This study aimed at comparing toxic element (Hg, Cd) bioaccumulation in relation to age for bottlenose (Tursiops truncatus) and striped dolphins (Stenella coeruleoalba) from Mediterranean and Atlantic waters. Metal concentrations were also measured in selected prey to infer metal exposure through the diet. As expected, Mediterranean prey exhibited the highest Hg levels, probably as a consequence of the Hg enrichment of the Mediterranean Sea. Comparing the predators from each area and taking age into account, Mediterranean bottlenose dolphins displayed higher Hg levels than Atlantic dolphins (p = 0.032), whereas Mediterranean striped dolphins did not (p = 0.691). The consumption of Myctophid fish, which showed the highest Hg levels (105 +/- 80 ng g(-1) w.wt.) among Atlantic prey, may explain the high Hg levels in the liver of the Atlantic striped dolphins and suggested a preferential offshore feeding behaviour in this area. Concerning Cd, no clear differences were found between geographical areas. (c) 2006 Elsevier Ltd. All rights reserved.

The objectives of this study were to simplify sample preparation and validate mercury detection in soil and plant samples using inductively coupled plasma atomic emission spectroscopy (ICP-AES). A set of mercury contaminated and mercury free soil and plant samples were digested and analyzed by ICP-AES, inductively coupled plasma mass spectrometry (ICP-MS), and cold vapor atomic absorption spectroscopy (CVAAS). Results show that mercury measurements in soil and plant samples using ICP-AES were in agreement with those analyzed using ICP-MS and CVAAS. The concentrations of mercury in soils and plant tissues determined by ICP-AES were 92.2% and 90.5% of those determined by CVAAS and ICP-MS, respectively. Digestion of soil samples with 4 M HNO₃ and direct measurement by ICP-AES without reduction of Hg²⁺ to Hg⁰ gave a reasonable and acceptable recovery (92%) for determining Hg in soils. We conclude that ICP-AES with optimized conditions (addition of gold chloride, extension of washing time, linear working range, and selection of wavelength - 194 nm) resulted in reliable detection of mercury in environmental samples.

Lake Vänern is Sweden's largest freshwater reservoir. It has been significantly affected by mercury contamination during the latter half of the 20th century. The aim of this study was to analyse the spatial and vertical mercury distribution, whereas 46 sediment cores were sampled in 2001 and analysed for total mercury. Several of these cores were dated presenting sediment accumulation rates varying from 6-8 mm yr-¹ outside major rivers to ~2 mm yr-¹ in the deeper areas. This was made using ¹³⁷ Cs, which was verified by ²¹⁰ Pb dating. Cluster analysis was used to identify five areas with similar accumulation and mercury concentration regimes. In areas far from shore, surface concentrations ranged from 0.1 to 0.5 ppm Hg, while the deeper layers in contaminated areas held concentrations up to 11 ppm Hg. In total, ~50 tonnes of mercury accumulated in the lake's sediment between ~1940-2001; almost 80% (or 37 tonnes) originate from before the mid 70's when the recovery period began, and at least 30 tonnes can be attributed to the former point source - a chlor-alkali industry.

Litterfall can be an important flux of mercury (Hg) to soils in forested landscapes, yet typically the only available data to evaluate Hg deposition is from precipitation Hg monitoring. Litterfall was collected at 39 sampling sites in two small research watersheds, in 2003 and 2004, and analyzed for total Hg. Four vegetation classes were designated in this study as hardwoods, softwoods, mixed and scrub. The mean litter Hg concentration in softwoods (58.8 ± 3.3 ng Hg g-¹ was significantly greater than in mixed (41.7 ± 2.8 ng Hg g-¹ and scrub (40.6 ± 2.7 ng Hg g-¹, and significantly lower than in hardwoods (31.6 ± 2.6 ng Hg g-¹. In contrast, the mean weighted litter Hg flux was not significantly different among vegetation classes. The lack of a significant difference in litter Hg flux between hardwoods and softwoods was attributable to the large autumnal hardwood litter Hg flux being balanced by the higher softwood litter Hg concentrations, along with the higher chronic litterfall flux throughout the winter and spring in softwoods. The estimated annual deposition of Hg via litterfall in Hadlock Brook watershed (10.1 μg m-² and Cadillac Brook watershed (10.0 μg m-² was greater than precipitation Hg deposition and similar to or greater than the magnitude of Hg deposition via throughfall. These results demonstrate that litterfall Hg flux to forested landscapes can be at least as important as precipitation Hg inputs.

Lake sediments are a potential source of mercury (Hg) for aquatic biota. Here, we investigated the predictive power of (a) key parameters for lake catchment morphometry and (b) organic matter composition of sediments in an effort to account for observed variations of total (THg) and methyl (MeHg) mercury concentrations in lake sediments. Using regression models we demonstrate that the morphometric parameters lake depth as well as inclination of catchment soils and lake bottoms can significantly predict variations of THg concentrations, but not MeHg, at profundal lake sediments. Although THg and MeHg concentrations in sediments could not be predicted by specific organic matter sources, as elucidated by atomic C/N ratios, our data suggest that wetland-derived total organic carbon (TOC) contained less THg concentrations than TOC derived from mostly forested watersheds. However, TOC concentrations could significantly predict MeHg concentrations and the proportion of methylated Hg at all sediment stations. Finally, from an ecotoxicological point of view, we propose that concentrations of TOC at surface lake sediments, rather than parameters of catchment morphometry, may predict dietary sources of MeHg for benthic consumers and consequently perhaps for organisms at higher trophic levels.