ABSTRACT
Coordination complexes [M(O2CCH2OC2H4OMe)2] (M = Co, 4; M = Mn, 5) are accessible by the anion exchange reaction between the corresponding metal acetates [M(OAc)2(H2O)4] (M = Co, 1; M = Mn, 2) and the carboxylic acid HO2CCH2OC2H4OMe (3). IR spectroscopy confirms the chelating or µ-bridging binding mode of the carboxylato ligands to M(ii). The molecular structure of 5 in the solid state confirms a distorted octahedral arrangement at Mn(ii), setup by the two carboxylato ligands including their α-ether oxygen atoms, resulting in an overall two-dimensional coordination network. The thermal decomposition behavior of 4 and 5 was studied by TG-MS, revealing that decarboxylation occurs initially giving [M(CH2OC2H4OMe)2], which further decomposes by M-C, C-O and C-C bond cleavages. Complexes 4 and 5 were used as CCVD (combustion chemical vapour deposition) precursors for the deposition of Co3O4, crystalline Mn3O4 and amorphous Mn2O3 thin films on silicon and glass substrates. The deposition experiments were carried out using three different precursor solutions (0.4, 0.6 and 0.8 M) at 400 °C. Depending on the precursor concentration, particulated layers were obtained as evidenced by SEM. The layer thicknesses range from 32 to 170 nm. The rms roughness of the respective films was determined by AFM, displaying that the higher the precursor concentration, the rougher the Co3O4 surface is (17.4-43.8 nm), while the manganese oxide films are almost similar (6.2-9.8 nm).
ABSTRACT
The purpose of this study was to determine if wetlands influence mercury concentrations in brook trout (Salvelinus fontinalis), benthic macroinvertebrates, and stream water. On September 26, 2005, water samples, benthic macroinvertebrates, and brook trout were collected from four streams in western Maryland under low-flow conditions. Water samples were also collected in these four streams under high-flow conditions in January 2006. The watersheds of Blue Lick and Monroe Run did not contain wetlands, but the watersheds of the Upper Savage River (3% of upstream area) and Little Savage River (7% of upstream area) contained wetlands. We found significantly (p = 0.05) higher average total mercury concentration in brook trout from Little Savage River (129 +/- 54 ng g(-1)); intermediate concentrations (66 +/- 19 ng g(-1)) in brook trout from Upper Savage River; and lowest concentrations in brook trout from Blue Lick (28 +/- 11 ng g(-1)) and Monroe Run (23 +/- 19 ng g(-1)). Brook trout in all streams accumulated mercury at the same rate over their lifetimes, but the youngest fish had significantly different mercury concentrations (Little Savage > Upper Savage > Blue Lick = Monroe Run), which may be due to differences in mercury concentrations in the eggs or food for the fry. Mercury concentrations in brook trout were not consistent with mercury concentrations in stream water and benthic macroinvertebrates. The Little Savage River had significantly higher total and methylmercury concentrations in stream water, but mercury concentrations in the other streams and in the benthic macroinvertebrates were not significantly different among streams. The unusually high methylmercury concentrations (0.5 to 2.1 ng L(-1)) in the Little Savage River may have been caused by production of methylmercury in the pools. The relatively low methylmercury concentrations in the Upper Savage River may be caused by a mercury concentration gradient downstream of the wetland.
