Lake trout and walleye composites were collected between 2004 and 2009 as part of the Great Lakes Fish Monitoring and Surveillance Program (GLFMSP) and analyzed for polybrominated diphenyl ethers (PBDEs). Yearly mean total PBDE concentrations (sum of congeners BDE-47, BDE-99, BDE-100, BDE-153, BDE-154) ranged from 44-192, 28-113, 50-107, 37-111, and 11-22 ng/g wet wt. for Lakes Michigan, Huron, Ontario, and Superior lake trout, and Lake Erie walleye, respectively. A 1980-2009 temporal record of PBDE concentrations in the Great Lakes' top predator fish (lake trout and walleye) was assembled by integrating previous GLFMSP data (1980-2003) with current results (2004-2009). Temporal profiles show obvious breakpoints between periods of PBDE accumulation and decline in trout for Lakes Huron, Michigan and Ontario with a significant (p < 0.0001 and r = 0.55, 0.72, and 0.51, respectively) decrease in concentration after 2000-2001. A similar transition was observed in Lake Superior for the nearshore site accompanied by a less significant decreasing trend (p = 0.016, r = 0.33), suggesting concentrations are declining very slowly or have leveled off. In contrast, Lake Erie walleye concentrations began leveling off in the late 1990s and no statistically significant trend (increasing or decreasing) has been observed in recent years. A decrease in the BDE-47/BDE-153 ratio was also recently observed, suggesting a transition to more highly brominated PBDEs is occurring in Great Lakes trout. This study provides region-wide evidence that PBDE concentrations are generally declining in Great Lakes trout, although there are clear exceptions to this trend. Results from this study reflect the positive impact of the 2004 PentaBDE ban on macro-scale aquatic freshwater ecosystems.
Tetrachlorophenol (T4CP) reactions to PCDD
products
in the presence of MSWI fly ash were measured as
a function of gas-phase precursor concentration,
reaction time, and reaction temperature. Tetrachlorophenol concentrations ranged from 150 to 700 ng/mL in 10% O2, and temperatures ranged from 250 to
400
°C, which resulted in PCDD formation rates from
about 0 to 35 μg of PCDD (g-fly ash)-1
min-1. Reaction
conditions were found such that the reactor approached differential behavior, which led to the
breakthrough of the T4CP and the desorption of
adsorbed
PCDD products into the gas-phase. At constant
temperature, the surface coverage of chlorophenols
on fly ash was found to be constant for reaction
times between 2 and 120 min, suggesting that the
system had quickly reached adsorption/desorption
equilibrium. Yields of PCDD were observed to increase
with increasing precursor concentration but either
peaked, leveled off, or increased as the temperature
was raised. Studies of T4CP reactions on
different
fly ashes showed a correlation between total conversion
of T4CPto unknown productsand total yield
of
the trace reaction forming PCDD.
Almost any combination of C, H, 0, and Cl can yield some polychlorinated dioxins/furans under suitable conditions of time and temperature. The quantities formed in incinerators, ng m~3 or ng g~l, need to be explained in terms of time/temperature regimes relevant to those units. Current evidence suggests that surface catalyzed reactions at relatively low temperatures (250-400°C) may play an important role. This paper reviews relevant evidence from incinerators, laboratory combustors, and surface-catalyzed experiments using single precursors. A global kinetic model is proposed and assumptions and parameters are discussed.
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