Plant response to mycorrhizal inoculation and amendments on a contaminated soil.

Understanding the combined effects of soil amendments and inoculation of mycorrhizal fungi on the response of different plant species during the phytostabilization process of trace elements contaminated soils is a challenge. This task is more difficult but more realistic when studied under field conditions. We assess the combined effects of two amendment doses and mycorrhizal inoculation on the response of saplings of two tree species planted in a contaminated field. The amendments were a mix of sugar beet lime and biosolid compost. The inoculation treatments were made with a commercial inoculum of arbuscular mycorrhizal fungi for wild olive and ectomycorrhizal fungi for stone pine. Results showed a weak or null effect of the mycorrhizal inoculation on plant growth, survival and trace element accumulation. There was a significant increase on P nutrition for stone pine, growing on non-amended conditions. Soil amendments were very effective reducing trace elements availability and their accumulation in both plant species, especially in roots. However, the effects on plant biomass were species-dependent and contrasted; low-dose amendments increased the biomass of wild olive by 33.3%, but reduced by 28% that of pine. The high doses of amendments (60 T ha-1) produced some negative effects on plant growth and nutrition, probably related to the increase of soil salinity. Both plant species, stone pine and wild olive, have been proved to be adequate for phytostabilization of contaminated soils under Mediterranean climate, due to their drought tolerance and the low transfer of trace elements from root to shoot, thus reducing toxicity for the food web. To implement microbial-assisted phytoremediation approaches, a better understanding of the diversity and ecology of plant-associated microorganisms is needed. The use of indigenous fungi, locally adapted and tolerant to contamination, would be more suitable for phytostabilization purposes.

Response of a Pioneering Species (Leptospermum scoparium J.R.Forst. & G.Forst.) to Heterogeneity in a Low-Fertility Soil.

Root foraging may increase plant nutrient acquisition at the cost of reducing the total volume of soil explored, thereby reducing the chance of the roots encountering additional patches. Patches in soil seldom contain just one nutrient: the patch may also have distinct textural, hydrological, and toxicological characteristics. We sought to determine the characteristics of root foraging by a pioneering species, Leptospermum scoparium, using pot trials and rhizobox experiments with patches of biosolids. The growth of L. scoparium was increased by <50 t/ha equiv. of biosolids but higher doses were inhibitory. Roots foraged patches of biosolids in a low-fertility soil. There was no evidence of chemotaxis, rather, the roots proliferated toward the patch of biosolids, following chemical gradients of nitrate. While the biosolids also contained high concentrations of other nutrients (P, K, and S), only significant chemical gradients of nitrate were found. Once the roots encountered a patch of biosolids, the growth of the plant increased to a level similar to plants growing in soil homogeneously mixed with biosolids or surface-applied biosolids. Our results indicate that roots forage nitrate, which is mobile in soil, and that gradients of nitrate may lead to patches containing other less mobile nutrients, such as phosphate or potassium.

Soil hydraulic properties as the main driver in the establishment of biomass crops in contaminated soils.

In recent years increasing attention has been given to the potential use of contaminated lands for biofuel production, because these degraded soils cannot be used for food production. To establish these crops in Mediterranean contaminated areas, where the soil quality is usually very poor, the addition of soil amendments might be necessary to improve soil productivity. In addition, the use of crops with low water demands, adapted to these particular conditions of climate and soil contamination, is a key requirement. We studied the development of Cynara cardunculus and Silybum mariamun crops (both suitable for the production of biomass for biofuel uses under a Mediterranean climate) in trace element contaminated soils under field conditions. To our knowledge, this is the first such work under these particular experimental conditions (soil contamination and field trial). Soil physical (hydraulic), chemical, and biochemical properties were monitored for one year in experimental plots, where we tested the effects of the addition of two different amendments (sugar lime and biosolid compost) on soil functioning and crop productivity. Seed germination and plant biomass production were low, although amendment addition improved both parameters. The chemical and biological indicators (enzyme activities, PLFA profiles, and soil respiration) tended to be slightly improved by the amendments, especially sugar lime. The hydraulic properties of the soil in the experimental area were very deficient, and the effect of the amendments was not enough to improve them; this was probably the main cause of the general low productivity of these rain-fed crops, as water infiltrated poorly through the root zone. To improve crop productivity under these soil conditions, certain aspects could be improved: higher doses of amendments should be applied and deeper tillage of the soil after amendment addition should be performed to facilitate water infiltration.

Soil-plant relationships and contamination by trace elements: A review of twenty years of experimentation and monitoring after the Aznalcóllar (SW Spain) mine accident.

Soil contamination by trace elements (TE) is a major environmental problem and much research is done into its effects on ecosystems and human health, as well as into remediation techniques. The Aznalcóllar mine accident (April 1998) was a large-scale ecological and socio-economic catastrophe in the South of Spain. We present here a literature review that synthesizes the main results found during the research conducted at the affected area over the past 20years since the mine accident, focused on the soil-plant system. We review, in depth, information about the characterization of the mine slurry and contaminated soils, and of the TE monitoring, performed until the present time. The reclamation techniques included the removal of sludge and soil surface layer and use of soil amendments; we review the effects of different types of amendments at different spatial scales and their effectiveness with time. Monitoring of TE in soil and their transfer to plants (crops, herbs, shrubs, and trees) were evaluated to assess potential toxicity effects in the food web. The utility of some plants (accumulators) with regard to the biomonitoring of TE in the environment was also evaluated. On the other hand, retention of TE by plant roots and their associated microorganisms was used as a low-cost technique for TE stabilization and soil remediation. We also evaluate the experience acquired in making the Guadiamar Green Corridor a large-scale soil reclamation and phytoremediation case study.

Potential Use of Biosolids to Reforest Degraded Areas with New Zealand Native Vegetation.

Biosolids could potentially be used for reforestation of degraded soils in New Zealand with native vegetation. Many native plant species of New Zealand thrive in low-fertility soils, and there is scant knowledge about their nutrient requirements. Therefore, it is unclear whether they will respond positively to the addition of biosolids. We used a pot trial to determine the responses of 11 native plant species to biosolids addition (10% w/w, ∼90 Mg hm) on two distinct degraded soils, Lismore stony silt loam and a Kaikoura sand. We also intended to prove that the soil microbial activity improves with the addition of biosolids, depending on the plant species. All species grew better in Lismore stony silt loam than the Kaikoura sand. All species in the Lismore stony silt loam responded positively to biosolids. The response to biosolids addition in the Kaikoura sand was variable, with four species showing no improvement in growth when biosolids were added. The nutrient status (N, P, S, Cu, and Zn) of all species improved when the two soils were amended with biosolids. However, some plant species, especially Sol. ex Gaertn. and Raoul, showed concerning concentrations of Cd (up to 2.4 mg kg). Dehydrogenase activity of soils (indicator of soil microbial activity) increased in biosolids-amended soils, with a strong species effect. Future work should involve field trials to determine the effect of biosolids addition on the establishment of native plant communities.

Novel energy crops for Mediterranean contaminated lands: Valorization of Dittrichia viscosa and Silybum marianum biomass by pyrolysis.

Establishing energy crops could be a cost-efficient alternative towards the valorization of the plant biomass produced in contaminated lands, where they would not compete with food production for land use. Dittrichia viscosa and Silybum marianum are two native Mediterranean species recently identified as potential energy crops for degraded lands. Here, we present the first characterization of the decomposition of the biomass of these species during thermo-chemical conversion (pyrolysis). Using a greenhouse study we evaluated whether the quality of D. viscosa and S. marianum biomass for energy production through pyrolysis could be substantially influenced by the presence of high concentrations of soluble trace element concentrations in the growing substrate. For each species, biomass produced in two different soil types (with contrasted trace element concentrations and pH) had similar elemental composition. Behavior during thermal decomposition, activation energies and concentrations of pyrolysis gases were also similar between both types of soils. Average activation energy values were 295 and 300 kJ mol-1 (for a conversion value of α = 0.5) for S. marianum and D. viscosa, respectively. Results suggest that there were no major effects of soil growing conditions on the properties of the biomass as raw material for pyrolysis, and confirm the interest of these species as energy crops for Mediterranean contaminated lands.

The potential of native species as bioenergy crops on trace-element contaminated Mediterranean lands.

The establishment of energy crops could be an option for the management of degraded and contaminated lands, where they would not compete with food production for land use. Here, we aimed to explore the potential of certain native Mediterranean species for the revegetation of contaminated lands for energy production purposes. A field survey was conducted in a trace-element (TE) contaminated area from SW Spain, where the patterns of biomass production, TE accumulation and the calorific value of some thistle species were analyzed along a soil contamination gradient. In a greenhouse experiment the response of two thistle species (Cynara cardunculus and Silybum marianum) and the shrub Dittrichia viscosa to soil contamination was assessed, as well as the effects of these species on some soil microbial parameters involved in nutrient cycling (enzyme activities and arbuscular mycorrhizal colonization in roots). Silybum marianum was able to colonize highly contaminated soils. Its aboveground biomass accumulated Cd and had a relatively high calorific value; this value was similar in biomass obtained from both heavily and moderately contaminated soils. Greenhouse experiment confirmed that S. marianum biomass production and calorific value is scarcely affected by soil contamination. In addition, some soil enzyme activities were clearly enhanced in the S. marianum rhizosphere. Dittrichia viscosa is another promising species, given its capacity to produce a high biomass with appreciable calorific value in acid contaminated soils. Germination of both species was hampered in the acid contaminated soil, and therefore soil pH correction would have to be accomplished before establishing these species on extremely acid soils. Further assessment of the risk of transfer of Cd and other TE to the food chain would be needed to confirm the suitability of these species for the revegetation of contaminated lands with energy production purposes.

Organic amendments increase phylogenetic diversity of arbuscular mycorrhizal fungi in acid soil contaminated by trace elements.

In 1998, a toxic mine spill polluted a 55-km(2) area in a basin southward to Doñana National Park (Spain). Subsequent attempts to restore those trace element-contaminated soils have involved physical, chemical, or biological methodologies. In this study, the restoration approach included application of different types and doses of organic amendments: biosolid compost (BC) and leonardite (LEO). Twelve years after the last addition, molecular analyses of arbuscular mycorrhizal (AM) fungal communities associated with target plants (Lamarckia aurea and Chrysanthemum coronarium) as well as analyses of trace element concentrations both in soil and in plants were performed. The results showed an improved soil quality reflected by an increase in soil pH and a decrease in trace element availability as a result of the amendments and dosages. Additionally, the phylogenetic diversity of the AM fungal community increased, reaching the maximum diversity at the highest dose of BC. Trace element concentration was considered the predominant soil factor determining the AM fungal community composition. Thereby, the studied AM fungal community reflects a community adapted to different levels of contamination as a result of the amendments. The study highlights the long-term effect of the amendments in stabilizing the soil system.

Three-year study of fast-growing trees in degraded soils amended with composts: Effects on soil fertility and productivity.

Currently, worries about the effects of intensive plantations on long-term nutrient supply and a loss of productivity have risen. In this study two composts were added to degraded soils where this type of intensive crops were growing, to avoid the soil fertility decrease and try to increase biomass production. For the experiment, two degraded soils in terms of low organic carbon content and low pH were selected in South-West Spain: La Rábida (RA) and Villablanca (VI) sites. Both study sites were divided into 24 plots. In RA, half of the plots were planted with Populus x canadensis "I-214"; the other half was planted with Eucalyptus globulus. At the VI site, half of the plots were planted with Paulownia fortunei, and the other plots were planted with Eucalyptus globulus. For each tree and site, three treatments were established (two organic composts and a control without compost), with four replications per treatment. The organic amendments were "alperujo" compost, AC, a solid by-product from the extraction of olive oil, and BC, biosolid compost. During the three years of experimentation, samples of soils and plants were analyzed for studying chemical and biochemical properties of soil, plant growth and plant nutritional status and biomass production. The composts increased total organic carbon, water-soluble carbon, nutrients and pH of soil only in the most acidic soil. Soil biochemical quality was calculated with the geometric mean of the enzymatic activities (Dehydrogenase, ß-glucosidase, Phosphatase and Urease activities) determined in soils. The results showed a beneficial improvement in comparison with soils without compost. However, the best results were found in the growth and biomass production of the studied trees, especially in Eucalyptus. Nutritional levels of leaves of the trees were, in general, in the normal established range for each species, although no clear effect of the composts was observed. The results of this study justify the addition of compost to guarantee good biomass production and maintain or improve soil management in degraded soils, especially in acid soils.

Improving sustainability in the remediation of contaminated soils by the use of compost and energy valorization by Paulownia fortunei.

The plantation of fast growing trees in contaminated sites, in combination with the use of organic wastes, could partially solve a dual environmental problem: the disposal of these wastes and the improvement of soil quality in these degraded soils. This study evaluated the effects of two compost on the quantity and quality of Paulownia fortunei biomass and on syngas production by biomass gasification, produced by plants growing on trace elements contaminated soils. Compost increased biomass production to values similar to those produced in non-contaminated soils, due to the improvement in plant nutritional status. Moreover, biomass quality for gasification was increased by compost addition. Trace element accumulation in the biomass was relatively low and not related to biomass production or the gas quality obtained through gasification. Thus, P. fortunei plantations could pose an opportunity to improve the economic balance of the revegetation of contaminated soils, given that other commercial uses such as food or fodder crop production is not recommended in these soils.

Soil plant interactions of Populus alba in contrasting environments.

The effects of the Populus alba tree on different biochemical soil properties, growing in a contaminated area, were studied for two years under field conditions. Two types of trace element contaminated soils were studied: a neutral contaminated soil (NC) and an acid contaminated soil (AC). One neutral non-contaminated area was studied as control. Soil samples were collected at depths of 0-20 cm and 20-40 cm. Leaves and litter samples were analysed. The addition of organic matter, through root exudates and litter, contributed to an increase in soil pH, especially in acid soil. Microbial Biomass Carbon (MBC) was significantly increased by the presence of the trees in all studied areas, especially in the upper soil layer. Similar results were also observed for protease activity. Both MBC and Protease activity were more sensitive to contamination than ß-glucosidase activity. These changes resulted in a decrease of available trace element concentrations in soil and in an improvement of soil quality after a 2-year study. The total concentration of Cd and Zn in soil did not increase over time due to litter deposition. Analysis of P. alba leaves did not show a significant nutritional imbalance and trace element concentrations were normal for plants, except for Cd and Zn. These results indicate that P. alba is suitable for the improvement of soil quality in riparian contaminated areas. However, due to the high Cd and Zn concentrations in leaves, further monitoring of this area is required.

The snail Theba pisana as an indicator of soil contamination by trace elements: potential exposure for animals and humans.

BACKGROUND: The ability of snails to accumulate trace elements is well known. We analysed the snail Theba pisana as an indicator of soil contamination by trace elements after a mine spill accident, to assess the exposure of animal and human consumption. Snails were collected in autumn and spring, when they are most active. RESULTS: In general, trace elements in the soft tissues reached greater concentrations in the contaminated soils than in the non-contaminated soils, although significant differences were only found for As, Cd, Cu Fe and Hg. Cadmium content in tissues, with a maximum value of 10 mg kg⁻¹ (dry matter), was the most worrying result. Trace element concentrations in the snail bodies were still of concern for human consumption; As and Cd concentrations were sometimes higher than the maximum concentration authorised in foodstuffs. Generally, nutritional status of the contaminated snails was not altered; concentrations of the main nutrients (Ca, K, Mg, P and S) were similar to those of the non-contaminated snails. CONCLUSIONS: Results reveal a potential risk for animal and human consumption of T. pisana. It seems thus advisable to avoid collecting this species for human consumption in the affected area. Periodic monitoring is recommended to assess the evolution of potential risk for animal consumption.

Natural remediation of an unremediated soil twelve years after a mine accident: trace element mobility and plant composition.

The long-term influence of a mine spill in soil was studied 12 years after the Aznalcóllar accident. Soils where the pyritic sludge was not removed, a fenced plot established for research purposes (2000 m(2)) and soils where the process of remediation was accomplished successfully were sampled and studied in detail. Soils were characterized at different depths, down to 100 cm depth, determining chemical parameters and total concentrations of major and trace elements. Moreover plants colonizing remediated (RE) and non remediated (NRE) soils were also analysed attending their potential risk for herbivores. Strong acidification was observed in the NRE soil except in surface (0-10 cm). The progressive colonization of natural vegetation, more than 90% of the fenced plot covered by plants, could facilitate this increased pH values in the top soil (pH 6). In the NRE soil, the successive oxidation and hydrolysis of sulphide in the deposited sludge on the surface after the accident resulted in a re-dissolution of the most mobile element (Cd, Cu and Zn) and a penetration to deeper layers. Trace element concentrations in plants growing in the NRE soil showed normal contents for higher plants and tolerable for livestock. Nitrogen and mineral nutrients were of the same order in both soils, and also normal for high plants and adequate for animal nutrition. Despite of the natural remediation of the NRE soil, results demonstrate that the remediation tasks carried out in all the area, the Guadiamar Green Corridor at present, were necessary to avoid the leaching of the most mobile elements and minimize the risk of contamination of groundwater sources, many of them close to the Doñana National Park.

Influence of control parameters in VOCs evolution during MSW trimming residues composting.

The influence of control parameters (aeration, moisture, and C/N ratio) during composting of a municipal solid waste (MSW)-legume-trimming residue (LTR) mixture was studied at a pilot plant scale. Factors measured included the composition of the main volatile organic carbons (VOCs) emitted including limonene, ß-pinene, 2-butanone, undecane, phenol, toluene, and dimethyl disulfide. Polynomial models were found to reproduce the experimental results with errors at less than 10%. The relative influence of the independent variables on temperature and selected VOCs followed the order: aeration > moisture > C/N. A high aeration rate results in higher (strong negative effect) values on selected VOCs emissions (41-71% on emitted VOCs variation). Moisture had a positive and negative effect depending on the selected VOCs. A high C/N ratio caused lower production of VOCs except for undecane and 2-butanone. Providing an aerobic environment (0.05 Lair kg(-1) min(-1)), high C/N ratios (>50), and medium moisture (55%) minimize emitted VOCs during MSW composting, ultimately resulting in less odors in the surrounding environment.

Phytostabilization of semiarid soils residually contaminated with trace elements using by-products: sustainability and risks.

We investigated the efficiency of various by-products (sugarbeet lime, biosolid compost and leonardite), based on single or repeated applications to field plots, on the establishment of a vegetation cover compatible with a stabilization strategy on a multi-element (As, Cd, Cu, Pb and Zn) contaminated soil 4-6 years after initial amendment applications. Results indicate that the need for re-treatment is amendment- and element-dependent; in some cases, a single application may reduce trace element concentrations in above-ground biomass and enhance the establishment of a healthy vegetation cover. Amendment performance as evaluated by % cover, biomass and number of colonizing taxa differs; however, changes in plant community composition are not necessarily amendment-specific. Although the translocation of trace elements to the plant biotic compartment is greater in re-vegetated areas, overall loss of trace elements due to soil erosion and plant uptake is usually smaller compared to that in bare soil.

In situ remediation of metal-contaminated soils with organic amendments: role of humic acids in copper bioavailability.

The purposes of this study were to determine the Cu(II) binding behavior of humic acids (HAs) isolated from biosolid compost (BI), leonardite (LE), a metal-contaminated soil, and the soil remediated with either BI or LE in relation to their structural properties, and to explore the role exerted by the HA fractions in controlling soil Cu(II) bioavailability. Potentiometric titrations at pH 5 and ionic strength 0.1M and the Langmuir model were used to obtain the Cu(II) complexing capacity of the HAs examined and the conditional stability constant of the Cu(II)-HA complexes. The Cu(II) complexing capacity increased as the content of acidic ligands, especially COOH groups, aromaticity, and humification degree increased, following the order BI-HA

Long-term impact of acid resin waste deposits on soil quality of forest areas II. Biological indicators.

In this study, we evaluated the effects of two acid resin deposits on the soil microbiota of forest areas by means of biomass, microbial activity-related estimations and simple biological ratios. The determinations carried out included: total DNA yield, basal respiration, intracellular enzyme activities (dehydrogenase and catalase) and extracellular enzyme activities involved in the cycles of C (beta-glucosidase and chitinase), N (protease) and P (acid-phosphatase). The calculated ratios were: total DNA/total N; basal respiration/total DNA; dehydrogenase/total DNA and catalase/total DNA. Total DNA yield was used to estimate soil microbial biomass. Results showed that microbial biomass and activity were severely inhibited in the deposits, whilst resin effects on contaminated zones were variable and site-dependant. Correlation analysis showed no clear effect of contaminants on biomass and activities outside the deposits, but a strong interdependence with natural organic matter related parameters such as total N. In contrast, by using simple ratios we could detect more stressful conditions in terms of organic matter turnover and basal metabolism in contaminated areas compared to their uncontaminated counterparts. These results stress that developed ecosystems such as forests can buffer the effects of pollutants and preserve high functionality via natural attenuation mechanisms, but also that acid resins can be toxic to biological targets negatively affecting soil dynamics. Acid resin deposits can therefore act as contaminant sources adversely altering soil processes and reducing the environmental quality of affected areas despite the solid nature of these wastes.

Long-term impact of acid resin waste deposits on soil quality of forest areas I. Contaminants and abiotic properties.

Acid resins are residues characterised by elevated concentrations of hydrocarbons and trace elements, which were produced by mineral oil industries in Central Europe during the first half of the last century. Due to the lack of environmental legislation at that time, these wastes were dumped into excavated ponds in public areas without further protection. In this work, the long-term effects of such resin deposits on soil quality of two forest areas (Bayern, Germany) were assessed. We evaluated the distribution and accumulation of contaminants in the surroundings of the deposits, where the waste was disposed of about 60 years ago. General soil chemical properties such as pH, C, N and P content were also investigated. Chemical analysis of resin waste from the deposits revealed large amounts of potential contaminants such as hydrocarbons (93 g kg(-1)), As (63 mg kg(-1)), Cd (24 mg kg(-1)), Cu (1835 mg kg(-1)), Pb (8100 mg kg(-1)) and Zn (873 mg kg(-1)). Due to the location of the deposits on a hillside and the lack of adequate isolation, contaminants have been released downhill despite the solid nature of the waste. Five zones were investigated in each site: the deposit, three affected zones along the plume of contamination and a control zone. In affected zones, contaminants were 2 to 350 times higher than background levels depending on the site. In many cases, contaminants exceeded the German environmental guidelines for the soil-groundwater path and action levels based on extractable concentrations. Resin contamination yielded larger total C/total N ratios in affected zones, but no clear effect was observed on absolute C, N and P concentrations. In general, no major acidification effect was reported in affected zones.

Trace element availability and plant growth in a mine-spill-contaminated soil under assisted natural remediation II. Plants.

In this second part, we evaluated the effects of different amendments on plant growth (Agrostis stolonifera L.), and trace element accumulation and removal by plants in a trace element (As, Cd, Cu, Pb and Zn) contaminated soil. Description of the various treatments is given in Part I of this work. The plants were grown for consecutive periods (2002, 2003, 2004), 5 months each and harvested twice in each period. Results showed that plant growth was enhanced and trace element concentrations in plant were reduced in SL, MWC, BC and LEO treatments in the first period. No significant differences were observed in subsequent periods. This seemed to be related with changes in soil pH. Removal of trace elements was higher in SL, MWC, BC and LEO treatments due to higher biomass production in the first period. In following years no significant differences between treatments were found. Data from Part I of this study were also used to compare trace element bioavailable concentrations extracted with 0.01 M CaCl2 and 0.05 M EDTA with trace elements in plant. We observed that 0.01 M CaCl2 was more suitable for determination of bioavailable concentrations and that extraction with EDTA overestimated biovailability of trace elements in amended treatments, especially in those where composts were added.

Nitrogen mineralization and nitrate leaching of a sandy soil amended with different organic wastes.

Organic wastes can be recycled as a source of plant nutrients, enhancing crop production by improving soil quality. However, the study of the dynamic of soil nutrient, especially the N dynamic, after soil application of any organic material is vital for assessing a correct and effective use of the material, minimizing the losses of nitrate in leachates and avoiding the negative environmental effects that it may cause in groundwater. To estimate the effect of three organic materials, a municipal solid waste compost (MWC), a non-composted paper mill sludge (PS), and an agroforest compost (AC) on the N dynamic of a sandy soil two experiments were carried out: an incubation experiment and a column experiment. The incubation experiment was conducted to estimate the N mineralization rate of the different soil-amendment mixtures. The soil was mixed with the organic amendments at a rate equivalent to 50,000 kg ha(-1) and incubated during 40 weeks at constant moisture content (70% of its water-holding capacity) and temperature (28 degrees C) under aerobic conditions. Organic amendment-soil samples showed an immobilization of N during the first weeks, which was more noticeable and longer in the case of PS-treated soil compared to the other two amendments due to its high C/N ratio. After this immobilization stage, a positive mineralization was observed for all treatment, especially in MWC treated soil. Contemporaneously a 1-year column (19 cm diameter and 60 cm height) experiment was carried out to estimate the nitrate losses from the soil amended with the same organic materials. Amendments were mixed with the top soil (0-15 cm) at a rate equivalent to 50,000 kg ha(-1). The columns were periodically irrigated simulating rainfall in the area of study, receiving in total 415 mm of water, and the water draining was collected during the experimental period and analysed for NO3-N. At the end of the experimental period NO3-N content in soil columns at three depths (0-20, 20-35 and 35-50 cm) was determined. The nitrate concentration in drainage water confirmed the results obtained in the incubation experiment: nitrate leaching was higher in soil treated with MWC due to its higher N-mineralization rate. Nevertheless, the nitrate losses represented a low amount compared with the total nitrogen added to soil. No clear signs of water-draining contamination were observed during the first year after the application of AC and PS; however, the nitrate leaching in soil treated with MWC slightly exceeded the limit allowed for the Drinking Water Directive 98/83/CE.