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At least 325 records · Page 18Linked to original sources
PubMed2005

The impact of seasonal variations in DOC arising from a moorland peat catchment on coagulation with iron and aluminium salts.

Natural organic matter (NOM) is one of the main sources of environmental pollution to drinking water supplies in much of the UK and the US. Whilst traditional treatment with trivalent coagulants has proven a successful strategy in the past, operational problems are now being reported during periods of elevated organic levels in the water. Characterisation of the pollutants in terms of polarity, molecular weight and charge, provides a method to understand the impact of the observed temporal and spatial variations in terms of a mechanistic parameter relevant to the treatment processes. Results from this study demonstrate that it is not simply the increased organic concentration, but also the change in NOM composition and character, which influences the impact on the treatment processes. Consequently, monitoring of these parameters provides an insight into how to manage the impact caused by environmental changes to the catchments.

Aluminum↗
PubMed2001

Effects of elevated CO2 on fen peat biogeochemistry.

Effects of elevated atmospheric CO2 concentration on northern peatland biogeochemistry was studied in a short-term experiment. Eight intact soil cores (11-cm diameter x 40-cm depth) with Juncus and Festuca spp. were collected from a calcareous fen in north Wales. Half of the cores were incubated under 350 ppm CO2 concentration, whilst the other four cores were maintained at 700 ppm CO2. After a 4-month incubation, significantly higher biomass (root + shoot + algal mat) was determined under elevated CO2 conditions. Higher emissions of N2O and CO2, and higher concentration of pore-water DOC (dissolved organic carbon) were also observed under elevated CO2. However, no significant differences were found in CH4 emission or soil enzyme activities (beta-glucosidase, phosphatase, and N-acetylglucosaminidase) in the bulk soil. Overall, the results suggest that elevated CO2 would increase the primary productivity of the fen vegetation, and stimulate N2O and CO2 emissions as a consequence of an enhanced DOC supply from the vegetation to the soil microbes.

Carbon↗
PubMed2004

Hydration of natural organic matter: effect on sorption of organic compounds by humin and humic acid fractions vs original peat material.

Natural organic matter (NOM) hydration is found to change activity-based sorption of test organic compounds by as much as 2-3 orders of magnitude, depending on the compound and the specific NOM sorbent. This is demonstrated for sorption on humin, humic acid, and the NOM source material. Hydration assistance in organic compound sorption correlates with the ability of the sorbate to interact strongly with hydrated sorbents, demonstrating the important role of noncovalent polar links in organizing the sorbent structure. Differences in hydration effect between the sorbents are caused mainly by differences in compound-sorbent interactions in the dry state. For a given compound, hydration of the sorbent tends to equalize the sorption capability of the three sorbents. No correlation was found between the strength of sorbate-sorbent interactions or the type of sorbate functional groups and the extent of sorption nonlinearity. Sorption nonlinearity compared over the same sorbed concentration range is greater on the original NOM than on either of the two extracted fractions. In elucidating sorption mechanisms on hydrated NOM, it is important to explicitly consider the participation of water molecules in organic compound interactions in the NOM phase.

Adsorption↗
PubMed2005

Record of metal workshops in peat deposits: history and environmental impact on the Mont Lozère Massif, France.

This study aims to document the history of the metallurgical activities on the Mont Lozère massif in the Cévennes Mountains in Southern France. Many medieval sites of metallurgical wastes (slags) have been reported on the massif. These sites are thought to represent ancient lead workshops. The impact of past metallurgical activity on the environment was studied using geochemical and palynological techniques on a core collected in the Narses Mortes peatland near medieval smelting area. Two main periods of smelting activities during the last 2200 years were revealed bythe lead concentration and isotopic composition along the core profile: the first period corresponds to the Gallic period (approximately ca. 300 B.C. to ca. 20 A.D.) and the second one to the Medieval period (approximately ca. 1000-1300 A.D.). Forest disturbances are associated with lead anomalies for the two metallurgical activities described. The impact of the first metallurgy was moderate during the Gallic period, during which beech and birch were the tree species most affected. The second period corresponds to the observed slag present in the field. Along with agropastoral activities, the medieval smelting activities led to the definitive disappearance of all tree species on the summit zones of Mont Lozère. The abundance of ore resources and the earlier presence of wood on the massif justify the presence of workshops at this place. The relationship between mines and ores has been documented for the Medieval period. There is no archaeological proof concerning the Gallic activity. Nevertheless, 2500-2100 years ago, the borders of the Gallic Tribe territory, named the Gabales, were the same as the present-day borders of the Lozère department. Julius Caesar reported the existence of this tribe in 58 B.C. in "De Bello Gallico", and in Strabon (Book IV, 2.2) the "Gabales silver" and a "treasure of Gabales" are mentioned, but to this day, they have not been found.

Archaeology↗
PubMed2005

Methanotrophic symbionts provide carbon for photosynthesis in peat bogs.

Wetlands are the largest natural source of atmospheric methane, the second most important greenhouse gas. Methane flux to the atmosphere depends strongly on the climate; however, by far the largest part of the methane formed in wetland ecosystems is recycled and does not reach the atmosphere. The biogeochemical controls on the efficient oxidation of methane are still poorly understood. Here we show that submerged Sphagnum mosses, the dominant plants in some of these habitats, consume methane through symbiosis with partly endophytic methanotrophic bacteria, leading to highly effective in situ methane recycling. Molecular probes revealed the presence of the bacteria in the hyaline cells of the plant and on stem leaves. Incubation with (13)C-methane showed rapid in situ oxidation by these bacteria to carbon dioxide, which was subsequently fixed by Sphagnum, as shown by incorporation of (13)C-methane into plant sterols. In this way, methane acts as a significant (10-15%) carbon source for Sphagnum. The symbiosis explains both the efficient recycling of methane and the high organic carbon burial in these wetland ecosystems.

Carbon↗
PubMed1999

Genetic structure in three haploid peat mosses (Sphagnum)

Over the past 20 years, studies have revealed levels of genetic variation in bryophytes that are similar to those found in vascular plants. This has led many to question the traditional view of bryophyte evolution, which holds that these organisms have a low evolutionary rate. RAPD and isozyme analyses were used to measure genetic variation in 18 populations of several Sphagnum taxa, with special emphasis on the bisexual S. lindbergii and the unisexual S. angustifolium, S. fallax and S. isoviitae. Both types of markers were found to be selectively neutral. A test of population differentiation showed no significant divergence between S. fallax and S. isoviitae growing in sympatry; these taxa were therefore treated as conspecific. Only S. angustifolium had polymorphic isozyme loci. The highest genetic variation in RAPD loci was found in S. angustifolium; the lowest in S. lindbergii. There seemed to be a high turnover rate of individuals in S. angustifolium populations. Populations of S. fallax coll. were strongly differentiated for RAPD markers, whereas S. angustifolium populations were only weakly differentiated for any marker, even for populations from different continents. Populations of S. lindbergii were not differentiated at all. Most studied populations did not fit the 'Conocephalum - Plagiomnium' model of bryophyte population structure. The observed patterns could best be explained by assuming a low evolutionary rate, at least in S. angustifolium, meaning that high levels of molecular variability seem not to be incompatible with slow evolution.

Journal Article↗