The Austrian soil sampling procedure tested in a field study (CEEM-project)

The Austrian soil sampling procedure requires sampling from representative, uniform areas. For chemical analyses a composite sampling procedure is proposed in which 15-25 single samples should be distributed evenly over the area. Sampling depth for top soils varies between 5 and 30 cm depending on land use. In a field experiment, the suitability and reliability of this sampling method for the determination of trace elements in soil was tested. A high degree of accordance with the results of the extensive and systematic CEEM-Reference Sampling Method was found; therefore the Austrian sampling procedure is recognized as a simple but valid method which can be also proposed as a basis for corresponding ISO- or CEN-Standards.     

Of the necessity of knowledge of the natural pedo-geochemical background content in the evaluation of the contamination of soils by trace elements

In order to evaluate the contamination of the Dornach (Switzerland) site within the framework of the CEEM-Soil project, each participating team was allowed to take a maximum of 15 samples. The French team's sampling was organized in such a way as to answer the following questions: (i) what is the natural concentration of the soils at this site (local pedo-geochemical background content)?; (ii) what are the levels of Cd, Cu, Pb and Zn contamination of the soil?; (iii) what is the depth reached by the surface contamination that is derived from atmospheric fallout?; (iv) how is the contamination spread along the longest axis of the area under study? The relationships between total Fe and the trace metals have allowed local variations in the natural pedo-geochemical background content to be detected and thus permitted the anthropogenic contamination to be estimated. There would appear to be a low level of Pb contamination over all the site investigated (an increase of the order of 5-10 mg kg(-1) on the background level), limited to the surface humus-bearing layers. There is also a significant contamination by Cu over all of the site (an increase of the order of 30-40 mg kg(-1)). This contamination has remained in the surface horizons (0-20 cm). Very high Zn and Cd concentrations have been found in the four surface (0-4 cm) and deep horizons (15-70 cm) taken under the forest and very much lower values in the samples taken from cultivated soils. The most likely explanation is an unequal inheritance between the upper part of the site (wooded with thinner very clayey soils) and the lower cultivated part of the site (with thicker less clayey soils developed in a loamy material). For various reasons, it seems unlikely that a contamination of the wooded part should be so much higher than the cultivated part due to the interception of atmospheric dust by the trees. The local pedo-geochemical background Cd and Zn content of the upper wooded part proved to be clearly higher than that which would be encountered in most soils of Switzerland and France. Given this evaluation of the background content, it seems that only the surface horizons have been affected by Zn contamination (an addition of approx. 60-100 mg kg(-1)). In the case of Cd, the increase in concentrations is only 0.5-1 mg kg(-1) for the ploughed horizons, as well as the for the A horizons.     

Assessing the Floristic Diversity of Hedge Networks: a landscape perspective

The type of land cover adjacent to hedges has been shown to influence the species composition of the ground flora. An assessment of the contribution of hedge networks to the biodiversity of landscapes therefore requires information on the relative lengths of hedge associated with different land covers. In the River Tyne catchment, Northern England, the association between hedges and land cover types differed between four landscapes. Overall, the greatest length of hedge was adjacent to arable crops, improved grasslands and roads. Hedges next to improved grassland and roads were the most species-rich, while those adjacent to arable crops were the least species-rich. Species which were common adjacent to arable crops were also common adjacent to other land covers. Hedges adjacent to improved grassland, roads and semi-natural broadleaved woodland supported species which were not common elsewhere in the hedge network. It was also found that hedges with different land cover on each side supported different floras on each side. When planning landscape-scale surveys of hedge biodiversity, it is important to survey both sides of hedges, and sampling should be stratified to include hedges adjacent to the different types of land cover present.     

Assessing the Floristic Diversity of Hedge Networks: A landscape perspective

The type of land cover adjacent to hedges has been shown to influence the species composition of the ground flora. An assessment of the contribution of hedge networks to the biodiversity of landscapes therefore requires information on the relative lengths of hedge associated with different land covers. In the River Tyne catchment, Northern England, the association between hedges and land cover types differed between four landscapes. Overall, the greatest length of hedge was adjacent to arable crops, improved grasslands and roads. Hedges next to improved grassland and roads were the most species-rich, while those adjacent to arable crops were the least species-rich. Species which were common adjacent to arable crops were also common adjacent to other land covers. Hedges adjacent to improved grassland, roads and semi-natural broadleaved woodland supported species which were not common elsewhere in the hedge network. It was also found that hedges with different land cover on each side supported different floras on each side. When planning landscape-scale surveys of hedge biodiversity, it is important to survey both sides of hedges, and sampling should be stratified to include hedges adjacent to the different types of land cover present.     

Semi-natural grassland continuity, long-term land-use change and plant species richness in an agricultural landscape on Öland, Sweden

The study characterizes historical land-use change and the development of semi-natural grassland habitats, over 274 years, within a mosaic agricultural landscape (22 km²) on the island of Öland (Sweden). We also explore the relationship between previous land-use, habitat continuity and present-day vascular plant species richness in grassland patches. Land-cover maps, based on cadastral maps and aerial photographs, were produced for six time-periods between 1723/1733 and 1994/1997. In 1723/1733, the landscape was dominated by grasslands, with arable land surrounding the villages. The grassland area decreased throughout the study period and grassland patches became progressively more fragmented. Present-day grasslands represent 18% of the grassland area in 1723/1733. The land-use structure of the early 18th century is still evident in the modern landscape. The majority of the present-day grasslands are situated on former common grazing land and have had a continuity of at least 274 years: the remaining grasslands are younger and developed during the 20th century on arable or forested land. The proportion of plant species that depend on grazing and are characteristic of semi-natural grasslands significantly reflects the continuity and previous land-use of grassland sites. The study illustrates the way in which information on historical land-use and habitat continuity can help to explain the structuring of plant assemblages in semi-natural grasslands within the modern landscape.     

Bumblebee communities as an indicator for landscape monitoring in the agri-environmental programme

The current article focuses on the possibilities of applying bumblebees as one of the biodiversity indicators in the monitoring and evaluation of the Estonian Agri-Environmental Programme (AEP) at landscape level. The need for agri-environmental indicators arises, at least partially, because the desired state of the environment sought by policy makers may not be directly observable. To develop agri-environmental measures favourable to landscape quality, it is necessary to know more about the relationship between landscape structure and composition and the number of different species. This study tested the relationship between the data sets of landscape elements and bumblebee communities from 11 agricultural areas in Estonia. The localities were divided into two groups: intensively used agricultural areas (IA) (the percentage of arable land was >65%) and less intensively used agricultural areas (LIA) (the percentage of arable land was <45%). The following elements of landscape structure were analysed: buffer zones narrower than 5 m and wider than 5 m, ecotones between cultivated land and broad-leaved forests, ecotones between cultivated land and mixed or coniferous forests, ditches and brooks, fallow land, mixed forests, coniferous forests, broad-leaved forests, bushes, wetlands, cultivated grasslands, pastures, legumes, arable land, semi-natural grasslands. Fifteen bumblebee species were recorded in LIA and 13 in IA. The most widely distributed and abundant species were Bombus lucorum, Bombus pascuorum and Bombus lapidarius. These species dominated in both types of agricultural area. Two species, Bombus jonellus and Bombus hypnorum were found only in LIA. Principal component analysis (PCA) was applied to the landscape elements and the bumblebee species found. Results showed that there was a significant co-structure between the data sets of landscape elements and bumblebee communities. The most important landscape features that correlated with the distribution of the bumblebee species were the ecotone length between cultivated land and forests, and the size of the area covered with mixed forests and wetlands.     

Mercury and other trace elements in soils affected by the mine tailing spill in Aznalcóllar (SW Spain)

The Aznalcóllar accident (28th April 1998) occurred because the collapse of the tailing-dam dike of the Aznalcóllar-Los Frailes mines. Soils were affected by a slurry of acidic water loaded with trace elements, finely divided metal sulphides, and materials used in the refining /floating process. Studies carried out before and after the soil restoration activities (sludge removal, amending, tilling, and afforestation) showed severe trace-element contamination (mainly As, Cd, Cu, Pb, Tl and Zn) in the superficial layer of the sludge-affected soils. Despite Hg being an important component of the Los Frailes ore and therefore of the contaminant sludge, data on Hg content of sludge-affected soils are scarce and sometimes controversial. The aim of this study was to determine the effect of the spill and of restoration measures on the Hg content of soils and how this related to other elements. Concentration of Hg immediately after the spill was 8-fold above background (0.061+/-0.012 mg kg(-1); mean+/-SD) at the surface (0-5 cm) and 3-4-fold greater in deeper layers (0-20; 0-50 cm). After the remediation measures, mean values of Hg and other elements (As, Cd, Cu, Pb and Zn) were very variable and remained above background values. These anomalies are due to the sludge left on the soil surface or buried during restoration operations, resulting in an irregular distribution of trace elements. The highest values for the less mobile elements (up to 176 mg kg(-1) As, 2.36 mg kg(-1) Hg and 1556 mg kg(-1) Pb) were observed in the area 1 km downstream of the tailings dam.     

Description of the test area and reference sampling at Dornach

The selected test area for the comparative evaluation of European methods on sampling and sample preparation of soils (CEEM Soil) at Dornach near Basel (Switzerland) is located at approximately 400 m a.S.l. on the north-west rolling footslope of the Jura mountain chain that has a temperate climate. The area is known to be airborne polluted by emissions of a non-ferrous metal recycling plant. The geology is dominated by Jurassic limestone and (decarbonated) loess loam. The land use is deciduous forest (beech, oak) in the upper part and traditional cherry orchards with permanent grassland which have mostly been converted into arable land. The detailed soil survey distinguishes four different soil mapping units in the test area of 0.61 ha. The reference sampling was performed in a 190-m-long and 20-40 m large transect area following four devices: (1) composite samples (0-10 cm and 0-20 cm), each from 25 stratified single samples of 61 squares of 10 x 10 m; (2) hypotheses and soil horizon-based composite samples at nine locations; (3) horizon-related samples from the four described soil profiles representing the mapping units; and (4) three soil cores with 5-cm interval samples taken in the major land use units. Altogether 301 reference soil samples were taken.     

Distribution and behavior of trace metals in the sediment and porewater of a tropical coastal wetland

Vertical profiles (0-30 cm below surface) of four trace metals-Cadmium (Cd), Chromium (Cr), Lead (Pb) and Zinc (Zn)-in the sediment and sediment porewater of an ecologically important intertidal mudflat in the Mai Po and Inner Deep Bay Ramsar Site were thoroughly studied over a period of 10 months (from March 1999 to January 2000). Two surveys, one in summer and another in winter, involving a total of eight sampling stations were conducted to study the seasonal variation of the remobilization characteristics of these trace metals in the mudflat sediment. The range of depth averaged concentration of these trace metals in the mudflat sediment was: 0.3-0.8 microg/g (Cd); 9.8-91.0 microg/g (Cr); 7.3-69.1 microg/g (Pb); and 39.5-192.0 microg/g (Zn), while that in the sediment porewater was: 0.3-121.1 microg/l (Cd); 3.0-2704.1 microg/l (Cr); 2.6-105.6 microg/l (Pb); and 32.6-4238.3 microg/l (Zn). In general, levels of dissolved trace metals in the sediment porewater were much higher in the summer than in the winter while their concentrations in the sediment were more or less the same throughout the year. Enrichment of Cd, Pb and Zn in the sediment porewater of the upper oxic layer and that of Cr in the oxic-sub-oxic boundary was generally observed. Regions in the vicinity of the Mai Po mangroves and the river mouths of Shenzhen River and Shan Pui River were found to be hotspots of trace metal pollution. Benthic diffusive fluxes of trace metals from the mudflat sediment were also estimated. Of the four trace metals, cadmium showed the greatest tendency toward remobilization from the sediment phase to the more bio-available porewater phase.     

Metal contamination in urban, suburban, and country park soils of Hong Kong: a study based on GIS and multivariate statistics

The urban environment quality is of vital importance as the majority of people now live in cities. Due to the continuous urbanisation and industrialisation in many parts of the world, metals are continuously emitted into the terrestrial environment and pose a great threat on human health. An extensive survey was conducted in the highly urbanised and commercialised Hong Kong Island area (80.3 km2) of Hong Kong using a systematic sampling strategy of five soil samples per km2 in urban areas and two samples per km2 in the suburban and country park sites (0-15 cm). The analytical results indicated that the surface soils in urban and suburban areas are enriched with metals, such as Cu, Pb, and Zn. The Pb concentration in the urban soils was found to exceed the Dutch target value. The statistical analyses using principal component analysis (PCA) and cluster analysis (CA) showed distinctly different associations among trace metals and the major elements (Al, Ca, Fe, Mg, Mn) in the urban, suburban, and country park soils. Soil pollution maps of trace metals (Cd, Co, Cr, Cu, Ni, Pb, and Zn) in the surface soils were produced based on geographical information system (GIS) technology. The hot-spot areas of metal contamination were mainly concentrated in the northern and western parts of Hong Kong Island, and closely related to high traffic conditions. The Pb isotopic composition of the urban, suburban, and country park soils showed that vehicular emissions were the major anthropogenic sources for Pb. The 206Pb/207Pb and 208Pb/207Pb ratios in soils decreased as Pb concentrations increased in a polynomial line (degree=2).     

Retention and release of Zn and Cd in spodic horizons as determined by pH(stat) analysis and single extractions

In the northern Campine in Belgium, large areas are contaminated by heavy metals such as Zn and Cd due to the (former) non-ferro metal industry. In the sandy soils, the heavy metal adsorption/attenuation in the spodic horizon represents the main retention mechanism of leached pollutants from the contaminated topsoils. In this study, the pH-dependent behaviour of the elements in these spodic horizons was tested by pH(stat) experiments and compared to sandy loam soils. Extractions with CaCl(2) 0.01 M and EDTA 0.05 M provided a further insight into the binding mechanisms. The results indicate that organic matter is the main factor responsible for the mobility of Cd, Zn and Ca in the spodic horizons. The binding of elements is not very strong, however, and highly dependent on pH. A slight decrease in pH can cause a significant release of metals from the spodic horizons, with up to 60% of Cd and 90% of Zn being released within a 1.5 unit change in pH (starting from the naturally occurring pH). This pH change can happen rapidly in these soils, due to the low buffering capacity, and is realistic given the acidification in Flanders. For the sandy loam soils, a pH decrease of 3 units is needed to release 40% of Cd and 20% of Zn, and the acid neutralization capacity is exhausted more gradually, suggesting that slower buffering mechanisms take place. For the sandy loam soils, Cd retention is mainly governed by organic matter, while for Zn other factors such as the clay minerals also play an important role. Despite the high potential mobility and pH dependence of the heavy metal retention in the spodic horizons, the actual risk for groundwater pollution is limited. For the diffusely contaminated areas, where traditional remediation is not an option, spodic horizons may therefore contribute to a natural attenuation of the soil contamination.     

Sediment reference concentrations of seldom monitored trace elements (Ag, Be, In, Ga, Sb, Tl) in four Swedish boreal lakes--comparison with commonly monitored elements

This paper presents reference and recent acid-leachable concentrations of some seldom monitored trace elements (SMTE; Ag, Be, Ga, In, Sb and Tl) in sediments from four boreal oligotrophic lakes in a south to north transect in Sweden. For comparison commonly monitored trace elements (As, Cd, Co, Cr, Cu, Ni, Pb and Zn) are included as well as those of relevance for redistribution processes (Al, Ca, Fe, Mg and Mn). Pore water pH and the corresponding solid/solution distribution coefficients (Kd) indicated that redistribution of the elements due to acidification is minor. The depth of impact was defined as the level in the sediment where the mean values became constant on successive exclusion of metal concentrations in overlying strata. Reference concentrations were calculated below the depth of impact. The present concentration changes are estimated by the ratio between the average concentration above the depth of impact and the reference concentration. Reference concentration ranges for the SMT-elements are (mg/kg, dry wt.): Ag 0.16-0.66; Be 1.6-3.7; Ga 2.0-5.1; In 0.05-0.22; Sb 0.05-0.11 and Tl 0.17-0.70. The concentration ratios for these elements ranged in the two most southern lakes from 1.5 to 4.5 and in the two northern ones from 0.6 to 1.6. A high correlation between Kd for the SMT-elements, and iron, except for Sb and Tl, infer that the biogeochemistry of iron is quantitatively important for the accumulation of these elements. The reference concentration ranges for the commonly monitored trace elements are (mg/kg, dry wt.): As 7.0-29.6; Cd 0.33-0.98; Co 5.7-23.8; Cr 15.2-26.1; Cu 27.6-58.4; Ni 5.4-20.8; Pb 44-96. The corresponding concentration ratios were 1.2-18 (second highest 3.9) in the two most southern lakes and 0.8-1.6 in the two northern ones. Declining ratios were found from south to north, most obvious for cobalt and zinc. The copper ratios did not show a regional pattern, partly because of the impact from old mine waste. Increased concentrations of Ag, Be, Ga, In, Sb and Tl in recent sediments up to 4.5 times the reference levels in combination with the geographical pattern infer an elevated loading of these elements.     

European soil sampling guidelines for soil pollution studies

The soil sampling guidelines used in European countries (ESSG), as kindly provided by the national institutions which participated in the project, have been recorded, studied, evaluated and presented in this paper. The aim has been to ascertain what soil sampling guidelines exist in Europe; to detect similarities and differences (comparable results), advantages and deficiencies; to identify incompatible strategies and evaluate how methodologies might affect data quality; to investigate sources of deviations or uncertainties; to improve comparability and representativeness of soil sampling; to investigate the need for harmonised sampling guidelines; and to develop suggestions for standard operating procedures (SOP). Soil sampling guidelines throughout Europe differ as to whether they are applied by law, or used throughout the country. In some countries these are ISO/DIS related or based (ISO 10381-1, 1995; ISO 10381-2, 1995), or are produced by a scientific society or a standardisation body. As far as sampling strategy is concerned, not all sampling guidelines clearly describe the sampling scale, the specifications for contamination risk precautions, the sampling plan and protocol structure and the pre-analysis treatment of the soil samples. The purpose for sampling, in descending order of frequency, is soil pollution, soil fertilisation, general soil monitoring, background risk assessment, or else it is not specified. The majority of countries do not sample the top organic matter separately. Sampling depth is either related to the morphogenetic horizon or to ad hoc sampling depth, which is not specified in all cases. They suggest mass- and volume-related soil sampling, while the sampling pattern is not presented in all national guidelines. The criteria for area, site, unit, sub-unit, and point selection are mainly based on pedology and land use, following the history and pre-screening information or geology, or is site related. Some guidelines suggest the division of sampling units into sub-units. The sampling pattern is mainly grid sampling, grid and random sampling, or not mentioned. Sampling density inside the sampling unit either varies greatly or it is not mentioned, while the size of the sampling unit varies widely. Most guidelines require the collection of composite instead of simple samples, while some prefer sampling soil profiles. In the European SSG many technical details and steps are either not defined or vary, while in the pre-analysis treatment quality assurance (QA) and quality control (QC) approaches are used either both in the lab and in the field, or only in the field, or are not mentioned. The common points and the points in which harmonisation could be started or achieved are discussed.     

Critical examination of trace element enrichments and depletions in soils: As, Cr, Cu, Ni, Pb, and Zn in Swiss forest soils

The aim of this study was to obtain an overview of trace element concentrations in Swiss forest soils and to critically assess the measured values with respect to anthropogenic input vs. lithogenic background. Twenty-three sites were selected which represent a broad range of natural forest sites, bedrock material and soil types of Switzerland. At each site, samples were collected from all genetic soil horizons down to a C or B/C horizon. Total concentrations of As, Cr, Cu, Ni, Pb, and Zn in all samples were determined by X-ray fluorescence spectrometry. There were distinct differences in the geological background values estimated from the concentrations measured in the samples from the lowest soil horizon. Background concentrations for Cr and Ni were lowest in granite and gneiss, whereas Pb and Zn were highest in limestone and marl. Enrichment or depletion of the trace elements was assessed using Zr as reference element. Within the same profile, the six trace elements showed completely different enrichment/depletion patterns with depth. The various natural processes and anthropogenic inputs that can lead to these patterns are critically discussed. Based on this critical assessment, pollution of the investigated forest soils was found to be most severe for Pb and Zn and to a somewhat lesser extent for As and Cu, whereas anthropogenic input of Cr and Ni seems to be less important. The data suggest that a critical evaluation of enrichment factors is a better tool to assess soil pollution with trace elements than the use of maximum allowable concentrations (MAC) for topsoil samples. The enrichment factors calculated as described here consider the effects of geological variation on metal abundances whereas the MAC does not. In order to obtain an estimate of soil solution concentrations, water extracts of the samples collected from a subset of 10 soil profiles were analyzed for the same trace elements. Solubility of all elements generally decreased with soil depth. An exception was Cr, Cu, and Ni solubility in the humus layer, which was lower than in the underlying mineral horizon. For all elements, solubility was higher for the collective of soil samples depleted in this element when compared to the samples, in which the element was enriched.     

A flexible methodology for the characterisation of soils: a case study of the heavy metal status of a site at Dornach

The sampling scheme devised to study the site at Dornach was successful in identifying most of the features and element distributions in the site using only 15 composite samples. The scheme was based on dividing the area into six individual sampling units each of which represented a different combination of land use and soil type. The three-dimensional information was obtained by taking samples at different depths, either on a fixed depth basis for cultivated soils or according to soil horizons for undisturbed soils. In each sampling unit the composite samples were bulked from 12 individual samples. The sampling point for each individual sample was chosen according to a stratified random plan. Key features of the scheme were the flexibility which required the use of experienced personnel and the fact that the sole task of the sampling exercise was to characterise the site with no preconceptions of possible outcomes. The results showed that the high concentrations of Cd in the soil probably resulted from the high concentrations of Cd in the underlying limestone and not primarily from atmospheric inputs. Higher levels of copper were found in soils close to fruit trees probably as a result of using sprays on the trees. The concentrations of Pb and Zn were relatively uniform throughout the site although there was some evidence of increased Zn concentrations with depth analogous to the Cd distributions. The fact that these findings were in agreement with the known characteristics of the site indicates the successful application of the chosen methodology in this study.     

Speciation of selected trace elements in three Ethiopian Rift Valley Lakes (Koka, Ziway, and Awassa) and their major inflows

The Ethiopian Rift Valley Lakes (ERVLs) are water resources which have considerable environmental, economic and cultural importance. However, there is an increasing concern that increasing human activities around these lakes and their main inflows can result in increased contamination of these water bodies. Information on total concentrations of some trace elements is available for these lakes and their inflows; however, data on the trace element speciation is lacking. Therefore, the objective of this study was to determine the low molecular mass (LMM) trace element species and also, evaluate the influence of flooding episodes on the LMM trace element fractions. At-site size and charge fractionation system was used for sampling of water from the lakes Koka, Ziway and Awassa and their main inflows during the dry and wet seasons. The results showed that chromium (Cr), manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), and lead (Pb) in Lake Koka and its inflows as well as in Lake Ziway were predominantly present as HMM (high molecular mass, i.e., > 10 kDa) forms, while arsenic (As), selenium (Se), cadmium (Cd) were more mobile during the dry season. In Lake Awassa, all except Cr and Mn were predominantly found as LMM species (low molecular mass, i.e. < 10 kDa) which can be attributed to the high concentrations of LMM DOC (dissolved organic carbon). During the wet season, results from the Lake Koka and its inflows showed that all trace elements were predominantly associated with HMM forms such as colloids and particles, demonstrating that the mobility of elements was reduced during the wet season. The colloidal fraction of elements such as Cr, Ni, and Cd was also correlated with dissolved Fe. As the concentration of LMM trace element species are very low, the mobility, biological uptake and the potential environmental impact should be low.     

Acidification of forested podzols in North Belgium during the period 1950-2000

Acidification of forest soils in Europe and North America has been an important concern over the last decades. The last area-covering survey of forest soil acidification in Flanders (North Belgium) goes back to 1985 [Ronse A, De Temmerman L, Guns M, De Borger R. Evolution of acidity, organic matter content, and CEC in uncultivated soils of North Belgium during the past 25 years. Soil Sci; 146, (1988), 453-460] and highlighted a significant acidification of the upper layer (0.3-0.4 m) of forested podzols during the period 1950-1985. The present study aimed to assess (1) to what extent further acidification of forested podzols occurred during the period 1985-2000 at different depths and (2) whether the average annual acidification rate accelerated or slowed down between 1985 and 2000 compared to the period 1950-1985. Average soil pH-KCl values of podzols in northern Belgium dropped during the period 1985-2000. This decline extends to a depth of about 50 cm but was most pronounced and significant in the A horizon. In the A(0), A(1) and A(2) horizons, average pH dropped with 0.2, 0.3 and 0.1 units, and in the B(ir) and C horizons with 0.1 units. No change in average pH value occurred in the B(h) horizon. Average annual acidification rate of the A(1) horizon was significantly higher in the period 1985-2000 than in the period 1950-1985. Changes in pH occurred in the entire soil profile during the period 1950/67-1985 likely because sulphate was the major form of acid deposition before 1985. After 1985, acid sulphur deposition decreased with more than 50% in North Belgium. In contrast, ammonium deposition almost doubled between 1950 and 1980, which may explain why soil acidification between 1985 and 2000 has been restricted to the upper soil horizons.     

Changes in arsenic speciation through a contaminated soil profile: a XAS based study

An impacted soil located near an industrial waste site in the Massif Central near Auzon, France, where arsenical pesticides were manufactured, has been studied in order to determine the speciation (chemical forms) of arsenic as a function of soil depth. Bulk As concentrations range from 8780 mg kg(-1) in the topsoil horizon to 150 mg kg(-1) at 60 cm depth. As ores (orpiment As2S3, realgar AsS, arsenopyrite FeAsS) and former Pb- and Al-arsenate pesticides have been identified by XRD at the site and are suspected to be the sources of As contamination for this soil. As speciation was found to vary with depth, based on XRD, SEM-EDS, EPMA measurements and selective chemical extractions. Based on oxalate extraction, As is mainly associated with amorphous Fe oxides through the soil profile, except in the topsoil horizons where As is hosted by another phase. SEM-EDS and EPMA analyses led to the identification of arseniosiderite (Ca2Fe3+3(AsVO4)3O2.3H2O), a secondary mineral that forms upon oxidation of primary As-bearing minerals like arsenopyrite, in these topsoil horizons. These mineralogical and chemical results were confirmed by synchrotron-based X-ray absorption spectroscopy. XANES spectra of soil samples indicate that As occurs exclusively as As(V), and EXAFS results yield direct evidence of changes in As speciation with depth. Linear combination fits of EXAFS spectra of soil samples with those of various model compounds indicate that As occurs mainly As-bearing Fe(III)-(hydr)oxides (65%) and arseniosiderite (35%) in the topsoil horizon (0-5 cm depth). Similar analyses also revealed that there is very little arseniosiderite below 15 cm depth and that As(V) is associated primarily with amorphous Fe oxides below this depth. This vertical change of As speciation likely reflects a series of chemical reactions downward in the soil profile. Arseniosiderite, formed most likely by oxidation of arsenopyrite, is progressively dissolved and replaced by less soluble As-bearing poorly ordered Fe oxides, which are the main hosts for As in well aerated soils.     

Land inputs of trace metals, major elements, particulate organic carbon and suspended solids to an industrial coastal bay of the NE Atlantic

Rivers, streams and municipal and industrial effluents flowing into the Ferrol Ria (NW Spain) were analyzed for dissolved and particulate trace elements (Cd, Cu, Pb, Zn), particulate major elements (Al, Fe, Si), particulate organic carbon and nitrogen (POC and PON), and total suspended solids. Trace metal clean techniques were applied. Mean annual fluxes of these components were calculated. Dissolved trace metal concentrations in the major freshwater inputs were found to be within typical values for uncontaminated rivers: Cd: 0.020-0.035 nM; Cu: 11.7-19.2 nM; Pb: 0.40-0.71 nM and Zn: 18-54 nM. Two sources of suspended particulate matter (SPM) were observed: (i) a detrital SPM, which becomes more important at high river discharges, with metal concentrations tending to lithogenic values; (ii) an organic- and metal-rich SPM, which becomes dominant at low discharges. Municipal and industrial effluents in the northern shore, despite of constitute a minor freshwater contribution to the bay, were responsible for more than 50% of total inputs of Cu, Cd, Pb, Zn, POC and PON. The fluxes of trace metals obtained for the Ferrol Ria are in the range of other inhabited world semi-enclosed embayments.