Production and Consumption of NO in Forest and Pasture Soils from the Amazon Basin

NO production and the rate constant of NO consumptionin soil samples from Amazonian forest and pasturesites were determined in the laboratory. The purposewas to study NO production and consumption in soilsfrom both types of land use as functions of soiltemperature and soil moisture. NO productionincreased exponentially with soil temperature. Thedegree of increase depended on soil moisture,indicating that the response of NO production to achange in soil temperature is most pronounced at acertain intermediate soil moisture. NO productionpeaked at a soil moisture of 0.10 g g^-1, correspondingto 0.27 and 0.38 water-filled pore space for forestand pasture soils, respectively. The optimum soilmoisture for which maximum NO release was observedwas independent of soil temperature. NO consumptionwas most efficient at high soil temperatures andunder dry soil conditions. NO release wasapproximately 10 times larger for forest than pasturesoil. The difference may be related to the higherNO₃ ^- content in forest soil.     

Levels and Characteristics of TOC in Throughfall, Forest Floor Leachate and Soil Solution in Undisturbed Boreal Forest Ecosystems

Total organic carbon (TOC) concentrations and fluxes in throughfall, forest floor leachate, soil solution (15 and 35 cm depths), and groundwater for coniferous forest sites in the boreal zone throughout Finland are described. Eight upland forest stands and one peatland forest stand are included in the study and the samples were collected during 1991–1997. Carbon (C) pools in the living tree biomass and soil compartments are presented, and the hydrophobic/hydrophilic and acidic components of dissolved organic carbon (DOC) in samples collected in autumn 1999 and spring 2000 from two of the sites are compared. Biomass (aboveground and belowground) pools of C averaged 88 Mg ha^-1 and soil (humus layer + 20 cm soil layer) averaged 55 Mg ha^-1. Stand throughfall TOC monthly mean concentrations ranged from 4.0 to 18.6 mg L^-1 and annual fluxes averaged 4.0 g m^-2 yr^-1. TOC concentrations in the water passing through the forest floor and soil decreased with depth. Plot mean concentrations at 35 cm depth values ranged from 4.1 to 21.2 mg L^-1 and fluxes averaged 3.7 g m^-2 yr^-1. Throughfall TOC concentrations were lowest during the winter, snowfall period and highest during the growing season. No monotonic trends in throughfall TOC concentrations over the 1991–1997 period were found. Soil solution TOC concentrations varied considerably, both within and between years. DOC in throughfall, forest floor, and soil solutions and in both autumn and spring seasons was dominated by hydrophobic fractions, particularly acids. Spruce canopies and litter appear to be important sources of soluble organic carbon, particularly acidic and hydrophobic compounds. Further studies on the nature and dynamics of organic carbon fluxing through coniferous, boreal forest ecosystems are needed.     

Changing of Lead and Cadmium Pools of Swedish Forest Soils

The aims of the paper are to; i)evaluate the rate and direction of present changesin lead (Pb) and cadmium (Cd) soil pools of Swedishforests; ii) discuss processes of importance forleaching of Pb and Cd in Swedish forest soils. Thepresently ongoing changes of Pb and Cd pools ofSwedish forest soils are evaluated by compilationof data from the literature and unpublishedsources. It is concluded that Cd pools arepresently decreasing in larger areas of Sweden. Therate of decrease is mainly determined by soilacidity status; Cd leaching is regulated by ionexchange with Ca²⁺, Mg²⁺, Al³⁺ andH⁺, and is higher in acid soils. The Pb poolsare presently increasing with 0.1 to 0.3 percentannually in the soil down to 0.5 meter. Pb isredistributed from the O horizon to the B horizon,most pronounced in spruce forests; the Pb pools ofthe O horizon are presently not increasing, but isslightly decreasing by 0.1 to 0.2 percent annually. The leaching of Pb in the soil is controlled byfactors regulating the solubility of organicmatter.     

Regional Variability of Cd,Hg, Pb and C Concentrations in Different Horizons of Swedish Forest Soils

Contents of cadmium (Cd), mercury (Hg), lead (Pb) and carbon(C) in the O, B and C horizons of podzolized forest soils inSweden were surveyed. Concentrations and storage of Cd, Hg andPb in the O and B horizons were high in southern Sweden and gradually decreased towards the north, though with considerablelocal variability. This pattern reflects the influence of anthropogenic emissions of these metals, as well as the effectsof soil-forming processes. Parent till material, as representedby the C horizon concentration of the respective metal, accountedfor little of the variation in metal concentration in the O horizon. For Cd and Pb, the correlations were not significant orslightly negative (R² = 0.12 and 0.09 respectively) depending on region, while for Hg the correlation was not significant or slightly positive (R² = 0.03 and 0.08). Furthermore, parent till material accounted for more of the variation in metal concentrations in the B horizons in the northern part of Sweden than in the middle and southernmost parts, where the concentration of total carbon had more influence. The correlation between the metal concentrationsin the B and C horizon was strongest for Pb (R² = 0.63 and 0.36 in the two northernmost regions), lower for Cd (R² = 0.19 and 0.16) and not significant for Hg. For allsoil horizons, total C concentration accounted for much of thevariation in Hg concentration in particular (O-horizon R² = 0.15–0.69, B horizon R² = 0.36–0.50, C horizon R² = 0.23–0.50 and ns in one region). Ratios of metal concentrations between the B and C horizons were highest for Hg(maximum value of 30), indicating a relatively larger addition or retention of Hg compared to Cd and Pb (maximum value of 10)in the B horizon. This study indicate that factors other than parent material account for the large scale variation in O horizon concentrationsof metals but patterns correspond well with those of atmosphericdeposition of heavy metals and acidifying substances. Furthermore, the study highlights the importance of soil organicmatter and the intensity of pedogenic processes for the content and distribution of metals throughout the soil horizons.     

Critical Loads and Exceedances of Acid Deposition and Associated Forest Growth in the Northern Hardwood and BorealConiferous Forests in Québec,Canada

We used the Québec forest monitoring network (`Réseaud'Étude et de Surveillance des Écosystèmes Forestiers' or RESEF)along with its atmospheric monitoring stations to assess criticalS and N loads and their combined soil acidification exceedancesfor natural ecosystems of the northern hardwood and borealconiferous forests in Québec, Canada. Critical loads (CL) forforest soil acidification were calculated using the simple mass-balance (SMB) approach and with the steady-state PROFILE model.Atmospheric deposition rates for water, S, N, Ca, Mg, Na, and K,for the years 1989–1993, and detailed, plot-specific forest andsoil characteristics were used as input. The SMB model alsorequired information regarding nutrient uptake and storage in theaboveground woody biomass. The CL calculations indicated that,from the 31 RESEF plots, 18 received atmospheric acidic inputs inexcess of their CL (55 and 61% of the hardwood and coniferousplots, respectively). The range of CL exceedance varied from 60to 470 eq ha^-1 yr^-1 for the hardwood stands, and from 10to 590 eq ha^-1 yr^-1 for the coniferous stands. The standswith CL exceedance were mainly located in the western and centralpart of the province. Stand growth associated with exceedanceclass of acidity was determined using the RESEF plots along withselected permanent forest survey plots having similar sitecharacteristics, but for which longer growth records wereavailable. We found a significant negative correlation betweenforest growth rates and critical soil acidification exceedancefor both the northern hardwood and the boreal conifer sites.Specifically, plots with critical load exceedances were found tohave a growth reduction of about 30% during the 1974–1982 andthe 1972–1990 measurement (plots with no soil acidificationexceedance served as a control). While this correlation is notnecessarily causal, it is nevertheless consistent with theexpectation that increased losses of soil base cations on accountof increased soil acidification should and could lead todeteriorating forest health conditions.     

Modeling Afforestation and the Underlying Uncertainties

A dynamic model of the carbon budget of an oak forest ecosystem that takes into account forest stand age was developed. A numerical experiment was designed to simulate the afforestation process, and a Monte Carlo simulation was performed to determine how parameter uncertainties and environmental variability influence the result. It was found that while the total amount of carbon stored in the ecosystem increases from 1.9 kg C/m² to 4.4 kg C/m² over the following 20 years, the relative standard deviation increases from 9 to 21%. The contribution of varying climate and carbon dioxide parameters to total uncertainty is substantial; for example, the standard deviation at the 10th modeling year for phytomass doubles and the uncertainties of the soil pool and total accumulated carbon increase by a factor of nearly 1.4, while the uncertainty of the litter pool stays almost at the same level.     

Mercury and Methylmercury in Runoff from a Forested Catchment – Concentrations, Fluxes, and Their Response to Manipulations

Measurements of TotHg (total mercury) and MeHg (methylmercury) in runoff from the covered catchment G1 and the reference catchment F1 at Lake Gårdsjön, Sweden, have been performed and evaluated. The roof over the covered catchment limits atmospheric deposition input of TotHg and MeHg and a response in runoff concentrations and transport was expected. Based on data from 10 yr of monitoring, no statistically significant change in runoff flux of TotHg or MeHg can be observed. A slight decrease in MeHg output in the covered catchment was observed after 2 yr of the experiment. This can be explained as a temporary effect caused by the roof construction. The main conclusion is that release of TotHg and MeHg from the forest soil is controlled by factors other that wet deposition input, for example the mineralisation of organic matter. Furthermore, there is no indication of a depletion of the Hg pool in the soil. In spring 1999, the reference catchment F1 was affected by forestry machinery significantly disturbing the forest soil layer in a limited area. This caused MeHg concentrations to increase dramatically in runoff and led to an increase of the annual transport by at least a factor of 3. This indicates that forestry and other activities that disturb forest soils may be important for controlling MeHg fluxes to aquatic ecosystems.     

Thermogravimetric and XRD study of the effects of chloride salts on the thermal decomposition of mercury compounds

In this paper, the effects of chloride salt (MgCl₂, CaCl₂ or NaCl) addition on the thermal decomposition of five inorganic mercury compounds (HgCl₂, HgS, Hg(NO₃)₂·H₂O, HgO, and HgSO₄) were investigated by thermogravimetric analysis. Mercury-contaminated soil samples collected from Inner Mongolia were used to verify the results. The desorption temperatures of the mercury compounds increased in the following order: HgCl = HgCl₂ < HgS < Hg(NO₃)₂·H₂O < HgO < HgSO₄. Among the chloride salts, MgCl₂ had the greatest effect on thermal desorption of the mercury compounds, with the greatest reduction in the initial temperature of thermal desorption. After MgCl₂ treatment, the mercury removal rates for the soil were 65.67–81.35 % (sample A), 70.74–84.91 % (sample B), and 69.08 % (sample C). The increase in the mercury removal rate for sample C with addition of MgCl₂ was particularly large (34.96–69.08 %). X-Ray diffraction analysis of white crystals from the thermal desorption with MgCl₂ indicated that MgCl₂ promoted conversion of the mercury compounds in the soil to mercury(II) chloride and dimercury dichloride. This transformation is beneficial for applying thermal desorption to remedy mercury-contaminated soils and treat of mercury containing waste.     

Air–Soil Exchange of NO,NO2 and O3 in Forests

The exchange of NO, NO₂ and O₃ at the soil surface wasmeasured with automatic dynamic chambers in a spruce forest and in abeech forest during periods of several months.NO was emitted from the soil at a rate of0–8 ng N m^-2 s^-1(spruce) and 0–15 ng Nm^-2 s^-1(beech), but there was no simple relationship between the flux andeither soil temperature or soil moisture. NO₂ and O₃ weredeposited at the soil surface. Deposition velocities forNO₂were on average 0.3 mm s^-1 (spruce) and 0.1 mms^-1(beech), and the deposition velocities of O₃ were on average 1.6 mm s^-1 (spruce) and 1.4 mm s^-1 (beech). The depositionvelocity of O₃ is fairly constant whereas the deposition velocityof NO₂ varies greatly, but the reasons remain to be investigated.     

Effects of Acidification and its Mitigation with Lime and Wood Ash on Forest Soil Processes in Southern Sweden. A Joint Multidisciplinary Study

A joint multidisciplinary investigation was undertaken to studythe effects of lime and wood ash applications on two Norway spruce forest Spodosolic soils. The two sites, typical for southern Sweden, were treated in 1994 with either 3.25 t ha^-1 dolomite or 4.28 t ha^-1 wood ash (Horröd site) or in 1984 with either 3.45 or 8.75 t ha^-1 dolomite (Hasslöv site). Both sites show signs of acidification by atmospheric anthropogenic deposition and possessed low soil pH(4.3) and high concentrations of inorganic Al (35 M) in theupper illuvial soil solution. The prevailing soil conditions indicated perturbed soil processes. Following treatment with lime or wood ash, the soil conditions were dramatically altered. Cation exchange capacity (CEC) and base saturation (BS) was considerable increased after addition. Four years after application most of the added Ca and Mg was still present in the mor layer. Fifteen years after application,Mg in particular, became integrated deeper in the soil profile with a greater proportion lost by leaching incomparison to Ca. The concentrations of these ions were greatestin the mor layer soil solutions and Mg had higher mobility givinghigher concentrations also deeper in the profile. Four years after treatment, the application of wood ash and limeresulted in lower pH values and higher inorganic Al in mineral subsoil solutions compared to the untreated soil. We hypothesize that this was probably due to an increased flow of hydrogen ionsfrom the upper soil as a result of displacement by Ca and Mg ionsin the enlarged exchangeable pool. In contrast, fifteen years after lime and wood ash application, the mineral subsoil horizonspossessed a higher pH and lower soil solution Al content than theuntreated plots.Liming promoted soil microbial activity increasing soil respiration 10 to 36%. This is in the same range as net carbon exchange for forests in northern Sweden and could potentially have a climatological impact. The turnover of low molecularweight organic acids (LMWOA) by the soil microbial biomass werecalculated to contribute 6 to 20% to this CO₂ evolution.At Horröd, citrate and fumarate were the predominant LMWOAs with lowest concentrations found in the treated areas. In contrast, at the Hasslöv site, propionate and malonate were the most abundant LMWOAs. Higher microbial activity in the upper soil horizons was also theprobable cause of the considerably higher DOC concentrations observed in the soil solution of ash and lime treated areas. Thelime-induced increase in DOC levels at Hasslöv could be attributed to increases in the 3–10 kDa hydrophobic size fraction. Liming also promoted nitrification with high liming doses leading to extreme concentrations of NO₃ ^- (1 mM) in soil solution.At Hasslöv the community of mycorrhizal fungi was dramatically changed by the addition of lime, with only four of 24 species recorded being common to both control and treated areas.Many of the observed effects of lime and ash treatment can be viewed as negative in terms of forest sustainability. After fouryears of treatment, there was a decrease in the pH of the soil solution and higher concentrations of inorganic Al and DOC. Increased organic matter turnover, nitrification and NO₃ ^-leakage were found at Hasslöv. Considering that the weathering rate and the mineral nutrient uptake by trees is mostprobably governed by mycorrhizal hyphae etchingmineral grains in the soil, it is important to maintain this ability of the mycorrhizal fungi. The lime and ash-induced changed mycorrhizal community structure may significantly affect this capability. In light of this investigation and others, as reviewed by Lundström et al. (2003), the implications ofliming on forest health are multifaceted with complex relationships occurring over both space and time.     

Treatment of mercury‐contaminated soils with activated carbon: A laboratory,field, and modeling study

A series of laboratory batch leaching tests was conducted to evaluate the performance of different activated carbons in stabilizing mercury in soils. Based on the results of these experiments, an amendment application rate of 5 percent powdered activated carbon (PAC) was selected for in situ field application at a former industrial facility. A geochemical model was also developed to simulate the interactions between mercury and activated carbon in vadose‐zone soils. Modeling was used to (1) better understand possible mercury sequestration mechanisms and (2) predict the in situ performance of PAC. Model results indicate dissolved mercury concentrations observed in batch tests are consistent with equilibrium partitioning of mercury between dissolved organic matter, soil organic matter, and PAC. Activated carbon is predicted to reduce dissolved mercury concentrations via two mechanisms: (1) the formation of stable mercury complexes on PAC surfaces and (2) the direct adsorption of dissolved organic matter that would otherwise be available for mercury dissolution. Study results demonstrate PAC effectiveness for site soils with mercury concentrations below 200 mg/kg. © 2010 Wiley Periodicals, Inc.     

The Transit of 35SO4 2- and 3H2O Added In Situ to Soil in a Boreal Coniferous Forest

A solution containing ³⁵SO₄ ^2- and ³H₂O was applied to four plots (5 × 5 m) in a boreal coniferous forest in the Laflamme Lake watershed, Québec, under two contrasting conditions: in summer (plots 1 and 2), and on the snowpack before snowmelt (plots 3 and 4). The transit of both these tracers in the soil solution was then followed through a network of soil lysimeters located at different depths. Four months after the summer application, ³H₂O had infiltrated the whole soil profile at plot 1, while ³⁵SO₄ ^2- was only observed in the LFH and Bhf horizons. A ³⁵SO₄ ^2- budget calculated from mid-August to November indicated that 89 and 10.6% of the added ³⁵SO₄ ^2- was retained within the LFH and the Bhf layers, respectively. Fifteen months later, the added ³⁵SO₄ ^2- was distributed in the following proportions within the soil horizons: LFH (73.7%), Bhf (11.8%) and Bf (12.8%), for a total retention rate of 98.3%. The superficial penetration of ³H₂O at plot 2 was indicative of a major lateral water movement that prevented the calculation of a ³⁵SO₄ ^2- budget. This situation also was observed at plot 4 during snowmelt. At plot 3, ³H₂O moved freely through the soil profile and a significant fraction of the added ³⁵SO₄ ^2- reached the B horizons, where it was presumably adsorbed on aluminum (Al) and ferric (Fe) oxides. The ³⁵SO₄ ^2- budget for plot 3 from March to November indicated that 87% of the added ³⁵SO₄ ^2- was retained within the soil profile, with most being retained in the B horizons (LFH = 33.1%, Bhf = 33.1%, Bf = 20.8%). The contrasting retention patterns of ³⁵SO₄ ^2- within the soil profile following the summer addition and snowmelt likely was caused by the contrastingsoil temperatures and soil solution residence times within the differentsoil layers. The persistence of ³⁵SO₄ ^2- in the soil solution of the entire profile long after the initial tracer infiltration, and the relative temporal stability of specific activity of SO₄ ^2-, point to the establishment of an isotopic equilibrium between the added ³⁵SO₄ and the active S-containing reservoirs within a given soil horizon. Overall, the results clearly illustrate the very strong potential for ³⁵SO₄ ^2- retention and recycling in forest soils.     

Topographic Controls of Nitrogen,Sulfur, and Carbon Transport from a Tolerant Hardwood Hillslope

The lateral down-slope movement of water, NO₃ ^-, NH₄ ⁺, SO₄ ^2-, H⁺ and DOC through an ablation till was examined from 1987 to 1990 for a one hectaresoil catena on a steep hillslope with uniform forest cover at the Turkey Lakes Watershed (TLW), Ontario, Canada. Natural variation in the export of nutrients from the soil profile via soil water to Little Turkey Lake was assessed in relation to nutrient distribution in soil at different topographic positions.Subsurface throughflow exhibited dramatic differences in nutrientconcentrations and fluxes with slope position, largely reflectingthat of the soil horizons through which the water passed. GreaterNO₃ ^-, SO₄ ^2-, and DOC concentrations in subsurface water in the upper, well-drained hillslope were a reflection of enrichment by contact with more acidic, more developed podzols, and more favorable soil physical and biological conditions for NO₃ ^- retention in solution.Nutrient inputs to the lake were strongly influenced by increaseddown-slope transport of water, and increased SO₄ ^2-, N, and C retention in wetter, less-developed podzolic soils that characterize lower slope positions. An understanding of water movement and soil development variation withtopographic position was required to accurately estimate nutrient budgets for steep slopes at TLW.     

Fluxes of NO3-, NH4+, NO,NO2, and N2O in an Old Danish Beech Forest

The fluxes of the major nitrogen compounds havebeen investigated in many ecosystem studies over the world.However, only in few studies has attention been drawn to theimportance of the fluxes of minor gaseous nitrogen compoundsto complete the nitrogen cycle. In Denmark a detailed study onthe nitrogen cycle in an old beech forest has been implementedin 1997 at Gyrstinge near Sorø, Zealand. The study includesthe fluxes of the gases NO, N₂O and water mediatedtransport of NO₃ ^- and NH₄ ⁺. Measurementsof the fluxes of the gaseous compounds are performed withmicro-meteorological methods (eddy-correlation and gradient)and with chambers. Water mediated fluxes encompass rain,throughfall, stem-flow and leaching from the root zone. Thehydrological model is verified by TDR measurements. The findings show that the total water mediated N input tothe forest floor with throughfall and stemflow was 25.6 kg Nha^-1 yr ^-1, and open field wet deposition withprecipitation was 19.0 kg N ha^-1 yr ^-1. The internalcycling of N in the ecosystem measured as turnover oflitterfall and plant uptake was 100 kg N ha^-1 yr ^-1and 14 kg N ha^-1 yr ^-1, respectively. The fluxes ofthe gaseous N compounds NO and N₂O were of minorimportance for the total N turnover in the forest, NO_xemission being <1 kg N ha^-1 yr ^-1 and N₂Oemission from the soil being 0.5 kg N ha^-1 yr ^-1 withno significant difference between wet and dry soils.Concentrations of NO₃ ^- and NH₄ ⁺ in thesoil solution beneath the rooting zone are very small andconsequently the N leaching is almost negligible. It isconcluded that the nitrogen mass balance of this old beechforest ecosystem mainly is controlled by the input by dry andwet deposition and a large internal N cycle with a fast litterturnover. The nitrogen input tothe forest ecosystem which currently exceeds the critical loadby 5 kg N ha^-1 yr ^-1is mainly accumulated in the soil and no significant nitrateleaching is occurring.     

Effects of Long-Term Application of Ammonium Sulphate on Nitrogen Fluxes in a Beech Ecosystem at Solling, Germany

To study the effects of elevated inputs of acidity and nitrogen (N), 1000 mmol m^-2 a^-1 of ammonium sulphate (NH₄NO₃) equivalent to an input of potential acidity of 2000 mmol m^-2 a^-1 was applied annually for 11 yr between 1983 and 1993 in a beech forest at Solling, Germany. Most of the applied NH₄ ⁺ was nitrified in the litter layer and in the upper mineral soil. N in soil leachate quickly responded to the elevated input, but most of the applied N was stored in the soil or left the ecosystem via pathways other than soil output. Leaching of N from the soil increased until the last year of N addition. After the last N application, N fluxes decreased rapidly to low values. The buffering of acidity produced by the nitrification of the applied NH₄ ⁺ was caused mainly by three different processes: (i) sulphur (S) retention, (ii) release of aluminium, (iii) release of base cations. Retention of S took place mostly in the subsoil. 72% of the S input was recovered in output after 14 years of the experiment. Due to the increased fluxes of mobile anions with soil solution, outputs of cations increased drastically.     

Mercury emission from sewage sludge incineration in Japan

Sewage sludge contains trace amounts of mercury, and sewage sludge incineration is a major source of mercury emissions. However, relatively few studies have reported on mercury emissions from sewage sludge incineration. Consequently, data on emissions from sewage sludge incinerators must be updated to estimate current emissions of mercury. In this study, we examined mercury emissions and speciation using continuous mercury analyzers in two incinerators. The mercury concentrations in stack gas from facilities A and B were 36.6 and 21.1???g/Nm³, respectively. As a result, the emission rate was calculated to be 0.282?C0.750?g/ton-dry sludge. Considering the total amount of sewage sludge incinerated in Japan, the mercury emissions from sewage sludge incinerators were estimated to be 0.49?C1.31?tons/year.     

Vertical Distribution of Atmospheric Pollution Lead in Swedish Boreal Forest Soils

In order to understand the fate of anthropogenic lead (Pb)pollution in boreal forest soils, and to predict future trends, it is important to know where in the soil the pollution Pb is accumulated and how large the pollution and natural Pb inventories are in different soil horizons. We combined stable Pb isotope (²⁰⁶Pb/²⁰⁷Pb ratios) and concentration analyses to study Pb in podzol profiles and mor samples from old-growth forest stands at seven sites distributed from southern to northern Sweden. Additional samples were taken from managed forests, and from an agricultural field, to give some idea of the effects of land-use. Pb concentrations are typically 60–100 g g^-1 dry mass in the mor layer in southern Sweden and about 30 g g^-1 in northern Sweden. Pb isotope analyses show that virtually all of this Pb is pollution Pb. The isotope composition also shows that pollution Pb has penetrated downwards between 20–60 cm in the forest soils. The total pollution Pb inventories vary between 0.7–3.0 g m^-2 ground surface, with larger inventories in southern compared to northern Sweden. Although the highest Pb concentrations occur in the mor layer, the largest inventories of pollution Pb are found in the Bs-horizon. The limited investigation of Pb distribution and inventories in soils from managed forests did not point to any major difference compared to the old-growth forests. The agricultural field revealed, however, a completely deviating Pb profile with all pollution Pb evenly distributed in the 20 cm thick top-soil.     

Using Fallout Lead-210 Measurements to Estimate Soil Erosion in Three Small Catchments in Southern Italy

Soil erosion and associated off-site environmental impacts have attracted increasing attention in recent decades, and there is a growing need for reliable information on rates of soil loss. The potential for using ¹³⁷Cs fallout to quantify rates and patterns of soil redistribution over medium-term timescales (ca. 45 years) has been successfully demonstrated in a wide range of environments around the world. The similar behaviour of fallout ²¹⁰Pb in soils offers potential for its use as an alternative to ¹³⁷Cs, in areas where ¹³⁷Cs inventories are low or are complicated by additional fallout from the Chernobyl accident. There have, however, to date been few attempts to validate the use of fallout ²¹⁰Pb measurements for assessing erosion rates. This paper reports an attempt to explore the use of fallout ²¹⁰Pb to estimate rates of water-induced soil erosion on uncultivated land. It focuses on three small forest/rangeland catchments located in Calabria, southern Italy, for which measurements of sediment output are available. Comparison of the estimates of net soil loss from the catchments derived from ²¹⁰Pb measurements with the measured sediment output, confirmed the validity of the ²¹⁰Pb approach. The soil redistribution rates estimated using ²¹⁰Pb measurements were also consistent with equivalent estimates obtained for the same study catchments using ¹³⁷Cs measurements.     

Characterisation of Organic Matter and Carbon Cycling in Rehabilitated Lignite-rich Mine Soils

Open-cast lignite mining in the Lusatian mining district resulted in rehabilitated mine soils containing up to four organic matter types: (1) recent plant litter, (2) lignite deposited by mining activity, (3) carbonaceous ash particles deposited during amelioration of the lignite-containing parent substrate and (4) airborne carbonaceous particles deposited during contamination. The influence of lignite-derived carbon types on the organic matter development and their role in the soil carbon cycle was unknown. This paper presents the findings obtained during a six year project concerning the impact of lignite on soil organic matter composition and the biogeochemical functioning of the ecosystem. The organic matter development after rehabilitation was followed in a chronosequence of rehabilitated mine soils afforested in 1966, 1981 and 1987. A differentiation of the organic matter types and an evaluation of their role within the ecosystem was achieved by the use of ¹⁴C activity measurements, ¹³C CPMAS NMR spectroscopy and wet chemical analysis of plant litter compounds. The results showed that the amount and degree of decomposition of the recent organic matter derived from plant material of the 30 year old mine soil was similar to natural uncontaminated forest soil which suggests complete rehabilitation of the ecosystem. The decomposition and humification processes were not influenced by the presence of lignite. On the other hand it was shown that lignite, which was thought to be recalcitrant because of its chemical structure, was part of the carbon cycle in these soils. This demonstrates the need to elucidate further the stabilisation mechanisms of organic matter in soils.