Influence of soil inorganic amendments on heavy metal accumulation by leafy vegetables

The present study aims to assess the effect of four inorganic soil amendments, such as lime (CaCO3), red mud consisting of 75% hematite (Fe2O3), gypsum (CaSO4·2H2O), and Al oxide (Al2O3), of an alkaline heavy metal-contaminated soil. For this purpose, a pot experiment was conducted by physically mixing individual six subsamples of a soil sample collected from Thessaly area with four inorganic soil amendments along with two leafy plants, spinach and lettuce. Al oxide causes the maximum reduction of the water-soluble Cu concentration, as its concentrations is no longer detectable. The Cu availability index decreases when aluminum oxide was used. The use of gypsum and red mud caused almost equal reduction while the smallest decrease was caused by the use of lime. The Zn availability index decreased equally when aluminum oxide and gypsum were mixed with the soil sample. The highest reduction of Cu and Zn transfer coefficient (TC) was observed when the Al2O3 was used. In spinach, Zn TC reduction was 39.8% and Cu TC reduction was 41.0%. In lettuce, the addition of Al2O3 led to Cu TC reduction of over 37.3% and Zn TC reduction of up to 38.7%. Generally, Al2O3 nanoparticles may function as suitable sorbents for the removal of Zn and Cu from soil samples, with an increasing effectiveness in spinach rather than lettuce. Liming materials seem to increase the soil alkalinity and promote the complexation of soluble heavy metals with hydroxide ions leading to immobilization of heavy metals in soil and reduce their amount in leafy vegetables. Remediation of contaminated soils is considered necessary to reduce environmental risks and to achieve the means available to increase agricultural production of safe and quality food.

Determination of Pesticide Residues in Honey by Single-Drop Microextraction and Gas Chromatography

A novel, simple, and rapid single-drop microextraction (SDME) procedure combined with GC has been developed, validated, and applied for the determination of multiclass pesticide residues in honey samples. The SDME was optimized using a Plackett-Burman screening design considering all parameters that may influence an SDME procedure and a consequent central composite design to control the parameters that were found to significantly influence the pesticide determination. The developed analytical method required minimal volumes of organic solvents and exhibited good analytical characteristics with enrichment factors ranging from 3 for -endosulfan to 10 for lindane, procymidone, and captan and method quantification limits ranging from 0.03 g/kg for phosalone to 10.6 g/kg for diazinon. The relative recoveries obtained ranged from 70.8 for captan to 120 for fenarimol, and the precision (RSD) ranged from 3 to 15. The proposed SDME procedure followed by GC with an electron capture detector for quantification and GC/MS for identification was applied with success to the analysis of 17 honey samples. Monitoring results indicated a low level of honey contamination by diazinon, chlorpyrifosethyl, procymidone, bromopropylate, and endosulfan (-, -, and endosulfan sulfate) residues that were far below the maximum residue limit values specified by the European Union for endosulfan (10 g/kg) and bromopropylate (100 g/kg) in honey samples.

Quantitative and qualitative differences in the metabolism of pesticides in biobed substrates and soil

Biobed substrates commonly exhibit high degradation capacity. However, degradation does not always lead to detoxification and information on the metabolic pathways of pesticides in biobeds is scarce. We studied the degradation and metabolism of three pesticides in selected biomixtures and soil. Biomixtures stimulated degradation of terbuthylazine and metribuzin, whereas chlorpyrifos degraded faster in soil. The latter was attributed to the lipophilicity of chlorpyrifos which increased adsorption and limited biodegradation in organic-rich biomixtures. Although the same metabolites were detected in all substrates, qualitative and quantitative differences in the metabolic routes of pesticides in the various substrates were observed. Chlorpyrifos was hydrolyzed to 3,5,6-tricholorpyridinol (TCP) which was further degraded only in compost-biomixture CBX1. Metabolism of terbuthylazine in compost biomixtures (BX) and soil resulted in the formation of desethyl-terbuthylazine (DES) which was fully degraded only in the compost-biomixture CBX2, whereas peat-based biomixture (OBX) promoted the hydroxylation of terbuthylazine. Desamino- (DA) (dominant) and diketo- (DK) metribuzin appear as intermediate metabolites in all substrates and were further transformed to desamino-diketo-metribuzin (DADK) which was fully degraded only in compost-biomixture GSBX. Overall, lower amounts of metabolites were accumulated in biomixtures compared to soil stressing the higher depuration efficiency of biobeds.

Optimization of biomixture composition and water management for maximum pesticide dissipation in peat-free biobeds

Biomixture composition and water management are key factors controlling biobeds performance. Although compost-biomixtures (BXs) possess high degradation efficiency, their low water-holding capacity compared with peat-biomixtures (OBX) limits their use. Thus, appropriate water management is required to optimize their performance. The dissipation capacity of selected BXs compared with OBXs was assessed in a column study under two water managements not differing in their total water load but in the intensity and frequency of water addition. Results showed that the less frequent application of large water volumes (water management scenario I) facilitated pesticide leaching (0.001-10.4% of initially applied), compared with the frequent application of low water volumes (water management scenario II) where leaching losses were always <1%. Water management affected differently the dissipation performance of substrates: OBX outperformed BXs under water management scenario I, whereas the grape marc compost-biomixture (BX1) was superior at water management scenario II. Substitution of grape marc compost (C1) with olive leaves compost (C2) or of straw with corn cobs or grape stalks reduced the dissipation capacity of BX1. Mass balance analysis revealed that the high dissipation capacity of OBX was mostly attributable to its high ability to retain rather than degrade pesticides, whereas the exact opposite was seen for BX1. Overall, our findings suggest that BXs-biobeds could treat large wastewater volumes under appropriate water management that extends the contact period between pesticides and BXs, thus exploiting their high biodegradation capacity.

On-farm biopurification systems for the depuration of pesticide wastewaters: recent biotechnological advances and future perspectives

Point source contamination of natural water resources by pesticides constitutes a serious problem and on-farm biopurification systems (BPS) were introduced to resolve it. This paper reviews the processes and parameters controlling BPS depuration efficiency and reports on recent biotechnological advances which have been used for enhancing BPS performance. Biomixture composition and water management are the two factors which either individually or through their interactions control the depuration performance of BPS. Which process (biodegradation or adsorption) will dominate pesticides dissipation in BPS depends on biomixture composition and the physicochemical properties of the pesticides. Biotechnological interventions such as augmentation with pesticide-degrading microbes or pesticide-primed matrices have resulted in enhanced biodegradation performance of BPS. Despite all these advancement in BPS research, there are still several issues which should be resolved to facilitate their full implementation. Safe handling and disposal of the spent biomixture is a key practical issue which needs further research. The use of BPS for the depuration of wastewaters from post-farm activities such as postharvest treatment of fruits should be a priority research issue considering the lack of alternative treatment systems. However, the key point hampering optimization of BPS is the lack of fundamental knowledge on BPS microbiology. The use of advanced molecular and biochemical methods in BPS would shed light into this issue in the future.

Key parameters and practices controlling pesticide degradation efficiency of biobed substrates

We studied the contribution of each of the components of a compost-based biomixture (BX), commonly used in Europe, on pesticide degradation. The impact of other key parameters including pesticide dose, temperature and repeated applications on the degradation of eight pesticides, applied as a mixture, in a BX and a peat-based biomixture (OBX) was compared and contrasted to their degradation in soil. Incubation studies showed that straw was essential in maintaining a high pesticide degradation capacity of the biomixture, whereas compost, when mixed with soil, retarded pesticide degradation. The highest rates of degradation were shown in the biomixture composed of soil/compost/straw suggesting that all three components are essential for maximum biobed performance. Increasing doses prolonged the persistence of most pesticides with biomixtures showing a higher tolerance to high pesticide dose levels compared to soil. Increasing the incubation temperature from 15 °C to 25 °C resulted in lower t(1/2) values, with biomixtures performing better than soil at the lower temperature. Repeated applications led to a decrease in the degradation rates of most pesticides in all the substrates, with the exception of iprodione and metalaxyl. Overall, our results stress the ability of biomixtures to perform better than soil under unfavorable conditions and extreme pesticide dose levels.

Determination of pesticide residues in honey by single-drop microextraction and gas chromatography

A novel, simple, and rapid single-drop microextraction (SDME) procedure combined with GC has been developed, validated, and applied for the determination of multiclass pesticide residues in honey samples. The SDME was optimized using a Plackett-Burman screening design considering all parameters that may influence an SDME procedure and a consequent central composite design to control the parameters that were found to significantly influence the pesticide determination. The developed analytical method required minimal volumes of organic solvents and exhibited good analytical characteristics with enrichment factors ranging from 3 for alpha-endosulfan to 10 for lindane, procymidone, and captan and method quantification limits ranging from 0.03 microg/kg for phosalone to 10.6 microg/kg for diazinon. The relative recoveries obtained ranged from 70.8% for captan to 120% for fenarimol, and the precision (RSD) ranged from 3 to 15%. The proposed SDME procedure followed by GC with an electron capture detector for quantification and GC/MS for identification was applied with success to the analysis of 17 honey samples. Monitoring results indicated a low level of honey contamination by diazinon, chlorpyrifos-ethyl, procymidone, bromopropylate, and endosulfan (alpha-, beta-, and endosulfan sulfate) residues that were far below the maximum residue limit values specified by the European Union for endosulfan (10 microg/kg) and bromopropylate (100 microg/kg) in honey samples.

Isolation of soil bacteria able to hydrolyze both organophosphate and carbamate pesticides

Two bacteria identified as Pseudomonas putida and Acinetobacter rhizosphaerae able to rapidly degrade the organophosphate (OP) fenamiphos (FEN) were isolated. Denaturating gradient gel electrophoresis analysis revealed that the two isolates were dominant members of the enrichment culture. Clone libraries further showed that bacteria belonging to α-, β-, γ-proteobacteria and Bacteroidetes were also present in the final enrichment but were not isolated. Both strains hydrolyzed FEN to fenamiphos phenol which was further transformed, only by P. putida. The two strains were using FEN as C and N source. Cross-feeding studies with other pesticides showed that P. putida degraded OPs with a P-O-C linkage and unexpectedly degraded the carbamates oxamyl and carbofuran being the first wild-type bacterial strain able to degrade both OPs and carbamates. The same isolate exhibited high bioremediation potential against spillage-level concentrations of aged residues of FEN and its oxidized derivatives.

Degradation and adsorption of terbuthylazine and chlorpyrifos in biobed biomixtures from composted cotton crop residues

BACKGROUND

Biobeds have been well studied in northern Europe, whereas little is known regarding their use in southern Europe. The degradation and adsorption of terbuthylazine (TA) and chlorpyrifos (CP) were studied in three different biomixtures composed of composted cotton crop residues, soil and straw in various proportions, and also in sterilised and non-sterilised soil.

RESULTS

Compost biomixtures degraded the less hydrophobic TA at a faster rate than soil, while the opposite was evident for the more hydrophobic CP. These results were attributed to the rapid abiotic hydrolysis of CP in the alkaline soil (pH 8.5) compared with the lower pH of the compost (6.6), but also to the increasing adsorption (K(d) = 746 mL g(-1)) and reduced bioavailability of CP in the biomixtures compared with soil (K(d) = 17 mL g(-1)), as verified by the adsorption studies.

CONCLUSIONS

Compost had a dual but contrasting effect on degradation that depended on the chemical nature of the pesticide studied: a positive effect towards TA owing to increasing biodegradation and a negative effect towards CP owing to increasing adsorption. Overall, composted cotton crop residues could be potentially used in local biobed systems in Greece, as they promoted the degradation of hydrophilic pesticides and the adsorption of hydrophobic pesticides.

Degradation and adsorption of pesticides in compost-based biomixtures as potential substrates for biobeds in southern Europe

Biobeds have been used in northern Europe for minimizing point source contamination of water resources by pesticides. However, little is known regarding their use in southern Europe where edaphoclimatic conditions and agriculture practices significantly differ. A first step toward their adaptation in southern Europe is the use of low-cost and easily available substrates as biomixture components. This study investigated the possibility of replacing peat with agricultural composts in the biomixture. Five composts from local substrates including olive leaves, cotton crop residues, cotton seeds, spent mushroom substrate, and commercial sea wrack were mixed with topsoil and straw (1:1:2). Degradation of a mixture of pesticides (dimethoate, indoxacarb, buprofezin, terbuthylazine, metribuzin, metalaxyl-M, iprodione, azoxystrobin) at two dose rates was tested in the compost biomixtures (BX), in corresponding peat biomixtures (OBX), and in soil. Adsorption-desorption of selected pesticides were also studied. Pesticide residues were determined by gas chromatography with nitrogen-phosphorus detector, except indoxacarb, which was determined with a microelectron capture detector. Overall, BX degraded the studied pesticides at rates markedly higher than those observed in soil and OBX, in which the slowest degradation rates were evident. Overall, the olive leaf compost biomixture showed the highest degradation capacity. Adsorption studies showed that OBX and BX had higher adsorption affinity compared to soil. Desorption experiments revealed that pesticide adsorption in biomixtures was not entirely reversible. The results suggest that substitution of peat with local composts will lead to optimization of the biobed system for use in Mediterranean countries.

Novel biomixtures based on local Mediterranean lignocellulosic materials: evaluation for use in biobed systems

The composition of biomixtures strongly affect the efficacy of biobeds. Typically, biomixture consists of peat (or compost), straw (STR) and topsoil (1:2:1 by volume). Straw guarantees a continuous supply of nutrients and high microbial activity. However, in south Europe other lignocellulosic materials including sunflower crop residues (SFR), olive leaves, grape stalks (GS), orange peels, corn cobs (CC) and spent mushroom substrate (SMS) are also readily available at no cost. Their potential utilization in biomixtures instead of STR was tested in pesticide degradation and adsorption studies. The microbial activity in these biomixtures was also assessed. The GS-biomixture was the most efficient in pesticide degradation, while CC- and SFR-biomixtures showed comparable degrading efficacy with the STR-biomixture. The SMS-biomixture was also highly efficient in degrading the pesticide mixture with degradation rates being correlated with the proportion of SMS in the biomixture. Microbial respiration was positively correlated with the degradation rates of metalaxyl, azoxystrobin and chlorpyrifos, compared to phenoloxidase which showed no correlation. Biomixtures containing alternative lignocellulosic materials showed a higher adsorption affinity for terbuthylazine and metribuzin compared to the STR-biomixture. We provide first evidence that STR can be substituted in biomixtures by other lignocellulosic materials which are readily available in south Europe.

Rapid gas chromatographic method for the determination of famoxadone, trifloxystrobin and fenhexamid residues in tomato, grape and wine samples

Trifloxystrobin, fenhexamid and famoxadone belong to the generation of fungicides acting against a broad spectrum of fungi and widely used in Integrated Pest Management strategies in different agricultural crops but mainly in viticulture. In the present work, a gas chromatographic (GC) method for their determination was developed and validated on tomato, grape and wine matrices. The method was based on a simple one step liquid-liquid microextraction with cyclohexane/dichloromethane (9+1, v/v) and determination of fungicides by gas chromatography with nitrogen phosphorous (NP-) and electron capture (EC-) detection, and ion trap mass spectrometry (ITMS) for confirmation. The method was validated by recovery experiments, assessment of matrix effect and calculation of the associated uncertainty. Recoveries for GC-NPD and GC-ECD were found in the range of 81-102% with RSD <12%, while matrix-matched calibration solutions were imposed for quantification. LOQs ranged from 0.005 to 0.05 mg/kg and 0.01 to 0.10 mg/kg for the GC-ECD and GC-NPD, respectively, depending on the sensitivity of each compound with trifloxystrobin being the most sensitive. The expanded uncertainty, calculated for a sample concentration of 0.10 mg/kg, ranged from 4.8 to 13% for the GC-ECD and from 5.4 to 29% for the GC-NPD. The concentration levels for famoxadone residues found in tomato and grape samples from field experiments were clearly below the EU established MRL values, thus causing no problems in terms of food safety.

Evaluation of solid sorbents for the determination of fenhexamid, metalaxyl-M, pyrimethanil, malathion and myclobutanil residues in air samples

A methodology is described for greenhouse air analysis by sampling fenhexamid, pyrimethanil, malathion, metalaxyl-M and myclobutanil in solid sorbents. Pesticides were determined by gas chromatography with NP Detector. The trapping efficiency of XAD-2, XAD-4, Supelpak-2, Florisil and C-18 at different sampling conditions (rate, time and air humidity) and pesticides concentration levels has been evaluated. No breakthrough was observed in the range of concentration studied (0.10-75 microg of each pesticide). In almost all the cases good stability results were obtained. Personal pumps have been used with selected sorbents (Supelpak-2 and C-18) in order to sample malathion and fenhexamid in air of experimental greenhouse after their application in a tomato crop. The dissipation process of the analytes in various time periods after application has been studied. Malathion concentrations varied between 20.1 microg m(-3) just after application and 1.06 microg m(-3) 3 days later. Fenhexamid concentrations, determined by high performance liquid chromatography with UV detection, fall rapidly; after 12 h post-application being below 0.50 microg m(-3).

Evaluation of teflubenzuron residue levels in grapes exposed to field treatments and in the must and wine produced from them

Dissipation of benzoylurea insecticide teflubenzuron in grapes exposed to field treatments was evaluated. Vines of a white grape vineyard located in central Greece were sprayed twice, at a 28-day interval, with a commercial formulation of the insecticide at 12 g of active ingredient/100 L. Residues were determined by HPLC diode array detection, after ethyl acetate extraction and cleanup on silica phase cartridges, with a detection limit of 0.005 mg/kg. Under field conditions teflubenzuron residues in grapes were found to be very stable with no significant reduction for the whole experimental period of 49 days. However, residues were slightly lower than the maximum residue limits set by individual countries. The fate of teflubenzuron during the vinification process was also studied. Residues were found to be transferred completely into the must but, due to their high affinity for the suspended matter, were removed by approximately 98%; thus, very low concentrations were detected in the produced wine. Among various clarifying agents studied, charcoal was the only one found to be effective for removing teflubenzuron residues from wine.

Dissipation of teflubenzuron and triflumuron residues in field-sprayed and cold-stored pears

Dissipation of residues of benzoylurea insecticides teflubenzuron (TFB) and triflumuron (TFM) under field conditions was evaluated on a pear orchard in Greece. Residues were determined by UV-HPLC analysis, with a detection limit of 0.030 mg/kg for both pesticides. TFB residues in pears were found to persist for 2 weeks and decline thereafter with 48% of the initial deposit remaining 42 days after the last application. TFM residues were found to decline following first-order kinetics and with a half-life of 39(+/-7) days. Residues of both pesticides found in pears collected at harvest maturity were lower than the maximum residue limits (MRLs) set by individual countries. Dissipation of TFB and TFM in cold-stored pears was also evaluated. TFB residues were very persistent for the whole storage period, whereas TFM residues did not dissipate for 6 weeks and then showed a constant decline; 7% of the initial concentration remained at the end of the storage period of 29 weeks.

High-performance liquid chromatographic determination of benzoylurea insecticides residues in grapes and wine using liquid and solid-phase extraction

A method for the determination of the benzoylurea insecticides diflubenzuron, triflumuron, teflubenzuron, lufenuron and flufenoxuron in grapes and wine by HPLC has been developed and validated. Grape samples (50 g) were homogenized and extracted with ethyl acetate-sodium sulfate and further cleaned-up by solid-phase extraction on silica sorbent. Wine samples (10 ml) diluted with water (1:3) were solid-phase extracted on an octadecyl sorbent using methanol as the eluent. The pesticides were separated on a reversed-phase octadecyl narrow-bore column by gradient elution and the residues were determined with a UV diode array detector. The calibration plots were linear over the range 0.05-5 micrograms/ml. Recoveries of benzoylurea pesticides from spiked grapes (0.02-2.0 mg/kg) and wine (0.01-0.2 mg/l) were 85.8-101.6% and 69.1-104.8%, respectively, and the limits of quantification for these insecticides were < 0.01 mg/kg for grapes and < 0.01 mg/l for wine. The method was applied to the determination of flufenoxuron and teflubenzuron residues in grapes from treated fields and in produced wine.

Field Persistence Studies on Pendimethalin Residues in Onions and Soil after Herbicide Postemergence Application in Onion Cultivation

Field studies were undertaken to evaluate the fate of pendimethalin residues in spring and dry onions, after postemergence application of the herbicide in a clay soil onion planting in central Greece, at rates of 1.32 and 2.0 kg of active ingredient (ai)/ha. Residues were determined with capillary GC-ECD after onion extraction with 2-propanol/toluene and extract cleanup in a AgNO(3-)coated alumina column; the recovery of pendimethalin from spiked onions was found to be 82-99% and the limit of determination 0.007 mg/kg. Pendimethalin residues were found to decline rapidly, and it was estimated that 7 days after the treatment only half of the initial concentrations remained for both the low recommended dose (LRD) and the high recommended dose (HRD) experiments. In all cases the residues in dry bulb onion were well below the lowest maximum residue limit (MRL) set by European countries, which is 0.05 mg/kg. Residues in spring onions at harvest time were also below this level when treated at the LRD and were only slightly above in case of the HRD. The pendimethalin concentration in planting soil for the investigated period declined with half-lives of 37 and 39 days for the LRD and the HRD experiments, respectively.