The concentration of oil in the wetlands ranged more than 5 orders of magnitude, and was aligned (X vs. Y axis) along a similar trajectory starting in 2010 through 2013. There was, in other words, proportionality between the target alkanes and PAHs that was
grossly maintained, in spite of differences in soil from shoreline to inland, wetland types, oiling amount, and time. There was no difference Copanlisib manufacturer in the alkane concentrations amongst the sampled estuaries for May or September 2010 (Fig. 8). The concentration of aromatics, however, were lower in Breton Sound (to the east) than in Terrebonne Bay. The concentration of alkanes and aromatics in the September 2010 samples, however, were much higher than in May 2010. The variance about the mean for these samples was often 2 orders of magnitude, which illustrates the large spatial difference in oiling that confounded the estimation of gross changes in concentration
over time using all data. Consequently, we did a similar analysis of data from the 30 permanently marked plots that were sampled 4 times between February 2011 and June 2012 (Fig. 9). The May 2010 data are included selleckchem for comparison. The concentration of alkanes and aromatics were higher, of course, than observed in the pre-oiled marshes (2010). The concentration of alkanes were not different from each in the first three of the four post-oiling intervals, but was in June 2012. The concentration of aromatics in each of the four samplings was determined not to be different from each other using the one-way ANOVA test. A different evaluation of the changes over time used the average values for each trip. There was a significant decline over three years in the average concentration of target alkanes, but not PAHs (Table 4). The decay rate for the concentration of the target alkanes was 0.39% day−1 for all samples and 0.59% day−1 for the 30 sites sampled four times (p = 0.01 and
0.01, respectively). The decline in concentration Thalidomide (% day−1) of polycyclic aromatics at all sites and the 30 sites was not significant (p = 0.08 and 0.23, respectively; Table 4). The trajectory of change for the target alkanes is such that the concentration would be similar to the ‘baseline’ values by the end of 2015. The changes in the concentrations of PAHs, however, demonstrate no statistically significant decline in concentration over time. The concentration appears to be declining so slowly that many decades will pass before the baseline values are reached in heavily-oiled areas. This persistence is contrary to PAH degradation rates determined from controlled laboratory microcosm studies using South Louisiana crude oil ( Atlas, 1981) and a much faster recovery rate observed in another wetland study ( Mills et al., 2003). A decade-long recovery from oiling has been documented on the heavily impacted shorelines of Alaska ( Peterson et al., 2003 and Boehm et al., 2008), Massachusetts ( Reddy et al., 2002, Peacock et al., 2007, Culbertson et al.