Environmental risk associated with accumulation of toxic metalloids in soils of the Odra River floodplain-case study of the assessment based on total concentrations, fractionation and geochemical indices.

The floodplain soils are often heavily enriched in metal(loid)s released from the industrial areas. A related environmental risk depends on their total concentrations and the forms and conditions conducive to mobilization. This study was aimed to examine the concentrations of metal(loid)s in the Odra floodplain soils and to assess the risk associated with their possible contamination. In this study, topsoil and deeper soil layer samples were collected from the inter- and out-of-embankment zones. Total concentrations of Pb, Zn, Cu, As, Mn and Fe, and their extractable fractions were determined in 1 M NH4NO3 (actual solubility) and by BCR sequential extraction. The environmental risk was assessed based on total concentrations, according to legal regulations, geochemical enrichment indices and extractability of elements, with considering soil morphological features. Some topsoil samples from the inter-embankment zone turned out considerably enriched in Pb, Zn, Cu, and As, as confirmed by geochemical indices. Zn and As concentrations in some samples exceeded the permissible values defined by Polish law. Zn and Mn showed a high actual solubility, but a simple experiment proved that it can be efficiently reduced by liming. BCR fractionation showed that all the elements occurred mainly in reducible forms. Therefore, the risk of their release from the layers that do not indicate redoximorphic features was assessed as negligible. The study showed that such a complementary approach is needed to assess the real environmental risk in the case of soils considerably enriched in potentially toxic elements.

Arsenic toxicity to earthworms in soils of historical As mining sites: an assessment based on various endpoints and chemical extractions.

Eisenia fetida is an earthworm species often used to assess the toxicity of contaminants in soils. Several studies indicated that its response can be unpredictable because it depends both on total concentrations of contaminants and also on their forms that differ in susceptibility to be released from soil solid phase. The issue is complex because two various uptake routes are concurrently involved, dermal and ingestion in guts, where the bioavailability of contaminants can considerably change. The aim of this study was to analyze the toxicity of arsenic (As) in various strongly contaminated meadow and forest soils, representative for former As mining and processing area, to earthworms E. fetida and its accumulation in their bodies. An attempt was made to find relationships between the response of earthworms and chemical extractability of As. In the bioassay, carried out according to the standard ISO protocol, different endpoints were applied: earthworm survival, fecundity measured by the numbers of juveniles and cocoons, earthworm weight and As accumulation in the bodies. The results proved that E. fetida can tolerate extremely high total As concentrations in soils, such as 8000 mg/kg, however, the individual endpoints were not correlated and showed different patterns. The most sensitive one was the number of juveniles. No particular soil factor was identified that would indicate an exceptionally high As susceptibility to the release from one of soils, however, we have demonstrated that the sum of non-specifically and specifically bound As (i.e. fractions F1 + F2 in sequential extraction according to Wenzel) could be a good chemical indicator of arsenic toxicity to soil invertebrates.

Residues of Persistent Organic Pollutants (POPs) in Agricultural Soils Adjacent to Historical Sources of Their Storage and Distribution-The Case Study of Azerbaijan.

The aim of this study was to identify and examine the levels of organochlorine pesticides (OCPs), polycyclic aromatic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs) in soil collected from the surroundings of historical pesticide storage facilities on former agricultural aerodromes, warehouses, and pesticide distribution sites located in the most important agricultural regions in Azerbaijan. The conducted research included determination of three groups of POPs (occurring together), in the natural soil environment influenced for many years by abiotic and biotic factors that could have caused their transformations or decomposition. In this study, soil samples were collected in 21 georeferenced points located in the administrative area of Bilasuvar, Saatly, Sabirabad, Salyan and Jalilabad districts of Azerbaijan. Soil chemical analysis involved determination of organochlorine compounds (OCP): hexachlorocyclohexanes (HCHs) (three isomers α-HCH, ß-HCH and γ-HCH) and dichlorodiphenyltrichloroethanes (DDTs) (six congeners 2,4'DDT; 4,4'DDT; 2,4'DDE; 4,4'DDE; 2,4'DDE; and 4,4'DDE); polycyclic aromatic hydrocarbons (PAHs): 16 compounds from the United States Environmental Protection Agency US EPA list and, PCBs (seven congeners identified with the following IUPAC numbers: 28, 52, 101, 118, 138, 153, and 180). Our research showed that OCPs reached the highest concentration in the studied areas. The total concentrations of OCPs ranged from 0.01 to 21,888 mg∙kg-1 with significantly higher concentrations of Σ6DDTs (0.01 µg kg-1 to 21880 mg kg-1) compared to ΣHCH (0.14 ng kg-1 to 166.72 µg kg-1). The total concentrations of PCBs in the studied soils was varied from 0.02 to 147.30 µg·kg-1 but only PCB138 and PCB180 were detected in all analyzed samples. The concentrations of Σ16 PAHs were also strongly diversified throughout the sampling areas and ranged from 0.15 to 16,026 mg kg-1. The obtained results confirmed that the agricultural soils of Azerbaijan contained much lower (up to by three orders of magnitude) concentrations of PCBs and PAHs than DDT. It is supported by the fact that PCBs and PAHs were not directly used by agriculture sector and their content results from secondary sources, such as combustion and various industrial processes. Moreover, the high concentrations of PAHs in studied soils were associated with their location in direct neighborhood of the airport, as well as with accumulation of contaminants from dispersed sources and long range transport. The high concentrations of pesticides confirm that deposition of parent OCPs have occurred from obsolete pesticide landfills.

Ecotoxicity of pore water in soils developed on historical arsenic mine dumps: The effects of forest litter.

Arsenic release from dump soils in historical mining sites poses the environmental risk. Decomposing forest litter can affect mobilization of As and other toxic elements, change their speciation in pore water and influence the toxicity to biota. This study examined the chemistry and ecotoxicity of pore water acquired from four soils that developed on the dumps in former As mining sites, in the presence and absence of forest litter collected from beech and spruce stands. Soils contained 1540-19600 mg/kg of As. Pore water was collected after 2, 7, 21 and 90 days of incubation, using MacroRhizon suction samplers. Its chemical analysis involved determination of pH, the concentrations of As, Cu and Pb (the elements with high enrichment factor Igeo>3), as well as metals considered most mobile: Cd, Zn and Mn. Ecotoxicity of pore water was examined in three bioassays: Microtox, MARA and Phytotox with Sinapis alba as test plant. The release of As, unlike heavy metals, was particularly intensive from the soils with neutral and alkaline pH. The concentrations of toxic elements in pore water were in broad ranges, up to dozens mg/L. The results of Phytotox had a poor precision, but their means correlated well with As concentrations in pore water, which indicates that As made a crucial factor of phytotoxicity. The outcomes of Microtox bioassay indicated poorer relationships between As concentrations and toxicity, and other factors contributed to ecotoxicity at very low and very high As concentrations. The highest toxicity was recorded from the soils treated with forest litter. MARA turned out to be not sensitive enough to give reproducible results in experimental conditions. The PCA analysis confirmed that the growth of microbes in MARA bioassay was poorly dependent on As and metals in pore water except for a yeast Pichia anomala (No 11). The results let us conclude that the bioassays Phytotox and Microtox can provide useful information on ecotoxicity of pore water in soils that develop on As-rich dumps whereas applicability of MARA in those conditions proved limited.

Antimony in soils of SW Poland-an overview of potentially enriched sites.

Great concern has been recently focused on antimony in the environment due to the potential risks posed by this metalloid to humans. In Poland, the concentrations of Sb in soils have not been well recognized. The aim of this study was to identify the sites in south-western Poland where soils are considerably enriched in Sb and to make a rough assessment of a related environmental risk. One hundred forty-four samples were collected from 20 Lower Silesian locations chosen as potentially enriched in Sb that included historical mining sites, tailings impoundments, close vicinities of operating copper smelters, and landfills as well as currently operating and historical shooting ranges. Total concentrations of Sb in soils were determined, and related pollution indices were calculated. Several locations were found where soils contain high concentrations of Sb, with a maximum that exceeded 5600 mg kg-1 Sb in the alluvial soil affected by historical mining. Sequential extraction showed a considerably high percentage of Sb extracted in potentially soluble fractions 1 (non-specifically sorbed) and 2 (specifically sorbed), particularly in the samples collected from shooting ranges and in some samples from historical mine areas. This result provides a strong premise for further risk- and remediation-oriented examination of soils in those sites. More detailed research is needed to determine a spatial extent of soil contamination in the sites identified as highly enriched in Sb. Contrary to these findings, soil material collected from copper tailings impoundments, surroundings of smelters, and landfills did not show any particular enrichment in Sb.

Single soliton solution to the extended KdV equation over uneven depth.

In this note we look at the influence of a shallow, uneven riverbed on a soliton. The idea consists in an approximate transformation of the equation governing wave motion over an uneven bottom to an equation for a flat one for which the exact solution exists. The calculation is one space dimensional, and so corresponds to long trenches or banks under wide rivers or oceans.

Seasonal dynamics of nitrate and ammonium ion concentrations in soil solutions collected using MacroRhizon suction cups.

The aims of the study were to analyse the concentration of nitrate and ammonium ions in soil solutions obtained using MacroRhizon miniaturized composite suction cups under field conditions and to determine potential nitrogen leaching from soil fertilized with three types of fertilizers (standard urea, slow-release urea, and ammonium nitrate) at the doses of 90 and 180 kg ha-1, applied once or divided into two rates. During a 3-year growing experiment with sugar sorghum, the concentration of nitrate and ammonium ions in soil solutions was the highest with standard urea fertilization and the lowest in variants fertilized with slow-release urea for most of the months of the growing season. Higher concentrations of both nitrogen forms were noted at the fertilizer dose of 180 kg ha-1. One-time fertilization, at both doses, resulted in higher nitrate concentrations in June and July, while dividing the dose into two rates resulted in higher nitrate concentrations between August and November. The highest potential for nitrate leaching during the growing season was in July. The tests confirmed that the miniaturized suction cups MacroRhizon are highly useful for routine monitoring the concentration of nitrate and ammonium ions in soil solutions under field conditions.

Some adverse effects of soil amendment with organic Materials-The case of soils polluted by copper industry phytostabilized with red fescue.

The study was aimed to examine the effects of soil amendment with organic waste materials on the growth of red fescue and the uptake of Cu and Zn by this grass, in view of its potential usage for phytostabilization of Cu-polluted soils. Five soils, containing 301-5180 mg/kg Cu, were collected from the surroundings of copper smelter Legnica, and amended with lignite (LG) and limed sewage sludge (SS). Plant growth and the concentrations of Cu and Zn in the shoots and roots of grass were measured in a pot experiment and related to the results of Pytotoxkit and Microtox® tests performed on soil solution. The effects of soil amendment with LG and SS differed greatly, and depended on soil properties. In some cases, the application of alkaline SS resulted in dramatic increase of Cu phytotoxicity and its enhanced uptake by plants, while application of LG to slightly acidic soil caused increased accumulation of Zn in plants, particularly in their roots. The study confirmed good suitability of red fescue for phytostabilization of Cu-contaminated soils except for those extremely polluted. Organic amendments to be used for metal immobilization should be thoroughly examined prior to application.

Arsenic uptake by Agrostis capillaris, as related to its genotypic diversity in the area of historical ore mining and processing.

Common bentgrass Agrostis capillaris L. is known as tolerant to toxic elements. A hypothesis was examined that its ecotypes growing in historically polluted sites show a limited arsenic uptake and have genetic features that distinguish them from commercially available cultivars. The study was conducted in Zloty Stok, a historical area of arsenic mining. Additionally, two commercial cultivars were grown in pots with arsenic-rich soils. Based on arsenic concentrations in plant roots and shoots, bioconcentration and translocation factors BCF and TF were calculated. Commercial cultivars indicated many times higher BCF shoots and TF values compared to field plants. DNA analysis of leaf blades showed a clear distinction between the plants growing in some sites and patches in the field, and also a gene overlap between the plants in the field and commercial forms. The research did not allow for identification of ecotypes with exceptionally limited arsenic uptake. Moreover, there were no significant differences between the genotypic characteristics of plants growing in polluted sites and those poorly tolerant grown from commercially available seeds. Apparently, other factors, and not genetically determined features, are responsible for A. capillaris tolerance to arsenic in Zloty Stok.

Profile Distributions of Potentially Toxic Metal(loid)s in Soils of the Middle Odra Floodplain (SW Poland).

Floodplain soils are often contaminated with potentially toxic elements of geogenic and anthropogenic origin. This also applies to a valley of the Odra river, which in its upper reach flows through areas of historical and contemporary mining and heavy industry. This study examined the distribution of typically anthropogenic metal(loid)s, i.e., Pb, Zn, Cu, As and Cd, and geogenic metals, i.e., Mn and Fe, in soil profiles of the middle Odra valley, and analyzed factors that determine their concentrations. Thirteen soil profiles, located inter the embankment area and outside the embankments, were examined. Most of profiles indicated stratification typical for alluvial soils. Topsoil layers in the inter-embankment zone showed considerable enrichment in Pb, Zn and Cd, and to a lesser extent in Cu and As. Low soil pH is an important factor of environmental risk; therefore, acidic soils definitely require liming. The soils located out of embankments did not show any considerable enrichment in the elements examined. Based on significant correlations between the concentrations of metal(loid)s in deep soil layers and soil texture, the values of local geochemical background were derived. Outliers, particularly in the case of As, were explained by possible redistribution under reducing conditions.

Aspergillus niger-mediated release of phosphates from fish bone char reduces Pb phytoavailability in Pb-acid batteries polluted soil, and accumulation in fenugreek.

Soil receiving discharges from Pb-acid batteries dismantling and restoring units (PBS) can have a high concentration of phytoavailable Pb. Reducing Pb phytoavailability in PBS can decline Pb uptake in food crops and minimize the risks to humans and the environment. This pot study aimed to reduce the concentration of phytoavailable Pb in PBS through Aspergillus niger (A. niger)-mediated release of PO43- from fish bone [Apatite II (APII)] products. The PBS (Pb = 639 mg kg-1 soil) was amended with APII powder (APII-P), APII char (APII-C), and A. niger inoculum as separate doses, and combining A. niger with APII-P (APII-P + A. niger) and APII-C (APII-C + A. niger). The effects of these treatments on reducing the phytoavailability of Pb in PBS and its uptake in fenugreek were examined. Additionally, enzymatic activities and microbial biomass carbon (MBC) in the PBS and the indices of plant physiology, nutrition, and antioxidant defense machinery were scoped. Results revealed that the APII-C + A. niger treatment was the most efficient one. Compared to the control, it significantly reduced the Pb phytoavailability (DTPA-extractable Pb fraction) in soil and its uptake in plant shoots, roots, and grain, up to 61%, 83%, 74%, and 92%. The grain produced under APII-C + A. niger were safe for human consumption as Pb concentration in grain was 4.01 mg kg-1 DW, remaining within the permissible limit set by WHO/FAO (2007). The APII-C + A. niger treatment also improved soil pH, EC, CEC, MBC, available P content and enzymatic activities, and the fenugreek quality parameters. A. niger played a significant role in solubilizing PO43- from APII-C, which reacted with Pb and formed insoluble Pb-phosphates, thereby reducing Pb phytoavailability in PBS and its uptake in plants. This study suggests APII-C + A. niger can remediate Pb-polluted soils via reducing Pb phytoavailability in them.

Impacts of oxalic acid-activated phosphate rock and root-induced changes on Pb bioavailability in the rhizosphere and its distribution in mung bean plant.

Rhizosphere acidification in leguminous plants can release P from the dissolution of phosphate compounds which can reduce Pb bioavailability to them via the formation of insoluble Pb compounds in their rhizosphere. A soil polluted from Pb-acid batteries effluent (SPBE), having total Pb = 639 mg kg-1, was amended with six different rates (0, 0.5, 1, 2, 4 and 6%) of oxalic acid-activated phosphate rock (OAPR) and their effects on pH, available P and bioavailable Pb concentrations in the rhizosphere and bulk soils of mung bean plant were evaluated. Furthermore, the effects of these variant OAPR rates on Pb concentrations in plant parts, bioaccumulation factor (BAF) and translocation factor (TF) for Pb in grain and traits like productivity, the activities of antioxidant enzymes, and grain biochemistry were investigated. Results revealed that increasing rates of OAPR significantly increased pH values and available P while decreased bioavailable Pb concentrations in the rhizosphere over control. The highest dissolution of P in the rhizosphere was with 4 and 6% OAPR rates. As a result, the formation of insoluble Pb compounds affected on reduced Pb concentrations in shoots, roots, and grain in addition to lower grain BAF and TF values for Pb over control. Likewise, the highest plant productivity, improved grain biochemistry, high Ca and Mg concentrations, least oxidative stress, and enhanced soil alkaline phosphatase activity were found with 4 and 6% OAPR rates. The OAPR 4% rate is suggested for reducing grain Pb concentration, cell oxidative injury, and improving grain biochemistry in mung bean.

Arsenic Uptake by Two Tolerant Grass Species: Holcus lanatus and Agrostis capillaris Growing in Soils Contaminated by Historical Mining.

The study focused on two grass species Holcus lanatus and Agrostis capillaris abundant in the sites of former As mining and processing in the Sudetes. Arsenic uptake from soils was examined to assess a risk associated with its accumulation in grass shoots and to check its dependence on soil fertilization. The research involved a field study and greenhouse experiment. In the field study, soil and plant samples were collected from 33 sites with 72-98,400 mg/kg total soil As. Arsenic uptake by grasses differed widely. Both species indicated a strategy typical for eliminators, although As concentrations in more than 50% of the shoot samples exceeded 4 mg/kg, a maximum permissible value for fodder. In the greenhouse experiment, commercial cultivars of both species were grown in five soils containing 394-19,600 mg/kg, untreated and fertilized. All seedlings died in the soil with highest total As, and considerable phytotoxicity was observed in other soils, particularly in nonfertilized ones. Fertilization resulted in the improvement of plant growth and reduction of As uptake except for Agrostis capillaris fertilized with manure. Further research should focus on identifying tolerant genotypes growing in extremely enriched sites and analysis of factors that will efficiently reduce As phytoaccumulation.

Accumulation of Arsenic by Plants Growing in the Sites Strongly Contaminated by Historical Mining in the Sudetes Region of Poland.

The uptake of As by various plants growing in highly enriched sites was examined in order to identify potential As accumulators and to assess the risk associated with As presence in plant shoots. Representative samples of 13 plant species, together with soil samples, were collected from various sites affected by historical As mining: mine and slag dumps, tailings and contaminated soils with As concentrations in a range 72-193,000 mg/kg. Potentially and actually soluble As forms, extracted with 0.43 M HNO3 and, 1M NH4NO3 were examined in relation to As concentrations in plant roots and shoots. The latter differed strongly among the species and within them and were in the ranges 2.3-9400 mg/kg and 0.5-509 mg/kg, respectively. The majority (over 66%) of plant samples had As shoot concentrations above 4 mg/kg, an upper safe limit for animal fodder. The uptake of As by plants correlated well with total and extractable soil As, though As concentrations in plants could not be predicted based on soil parameters. Equisetum spp. and C. epigejos indicated a particularly strong accumulation of As in shoots, while A. capillaris, and H. lanatus showed a limited As root-to-shoot transfer, apparently associated with species-related tolerance to As.

Arsenic accumulation by red fescue (Festuca rubra) growing in mine affected soils - Findings from the field and greenhouse studies.

Soils strongly enriched in arsenic in historical mining sites pose the environmental risk. Phytostabilization is a reasonable method for their remediation. A suitability of red fescue (Festuca rubra L.) for this purpose was examined. Plant and soil material was collected from four study objects: mine dumps in Zloty Stok and Czarnów and two areas formerly flooded by tailings. Total As in soils ranged 72-48900 mg/kg, while the shoots and roots of red fescue contained 1.5-65.5 and 2.3-824 mg/kg As, respectively. Bioaccumulation BAF and translocation TF factors were typical for excluders, however, in most cases, As in shoots exceeded 4 mg/kg, an EU threshold for As in fodder. A greenhouse experiment, that involved treatment with mineral fertilizers, manure, and forest litter, was performed to closer examine the factors governing As uptake by red fescue. A stress-resistant cultivar Leo-Pol was used as a test plant. Grass shoots were harvested after 6 and 12 weeks. Manure treatment increased strongly As extractability but did not increase As uptake by plants. Though, As concentrations in plants were in the pot experiment by manifold higher than those in the field. Particularly high (66.5-1580 mg/kg) was As in the second shoot harvest. Differences between the field and greenhouse data indicate that the populations of red fescue, that develop in As rich sites, are specifically As-tolerant. Possible mechanisms of tolerance are discussed. The conclusion is that the commercial cultivar, despite declared stress-resistance, cannot be used for phytostabilization of barren As-rich soils.

The Release of Antimony from Mine Dump Soils in the Presence and Absence of Forest Litter.

This study examined the changes in antimony (Sb) solubility in soils, using organic matter introduced with forest litter, in various moisture conditions. Soils containing 12.8⁻163 mg/kg Sb were taken from the top layers of dumps in former mining sites in the Sudetes, South-West Poland. Soils were incubated for 90 days either in oxic or waterlogged conditions, with and without the addition of 50 g/kg of beech forest litter (FL). Water concentrations of Sb in some experimental treatments greatly exceeded the threshold values for good quality underground water and drinking water, and reached a maximum of 2.8 mg/L. The changes of Sb solubility caused by application of FL and prolonged waterlogging were, in various soils, highly divergent and in fact unpredictable based on the main soil properties. In some soils, the application of forest litter prompted the release of Sb from soil solid phase, while in the others it acted contradictorily. Soil waterlogging resulted, in most cases, in the increased release of Sb compared to oxic conditions, and this effect was enhanced by the addition of forest litter. However, in two soils the presence of forest litter counteracted the effects of waterlogging and diminished the quantities of released Sb.

Arsenic extractability in soils in the areas of former arsenic mining and smelting, SW Poland.

Arsenic (As) concentrations in soils and waste material in two areas of former As mining and processing: Zloty Stok (Zlote Mts.) and Zelezniak (Kaczawskie Mts.), SW Poland, were measured to assess levels and environmental risk associated with possible increases in arsenic mobility under changing pH and redox conditions. Twenty six soil samples were collected from 12 sites, and represented a broad spectrum of soil properties and parent material origin, including natural soils, mine spoils, slags and tailings. Arsenic species were examined using a sequential extraction technique. The changes in As solubility were determined from extraction test solutions adjusted to solution pH values varying from 2 to 8. The effects of reducing conditions on As mobility were examined in incubation tests. Most of soils demonstrated extremely high concentrations of As, both of natural and anthropogenic origin. Total As concentrations in all samples were in the range 100-43,500 mg/kg. Sequential extraction techniques suggested that the main species of As in all soils were those bound to iron (Fe) oxides, in particular amorphous ones, whereas the contributions of mobile and specifically sorbed As forms were relatively low. In tailings and tailings-affected alluvial soils, As occurred mainly in residual forms, however these soils also had considerable amounts of mobile As. In all other soils, mobile As forms were very low. Arsenic mobilization could be possible at extremely low or high pH conditions (pH<2 or pH>8), and this may be of particular practical importance in the case of tailings, which are highly alkaline. High pH promotes solubilization of As forms in reducing conditions, whereas in neutral and acidic soils the risk of As release under reducing conditions is limited.

Energy invariant for shallow-water waves and the Korteweg-de Vries equation: Doubts about the invariance of energy.

It is well known that the Korteweg-de Vries (KdV) equation has an infinite set of conserved quantities. The first three are often considered to represent mass, momentum, and energy. Here we try to answer the question of how this comes about and also how these KdV quantities relate to those of the Euler shallow-water equations. Here Luke's Lagrangian is helpful. We also consider higher-order extensions of KdV. Though in general not integrable, in some sense they are almost so within the accuracy of the expansion.

Shallow-water soliton dynamics beyond the Korteweg-de Vries equation.

An alternative way for the derivation of the new Korteweg-de Vries (KdV)-type equation is presented. The equation contains terms depending on the bottom topography (there are six new terms in all, three of which are caused by the unevenness of the bottom). It is obtained in the second-order perturbative approach in the weakly nonlinear, dispersive, and long wavelength limit. Only treating all these terms in the second-order perturbation theory made the derivation of this KdV-type equation possible. The motion of a wave, which starts as a KdV soliton, is studied according to the new equation in several cases by numerical simulations. The quantitative changes of a soliton's velocity and amplitude appear to be directly related to bottom variations. Changes of the soliton's velocity appear to be almost linearly anticorrelated with changes of water depth, whereas correlation of variation of soliton's amplitude with changes of water depth looks less linear. When the bottom is flat, the new terms narrow down the family of exact solutions, but at least one single soliton survives. This is also checked by numerics.

Arsenic extractability and uptake by velvetgrass Holcus lanatus and ryegrass Lolium perenne in variously treated soils polluted by tailing spills.

Phytostabilization should be considered as an appropriate phytoremediation technique to restore the area affected by tailing spills in Zloty Stok, where arsenic ores were mined and processed for several centuries. The study aimed to compare the suitability of velvetgrass (Holcus lanatus L.) and ryegrass (Lolium perenne L.) for development of plant cover in that area. Various treatments commonly applied to support phytostabilization were examined. A pot experiment was carried out to assess the effects of soil amendment with phosphate (P), sewage sludge (SS) and iron salts (Fe) on arsenic extractability and its uptake by grass. Four kinds of soil material, containing 356-5350 mg kg(-1) As, were examined. Velvetgrass proved to be more resistant than ryegrass to the toxicity of soil arsenic. Ammonium sulphate extractability of As in soils correlated well with As concentrations in the biomass of both grass species. In three of four tested soils, application of Fe failed to decrease As extractability and to reduce its concentrations in the aboveground parts of grasses. Application of P and SS resulted in increased As solubility in soils, but their effects on plant biomass and As uptake were ambiguous. SS had a strong beneficial influence on the growth of velvetgrass, while such an effect was not observed for ryegrass.