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On-farm biopurification systems for the treatment of pesticide-contaminated wastewater are now found all over the world. The first type, called ground filled with a mixture of soil, peat and wood chips developed in Sweden in 1997 (Castillo et al., 2008). However, the b
Introduction
ground filled with a mixture of soil, peat and wood chips developed in Sweden in 1997 (Castillo et al., 2008). However, the bdurability of substrates in other environments, such as in a Mediterranean climate, has still to be defined.
A lined biobed was built at the University Experimental Farm in Legnaro (PD) using a mixtureand wood chips as organic material to assess efficiency and microbial community evolution(terbuthylazine: TERB and metolachlor: METO) were applied at the beginning of the seasonat high concentration to simulate a worst-case scenario. Leached water was sampled everyto autumn and, at the end of 2012, the substrate was also sampled.To determine herbicide concentration in soil, samples of 20 g were shaken for 1 hourmethanol:0.1 N HCl followed by centrifugation. The supernatants were filtered, evaporatedevaporator, re-dissolved in 50 ml of HCl, cleaned by solid phase extraction and re-dissolveddetermine herbicide concentration in water, 1 liter samples were filtered at 0.45 mm
Materials and Methods
determine herbicide concentration in water, 1 liter samples were filtered at 0.45 mmsolid phase extraction and re-dissolved in methanol. The analyses were performed by LC-To determine microbial community evolution two approaches were used: 1) ARISAIntergenic Spacer Analysis) to test the extent of PCR-detectable biodiversity ofassemblages in both untreated and treated substrate and 2) a newly-patented device (Fertimetersoil microbial activities of cellulolysis and proteolysis as functions of the extent of degradationfibres buried in the soil for fixed lengths of time and measured by residual dynamometricbreakage. The measures were repeated monthly for two years.
Results and Discussion
In general each sampling season showed a similar trend with the highestconcentration found in leached water a few days after the herbicide application
Low herbicide concentrations werefound in leached water at the end ofeach season, with the highest valuesvarying from 4.7 to 17 g l-1 for METOand TERB respectively in 2011.METO and TERB were also found in theprofile at the end of 2012. Theirconcentrations were about 30 g Kg-1.
concentration found in leached water a few days after the herbicide applicationand a reduction in concentration at the end of the year.
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Figure 4. Herbicide concentrations in leached water in three year experiment.
Conclusions
Notwithstanding its use, the biobed did not appear to depress functionalmicrobial activities in comparison to cropped soils. After four years the farmbiobed still showed good performances.
contaminated wastewater are now found all over the world. The first type, called biobed, was a hole in the ground filled with a mixture of soil, peat and wood chips developed in Sweden in 1997 (Castillo et al., 2008). However, the best solution in terms of efficiency and
Consiglio Nazionale delle Ricerche
ground filled with a mixture of soil, peat and wood chips developed in Sweden in 1997 (Castillo et al., 2008). However, the best solution in terms of efficiency and durability of substrates in other environments, such as in a Mediterranean climate, has still to be defined.
mixture of wheat strawevolution. Two herbicidesseason from 2009 to 2012
every month from spring
hour with 60 ml of 9:1evaporated in a rotary
dissolved in methanol. Topore size, cleaned by
Figure 1. Lined biobed atUniversity Experimental Farm inLegnaro
pore size, cleaned by-MS.(Amplified Ribosomalbacterial and fungal
Fertimeter) that reportsdegradation of cotton or silkdynamometric resistance to
Results and Discussion
ARISA tests showed no evidence of biobed-related impact in terms of taxa richness,
Simpson index
Shannonindex
Figure 2. Cotton and silk fibres forfertimeter
Figure 3. Dynamometer tomeasure the fibre resistance tobreakage
The biobed did not appear to depress functional microbial activities incomparison to cropped soils. An active season-dependent level of degradationwas observed with peaks of 40-50% occurring between late May and June.Interestingly, during the brief peak period, soil microorganisms were observedto experience a non-limiting availability of soil nitrogen and phosphorus (Table2). This condition did not occur earlier or later in the year.
related impact in terms of taxa richness,Simpson or Shannon diversity index, withvalues (Table 1) that were in line with thoseoccurring in agricultural soils of the sameregion (unpublished data).
BACTERIA 0.94 (± 0.01) 3.41 (± 0.08)
FUNGI 0.91 (± 0.03) 3.11 (± 0.13)
Table 1. Diversity index (standarddeviation on brackets).
COTTON SILKSAMPLING DAY CT N P CT N P
Table 2. Degradation of the fertimeter cotton and silk fibers in 2011-12 (CT: control; N:nitrogen solution; P: phosphorus solution; standard deviation on brackets).
% %21/03/2011 2.3 (1.4) 20.6 (5.5) 13.6 (4.7) 21.1 (5.1) 23.5 (6.6) 26.5 (3.7)21/04/2011 10.3 (6.4) 12.5 (6.7) 21.3 (9.2) 18.7 (3.2) 19.0 (6.5) 39.0 (3.0)21/05/2011 66.8 (17.5) 59.9 (11.5) 62.2 (14.2) 15.5 (5.2) 24.4 (3.7) 25.3 (6.1)21/06/2011 6.6 (3.7) 26.2 (7.4) 31.5 (6.6) 23.8 (3.3) 26.9 (3.6) 36.3 (6.8)21/07/2011 11.7 (5.5) 27.1 (10.0) 23.6 (3.8) 18.1 (3.7) 27.4 (4.1) 29.3 (3.2)08/09/2011 16.5 (14.1) 41.2 (11.2) 45.0 (12.6) 20.7 (4.1) 31.3 (8.1) 35.8 (9.8)20/09/2011 16.0 (5.1) 36.5 (5.3) 43.0 (1.7) 22.1 (3.4) 26.8 (3.4) 33.3 (5.0)20/10/2011 10.2 (5.8) 17.0 (5.8) 15.6 (3.4) 19.5 (2.9) 19.4 (3.6) 21.1 (3.2)
19/03/2012 1.9 (1.4) 16.5 (2.8) 5.8 (3.2) 20.0 (1.9) 17.2 (3.8) 21.8 (2.5)16/04/2012 8.0 (2.8) 18.5 (7.1) 13.1 (6.3) 21.5 (3.8) 19.6 (2.6) 38.4 (7.6)25/05/2012 21.6 (28.1) 34.7 (14.4) 27.8 (9.5) 28.0 (2.7) 30.4 (7.9) 33.9 (11.7)20/06/2012 43.0 (16.4) 45.3 (20.0) 40.8 (24.1) 29.3 (11.2) 31.0 (8.6) 36.3 (15.9)23/07/2012 3.7 (4.3) 22.7 (4.0) 16.9 (6.9) 41.0 (19.9) 28.6 (9.5) 49.6 (18.6)29/08/2012 14.0 (8.6) 28.3 (5.4) 24.2 (11.5) 26.1 (4.2) 24.4 (1.9) 30.6 (1.6)17/09/2012 4.1 (5.2) 21.2 (6.4) 18.0 (5.5) 23.5 (1.7) 25.5 (1.5) 31.0 (5.5)19/10/2012 3.7 (5.3) 16.9 (4.0) 14.9 (7.9) 22.0 (4.1) 17.6 (2.2) 24.4 (5.1)
ReferencesCastillo MdP, Torstensson L, Stenström J (2008). Biobeds for environmental protection from pesticide use-a review. J. Agric. FoodChem. 56 (15):6206-6219.
Method and device for assessing the level of microbial activity in soil (University of Padova, Italy, International PatentCooperation Treaty n. PCT/IB2012/001157, June 13, 2012, Squartini, Concheri, Tiozzo).
