Publications (44)106.03 Total impact
- [Show abstract] [Hide abstract] ABSTRACT: Citrus fruit-packaging plants (FPP) produce large wastewater volumes with high loads of fungicides like ortho-phenylphenol (OPP) and imazalil (IMZ). No methods are in place for the treatment of those effluents and biobeds appear as a viable alternative. We employed a column study to investigate the potential of spent mushroom substrate (SMS) of Pleurotus ostreatus, either alone or in mixture with straw and soil plus a mixture of straw /soil to retain and dissipate IMZ and OPP. The role of P. ostreatus on fungicides dissipation was also investigated by studying in parallel the performance of fresh mushroom substrate of P. ostreatus (FMS) and measuring lignolytic enzymatic activity in the leachates. All substrates effectively reduced the leaching of OPP and IMZ which corresponded to 0.014-1.1% and 0.120-0.420% of their initial amounts respectively. Mass balance analysis revealed that FMS and SMS/Straw/Soil (50/25/25 by vol) offered the most efficient removal of OPP and IMZ from wastewaters respectively. Regardless of the substrate, OPP was restricted in the top 0-20cm of the columns and was bioavailable (extractable with water), compared to IMZ which was less bioavailable (extractable with acetonitrile) but diffused at deeper layers (20-50, 50-80cm) in the SMS- and Straw/Soil-columns. PLFAs showed that fungal abundance was significantly lower in the top layer of all substrates from where the highest pesticide amounts were recovered suggesting an inhibitory effect of fungicides on total fungi in the substrates tested. Our data suggest that biobeds packed with SMS-rich substrates could ensure the efficient removal of IMZ and OPP from wastewaters of citrus FPP.
- [Show abstract] [Hide abstract] ABSTRACT: Compost derived from olive tree pruning waste (COTPW) was modified with 0.1 M (COTPW-1) and 1 M (COTPW-2) NaOH. The two biosorbents were tested for their ability to remove Pb2+ and Ni2+ ions from aqueous solutions. The effects of contact time, initial heavy metal concentration and solution temperature on the removal efficiency of COTPW-1 and COTPW-2 were also investigated. Among the two biosorbents, COTPW-1 showed a higher cation-exchange capacity (COTPW-1 = 130.4 cmolc/kg, COTPW-2 = 119.5 cmolc/kg) and lower % biomass loss due to the alkali treatment (COTPW-1 = 39.16, COTPW-2 = 60.6). Maximum Pb2+ and Ni2+ biosorptions at pH 5 and 25°C was 357.14 and 172.41 mg/g for COTPW-1, whereas for COTPW-2 they were 294.12 and 147.06 mg/g, respectively. The equilibrium adsorption data fitted well with the Langmuir isotherm and the pseudo-second-order model. Slightly reduced removal of Ni2+ from the solutions was observed in the presence of Pb2+, but Pb2+ removal was not affected by the presence of Ni2+ in the solutions. About 0.1 N HNO3 sufficiently recovered both metals from the tested materials (>95.01%). Overall, mild treatment of COTPW with NaOH greatly improved sorption characteristics.
- [Show abstract] [Hide abstract] ABSTRACT: Wastewaters from the fruit-packaging industry constitute a serious point source contamination with pesticides. In the absence of effective depuration methods, they are discharged in municipal wastewater treatment plants or spread to land. Modified biobeds could be an applicable solution for their treatment. We studied the dissipation of thiabendazole (TBZ), imazalil (IMZ), ortho-phenylphenol (OPP), diphenylamine (DPA) and ethoxyquin (EQ), used by the fruit-packaging industry, in anaerobically digested sewage sludge, liquid aerobic sewage sludge and in various organic substrates (biobeds packing materials) composed of soil, straw and spend mushroom substrate (SMS) in various volumetric ratios. Pesticide sorption was also determined. TBZ and IMZ showed higher persistence especially in the anaerobically digested sewage sludge (DT50=32.3-257.6d), in contrast to OPP and DPA which were rapidly dissipated especially in liquid aerobic sewage sludge (DT50=1.3-9.3d). EQ was rapidly oxidized mainly to quinone imine (QI) which did not persist and dimethyl ethoxyquinoline (EQNL, minor metabolite) which persisted for longer. Sterilization of liquid aerobic sewage sludge inhibited pesticide decay verifying the microbial nature of pesticide dissipation. Organic substrates rich in SMS showed the highest dissipation capacity with TBZ and IMZ DT50s of ca. 28d compared to DT50s of >50d in the other substrates. TBZ and IMZ showed the highest sorption affinity, whereas OPP and DPA were weakly sorbed. Our findings suggest that current disposal practices could not guarantee an efficient depuration of effluents from the fruit-packaging industry, whereas SMS-rich biobed organic substrates show efficient depuration of effluents from the fruit-packaging industry via accelerated dissipation even of recalcitrant fungicides. Copyright © 2015 Elsevier B.V. All rights reserved.
- [Show abstract] [Hide abstract] ABSTRACT: Residues and by-products of the olive-oil production chain have been widely studied as biosorbents for the removal of various pollutants from environmental media due to their significant adsorption properties, low cost, production at local level and renewability. In this review, adsorbents developed from olive-tree cultivation residues and olive-oil extraction by-products and wastes are examined, and their sorption characteristics are described and discussed. Recent information obtained using batch sorption studies is summarized and the adsorption mechanisms involved, regarding various aquatic and soil pollutants (metal ions, dyes, radionuclides, phenolic compounds, pesticides) are presented and discussed. It is evident that several biosorbents show the potential to effectively remove a wide variety of pollutants from aqueous solutions, especially Pb and Cd. However, there is need to (a) develop standardized batch study protocols, and potentially reference materials, for effective cross-evaluation of biosorbents of similar nature and for improved understanding of mechanisms involved and (b) investigate scaling-up and regeneration issues that hold back industry-level application of preselected adsorbents.
- [Show abstract] [Hide abstract] ABSTRACT: Forty-nine white-rot strains belonging to 38 species of Basidiomycota were evaluated for olive-mill wastewater (OMW) degradation. Almost all fungi caused high total phenolics (>60%) and color (⩽70%) reduction, while COD and phytotoxicity decreased to a lesser extent. Culture extracts from selected Agrocybe cylindracea, Inonotus andersonii, Pleurotus ostreatus and Trametes versicolor strains showed non-altered physicochemical and enzymatic activity profiles when applied to raw OMW in the presence or absence of commercial catalase, indicating no interaction of the latter with fungal enzymes and no competition for H2O2. Hydrogen peroxide's addition resulted in drastic OMW's decolorization, with no effect on phenolic content, suggesting that oxidation affects colored components, but not necessarily phenolics. When fungal extracts were heat-treated, no phenolics decrease was observed demonstrating thus their enzymatic rather than physicochemical oxidation. Laccases added to OMW were reversibly inhibited by the effluent's high phenolic load, while peroxidases were stable and active during the entire process. Copyright © 2015 Elsevier Ltd. All rights reserved.
- [Show abstract] [Hide abstract] ABSTRACT: Composting may alter the sorption properties of organic materials deriving from renewable sources. The widely available olive tree pruning waste (OTPW) and its composted form (COTPW) were comparatively tested for Pb2+ and Ni2+ removal in single- and double-metal systems. Pb2+ biosorption was higher than that of Ni2+ and increased metal biosorption was observed up to pH 5.0. The process followed pseudo-second order kinetics and described by the Langmuir isotherm. Surface area, total pore volume and zeta potential values were increased following composting, while cation exchange capacity was over-doubled (from 37.6 to 87.4 cmolc kg−1) leading to higher Pb2+ and Ni2+ biosorption and improved biosorption at elevated temperatures. There was 144%, 78%, and 148% increase in the maximum sorption capacity for Pb2+ and 29%, 59%, and 108% for Ni2+ at 10, 25 and 60 °C respectively. FTIR analysis indicated significant shifts in the chemical structure of OTPW as a result of composting, in line with oxidative decomposition processes. Among the desorption solutions tested, HNO3 and EDTA showed maximum recovery of both metals. Physisorption of both metals was greatly reduced by composting, leading to a biosorbent that retained Pb2+ and Ni2+ more efficiently. The suppressive effect of Ni2+ on Pb2+ sorption on OTPW throughout the whole range of Pb+2 concentrations, and the suppressive effect of Pb+2 on Ni+2 sorption at low Ni+2 concentrations were both alleviated when composted OTPW was used. Overall, OTPW proved to be a highly efficient biosorbent, especially for Pb2+, and composting resulted in multifunctional improvement of sorption characteristics.
- [Show abstract] [Hide abstract] ABSTRACT: Two composts were prepared from olive press cake (OPC) repeatedly turned and moistened with either olive mill wastewater (OPC+OMW) or water (OPC+W). When phytotoxicity was drastically reduced and the pH of the composts had reached 8.6 and 7.55 respectively, elemental sulfur was added at 0.9% of dry weight to the OPC+OMW compost and at five different doses (0.1 – 1.0% of dry wt) to the OPC+W compost. During the following six months, an exponential pH decline was observed in both compost materials. The pH reached a final value of 5.8 in the OPC+OMW compost whereas a pH decline related to the amount of added sulfur was observed in the OPC+W compost (final values from 6.8 to 4.3). Over 80% of the pH decline occurred during the first two months following the sulfur addition. Sulfur was applied following the stabilization of the material in the case of OPC+W. No phytotoxic effects of the final products were observed at sulfur application doses up to 0.5% of dry compost weight, but a significant germination index reduction was observed at the 1% dose, probably related to the increased conductivity of the compost leachate. Sulfur was applied before stabilization of the compost material, in the case of OPC+OMW, to also investigate the effects of sulfur addition on the composting process. A thermophilic phase similar to that observed after the last OMW application exceeding 50°C followed, and no effects on microbial activity profiles of the compost were observed. The results indicate that small amounts of elemental sulfur may efficiently control high pH values in the final compost products and could be safely applied at late composting stages or after composting. This may broaden the utilization of these composts in potting media and alkaline soils.
- [Show abstract] [Hide abstract] ABSTRACT: The effects of time and a labile carbon (C) source on the fates of zinc (Zn) and copper (Cu) were investigated in a slightly acidic soil in a two-factor experiment. Glucose was used as the C source to examine the effect of the expected flush of microbial activity on Zn and Cu extractability during the experimental period. The soil was amended with 500 mg kg−1 soil of Zn and Cu in the form of nitrate salts and with 4 g kg−1 glucose where appropriate, producing M (heavy metals, no glucose) and MG (heavy metals, with glucose) treatments. The treated soil samples were incubated for 3 h, 1 day (24 h), 3 days (72 h), 10 days (240 h), 30 days (720 h), and 60 days (1440 h) at 20 °C at constant moisture (≈50% of the soil's water-holding capacity). At the end of each incubation period, destructive sampling was followed by a Tessier sequential extraction procedure that yielded five metal fractions for both Zn and Cu, defined as exchangeable, acid-soluble, reducible, oxidizable, and residual. The exchangeable fraction of Zn and Cu (considered to be an availability measure) showed decreasing trends over time, while the opposite was observed for the other fractions. The presence of glucose resulted in significantly lower exchangeable fractions in the “polluted soil” for both metals up to 720 h, pointing to lower Zn and Cu availability. Redistribution from less-available forms back to exchangeable forms occurred during the second month of incubation, suggesting a sharp decline in microbial activity and a consequent remobilization and potentially increased Zn and Cu bioavailability. However, glucose did not affect Zn and Cu availability in the control soil; this indicated that its effect is mainly observed following recent pollution events. Field applications of glucose at 4 g kg−1 soil is impractical in practice; future experimentation to estimate a minimum effective application rate or an alternative form of labile C, probably derived from recycling renewable labile organic materials, is warranted.
- [Show abstract] [Hide abstract] ABSTRACT: Glucosinolates (GSLs) are secondary metabolites found in Brassica species. Upon tissue disruption GSLs are hydrolyzed by myrosinase enzymes to isothiocyanates (ITCs) which are highly toxic to microbes. Therefore the incorporation of fresh Brassicaceae tissues into soil for the control of soil-born plant pathogens is viewed as a biofumigation process. Its efficacy relies on the rate of GSL conversion to ITCs, but also on environmental factors controlling GSL availability in the soil matrix. We studied the dissipation of GSLs, applied either by broccoli leaves or as pure compounds, in a clay loam soil at two soil moisture content levels. Regardless of their mode of application, GSLs were rapidly dissipated in soil with half-life values ranging from 3.2 to 15.5 h. Increasing moisture from 20 to 90% of the soil water holding capacity significantly accelerated their dissipation. Indolyl broccoli-derived GSLs dissipated faster than aliphatic GSLs at high moisture levels, while at low moisture levels a three-fold reduction in their dissipation rates was observed. The dissipation of aliphatic GSLs was less affected by soil moisture levels. Application of pure GSLs resulted in increased soil metabolic quotients (qCO2), suggesting a decline is microbial metabolic efficiency. Their dissipation was related to myrosinase activity apparently derived from soil microbes.
- [Show abstract] [Hide abstract] ABSTRACT: Horticultural crops in the Mediterranean basin have to cope with severe drought conditions. The effect of inoculating watermelon plants grown under limited water availability conditions with AM fungi on the fruit yield, water use efficiency (WUE), root-N and -P content was examined. We focused on the impact of watering level and inoculation with allochthonous AM fungi on the diversity and presence of AM fungi in the watermelon roots using molecular techniques. An open field experiment was conducted and plants were grown with (M) and without AM fungal inoculum (NM), subjected to water stress (NW) and no stress conditions (W). Suboptimal water application (NW) resulted in significant reduction of fruit yield, root-N and -P content. Inoculation of plants grown under water stress resulted in a significant increase of WUE (19%), fruit yield (19%), root-N (27%) and -P (40%). However, only root-P responded to AM inoculation under non water stress conditions demonstrating 23% increase in M plants. DNA extracted from root samples was subjected to PCR–DGGE analysis. The native mycorrhizal population colonized watermelon roots, as indicated by DGGE bands in NM treatments. Some members of this colonizer community appear sensitive to the introduction of allochthonous inocula and to water stress conditions. Cloning and sequencing of AM fungi revealed that watermelon roots were colonized by Glomus and Paraglomus species. A TaqMan real-time PCR assay was also carried out targeting the 18S rRNA gene for the quantification of AM nucleic acids. The 18S rRNA copy numbers of AM fungi were significantly increased in M plants compared to NM plants under water stress. On the contrary, under non stress conditions M and NM plants did not show significant differences, indicating that inoculation with AM fungi was related to the response of plants to water stress conditions. Principle coordinate analysis of the DGGE banding patterns showed that the diversity of AM fungal colonizers was strongly affected (i) by inoculation and (ii) by water stress in the inoculated plants. Inoculation affected fungal presence under water limitation conditions only. The latter was in line with the significant beneficial effect of inoculation on both WUE and yield only under water limitation.
- [Show abstract] [Hide abstract] ABSTRACT: Background and Aims Rocket salad (Eruca sativa Mills) is one of the major leafy vegetables produced worldwide and has been characterized as a rich source of chemoprotective glucosinolates (GSL). The relationship between N fertilization and the resulting plant biomass and N status with GSL quantity and quality in rocket leaves was examined. Methods A pot experiment was conducted, applying ten different N-rates and destructive sampling was carried out 15, 30 and 45 days after transplanting (DAT). The Mitscherlich equation was used to establish NO3-N critical levels at each growth stage and as an indicator of N demand for relative maximum dry matter accumulation and glucosinolate content and composition was determined. Results Glucosinolate content was significantly influenced by N rate, growth stage and their interaction. Different GSL types showed dissimilar responses to N fertilization: aliphatic GSLs were significantly reduced under increased N rates whereas indole GSL showed the reverse. Under excess N fertilization (>1.04 g/plant), dry matter accumulation remained constant, NO3-N was significantly increased and total GSL content was significantly reduced, factors that could lead to an anticipated product quality decline. Conclusions The application of the critical NO3-N level approach used to identify optimal N fertilization rates for plant growth could serve as means to obtain optimized GSL content in the edible plant parts.
- [Show abstract] [Hide abstract] ABSTRACT: Thirty-nine white-rot fungi belonging to nine species of Agaricomycotina (Basidiomycota) were initially screened for their ability to decrease olive-mill wastewater (OMW) phenolics. Four strains of Ganoderma australe, Ganoderma carnosum, Pleurotus eryngii and Pleurotus ostreatus, were selected and further examined for key-aspects of the OMW biodegradation process. Fungal growth in OMW-containing batch cultures resulted in significant decolorization (by 40-46% and 60-65% for Ganoderma and Pleurotus spp. respectively) and reduction of phenolics (by 64-67% and 74-81% for Ganoderma and Pleurotus spp. respectively). COD decrease was less pronounced (12-29%). Cress-seeds germination increased by 30-40% when OMW was treated by Pleurotus strains. Toxicity expressed as inhibition of Aliivibrio fischeri luminescence was reduced in fungal-treated OMW samples by approximately 5-15 times compared to the control. As regards the pertinent enzyme activities, laccase and Mn-independent peroxidase were detected for Ganoderma spp. during the entire incubation period. In contrast, Pleurotus spp. did not exhibit any enzyme activities at early growth stages; instead, high laccase (five times greater than those of Ganoderma spp.) and Mn peroxidases activities were determined at the end of treatment. OMW decolorization by Ganoderma strains was strongly correlated to the reduction of phenolics, whereas P. eryngii laccase activity was correlated with the effluent's decolorization.
- [Show abstract] [Hide abstract] ABSTRACT: The high wastewater volumes produced during citrus production at pre- and post-harvest level presents serious pesticide point-source pollution for groundwater bodies. Biobeds are used for preventing such point-source pollution occurring at farm level. We explored the potential of biobeds for the depuration of wastewaters produced through the citrus production chain following a lab-to-field experimentation. The dissipation of pesticides used pre- or post-harvest was studied in compost-based biomixtures, soil, and a straw-soil mixture. A biomixture of composted grape seeds and skins (GSS-1) showed the highest dissipation capacity. In subsequent column studies, GSS-1 restricted pesticides leaching even at the highest water load (462 Lm(-3)). Ortho-phenylphenol was the most mobile compound. Studies in an on-farm biobed filled with GSS-1 showed that pesticides were fully retained and partially or fully dissipated. Overall biobeds could be a valuable solution for the depuration of wastewaters produced at pre- and post-harvest level by citrus fruit industries.
- [Show abstract] [Hide abstract] ABSTRACT: a b s t r a c t Fusarium solani strain FsK (FsK), isolated from a plant pathogen-suppressive compost, grows endo-phytically in tomato roots and controls infestations by Fusarium oxysporum f.sp. radicis-lycopersici (FORL). The effect of root colonization by the two fungi on the diversity of rhizosphere microbial community was studied. Tomato plants were inoculated with FsK and/or FORL and rhizosphere soil was collected 8, 15 and 30 days post inoculation (dpi) and analyzed by denaturating gradient gel electrophoresis (DGGE) of PCR-amplified internal transcribed spacer (ITS) sequences of fungi and 16S rRNA gene sequences of common rhizosphere bacterial guilds like alpha-proteobacteria and pseudomonads. Cluster analysis of DGGE fingerprints showed that FsK had a transient impact on the fungal and alpha-proteobacterial community only during its endophytic stage (15 dpi), while FORL had a readily distinguished and persistent effect on the fungal community. The changes observed in the rhizosphere fungal and bacterial communities may depict the interactions of the two fungal inocula with the plant. Cloning of selected DGGE bands stimulated by FsK showed that the responsive bacteria were closely related to species known to include biological control agents (BCA). Overall, the inoculation of FsK in tomato rhizosphere did not appear to have a significant impact on the diversity of non-target microbial groups inhabiting plant rhizosphere.
- [Show abstract] [Hide abstract] ABSTRACT: Wastewaters from the fruit packaging industry contain a high pesticide load and require treatment before their environmental discharge. We provide first evidence for the potential bioremediation of these wastewaters. Three white rot fungi (WRF) (Phanerochaete chrysosporium, Trametes versicolor, Pleurotus ostreatus) and an Aspergillus niger strain were tested in straw extract medium (StEM) and soil extract medium (SEM) for degrading the pesticides thiabendazole (TBZ), imazalil (IMZ), thiophanate methyl (TM), ortho-phenylphenol (OPP), diphenylamine (DPA) and chlorpyrifos (CHL). Peroxidase (LiP, MnP) and laccase (Lac) activity was also determined to investigate their involvement in pesticide degradation. T. versicolor and P. ostreatus were the most efficient degraders and degraded all pesticides (10 mg l⁻¹) except TBZ, with maximum efficiency in StEM. The phenolic pesticides OPP and DPA were rapidly degraded by these two fungi with a concurrent increase in MnP and Lac activity. In contrast, these enzymes were not associated with the degradation of CHL, IMZ and TM implying the involvement of other enzymes. T. versicolor degraded spillage-level pesticide concentrations (50 mg l⁻¹) either fully (DPA, OPP) or partially (TBZ, IMZ). The fungus was also able to rapidly degrade a mixture of TM/DPA (50 mg l⁻¹), whereas it failed to degrade IMZ and TBZ when supplied in a mixture with OPP. Overall, T. versicolor and P. ostreatus showed great potential for the bioremediation of wastewaters from the fruit packaging industry. However, degradation of TBZ should be also achieved before further scaling up.
- [Show abstract] [Hide abstract] ABSTRACT: The majority of innovations pioneered within/for the organic olive oil production (OOOP) chain may, and are, increasingly becoming, adopted by the conventional olive oil production chain, especially regarding cultivation, inputs related to plant/ecosystem protection and trade/promotion of specialized high quality products. Therefore the OOOP-chain may become a pioneering paradigm, for the implementation and convergence of agricultural production, marketing, sustainable rural development and environmental/biodiversity protection EU policies in the Mediterranean. Moreover, it appears that OOOP systems are increasingly becoming model systems for developing, applying and evaluating innovations that may have far more general applicability for Mediterranean agriculture. There is little divergence between conventional and organic production regarding water consumption and waste production, but the OOOP-chain has a lower impact as regards to soil erosion, desertification, pollution due chemicals and fertilizers (minimal), and effects on wildelife/vegetation biodiversity. Regarding pest and disease control, Bactrocera oleae is the most common pest problem, but effective means of control are available. On the contrary, Verticillium wilt is constantly expanding and, although not still a widespread problem, it is difficult to manage. Bottom-up demand for innovations, however, tends to underrate the need for innovations on common marketing priorities, trade policies, infrastructure and joint promotion strategies. Regarding “biopesticides” and “natural products”, approval protocols and legislation regarding synthetic inputs should also be fully applied to these products, to assure safe development of the OOOP sector. Key words: innovations, organic olive oil, sustainability , environmental protection, Biolmed project.
- [Show abstract] [Hide abstract] ABSTRACT: Biofumigation (BIOF) is carried out mainly by the incorporation of brassica plant parts into the soil, and this fumigation activity has been linked to their high glucosinolate (GSL) content. GSLs are hydrolyzed by the endogenous enzyme myrosinase to release isothiocyanates (ITCs). A microcosm study was conducted to investigate the effects induced on the soil microbial community by the incorporation of broccoli residues into soil either with (BM) or without (B) added myrosinase and of chemical fumigation, either as soil application of 2-phenylethyl ITC (PITC) or metham sodium (MS). Soil microbial activity was evaluated by measuring fluorescein diacetate hydrolysis and soil respiration. Effects on the structure of the total microbial community were assessed by phospholipid fatty acid analysis, while the impact on important fungal (ascomycetes (ASC)) and bacterial (ammonia-oxidizing bacteria (AOB)) guilds was evaluated by denaturating gradient gel electrophoresis (DGGE). Overall, B, and to a lesser extent BM, stimulated microbial activity and biomass. The diminished effect of BM compared to B was particularly evident in fungi and Gram-negative bacteria and was attributed to rapid ITC release following the myrosinase treatment. PITC did not have a significant effect, whereas an inhibitory effect was observed in the MS-treated soil. DGGE analysis showed that the ASC community was temporarily altered by BIOF treatments and more persistently by the MS treatment, while the structure of the AOB community was not affected by the treatments. Cloning of the ASC community showed that MS application had a deleterious effect on potential plant pathogens like Fusarium, Nectria, and Cladosporium compared to BIOF treatments which did not appear to inhibit them. Our findings indicate that BIOF induces changes on the structure and function of the soil microbial community that are mostly related to micro.
Dataset: Supplementary Material
- [Show abstract] [Hide abstract] ABSTRACT: Vegetable production demands high nitrogen inputs. Fertigation is a means to increase fertilizer-N use by plants. However, the effect of different N sources and doses, and how they relate to the total available N in soils are poorly known. In this study we applied 15N-labeled fertilizers to green pepper in the field using a drip irrigation system during the dry summer. KNO3-N and urea-N were applied at a total of 6, 12 and 18 g plant−1. Our results show that urea was as effective as KNO3 as a N source. The fertilizer-N utilization efficiency was dramatically reduced at higher N doses, from 48% for the 6 g N plant−1 dose to 36% and 26% for the 12 and 18 g N plant−1 doses, respectively. However, the N in plants derived from fertilizer consistently exceeded 60%, indicating high availability of fertilizer-N even at the lowest dose. Negative added nitrogen interactions — the effect of added N on the fate of soil-N — were observed, particularly at high fertilizer-N doses. The fertilizer-N utilization efficiency calculated by the difference method was lower compared with the 15N enrichment method. This clearly indicates luxury N applications and excess N availability brought about by precise localized placement of fertilizer-N that leads to limited uptake of the available soil-N. N leaching risks in the following rain period should therefore be based on both the residual fertilizer-N and the increased amounts of residual soil mineral-N.
- [Show abstract] [Hide abstract] ABSTRACT: This study reports on the concentrations, distribution, and availability of heavy metals in the children’s playground soils of Athens. Playgrounds were chosen because they are open city areas; they show relatively even spatial distribution within the district of Athens and are used by a great number of young children and their escorts on a regular basis. Samples were collected from 70 playground surface soils, representing more than 70% of the city’s playgrounds. Cu, Zn, Pb, Cr, Ni, Co, Mn, and Fe were extracted by aqua regia and by diethylene triamine pentaacetic acid (DTPA) to estimate total and available metal forms, respectively. Their mean total concentrations were 43, 174, 110, 80, 82, 22, 312, and 17 × 103 mgkg−1, respectively. The DTPA-extracted fraction showed much lower values, with means of 2.5, 7.8, 5.8, 1.5, 1.3, 0.4, 8.4, and 2.0mgkg−1 respectively, which, however, should be carefully monitored since they relate directly to the bioavailable fraction of heavy metals. Though mean values of metal concentrations are not particularly high, the calculated enrichment factors indicate site-specific cases of high enrichment with heavy metals. Considering that the bioavailable fraction of a metal is possibly a more appropriate indicator for the recent soil pollution history, availability ratios were calculated and their distribution was visualized over the entire city profile using the appropriate GIS software. It was shown that recent metal pollution events appear to have affected mostly playground sites in the southern and eastern part of the municipality. KeywordsUrban soils-Heavy metals-Playgrounds-Enrichment factor-Metal availability-Metal pollution
Agricultural University of Athens
Athínai, Attica, Greece
- • Laboratory of Soil Science and Agricultural Chemistry
- • Laboratory of Pesticide Science