Mercury contamination in Marano Lagoon (Northern Adriatic sea,Italy): Source identification by analyses of Hg phases

Total Hg concentrations and Hg speciation were determined in bottom sediments of Marano lagoon to investigate the consequences of Hg phases on fish farms and shellfish cultivation areas. Mercury phases were separated into cinnabar (HgS) and non-cinnabar compounds, via a thermo-desorption technique, in surface and core sediments; both of which had been contaminated by industrial wastes and mining activity residues. The former are due to an industrial complex, which has been producing cellulose, chlor-alkali and textile artificial fibres since 1940. Processing and seepage wastewaters, which were historically discharged into the Aussa-Corno river system and therefore into the lagoon, have been significantly reduced since 1984 due to the construction of wastewater treatment facilities. The second source is the Isonzo River, which has been the largest contributor of Hg into the northern Adriatic Sea since the 16th century due to Hg mining at the Idrija mine (western Slovenia). Red cinnabar (HgS) derived from the mining area is mostly stable and insoluble under current environmental conditions. In contrast, organically bound Hg, such as Hg bound to humic acids, has the potential to be transformed into bioavailable Hg compounds (for example, methylmercury). The presence of the two Hg forms permitted each Hg source to be quantified. It also allowed the areas with the highest risk of Hg contamination from Hg-rich sediment to be identified; thus potentially avoiding the transfer of Hg from the sediment into the water column and eventually into living biota. The results show that Hg Enrichment Factors in bottom sediments exceed values of 10 and cinnabar dominates the central sector near the main tidal channel where tidal flux is more effective. Non-cinnabar compounds were found to be enriched in fine grained material and organic matter. In fact, up to 98% of total Hg at the Aussa-Corno river mouth and in the inner margin of the basin occurred in an organic form. This evidence, combined with the high contents of total Hg (4.1–6.6 μg g⁻¹ and EF > 10) measured in surface sediments, suggest that Hg in Marano lagoon is involved in biogeochemical transformations (e.g., methylation).     

Geochemical characteristics of heavy metals in coastal sediments from the northern Beibu Gulf (SW China): the background levels and recent contamination

Four sediment cores and one hundred surface sediments were collected from the intertidal zone of the northern Beibu Gulf (SW China). In order to detect the intensity of metal contamination recently, the background levels were successfully established for Pb, Zn, Cd and Cr, based on the linear regression of deeper sediments (pre-industrial). Aluminum is a better geochemical normalizer than Fe and it is commonly used to describe the natural metal variability of the coastal sediments. The evident enrichment of Zn and Cd is recorded in the surface sediments of the eastern side of the Guangxi coast and the central part of the Qinzhou Bay, but it does not exceed the effects range-low values, due to a low percentage of fine-grained sediments in the region. Although the Pb and Cr concentrations are mainly of natural origin, 3 and 6% sites exceed the effects range-low values, respectively; indicating the potential for adverse ecological effects of metals on the benthic communities.     

Chernobyl fallout and radionuclide activity in bottom sediments at the River Adige estuary (northern Adriatic Sea, Italy)

The artificial radionuclides ¹³⁷Cs, ¹³⁴Cs and ¹⁰⁶Ru have been determined up to 16 cm deep in two sediment cores collected in March 1988 at the River Adige estuary in the northern Adriatic Sea. Interdependent relations between the properties of the sediment levels and the activity of radionuclides have been investigated using multivariate statistical analysis. The interactions between radiocontaminants and the particulate matter or water phase are discussed during their transfer processes from the river to the estuary and the marine environment. Diffusion phenomena within the sedimentary column have also been considered. The vertical distribution of the artificial radionuclides due to Chemobyl fallout in sediment cores from the River Adige mouth, compared to those from similar estuarine environments in the Adriatic Sea, point out a general rapid accumulation of river-borne solid material in coastal zones of the North Adriatic Sea.     

Assessment of mercury contamination and human exposure associated with coastal disposal of waste from a cinnabar mining operation, Palawan, Philippines

 An integrated geochemical and toxicological assessment of environmental mercury contamination and attendant human exposure in Honda Bay, Palawan was undertaken in 1995 following a nationally reported pollution scare centered on a coastal jetty, Sitio Honda Bay, constructed using approximately 1 million tons of tailings and beneficiation waste from a cinnabar mine. Mercury (Hg) data for marine and fluvial sediments, fish tissues and human hair indicate that the toxicological hazard is considerably lower than initially reported by state environment and health officials. Typical Hg concentrations in surficial Honda Bay sediments were found to lie within the global background range (<60 μg/kg). Downcore profiles provide no evidence of enhanced Hg fluxes coincident with the onset of mining and/or coastal tailings disposal. The mean and median Hg concentrations recorded in tissues of six species of Honda Bay fish are compliant with thresholds established by the US Environmental Protection Agency (US-EPA) for marketable stocks. Earlier reports of 'Minamata range' Hg concentrations in fish and shellfish from Honda Bay remain unsubstantiated. Geochemical analyses of samples of the Sitio Honda Bay substrate have confirmed the prevalence of solid-phase Hg concentrations to ca. 340 mg/kg. The speciation of Hg is, however, dominated by secondary oxides of low bioavailability. The mean Hg concentration in hair from Sitio Honda Bay residents (4.41 mg/kg) was found to be statistically analogous to that for a neighbouring coastal community unimpacted by the coastal disposal of mine waste. A negligible residential exposure factor is thus inferred for the former. Relatively high hair Hg burdens prevail throughout the coastal Honda Bay population, consistent with significant methyl Hg ingestion through daily fish consumption. The data presented provide no environmental or toxicological justification for immediate remedial action. Received: 14 May 1998/Accepted: 1 September 1998     

Mercury contents in the vertical profiles through alluvial sediments as a reflection of mining in Idrija (Slovenia)

The influence of geomorphological factors to Hg contamination of the Idrijca River alluvial sediments because of the historical mining and ore roasting activities has been studied. Main source of Hg in alluvial sediments was dumping of ore roasting residues and mining waste into the river channel and its erosion downstream. The position of the material in relation to the geomorphological properties is highly related with its Hg content. Floodplains were found to be the most contaminated geomorphological units (mean Hg content 335 mg/kg), with Hg concentration rapidly dropping in the first terrace (155 mg/kg). The least contaminated material was found in the higher terraces (3.8 mg/kg). Sampling upstream Idrija (average Hg content is 22.1 mg/kg) shows that not only mine and ore roasting plant increased Hg levels in alluvial deposits but also contaminated sites upstream Idrija contribute to Hg contamination. Geochemical background for alluvial sediments for this area is estimated to be 0.75 mg/kg. Downstream Idrija, 9 hotspots were determined where highly contaminated material is actively eroded and carries a high risk of further contamination of the So?a River and northern Adriatic Sea ecosystems.     

Benthic foraminifera in sandy (siliciclastic) coastal sediments of the Arabian Gulf (Saudi Arabia): a technical report

The Uromia–Dokhtar Magmatic Arc (UDMA) is a northwest–southeast trending magmatic belt which is formed due to oblique subduction of Neotethys underneath Central Iran and dominantly comprises magmatic rocks. The Jebal-e-Barez Plutonic Complex (JBPC) is located southeast of the UDMA and composed of quartz diorite, granodiorite, granite, and alkali granite. Magmatic enclaves, ranging in composition from felsic to mafic, are abundant in the studied rocks. Based on the whole rock and mineral chemistry study, the granitoids are typically medium-high K calc-alkaline and metaluminous to peraluminous that show characteristics of I-type granitoids. The high field strength (HFS) and large ionic radius lithophile (LIL) element geochemistry suggests fractional crystallization as a major process in the evolution of the JBPC. The tectonomagmatic setting of the granitoids is compatible with the arc-related granitic suite, a pre-plate collision granitic suite, and a syncollision granitic suite. Field observations and petrographic and geochemical studies suggest that the rocks in this area are I-type granitoids and continental collision granitoids (CCG), continental arc granitoids (CAG), and island arc granitoid (IAG) subsections. The geothermobarometry based on the electron probe microanalysis of amphibole, feldspars, and biotite from selected rocks of JBPC implies that the complex formed at high-level depths (i.e., 9–12 km; upper continental crust) and at temperatures ranging from 650 to 750 °C under oxidation conditions. It seems that JBPC is located within a shear zone period, and structural setting of JBPC is extensional shear fractures which are product of transpression tectonic regime. All available data suggested that these granitoids may be derived from a magmatic arc that was formed by northeastern ward subduction of the Neotethyan oceanic crust beneath the Central Iran in Paleogene and subsequent collision between the Arabian and Iranian plates in Miocene.

     

Sedimentological characteristics of the surficial sediments of the Kuwaiti marine environment, northern Arabian Gulf

The textural characteristics, carbonate content and the coarse fraction components of the Recent bottom sediments of the marine environment off Kuwait are described and the faunal-sediment associations discussed. The sediments were subdivided into seven textural classes, namely sand, silty sand, muddy sand, sandy silt, sandy mud, silt and mud. Most of the study area is covered with muddy sediments whereas sandy deposits are restricted to the rocky bottoms near the southern flat of Kuwait Bay, the southern coast of Kuwait and around the islands and bathymetric highs. The textural classes, carbonate contents and faunal types of the coarse fraction were used to construct a biolithofacies map of the marine bottom sediments off Kuwait, in which nine facies are identified. The sedimentological characteristics of the Recent marine bottom sediments off Kuwait reflect the interaction between autochthonous calcareous fragments mostly of biogenic origin, lime rock fragments derived from beachrocks and submerged reef flats, and allochthonous terrigenous detritus transported to the area mainly by dust storms. The Kuwaiti offshore area is generally a low energy depositional environment with little sediment transport.     

Heavy metal contamination of coastal lagoon sediments by anthropogenic activities: the case of Nador (East Morocco)

Nador lagoon sediments (East Morocco) are contaminated by industrial iron mine tailings, urban dumps and untreated wastewaters from surrounding cities. The lagoon is an ecosystem of biological, scientific and socio-economic interests but its balance is threatened by pollution already marked by biodiversity changes and a modification of foraminifera and ostracods shell structures. The aim of the study is to assess the heavy metal contamination level and mobility by identifying the trapping phases. The study includes analyses by ICP-AES and ICP-MS, of, respectively, major (Si, Al, Mg, Ca, Fe, Mn, Ti, Na, K, P) and trace elements (Sr, Ba, V, Ni, Co, Cr, Zn, Cu, As, Pb, Cd) in sediments and suspended matter, heavy metals enrichment factors calculations and sequential extractions. Results show that sediments contain Zn, Cu, Pb, V, Cr, Co, As, Ni with minimum and maximum concentrations, respectively, of 4–1190 μg/g, 4–466 μg/g, 11–297 μg/g, 11–194 μg/g, 9–139 μg/g, 1–120 μg/g, 4–76 μg/g, 2–62 μg/g. High concentrations in Zn are also present in suspended matter. The enrichment factors show contamination in Zn, Pb and As firstly induced by the mining industry and secondly by unauthorized dumps and untreated wastewaters. Cr and Ni are bound to clays, whereas V, Co, Cu and Zn are related to oxides. Thus, the risk in metal mobility is for the latter elements and lies in the oxidation–reduction-changing conditions of sediments.     

Distribution of trace elements in the coastal sea sediments of Maslinica Bay, Croatia

Spatial distributions of trace elements in the coastal sea sediments and water of Maslinica Bay (Southern Adriatic), Croatia and possible changes in marine flora and foraminifera communities due to pollution were investigated. Macro, micro and trace elements’ distributions in five granulometric fractions were determined for each sediment sample. Bulk sediment samples were also subjected to leaching tests. Elemental concentrations in sediments, sediment extracts and seawater were measured by source excited energy dispersive X-ray fluorescence (EDXRF). Concentrations of the elements Cr, Cu, Zn, and Pb in bulk sediment samples taken in the Maslinica Bay were from 2.1 to over six times enriched when compared with the background level determined for coarse grained carbonate sediments. A low degree of trace elements leaching determined for bulk sediments pointed to strong bonding of trace elements to sediment mineral phases. The analyses of marine flora pointed to higher eutrophication, which disturbs the balance between communities and natural habitats.     

Organic tracers in sediments from the coastal zone of Ras Abu el-Darag,Gulf of Suez

Sediment samples from the coastal zone of the Gulf of Suez contain a variety of organic compounds from anthropogenic and natural sources. A total of 12 surface samples of bottom sediments were collected with an Ekman grab sampler along an off-shore transect south of Ras Abu el-Darag. The samples were extracted with a mixture of dichloromethane and methanol (3:1 v/v) after drying and sieving through 250 μm mesh. The extracts were derivatized and analyzed by gas chromatography–mass spectrometry in order to characterize the chemical composition and sources of the organic components. Marine with minor terrestrial biota were the major natural sources of organic tracers and included n-alkanoic acids, sterols and saccharides (5.7–76.7%). Anthropogenic sources, from petroleum related activities, detergent usage for spill cleaning and littering, are indicated by the presence of n-alkanes with carbon preference index ≤1.0, hopanes, steranes, unresolved complex mixture of branched and cyclic hydrocarbons, alkyl nitriles, alkamides and plasticizers. Their total relative concentrations ranged from 23.3 to 97.3% of the total extracts. Petroleum residues from natural seepage may also be part of these hydrocarbons. The levels of anthropogenic inputs decrease from about 94% in coastal zone sediments to about 20% in sediments from the reef front.     

Mineralogy,geochemistry, and radiocarbon ages of deep sea sediments from the Gulf of Mexico,Mexico

The mineralogy, geochemistry, and radiocarbon ages of two sediment cores (GMX1 and GMX2) collected from the deep sea area of the Southwestern Gulf of Mexico (∼876–1752 m water depth) were studied to infer the sedimentation rate, provenance, heavy metal contamination, and depositional environment. The sediments are dominated by silt and clay fractions. The mineralogy determined by X-Ray diffractometry for the sediment cores reveals that montmorillonite and muscovite are the dominant clay minerals. The sections between 100 and 210 cm of the sediment cores GMX1 and GMX2, respectively, are characterized by the G. menardii group and G. Inflata planktonic foraminiferal species, which represent the Holocene and Pleistocene, respectively. The radiocarbon-age measurements of mixed planktonic foraminifera varied from ∼268 to 45,738 cal. years B.P and ∼104 to 25,705 cal. years B.P, for the sediment cores GMX1 and GMX2, respectively. The variation in age between the two sediment cores is due to a change in sediment accumulation rate, which was lowest at the location GMX1 (0.006 cm/yr) and highest at the location GMX2 (0.017 cm/yr).The chemical index of alteration (CIA), chemical index of weathering (CIW), and index of chemical maturity (ICV) values indicated a moderate intensity of weathering in the source area. The total rare earth element concentrations (∑REE) in the cores GMX1 and GMX2 vary from ∼94 to 171 and ∼78 to 151, respectively. The North American Shale Composite (NASC) normalized REE patterns showed flat low REE (LREE), heavy REE (HREE) depletion with low negative to positive Eu anomalies, which suggested that the sediments were likely derived from intermediate source rocks.The enrichment factor of heavy metals indicated that the Cd and Zn concentrations in the sediment cores were impacted by an anthropogenic source. The redox-proxy trace element ratios such as V/Cr, Ni/Co, Cu/Zn, (Cu + Mo)/Zn, and Ce/Ce* indicated that the sediments were deposited under an oxic depositional environment. The similarity in major element concentrations, REE content, and the NASC normalised REE patterns between the cores GMX1 and GMX2 revealed that the provenance of sediments remained relatively uniform or constant during deposition for ∼4.5 Ma. The major and trace element based multidimensional discrimination diagrams showed a rift setting for the core sediments, which is consistent with the geology of the Gulf of Mexico.     

Organic carbon isotope ratios of recent sediments from coastal lagoons of the Gulf of Mexico,Mexico

The stable carbon isotope composition sedimentary organic carbon was determined in the sediments of seven coastal lagoons of the Gulf of Mexico, Mexico. For most of the lagoons the δ¹³C values for sediments ranged from ?20.1 to ?23.9%. Anomalously low values, ?26.8 to 29.3%. were determined in sediments of two of the studied lagoons, probably due to the presence of organic carbon from anthropogenic sources, naturally absent in these environments. The δ¹³C values determined in the tissues of oysters collected at the same time in the different lagoons were very similar to those recorded in the sediments.     

Organic contamination identification in sediments from a Mediterranean coastal ecosystem: The case of the Nador lagoon (Eastern Morocco)

The Nador lagoon ecosystem (North-East of Morocco) displays a major socioeconomic interest. In fact, it is essential to evaluate consequences of anthropogenic activities in the lagoon especially by organic matter studies (nature and distribution) in the sedimentary compartment. Surface sediments show variable rates in total organic carbon and in sulfur, high in some cases (7.5 and 1.8% respectively). These high contents are recorded in the center of the lagoon. Their distributions are controlled by the hydrodynamism and the anthropogenic degree. The molecular biomarkers analyses and especially n-alkanes distribution reveal: a zone of marine influence; and a zone of continental influence. The occurrence of pentacyclic triterpanes with a typical distribution of a thermally mature organic matter reveals a contamination due to petroleum products in the entire lagoon except for the center. Coprostanol occurrence near cities indicates wastewater effluents inputs and reducing conditions underlined by high values of stanols/sterol ratios. Thus, the organic contamination (petroleum by-products and wastewater effluents) occurs in the vicinity of the cities whereas the littoral edge and center remain weakly affected by these contaminations.     

Metal contamination and retention of the former mining site Schwarzwand (Salzburg,Austria)

The Schwarzwand is a unique hygric, Cu-contaminated habitat formed by mining activities from the 16th to 18th century. Today, a large spoil heap and several creeks fed by Cu-rich mine drainage are present. The vegetation of the Schwarzwand differs clearly from the surrounding subalpine forests. It is by no means impoverished but rather a hotspot of biodiversity. Interestingly, most of the Cu precipitates within the Schwarzwand and the creeks leave the Schwarzwand virtually clean. This study maps the distribution of Cu within the Schwarzwand and within selected vascular plants, moss and microorganisms and correlates them with water and soil chemistry in order to identify the sinks of Cu and to elucidate the remarkable capability of the Schwarzwand for natural attenuation.Two types of water could be distinguished, one acidic precipitating limonite with a constant Cu content of about 0.6 mg L⁻¹, and one circumneutral, which decreases far more rapidly in Cu content than would be expected due to chemical considerations. A dense microbial mat covering most of the bed of the circumneutral creeks could be identified as the main sink. It consists of the cyanobacterium Phormidium sp. and retains Cu both by adsorption to mucilaginous sheaths and by precipitation as secondary minerals such as sampleite. Layers of dead biofilm can be found covered by a few centimetres of soil at the banks of the circumneutral creeks; the extremely high concentration and the low solubility of Cu in this soil indicates permanent immobilisation of the metals. High concentrations of Cu were also found in mosses of the family Bryaceae which, however, play a negligible role for the metal retention of the habitat due to their low biomass.The retention of Cu within the Schwarzwand is a remarkable example of the sustainable self-cleaning of a contaminated habitat which takes place without any human intervention. The artificial establishment of microbial communities similar to the Schwarzwand could result in cheap and sustainable strategies for the remediation of suitable metal-contaminated waters.     

A study of coastal transformation at Tuticorin as a result of emerged and submerged natural breakwaters of Van Island,Gulf of Mannar

Similar to artificial offshore structures, natural structures such as an island also protect the low-lying shoreline and shape the pocket beaches. In the Gulf of Mannar, many long islands have formed protruding from shorelines. Formation of these indirect morphological structures depends upon a number of factors, such as the width of the island, offshore distance of the island to the morphological structure, supply of sediments and other geological conditions. The hydrodynamic conditions between Tuticorin Harbour and Van Island have changed because of various factors over the years. Van Island coral reef formation had attracted man-induced mining causing irreparable damage to the fragile ecosystem. The emerged natural breakwater and the submerged coral reef, together with the artificial breakwaters of Tuticorin Harbour, have been contributory to quantifiable change in hydrodynamic conditions around Tuticorin. As a result, the transmission of wave power to the shoreline has increased and the salient growth at Salaipatorri Point, Tuticorin, has started to recede. The bathymetric chart published in 1978 is used for all dimensions of Van Island and receding salient growth at Salaipatorri Point.     

Influence of mining activity on the downstream sediments of scheelite mines in Currais Novos (NE Brazil)

The study area is one of the most important mineral provinces of the Rio Grande do Norte State (NE Brazil), which has been extensively exploited since 1940. This article presents a geochemical investigation of stream sediments taken in the drainage system between the Brejuí and Barra Verde scheelite mines, and the Gargalheiras municipal reservoir, in Acari city. In addition to the major elements, the trace elements V, Cr, Co, Ni, Cu, Zn, As, Rb, Sr, Zr, Mo, Sn, Ba, W were analyzed and compared to metal levels reported in the literature for the same area. The elements W, Mo, Cu, Sn and in part Zn are enriched in sediments of rivulets forming the drainage system close to the mining district. This is due to emission from uncovered mine waste dumps. Dispersion of elements is controlled by both, aeolian as well as fluvial transport. The concentration of Cu in stream sediments close to the mines reaches toxic levels. At the mouth of the drainage system to the reservoir, the elements W and Mo are still enriched in the stream sediments relative to the geogenic background by factors of 15 and 11, respectively. This indicates the probable influence of mining activity to the reservoir sediments, and mobilization of W and Mo in the reservoir water cannot be ruled out.     

Heavy metal contamination in overbank sediments of the Geul river (East Belgium): Its relation to former Pb-Zn mining activities

Overbank sediments of the Geul River (East Belgium) are highly contaminated by the heavy metals Pb, Zn, and Cd due to former Pb-Zn mining activities in the drainage basin. Geochemical variations in vertical overbank sediment profiles sampled 1 km north of the mine tailings of Plombiéres allow metal fluxes back to the 17th century to be reconstructed. The vertical profiles are subdivided into three major units corresponding to different industrial periods based on sedimentological criteria as well as on the distribution of contaminants. Alluvial sediments with the highest heavy metal concentrations correspond to the major period of mining activity of the 19th century. The fact that Zn mining at the La Calamine open mine started before large-scale mining of the PbS-ZnS subsurface exploitations is reflected in the vertical profiles by an increase in Zn content before a marked increase in Pb and Cu. The regional extent of contamination in the alluvial deposits was evaluated on the basis of the geochemical analysis of sediments at depths of the 0–20 cm and 80–100 cm. Most of the upper samples are extremely contaminated. Significant local variations in heavy metal concentration in the lower samples are interpreted in terms of which overbank sediment horizon has been sampled at a depth of 80–100 cm. This indicates that blind sampling of overbank sediments to characterize the degree of contamination in shallow boreholes can give very erratic results.     

Application of micromagnetic mapping for defining geological and anthropogenic heterogeneities in recent coastal sediments of the Ekspeditsii Bay (Petr Velikii Gulf, Sea of Japan)

The comprehensive analysis of the multiparameter and diverse information made it possible to reconstruct sedimentation patterns in the coastal zone of the Ekspeditsii Bay at the recent development stage of the geological environments. Geological and anthropogenic sources of the anomalous magnetic field are distinguished based on the measured module of a complete magnetic field vector. It is inferred that sedimentary material constituting the cultural layer in the Kraskino site of the ancient settlement that represents the largest archeological monument of the Bohai State in the Primorye region originates from different sources. The internal topography of the cultural layer of the medieval flat site of the ancient settlement is first reconstructed in the southern Russian Far East based on a micromagnetic survey with defining of the most informative objects important for understanding the cultural-historical development of the archaeological monument.     

Soil contamination from urban and industrial activity: example of the mining district of Linares (southern Spain)

The Linares region (southern Spain) has been subjected to two important sources of pollution: the intensive mining works and the urban-industrial activity. To obtain a geochemical characterisation of the soil, 31 trace elements were analysed and 669 soil samples were collected. By means of clustering analysis, we identified groups of elements and grid squares in which relations could be established concerning soil lithology, urban and industrial activities and the degree of pollution impact; in addition, we were able to characterise the geochemical background of the study area. The multivariate study led us to identify four factors. Particularly important was factor 2, which represented the elements associated with mineral paragenesis (Cu, Pb, As, Co, Mn, Zn, Sn, Ba). This factor also contains elements related with an urban-industrial activity, such as Pb, Cu, Zn, As and Ba. Furthermore, we identified factor 4, associating Ni, V and Cr, and which is related to the use of fuels.     

Geostatistical estimation of chemical contamination in stream sediments: The case study of Vale das Gatas mine (northern Portugal)

Based on an environmental geochemistry case study carried out in the neighbourhood of a W–Sn abandoned mine, the pollution in stream sediments was modelled through a Global Contamination Index. Such an index permits one to summarize the combination of deleterious elements in a single variable, obtained by the projection of samples onto the first axis of a PCASD (Principal Components Analysis of Standardized Data) applied to the entire n × p matrix containing the available concentrations of p = 16 elements in the set of n = 220 collected samples.In order to provide a sound basis for a coherent planning of the remediation process which will be put in operation in the affected area, it is necessary to balance the costs of reclaiming with the probabilities of exceeding the upper limits accepted for concentrations of environmentally harmful elements in sediments. Given these limits, they are back-transformed in the index values, providing a practical threshold between ‘clean’ and ‘contaminated’ samples. On the other hand, the minimum dimension of the cell to be reclaimed is restrained by the selected remediation process to be applied in the affected area. Hence, to meet the constraints of such a remediation process, it is required to estimate the probabilities of exceeding the index threshold in technologically meaningful sub-areas. For this end, the Indicator Block Kriging technique was applied, producing a series of maps where sub-areas to be reclaimed can be spotted for different probability levels. These maps, on which the decision making remediation agency can rely for its cost-benefit analysis, take into account both the spatial structure of ‘clean’ vs. ‘contaminated’ samples and the constraints of the reclaiming process.