samples 

 derived from petroleum and combustion sources. Concentrations of PAH appear to be similar both 

 in range of concentration and in proportion of samples with specific concentration distributions, to 

 PAH concentrations in bivalve samples from the U.S. coast reported by the U.S. National Status 

 and Trends program (NOAA, 1989). 



57 



