E. García-Rodeja

Four Thousand Years of Atmospheric Pb, Cd and Zn Deposition Recorded by the Ombrotrophic Peat Bog of Penido Vello (Northwestern Spain)

The Northwestern Iberian Peninsula is a mid-latitude oceanic region with areas where different types of bogs are frequent or abundant. The ombrotrophic nature of some bogs make them suitable for the study of accumulation patterns of heavy metals. One of these bogs, Penido Vello, was sampled to a depth of 2.5 m and analyzed in detail for its physico-chemical properties and Pb, Zn and Cd concentrations. Ash and organic carbon content, Ca/Mg molar ratios and a number of other characteristics support an ombrotrophic interpretation of the core. Concentrations of Pb, Zn and Cd were measured, showing important variations in the core. While Zn and Cd are concentrated mainly in the upper sections of the core with minor changes with depth, the Pb profile shows significant peaks in the deeper layers suggesting pre-industrial atmospheric pollution. Enrichment factors (EFs) calculated by normalising to Al correlate well with those calculated by normalising to Ti. Maximum EFs are 33, 56 and 52 for Pb, Zn and Cd respectively. While for Pb these values are comparable to those obtained by other authors, maximum Zn EFs are greater than those mentioned in the literature and may be attributed to the emissions of a nearby coal-burning power plant. At least for Pb the accumulation pattern suggests that atmospheric pollution can be dated back some 2800 years, and that pollution increased steadily since the Iron Age to reach considerably elevated levels, up to 5 times the ‘background’, during the Roman Empire. Changes in Pb emissions through time are in good accord with the prehistorical and historical record of the Iberian Peninsula.

A 14 500 year record of the accumulation of atmospheric mercury in peat: volcanic signals, anthropogenic influences and a correlation to bromine accumulation

A 14 500 calendar year record of mercury accumulation rates has been obtained from an ombrotrophic peat bog in the Swiss Jura mountains. The range of natural (pre-industrial) mercury accumulation rates varied from 0.3 to 8.0 W gm 32 yr 31 . During the Late Glacial and Holocene, climatic and volcanic signals were evident in the mercury record. Mercury accumulation rates increased by a factor of ca 5 during the Younger Dryas cold period. Short-term spikes in mercury accumulation rates, which correspond in time to known volcanic eruptions, occur during the late Boreal and Older Atlantic periods, when volcanic influences on mercury deposition appear to have been intensified due to increased atmospheric humidity. A correlation of mercury to bromine accumulation is observed throughout the preanthropogenic period. During the Holocene, mercury accumulation only exceeded the range of this correlation for a few short periods of elevated mercury deposition which correspond to known volcanic eruptions during the Older Atlantic. During historical times, mercury accumulation rates have exceeded the range of the correlation of mercury to bromine continuously since ca 1330 AD. This excess in mercury accumulation is interpreted as an indication of pollution. During the industrial period, mercury accumulation rates reached 107.6 W gm 32 yr 31 , of which 84% was mercury that exceeded the correlation range. Mercury accumulation rates peaked again during the 1970s, with 78.8 Wg m 32 yr 31 . Early 20th century pollution appears to have been dominated by non-Swiss emissions from coal burning, whereas Swiss mercury emissions appear to have been the dominant pollution source during the mid and late 20th century. Current mercury accumulation rates at the site are similar to those ca 10 years ago, with modern deposition rates being ca 15 times their prehistorical average. Anthropogenic emissions of reactive brominated compounds could be contributing to increased atmospheric deposition rates of mercury. A 2002 Elsevier Science B.V. All rights reserved.

Soils of volcanic regions in Europe

Soils of volcanic areas often exhibit unique properties differentiating them from other soils on Earth. This book gives comprehensive coverage of soils in volcanic regions within Europe, dealing with most aspects of modern day soil science. It covers a range of issues such as mineralogy, chemistry, physics, soil genesis, classification, and more.

Speciation and Solubility Control of Aluminium in Soils Developed from Slates of the River Sor Watershed (Galicia, NW Spain)

The Al species in the soid and liquid phases were studied in eight soils developed from slates in a watershed subjected to acid deposition. From soil solution data the mechanisms possibly controlling Al solubility are also discussed. The soils are acidic, organic matter rich and with an exchange complex saturated with Al. In the solid phase, more than 75% of non-crystalline Al was organo-Al complexes, mostly highly stable. In the soil solutions, monomeric inorganic. Al forms were predominant and fluoro-Al complexes were the most abundant species, except in soil solutions of pH<4.8 and Al L/F ratio >3, in which Al3+ predominated and sulphato-Al complexes were relatively abundant. The most stable phases were kaolinite, gibbsite and non-crystalline Al hydroxides. In most samples, Al solubility was controlled by Al-hydroxides. Only in a few cases (solutions of pH 4-5, Al3+ activity >40 µmol L-1 and SO4 content >200 µmol L-1), Al-sulphates such as jurbanite also could exert some control over Al solubility. In adition to these minerals, a possible role of organo-Al complexes or the influence of adsorption reactions of sulphate is considered, especially for samples with very low Al3+ content (<0.5 µmol L-1).

Aluminium dynamics in experimental acidified soils from a humid-temperate region of South Europe

The processes of At mobilization in soils from NW Spain subjected to an intense acidification were studied The experiment consisted of the addition of a solution of H 2 SO 4 , pH 2.7 to five soils developed from different parent materials and with contrasting properties in the soils from schist, granulite and serpentinite the treatment led to moderate At release. In the most acidic soils, those developed from shale and granite. the addition of acid provoked a high degree of mobilization of Al to the soil solution, where Al 3+ was found in high concentrations The analysis of solid fraction and mineral stability calculations revealed that in mineral horizons mobilized At originated in the inorganic non-crystalline material, whereas in the organic horizons, organic matter constitued the major source of Al.

Sulfide oxidation in coal-mine dumps: Laboratory measurement of acidifying potential with H2O2 and its application to characterize spoil materials

A method for rapidly determining potential H+ production by sulfide oxidation with H2O2 in mine-spoil materials has been tested. Measuring pH 6 h after the addition of the H2O2 in a 1:20 sample-solution (w/v) ratio, seems to be an adequate period for most of the samples. The method was applied to spoil samples, being recommended as a measure of the potential of a material to acidify the environment, in the first steps of characterization of the tailings materials. The same procedure after grinding can also indicate the inherent ability to neutralize the acidity. This will allow the selection of the most suitable materials to be mixed in the spoil with the sulfide-rich ones, facilitating the later field work.

Chapter 8 The redox–pH approach to the geochemistry of the Earth's land surface, with application to peatlands

Publisher Summary Redox–pH diagrams given in this chapter provide a concise graphical way in which to depict Earth surface environments in terms of the activities of electrons, the operators involved in the two commonest types of reaction in the weathering zone on land, i.e., redox and acid–base reactions. Peatlands tend to fall on the acid side of the diagrams with ombrotrophic bogs showing least overlap with common soil-forming environments. Minerotrophic mires overlap the field of ombrotrophic bogs under relatively high redox conditions, though with depth they move along a line defined by ferrous–ferric equilibria, to a near-neutral pH. The same kind of equilibria also plays a controlling influence on ambient conditions in mineral soils at the low limit of their pH range.

Atmospheric deposition and ionic concentration in soils under pine and deciduous forests in the river Sor catchment (Galicia, NW Spain)

Abstract The chemistry of rainwater, throughfall, soil solution and runoff was studied in a Pinus sylvestris forest and in a mixed forest with Quercus robur and Betula alba from November 1991 to October 1993 in the river Sor watershed, NW Spain. Rainwater had an average pH of around 4.8 and the dominant ions were Cl, SO4 and Na. Throughfall was remarkably enriched in SO4, base cations (mainly K) and H, while concentrations of NO3 were similar to those observed in rainwater; pine forest throughfall was notable for the high content of SO4, H and Al. Soil solutions from Ah (0–10 cm) horizons had similar ionic concentrations in both forests. Soil solutions were also characterized by NH4+ levels tending to decrease with depth. This, accompanied by a parallel increase in NO3 in both soils and a strong H+ neutralization in the pine forest soil are remarkable features in soil solutions. Stream waters showed lower levels of SO4, NO3 and K compared to throughfall, while Ca and Mg levels were similar; levels of NH4 and Al in runoff waters were negligible. The differences between soil solutions and stream waters implies that important changes in water chemistry occurred in the subsoils.

Input-output ion fluxes in the River Sor catchment (Galicia, NW Spain)

Ion fluxes, measured during a two year-period in the river Sor catchment and four subcatchments are presented. Inputs were calculated either from hulk deposition (open areas) or throughfall (forested areas) while outputs were obtained from runoff water quality, considering that Cl - moves freely in the system. Annual inputs (SO 4 2. : 124-257, NO 3 - :12-30 and H + : 42-122 meq m -2 y -1 ), were 1.5-2 times higher during the second year, according in a higher trial precipitation. Outputs exceeded inputs for Ca 2+ , Mg 2+ and Na + , while SO 4 2- , NH 4 + , K + were retained in the catchment Mineral weathering (output fluxes of Si: 11 to 31 kg ha -1 ) and sulphate retention (34-43% in Sot catchment) were the main mechanisms involved in H + consumption.

Mineralogical variability in weathering microsystems of a granitic outcrop of Galicia (Spain)

Summary Several products of weathering have been studied in a granitic outcrop in Galicia (N.W. Spain). Spain). Alteration took place under a humid temperate climate. The various materials and the microsystems in which they occur are: (1) fissures containing gibbsite and/or 1:1 sheet silicates of varying degrees of crystallinity, (2) fissures containing 2:1 sheet silicates of beidellite type, (3) encrustations of siliceous material showing varying degrees of structural order, with or without organic matter, and (4) encrustations of non-crystalline matter composed chiefly of Al, P and Si. The results demonstrate the importance of considering the different microsystems which contribute to the formation of secondary products in a given weathering system.