Assessment of mercury mobility and bioavailability by fractionation method in sediments from coastal zone inundated by the 26 December 2004 tsunami in Thailand

The 26 December 2004 tsunami covered significant portion of a coastal zone with a blanket of potentially contaminated sediments. In this report are presented results on mercury concentrations in sediments deposited by the tsunami in a coastal zone of Thailand. Since the total mercury concentrations are insufficient to assess mercury mobility and bioavailability in sediment, its fractionation was applied. Sediments were sampled within 50 days after the event and analyzed by sequential extraction method. The procedure of sequential extraction involved five subsequent stages performed with solutions of chloroform, deionized water, 0.5 M HCl, 0.2 M NaOH, and aqua regia. The mean concentration of total mercury in sediments was 119 ± 50 ng g⁻¹ dry mass (range 66–230). The fractionation revealed that mercury is mainly bound to the least bioavailable sulphides 75 ± 6% (range 62–86), organomercury compounds 14 ± 7% (range 4–26), and humic matter 9 ± 7% (range 1–27). The lowest contributions bring fractions of water-soluble mercury 0.8 ± 1.0% (range 0.1–3.6) and acid soluble mercury 0.9 ± 0.5% (range 0.2–2.1). Although, the total mercury content is similar in a reference sample and in the tsunami sediments, the highly toxic organomercury fraction contribution is higher in the latter. The results were compared with chemical and sedimentological properties of the sediments but no significant correlations were obtained between them.     

Mercury mobility in mine waste from Hg-mining areas in Almería,Andalusia (Se Spain)

Mining wastes and calcines from two abandoned mining areas (Valle del Azogue and Bayarque in Almería) have been characterized. In the mining wastes, the dominant mercury phases are cinnabar and elemental mercury in the matrix. In the calcines, however, the dominant mercury phase is elemental mercury bounded to the matrix. Water-leaching experiments were conducted on low-grade stockpiles and calcines in order to simulate the mobilization of mercury by runoff under environmental conditions. The laboratory column-leaching experiments show a possible mobilization of mercury from Hg⁰ dissolution, colloid transport and a possible dissolution of calomel and other soluble phases in the mine wastes from the Valle del Azogue and Bayarque mines. Equilibrium speciation modeling of Hg, conducted using the numerical code MINTEQ, showed that the theoretical dominant mercury species in the calcine and mining wastes samples are Hg(OH)₂, HgCl₂, HgClOH and Hg⁰. In some leachates obtained from the Valle del Azogue mining wastes (sample A06), the high Hg concentrations may indicate the possible dissolution of mineral phases such as calomel and other soluble phases, which are subsaturated. The environmental results indicate a great environmental mobility of mercury, especially during wet episodes associated with intense precipitation events, when there are significative amounts of secondary soluble minerals.     

Speciation and mobility of heavy metals in mud in coastal reclamation areas in Shenzhen,China

Coastal reclamation has been carried out along the coastal areas near Shenzhen, China in a large scale since 1980s by dumping fill materials over the marine mud at the sea bottom. Usually the area to be reclaimed is drained first and some of the mud is air-dried for a few weeks before it is buried by fill. After reclamation, the terrestrial groundwater, which is relatively acidic and with high dissolved oxygen, gradually displaces the seawater, which is alkaline with high salinity. The changes in the burial conditions of mud and the properties of the pore water in the mud may induce the release of some heavy metals into the mud. Field survey confirms that the pH and salinity of the groundwater in the reclamation site are much lower than the seawater. Chemical analyses of mud and groundwater samples collected from the reclamation sites reclaimed in different years indicate that most of the heavy metals in the mud decrease gradually with time, but the heavy metals in the groundwater are increased. The release of heavy metals into pore water due to reactivation of heavy metals in the mud is of environmental concern. To understand why some of the heavy metals can be released from the mud more easily than others, a sequential extraction method was used to study the operationally determined chemical forms of five heavy metals (Cu, Ni, Pb, Zn, and Cd) in the mud samples. Heavy metals can be presented in five chemical forms: exchangeable, carbonate, Fe–Mn oxide, organic, and residual. Ni and Pb were mainly associated with the Fe–Mn oxide fraction and carbonate fraction; Zn was mainly associated with organic fraction and Fe–Mn oxide fraction, while Cu and Cd were associated with organic fraction and carbonate fraction, respectively. If the residual fraction can be considered as an inert phase of the metal that cannot be mobilized, it is the other four forms of heavy metal that cause the noticeable changes in the concentration of heavy metals in the mud. On the basis of the speciation of heavy metals, the mobility of metals have the following order: Pb (36.63%) > Cu (31.11%) > Zn (20.49%) > Ni (18.37%) > Cd (13.46%). The measured metal mobility fits reasonably well with the degree of concentration reduction of the metals with time of burial observed in the reclamation site.     

Mercury contamination of active channel sediment and floodplain deposits from historic gold mining at Gold Hill,North Carolina,USA

A reconnaissance investigation of mercury contamination associated with historic gold mining in North Carolina, USA, revealed high concentrations of mercury in channel and floodplain sediments downstream from the Gold Hill mining district. The most intense period of mining activities in this region occurred in the 1840s and 1850s when mercury amalgamation was used to recover fine gold particles from milled ore. This paper evaluates mercury concentrations measured in active channel sediments and two cores recovered from historic floodplain deposits of the lower portion of Dutch Buffalo Creek. Mercury concentrations in these cores range from 0.01 to 2.2 mg/kg, with maximum concentrations more than 35 times background levels. A later peak in copper concentrations is associated with the operation of a large copper mine between 1899 and 1906. Following the most intense periods of mining, both mercury and copper concentrations decrease upcore to constant levels of about twice pre-mining background concentrations. Results suggest that vertical trends in mercury and other trace metals provide a useful tool for interpreting rates of historic floodplain sedimentation in the Piedmont of North Carolina.     

Total concentration,speciation and mobility of potentially toxic elements in soils around a mining area in central Iran

The current study was designed to investigate the extent and severity of contamination as well as the fractionation of potentially toxic elements (As, Cd, Cr, Cu, Pb, Zn, Ni) in minesoils and agricultural soils around a Pb–Zn mine in central Iran. For this purpose, 20 agricultural soils and eight minesoils were geochemically characterized. Results showed that minesoils contained elevated concentrations of As (12.9–254 mg kg⁻¹), Cd (1.2–55.1 mg kg⁻¹), Pb (137–6239 mg kg⁻¹) and Zn (516–48,889 mg kg⁻¹). The agricultural soils were also polluted by As (5.5–57.1 mg kg⁻¹), Cd (0.2–8.5 mg kg⁻¹), Pb (22–3451 mg kg⁻¹) and Zn (94–9907 mg kg⁻¹). The highest recorded concentrations for these elements were in soils influenced directly by tailing ponds. Chromium, Cu and Ni content in agricultural soils (with average value of 74.1, 34.6 and 50.7 mg kg⁻¹, respectively) were slightly higher than the minesoils (with average value of 54.5, 33.1 and 43.4 mg kg⁻¹, respectively). Sequential extraction data indicated that there were some differences between the speciation of PTEs in soil samples. In the agricultural soils, Zn and Cd were mainly associated with carbonate bound fraction, As and Pb with reducible fraction, Cu with oxidisable fraction and Cr and Ni with residual phase. With respect to mobility factor values, Zn and Cd in the agricultural soils have been found to be the most mobile while As mobility is negligible. Also, the mobility factor of As, Cd and Pb in agricultural soils adjoining tailing ponds was high. In minesoil sample Cd was most abundant in the carbonate form, whereas other studied elements were mainly present in the reducible and residual fractions; therefore, despite the high total concentrations of As, Pb and Zn in the minesoils, the environmental risk of these elements was low. Based on the obtained data, a portion of Cu, Cr and Ni input was from agricultural activities.     

A model for estimating the value of sampling programs and the optimal number of samples for contaminated soil

A model is presented for estimating the value of information of sampling programs for contaminated soil. The purpose is to calculate the optimal number of samples when the objective is to estimate the mean concentration. A Bayesian risk–cost–benefit decision analysis framework is applied and the approach is design-based. The model explicitly includes sample uncertainty at a complexity level that can be applied to practical contaminated land problems with limited amount of data. Prior information about the contamination level is modelled by probability density functions. The value of information is expressed in monetary terms. The most cost-effective sampling program is the one with the highest expected net value. The model was applied to a contaminated scrap yard in Göteborg, Sweden, contaminated by metals. The optimal number of samples was determined to be in the range of 16–18 for a remediation unit of 100 m². Sensitivity analysis indicates that the perspective of the decision-maker is important, and that the cost of failure and the future land use are the most important factors to consider. The model can also be applied for other sampling problems, for example, sampling and testing of wastes to meet landfill waste acceptance procedures.     

Accumulation and speciation of selenium in evaporation basins in California,USA

The accumulation of selenium in evaporation basins (or ponds) in the San Joaquin Valley, California is of a great concern due to its potential hazards to environments. In this study, the accumulation, speciation and concentrations of Se were examined in waters as well as sediments in a system of the evaporation ponds. A significant decrease in the total dissolved Se concentration in Cell 1 in which drainage water with higher Se concentration was pumped from Inlet Channels indicated that the immobilization of Se was active in the Cell 1 and resulted in the higher Se concentration in sediments compared to the terminal cell such as Cell 9. The percentage of reduced Se species such as selenite [Se(IV)] and org-Se of total Se in drainage waters was also found increased in Cell 1 compared to Inlet Channels. The total dissolved Se concentrations in water along flow paths from Cell 1 were relatively constant except for terminal cells such as Cells 9 and 10, which showed higher total dissolved Se concentrations due to evapoconcentration. The percentage of reduced Se forms of total Se was inversely proportional to the percentage of Se(VI) depending on the redox condition of evaporation ponds along the flow paths. Sequential extractions of Se species in sediments indicated that organic associated Se and elemental Se were prevalent forms in sediments in the ponds system. The higher concentrations of elemental Se and organic associated Se in sediments in Cell 1 indicated that the immobilization of Se was active in the sediments compared to Cell 9, while the percentage of both fractions of total Se in sediments in Cells 1 and 9 was relatively constant. The organic materials from algae might provide carbon sources for Se reduction and Se sink in sediments in its elemental and organic associated forms.     

Contamination of soil and grass in the Tsumeb smelter area,Namibia: Modeling of contaminants dispersion and ground geochemical verification

The area of the city of Tsumeb in northern Namibia is strongly affected by gaseous emissions and by dust fallout from the local smelter. This is also reflected in increased concentrations of lead and arsenic in blood and urine of the residents. Consequently, modeling of the dispersion of dust and SO₂ emissions from the smelter was used in this study to delineate the contaminated area and to assess the health risks. The modeling results were verified by ground-based geochemical survey of soil and grass in the area. The results of modeling revealed that the concentrations of SO₂ in the Tsumeb town were relatively low, whereas the highest dust fallout concentrations were found around the Tsumeb smelter. The Tsumeb town residential area was less affected due to favorable landscape morphology between the smelter and the city (the Tsumeb Hills).The results of modeling of dust fallout and geochemical survey coincided very well. Since the anthropogenic contamination was bound only to the surface layer of soil, the local soils were sampled at two depth horizons: topsoil and the deeper soil horizon. This enabled us to distinguish between the anthropogenic contamination of soil surface from natural (geogenic) concentrations of studied metals in the deeper part of the soil profile. Concentrations of metals in grass correlated with the concentration of metals in topsoil.In contrast to a good conformity with the modeling of dust fallout from the smelter and geochemical survey, the results of modeling of SO₂ contents in the air, and total sulfur content in soils were different. Differences can be explained by additional sources of contamination, as for example a sulfate-rich dust fallout from local tailings ponds and slag dumps that were not considered in the SO₂ dispersion model.The results of the present investigation can be used by the mining companies in the management of air quality, assessment of the efficacy of applied remediation measures, and in reducing the impact of dust fallout on the local ecosystem. The Municipal Administration may use these results to plan further development of the city of Tsumeb, especially in terms of further expansion of housing construction.     

Metal retention in a thin karstic soil, Christian County, Missouri

 The response of a Wilderness cherty loam series soil to repeated dosages of metals (as sewage sludge) using a two-step sequential extraction procedure was investigated. Variations in metal content between amended and control soils were related to organic matter, clay content, and clay mineralogy. Of the four metals investigated, Cu was found to accumulate in the top 20 cm of amended soils; Pb and Zn were present in even smaller amounts with respect to the control soils, and Cr concentrations were unaffected with respect to both depth and amendment. None of the metals indicated accumulation in deeper (>20 cm) parts of the soil profile. Overall, results suggest that the metals remobilize in the top 20 cm, being readily uptaken by the fescue grass growing in this lot. Precipitation of insoluble forms of metal into deeper parts of the soil profile was proven unlikely based on the distribution of metal concentrations throughout the profile. Received: 15 December 1997 · Accepted: 23 March 1998     

Geochemical fractionation of Ni,Cu and Pb in the deep sea sediments from the Central Indian Ocean Basin: An insight into the mechanism of metal enrichment in sediment

Metal speciation study in combination with major element chemistry of deep sea sediments provided possible metal enrichment pathways in sediments collected from environmentally different locations of Central Indian Ocean Basin (CIB). Metal speciation study suggests that Fe–Mn oxyhydroxide phase was the major binding phase for Ni, Cu and Pb in the sediments. The second highest concentrations of all these metals were present within the structure of the sediments. Easily reducible oxide phase (within the Fe–Mn oxyhydroxide binding phases) was the major host for all the three metals in the studied sediments. Major element chemistry of these sediments revealed that there was an increased tendency of Cu and Ni to get incorporated into the deep sea sediment via the non-terrigenous Mn-oxyhydroxide fraction, whereas, Pb gets incorporated mostly via amorphous Fe-hydroxides into the sediment from the CIB. This is the first attempt to provide an insight into the mechanism of metal enrichment in sediment that host vast manganese nodule.     

Quantification of methylmercury and geochemistry of mercury in sediments from a contaminated area of Descoberto (MG), Brazil

In 2002, metallic Hg was found buried in a rural area of Descoberto city, Brazil. The origin of the Hg was a gold mining explotation plant established nearly one century ago. Although a number of studies have been conducted in order to assess the contamination of the area, none of them investigated the presence of methylated Hg in the hydric system. In this work methylmercury (CH₃Hg⁺) was determined using gas chromatography-pyrolysis-atomic fluorescence detection (CG-pyro-AFS) in material from rain sedimentation boxes and stream sediments near the contaminated area. Total Hg concentration (HgT) along with the chemical speciation by thermo-desorption were performed. HgT in material from the sedimentation boxes was found to be very high, up to 41,580 μg kg⁻¹, even in the rainy season, when in general HgT were much lower than in dry season. The samples from the Grama and Rico streams show a range of HgT from 5.8 to 266 μg kg⁻¹. The thermo-desorption analysis showed predominance of Hg²⁺, possibly linked to organic sulfur, suggested by a good positive correlation between Hg²⁺, HgT, organic mater (OM) and total S. The CH₃Hg⁺ concentration in stream sediment samples ranged from <0.07 to 1.87 μg kg⁻¹ and in the samples of sedimentation boxes the concentrations were 1.33 and 8.0 μg kg⁻¹ during dry season. The sample with the highest percentage of HgT as Hg²⁺ (98%) presented also the highest percentage of CH₃Hg⁺ (0.7%). These are high values, showing that care should be taken to avoid the transport of this material to the hydrological system. Further studies on the transfer through the food chain would be very important.     

Changes in mobility and speciation of heavy metals in clay-amended incinerator fly ash

The generation of municipal solid waste incinerator fly ash (MSWIF) has been increasing significantly over the recent past, and its disposal is problematic and costly due to high concentration of leachable heavy metals present in the material. This study explored a potential stabilization of MSWIF by blending with a natural sorbent material with low permeability, clay, and assessed the potential release of heavy metals from the stabilized mixtures under various simulated subsurface environments. The leachability of heavy metals such as Pb, Cd, Cr, Zn and Cu in the MSWIF-clay mixtures cured for 1 to 360 days was investigated by performing leaching tests and sequential chemical extractions (SCE). Leaching tests were performed at acidic, neutral and alkaline pH values. The leaching test results suggested that the natural clay could turn the MSWIF into non-hazardous material. All the MSWIF-clay mixtures demonstrated leaching behavior different from that of the original MSWIF. SCE results revealed that the acidic and reducing conditions were the most unfavorable to the immobilization of the heavy metals in the stabilized MSWIF-clay matrix. Conversely, the oxidizing and alkaline conditions were not critical to the stabilized MSWIF-clay mixtures. Apparently, clay in the mixtures could function as an adsorptive micro-barrier to retain the heavy metals within the MSWIF-clay matrices.     

Mercury speciation and mobilization in contaminated soils of the Valle del Azogue Hg mine (SE,Spain)

Hg mobilization from contaminated soils and mine wastes was the source of environmental contamination in the Valle del Azogue mining area. We researched solid-phase speciation and aqueous mobility of Hg through Scanning electron microscopy-energy dispersive X-ray spectroscopy and electron probe microanalysis analysis, solid-phase-Hg-thermo-desorption (SPTD) and laboratory column experiments. We found that in contaminated soils and mine wastes, the predominant Hg species was cinnabar (HgS), mainly formed from the weathering of Hg-rich pyrite, and metallic Hg (0) in the matrix, whereas in calcines and tailings the dominant species was metallic Hg (0). The mobilization of Hg in the aqueous phase seems to have originated from the dissolution of elemental Hg (0) present in soils and wastes, reaching concentrations of up to 67 μg l⁻¹, and showing a higher long-term environmental potential risk, in addition to atmospheric emissions.     

Factors controlling the heterogeneous distribution of Cr(VI) in soil, plants and groundwater: Evidence from the Assopos basin, Greece

The effective influence of industry or ultramafic rocks by natural processes to soil, plants and groundwater contamination by chromium, which is often a subject of debate, was investigated for the case of the Assopos basin, Greece. The Neogene Assopos basin, is mainly composed by Tertiary and Quaternary sediments of more than 400 m thick and is characterized by brittle type deformation (fault zones, faults). Chromium in soil, ranging from 67 to 204 ppm, is mostly hosted in chromite, Fe-chromite, Cr-bearing goethite and silicates.Special attention was given to the plants, which are a major source of organic matter that serves as the driving force for Cr(VI) reduction. The increase of the Fe, Mn and Ni contents, with the increasing Cr content in the plant-roots, in particular at the external parts of roots and those of bulb-type plants, suggest reduction and immobilization of Cr(VI) and that redox reactions play a significant role to the translocation processes from root to shoot.Groundwater samples from the Assopos aquifer showed a wide spatial variability, ranging from <2 to 180 ppb Cr_total content [almost same to the Cr(VI)-values] despite their spatial association. The presence of Cr(VI)-contaminated groundwater at depths >200 m is attributed to a direct injection of Cr(VI)-rich industrial wastes at depth rather than that Cr(VI) is derived from the Assopos river or by the interaction between water and Cr-bearing rocks. The heterogeneous distribution of Cr in groundwater may be related with the intense neotectonic deformation, as is exemplified by several sharp tectonic contacts between sediment types, while the Cr content in soil is mostly depend on the transported chromite grains.     

Spatial analysis and hazard assessment of mercury in soil around the coal-fired power plant: a case study from the city of Baoji, China

Based on systematic sampling of soil around the coal-fired power plant (CFPP), the content of Hg was determined, using atomic fluorescence spectrometry. The result shows that the content of Hg in soil is different horizontally and vertically, ranges from 0.137 to 2.105 mg/kg (the average value is 0.606 mg/kg) and is more than the average content of Hg in Shaanxi, Chinese and world soil. In this study, spatial distribution and hazard assessment of mercury in soils around a CFPP were investigated using statistics, geostatistics and geographic information system (GIS) techniques. Ordinary kriging was carried out to map the spatial patterns of mercury and disjunctive kriging was used to quantify the probability of the Hg concentration higher than the threshold. The maps show that the spatial variability of the Hg concentration in soils was apparent. These results of this study could provide valuable information for risk assessment of environmental Hg pollution and decision support. An erratum to this article can be found at     

Selective chemical extraction of heavy metals in tailings and soils contaminated by mining activity: Environmental implications

Total concentrations of chemical elements in soils may not be enough to understand the mobility and bioavailability of the elements. It is important to characterise the degree of association of chemical elements in different physical and chemical phases of soil. Another geochemical characterisation methodology is to apply sequential selective chemical extraction techniques. A seven-step sequential extraction procedure was used to investigate the mobility and retention behaviour of Al, Fe, Mn, Cu, Zn, Pb, Cr, Co, Ni, Mo, Cd, Bi, Sn, W, Ag, As and U in specific physical–chemical and mineral phases in mine tailings and soils in the surroundings of the abandoned Ervedosa mine. The soil geochemical data show anomalies associated with mineralised veins or influenced by mining. Beyond the tailings, the highest recorded concentrations for most elements are in soils situated in mineralised areas or under the influence of tailings. The application of principal components analysis allowed recognition of (a) element associations according to their geochemical behaviour and (b) distinction between samples representing local geochemical background and samples representing contamination. Some metal cations (Mn, Cd, Cu, Zn, Co, Cr, Ni) showed important enrichment in the most mobilisable and bioavailable (i.e., water-soluble and exchangeable) fractions due likely to the acidic conditions in the area. In contrast, oxy-anions such as Mo and As showed lower mobility because of adsorption to Fe oxy-hydroxides. The residual fraction comprised largest proportions of Sn and Al and to a lesser extent Zn, Pb, Ni, Cr, Bi, W, and Ag, which are also present at low concentrations in the bioavailable fractions. The elements in secondary mineral phases (mainly Fe, Mn, Cu, Zn, Cd, Pb, W, Bi, Mo, Cr, Ni, Co, As and U) as well as in organic matter and sulphides are temporarily withheld, suggesting that they may be released to the environment by changes in physico-chemical conditions.     

A GIS-based approach for detecting pollution sources and bioavailability of metals in coastal and marine sediments of Chabahar Bay,SE Iran

Chabahar Bay in SE of Iran is a shallow semi-enclosed environment affected by anthropogenic activities. In this paper, 19 sediment samples were collected and concentration of selected metals (Cu, Pb, Zn, Cd, Ni, Cr, Co, V and Fe) was determined using ICP-MS analytical method. Sediment samples from five stations were also selected for sequential extraction analysis and concentration of metals in each fraction was determined using ICP-OES. In order to investigate the environmental quality of Chabahar Bay, geographic information system (GIS) along with geochemical data, environmental indices and statistical analyses were used. Calculated contamination degree (C_d) revealed that most contaminated stations (Ch3, S1 and S3) are located SE of Chabahar Bay and contamination decreases in a NW direction. The S9 station, west of the bay, is also contaminated. High organic matter (OM) content in the sediments is most likely the result of fuel and sewage discharge from fishing vessels along with discharge of fishing leftovers. Significant correlation coefficient among OM, Fe, Cu, Pb, Zn and Cd seemingly reflects the importance of the role that OM and Fe oxy-hydroxides play in the metals mobility. The results of hierarchical cluster analysis (HCA), computed correlation coefficient and sequential extraction analysis suggest that Cu, Pb, Zn and Cd probably come from antifouling and sea vessel paints, while Ni, Cr, Co, V and Fe are most likely contributed by ophiolitic formations located north of the bay and/or deep sea sediments. Average individual contamination factors (ICFs) indicated that the highest health hazard from the bay is posed by Cu, Pb and Zn.     

Impact of mining activities on soils and sediments at the historical mining area in Podljubelj,NW Slovenia

The abandoned Hg mine in Podljubelj was in operation with interceptions from 1557 to 1902. The entire operating period yielded about 110 000 tons of ore, from which 360 tons of Hg was produced. The objective of the research project was to establish the contents and spatial distribution of Hg in soils and stream sediments in the vicinity of the mine. On an area of 88 ha the soil was sampled in a 100 × 100 m grid. Two soil horizons (0–5 cm and 20–30 cm) were sampled in order to distinguish between geogenic and anthropogenic Hg sources. It was established that on an area of about 9 ha Hg content in soil exceeds The New Dutchlist action value for Hg (10 mg/kg). Total Hg concentrations in soil samples vary between 0.17 and 719 mg/kg, with a mean of 3.0 mg/kg. Mercury contents in stream sediments range from 0.065 to 1.4 mg/kg, with a mean of 0.64 mg/kg. The highest determined value in soils was found in the area around the former roasting furnace, where the ore was processed. Increased Hg concentrations were also found on the mine waste dump (108 mg/kg). Mercury contents in soils generally decrease with soil profile depth and with the distance from the mine and from the roasting furnace location. Mercury also appears in higher concentrations along the road that runs through the valley, which results from the use of Hg-bearing ore residues in road construction. The average enrichment factor (EF) of Hg in topsoil with respect to subsoil is 3.3. Calculated enrichment factors show higher values also for Cd (3.2), Pb (2.7), Ca (2.4) and P (1.9). The average enrichment factor of Hg in topsoil with regard to the established Slovenian soil averages (EF_slo) is 19. EF_slo of other determined chemical elements do not exceed 3.0.     

Analysis of the distribution coefficients and mobility characteristics of phenols in different soil types

Adsorption studies were carried out on soil samples of high organic and low organic content to analyze the distribution coefficient and mobility of phenols. The results show that the amount of phenols adsorbed by the soil varies linearly with the fraction of organic carbon. Soils that are highly organic compared to those with low organic matter content retain the phenols to a greater extent. Adsorption studies on the different soil types indicated that the extent of adsorption of phenols by different kinds of soils is important, as a smaller amount of adsorption by the soil increases the risk of contamination of the groundwater supply.     

石嘴山地区碱性土壤硒地球化学特征及生物有效性

以石嘴山地区碱性土壤为研究对象,全面采集了石嘴山地区表层土壤样品,分析了土壤中硒及有效硒等地球化学指标.结果 表明:研究区土壤硒的主要来源为贺兰山区黑色岩系,其次为引黄灌溉淤积;研究区硒的生物有效性处于较高水平,有效硒富集及以上的区域占全区的79.2％,面积约为777.2 km2;硒不同形态含量依次为残渣态＞强有机结合...