A new environmental scanning electron microscopic (ESEM) technique at low vacuum (5 torr) and 99% humidity, where the sample never has been exposed to high vacuum and coating of carbon or gold, has revealed a new insight into the nature of iron mineralization that develops in association with the stalked bacteria Gallionella. The stalk fibers contain minute flaky iron precipitates. The size of the crystallites is 0.1-0.5 micron and some of them exhibit a hexagonal feature. EDAX analyses on individual crystallites give an atomic ratio between Fe and O very close to 0.67. The stoichiometric formula would thus be Fe 2 O 3 . Stoichiometry and crystallinity are in accordance with the mineral hematite. The mineralization seems to take place inside the fibers of the stalk. With time the Gallionella stalk is covered with iron oxihydroxides of different kinds that probably are controlled by inorganic processes more than by the organic chemistry of the stalk. From a thermodynamic point of view, oxygen as well as carbon dioxide are required to explain the formation of hematite inside the fibers. The precipitation takes probably place at a pH close to 5.

No abstract

No abstract

Environmental changes in Lake Brunnsviken, its watershed, and the greater Stockholm region since the middle of the nineteenth century have left interpretable geochemical imprints in the bottom sediments. These humaninduced perturbations within the lake's watershed included agriculture, urbanization, sewage and industrial disposal, and water column aeration. Smaller ␦ 15 N total values, high organic carbon mass accumulation rates, low C : N ratios, and larger ␦ 13 C org values identify periods of increased nutrient delivery and elevated primary productivity in the lake. C : S ratios that change from high to low trace the transition from an oxic hypolimnion to an anoxic one during the periods of high productivity. Accumulations of redox-sensitive trace elements increase during the anoxic period and are further magnified during a time of industrial waste discharge into the lake. A recent decrease in black carbon concentrations in sediments reflects the conversion from wood and coal to cleaner forms of energy.The composition of lake sediments generally reflects the environmental conditions in and around a water body that existed at the time of their accumulation. Organic matter is a small yet important component of sediments because of its associations with biota, nutrient cycles, and geochemical processes. Photosynthetic plants and microbes that inhabit the lake and its surroundings produce organic matter, and organisms that dwell in the lake depths and sediments consume it. Metabolism and oxidation of organic carbon remove dissolved oxygen from the lake waters and sediments, increase their alkalinity, and lead to CaCO 3 dissolution. Lowered oxygen levels drive redox reactions that simultaneously redistribute trace elements and nutrients. Environmental changes in and around a lake affect how much and what kind of organic matter is delivered to the aquatic system and 1 Corresponding author (joyanto.routh@geo.su.se). AcknowledgmentsWe thank Tomas Hjorth, who helped us on numerous occasions with the fieldwork; Lars Erik Bågander, who provided data for trace metals and pore-water chemistry; and Birgitta Boström, who translated some of the Swedish history for the area. Stefano Bernasconi helped us make the Suess-effect corrections. Thoughtful reviews by Mark Brenner and an anonymous reviewer are greatly appreciated. Funding for this study was provided through grants from Kungliga Vetenskapsakademien and J. Rickert stiftelsen to J.R.

Indigenous fungi isolated from soil of a former gasworks site were investigated in submerged cultures with pyrene as the sole carbon source. Five fungal strains capable of degrading pyrene included one strain of Trichoderma harzianum and four strains with characteristics of the genus Penicillium. These are identified as Penicillium simplicissimum, Penicillium janthinellum, Penicillium funiculosum and Penicillium terrestre. A maximum of 75% of 50 mg l(-1) and 67% of 100 mg l(-1) of pyrene was removed by the fast degrading strain P. terrestre at 22 degrees C during 28 days of incubation. The slower degrader P. janthinellum was able to remove 57% of 50 mg l(-1) and about 31.5% of 100 mg l(-1) pyrene. Degradation of pyrene is directly correlated with biomass development. To the best of our knowledge, this is the first time that fungi have been reported to use pyrene as the sole carbon and energy source. They may be ideal candidates for effective bioremediation of polycyclic aromatic hydrocarbons.