Impact of PVC microplastics on soil chemical and microbiological parameters.

Microplastics (MPs) are emerging pollutants whose occurrence is a global problem in natural ecosystems including soil. Among MPs, polyvinyl chloride (PVC) is a well-known polymer with remarkable resistance to degradation, and because its recalcitrant nature serious environmental concerns are created during manufacturing and waste disposal. The effect of PVC (0.021% w/w) on chemical and microbial parameters of an agricultural soil was tested by a microcosm experiment at different incubation times (from 3 to 360 days). Among chemical parameters, soil CO2 emission, fluorescein diacetate (FDA) activity, total organic C (TOC), total N, water extractable organic C (WEOC), water extractable N (WEN) and SUVA254 were considered, while the structure of soil microbial communities was studied at different taxonomic levels (phylum and genus) by sequencing bacterial 16S and fungal ITS2 rDNA (Illumina MiSeq). Although some fluctuations were found, chemical and microbiological parameters exhibited some significant trends. Significant (p < 0.05) variations of soil CO2 emission, FDA hydrolysis, TOC, WEOC and WEN were found in PVC-treated soils over different incubation times. Considering the structure of soil microbial communities, the presence of PVC significantly (p < 0.05) affected the abundances of specific bacterial and fungal taxa: Candidatus_Saccharibacteria, Proteobacteria, Actinobacteria, Acidobacteria and Bacteroides among bacteria, and Basidiomycota, Mortierellomycota and Ascomycota among fungi. After one year of experiment, a reduction of the number and the dimensions of PVC was detected supposing a possible role of microorganisms on PVC degradation. The abundance of both bacterial and fungal taxa at phylum and genus level was also affected by PVC, suggesting that the impact of this polymer could be taxa-dependent.

Basic features of Ne*-HX (X = Cl, Br) chemi-ionization reactions.

Total and partial ionization cross sections for Ne*(3P2,0)-HX (X = Cl, Br) are presented in a comparative way as a function of the collision energy between 0.02-0.5 eV. New mass spectrometric data on Ne*-HBr chemi-ionization are discussed and analyzed with already published data on Ne*-HCl, highlighting similarities and differences of the collisional stereodynamics of the two systems. Basic features of the interaction potentials, driving reactive collisions, suggest that reaction channels, leading to the formation of parent HX+ ions in the ground and excited electronic state and to the formation of associated NeHX+ ions as well as of NeH+ proton transfer species, are selectively opened within angular cones exhibiting different orientation and acceptance.

Environmental consequences of the treatment of corn contaminated by aflatoxin B1 with co-digestion and co-composting in a life cycle perspective.

Global environmental performances of anaerobic co-digestion and co-composting of aflatoxin B1 (AFB1) contaminated corn were investigated by a life cycle assessment approach. Anaerobic co-digestion of pig slurry and corn with 25 µgkg-1 ww AFB1 concentration resulted able to generate 627 NLkgVS-1 of biogas with a reduction of the AFB1 concentration in the digestate of 44%. At AFB1 concentration of 100 µg kg-1 ww, the process resulted strongly inhibited with a biogas generation of 122 NLkgVS-1 and AFB1 concentration reduction in the digestate of 25%. Co-composting of 100 µg kg-1 dw AFB1 contaminated corn with other substrates as organic fraction of municipal waste, pig slurry, and other lignin-cellulosic residues showed a removal efficiency of AFB1 ranging from about 80 up to 95% depending on the different mixtures adopted. Environmental consequences associated to the removal of 1 mg of AFB1 in different scenarios investigated, including also the use on land of the digestate and of the compost, indicated that global warming was affected equally by co-digestion and co-composting, about 95 kgCO2eq. Co-digestion showed also the possibility of achieving avoided emissions of about - 0.007 kgNMVOCeq, - 2.5E-3 kgPeq, and - 30CTUe. Benefits concerning resource depletion resulted higher for co-composting due to the high amount of mineral fertilizer replaced. Contribution of AFB1 in the determination of human health (DALY) resulted lower than about 4% for co-digestion and practically negligible for co-composting.

Benefits and risks of long-term recycling of pharmaceutical sewage sludge on agricultural soil.

European policy is direct towards increasing the agricultural reuse of sludge on soil for improving the fertility; however, the effects of long-term pharmaceutical sewage sludge (PSS) application on soil properties are still unknown. Thus, the aim of this work was to evaluate the agronomic and environmental effects on soil after 17 years of organic amendment with PSS derived from daptomycin production. Five different doses of PSS were spread on lands located in Anagni, Central Italy. Physico-chemical soil properties were investigated, as well as total and bioavailable heavy metals, changes in the soil organic matter quality and biochemical functioning. PSS application showed a positive agronomic potential, improving SOM quality, increasing soil humified organic matter and raising plant nutrients. SOM dynamic was different at low and high PSS supplies, as confirmed by the chemical and biochemical analysis (e.g. C biomass, FDA hydrolysis activity, basal respiration, dehydrogenase, urease and phosphatase activities). However, in a long-term agricultural reuse, environmental risks of PSS recycling were related to the increase of some heavy metals (Hg, Zn and Cu) and exchangeable Na.

Effect of the mycotoxin aflatoxin B1 on a semi-continuous anaerobic digestion process.

Cereals are primary crops and are the most important raw material for feed and food production. Increasing aflatoxin B1 (AFB1) contamination of corn is an emerging issue, and disposal procedures for AFB1-contaminated corn are not currently defined. Recovery of contaminated corn through anaerobic digestion may represent a suitable strategy for its valorisation; however, only a few studies concerning the effect of AFB1 on anaerobic processes can be found. Thus, the purpose of the present work was to evaluate the effect of the mycotoxin AFB1 on a semi-continuous anaerobic digestion (AD) process. Semi-continuous trials were carried out, and the biomethane production from ABF1-contaminated feedstocks (25, 50, and 100 µg kg-1 AFB1 wet weight) was compared to that from non-contaminated feedstock. Moreover, the feasibility of the agronomic re-use of the digestate, and the fate of AFB1 during AD was assessed. No adverse effect of 25 µg kg-1 AFB1 contamination of feedstock on biomethane yield was observed. In contrast, 100 µg kg-1 AFB1 in the feedstock resulted in inhibition of the process due to the accumulation of organic acids, and to the decrease of the pH in the digestate (from 8.1 to 5.4). The continuous addition of AFB1-contaminated feedstock led to accumulation of the mycotoxin in the digestates. Consequently, a composting process should always precede the agricultural re-use of digestates in order to remove AFB1 and the residual phytotoxicity.

Valorization of a pharmaceutical organic sludge through different composting treatments.

Nowadays, the agricultural reuse of pharmaceutical sludge is still limited due to environmental and agronomic issues (e.g. low stabilization of the organic matter, phytotoxicity). The aim of the present study was to evaluate the characteristics of a pharmaceutical sludge derived from the daptomycin production and to study the possibility of improving its quality through composting. The pharmaceutical sludge showed high content of macronutrients (e.g. total Kjeldahl N content was 38 g kg-1), but it was also characterized by high salinity (7.9 dS m-1), phytotoxicity (germination index was 36.7%) and a low organic matter stabilization. Two different mixtures were prepared (mixture A: 70% sludge + 30% wood chips w/w, mixture B: 45% sludge + 45% wood chips + 10% cereal straw w/w) and treated through static composting using two different aeration systems: active and passive aeration. The mixtures resulted in the production of two different compost, and the evolution of process management parameters was different. The low total solids and organic matter content of mixture A led to the failure of the process. The addition of cereal straw in mixture B resulted in increased porosity and C/N ratio and, consequently, in an optimal development of the composting process (e.g. the final organic matter loss was 54.1% and 63.1% for the passively and actively aerated treatment, respectively). Both passively and actively aerated composting of mixture B improved the quality of the pharmaceutical sludge, by increasing its organic matter stabilization and removing phytotoxicity.

Evaluation of benefits and risks associated with the agricultural use of organic wastes of pharmaceutical origin.

Industrial fermentations for the production of pharmaceuticals generate large volumes of wastewater that can be biologically treated to recover plant nutrients through the application of pharmaceutical-derived wastes to the soil. Nevertheless, benefits and risks associated with their recovery are still unexplored. Thus, the aim of the present work was to characterize three potential organic residues (sludge, anaerobic digestate and compost) derived from the wastewater generated by the daptomycin production process. The main parameters evaluated were the physico-chemical properties, potential contaminants (heavy metals, pathogens and daptomycin residues), organic matter stabilization and the potential toxicity towards soil microorganisms and plants. The results showed that all the studied materials were characterized by high concentrations of plant macronutrients (N, P and K), making them suitable for agricultural reuse. Heavy metal contents and pathogens were under the limits established by European and Italian legislations, avoiding the risk of soil contamination. The compost showed the highest organic matter stabilization within the studied materials, whereas the sludge and the anaerobic digestate were characterized by large amounts of labile organic compounds. Although the pharmaceutical-derived fertilizers did not negatively affect the soil microorganisms, as demonstrated by the enzymatic activities, the sludge and the anaerobic digestate caused a moderate and strong phytotoxicity, respectively. The compost showed no toxic effect towards plant development and, moreover, it positively affected the germination and growth in lettuce and barley. The results obtained in the present study demonstrate that the valorization of pharmaceutical-derived materials through composting permits their agricultural reuse and also represents a suitable strategy to move towards a zero-waste production process for daptomycin.

Assessing the agricultural reuse of the digestate from microalgae anaerobic digestion and co-digestion with sewage sludge.

Microalgae anaerobic digestion produces biogas along with a digestate that may be reused in agriculture. However, the properties of this digestate for agricultural reuse have yet to be determined. The aim of this study was to characterise digestates from different microalgae anaerobic digestion processes (i.e. digestion of untreated microalgae, thermally pretreated microalgae and thermally pretreated microalgae in co-digestion with primary sludge). The main parameters evaluated were organic matter, macronutrients and heavy metals content, hygenisation, potential phytotoxicity and organic matter stabilisation. According to the results, all microalgae digestates presented suitable organic matter and macronutrients, especially organic and ammonium nitrogen, for agricultural soils amendment. However, the thermally pretreated microalgae digestate was the least stabilised digestate in comparison with untreated microalgae and co-digestion digestates. In vivo bioassays demonstrated that the digestates did not show residual phytotoxicity when properly diluted, being the co-digestion digestate the one which presented less phytotoxicity. Heavy metals contents resulted far below the threshold established by the European legislation on sludge spreading. Moreover, low presence of E. coli was observed in all digestates. Therefore, agricultural reuse of thermally pretreated microalgae and primary sludge co-digestate through irrigation emerges a suitable strategy to recycle nutrients from wastewater.

Multi-approach characterization of organic sediment produced by an anaerobic digestion plant fed with pig slurry and stored for a long term in a lagoon.

This study combined different approaches to characterize organic sediments produced by an anaerobic digestion plant feed with pig slurry, and accumulated for many years in a lagoon. The results of all analyses identified a certain homogeneity of the sediments. As a consequence of the pig diet, the sediment contained an high concentration of Zn (about 4gkg-1) and Cu (about 1.2gkg-1), which were mostly associated to the particles with a size ranging from 2 to 53µm. The sediment was made of large amount of organic matter, mostly cellulose and recalcitrant molecules, and 30-40% mineral fraction. XANES and XES spectroscopies indicated the presence of zinc phosphate (38%), zinc sulfide (32%), zinc carbonate (19%), and zinc oxide (11%). The presence in the sediment of forms characterized by a very scarce solubility, as also confirmed by the Zn and Cu chemical speciation, indicated a low bioavailability of these metals. However, although their low mobility, the high concentrations of Zn and Cu allowed to consider the sediment not suitable to use as a fertiliser due to the potential risk of metal interaction with the food chain.

Co-treatment of fruit and vegetable waste in sludge digesters: Chemical and spectroscopic investigation by fluorescence and Fourier transform infrared spectroscopy.

In a previous work co-digestion of food waste and sewage sludge was performed in a pilot apparatus reproducing operating conditions of an existing full scale digester and processing waste mixed sludge (WMS) and fruit and vegetable waste (FVW) at different organic loading rates. An analysis of the relationship among bio-methane generation, process stability and digestate phytotoxicity was conducted. In this paper we considered humification parameters and spectroscopic analysis. Humification parameters indicated a higher not humified fraction (NH) and a lower degree of humification (DH) of FVW with respect to WMS (NH=19.22 and 5.10%; DH=36.65 and 61.94% for FVW and WMS, respectively) associated with their different chemical compositions and with the stabilization process previously undergone by sludge. FVW additions seemed to be favourable from an agronomical point of view since a lower percentage of organic carbon was lost. Fourier transform infrared spectra suggested consumption of aliphatics associated with rising in bio-methane generation followed by accumulation of aliphatics and carboxylic acids when the biogas production dropped. The trend of peaks ratios can be used as an indicator of the process efficiency. Fluorescence intensity of peak B associated with tryptophan-like substances and peak D associated with humic-like substances observed on tridimensional Excitation Emission Matrix maps increased up to sample corresponding to the highest rate of biogas production. Overall spectroscopic results provided evidence of different chemical pathways of anaerobic digestion associated with increasing amount of FVW which led to different levels of biogas production.

Co-treatment of fruit and vegetable waste in sludge digesters. An analysis of the relationship among bio-methane generation, process stability and digestate phytotoxicity.

The co-digestion of a variable amount of fruit and vegetable waste in a waste mixed sludge digester was investigated using a pilot scale apparatus. The organic loading rate (OLR) was increased from 1.46 kg VS/m(3) day to 2.8 kg VS/m(3) day. The hydraulic retention time was reduced from 14 days to about 10 days. Specific bio-methane production increased from about 90 NL/kg VS to the maximum value of about 430 NL/kg VS when OLR was increased from 1.46 kg VS/m(3) day to 2.1 kg VS/m(3) day. A higher OLR caused an excessive reduction in the hydraulic retention time, enhancing microorganism wash out. Process stability evaluated by the total volatile fatty acids concentration (mg/l) to the alkalinity buffer capacity (eq. mg/l CaCO3) ratio (i.e. FOS/TAC) criterion was <0.1 indicating high stability for OLR <2.46 kg VS/m(3 )day. For higher OLR, FOS/TAC increased rapidly. Residual phytotoxicty of the digestate evaluated by the germination index (GI) (%) was quite constant for OLR<2.46 kg VS/m(3)day, which is lower than the 60% limit, indicating an acceptable toxicity level for crops. For OLR>2.46 kg VS/m(3) day, GI decreased rapidly. This corresponding trend between FOS/TAC and GI was further investigated by the definition of the GI ratio (GIR) parameter. Comparison between GIR and FOS/TAC suggests that GI could be a suitable criterion for evaluating process stability.

Chemical and spectroscopic characterization of organic matter during the anaerobic digestion and successive composting of pig slurry.

In this work, anaerobic digestion of pig slurry and successive composting of the digestate after centrifugation were studied by means of chemical analysis, FTIR and fluorescence spectroscopy as excitation-emission matrix (EEM). Chemical analysis highlighted the organic matter transformation occurring during the processes. A decrease of volatile solids and total organic carbon were observed in the digestate with respect to the fresh pig slurry as a consequence of the consumption of sugars, proteins, amino acids and fatty acids used by microorganisms as a C source. Water Extractable Organic Matter (WEOM) was obtained for all samples and fractionated into a hydrophilic and a hydrophobic fraction. The highest WEOM value was found in the pig slurry indicating a high content of labile organic C. The digestate centrifuged and the digestate composted showed lower hydrophilic and higher hydrophobic contents because of the decrease of labile C. Total phenolic content was lower in the digestate with respect to fresh pig slurry sample (36.7%) as a consequence of phenolic compounds degradation. The strong decrease of total reducing sugars in the digestate (76.6%) as compared to pig slurry confirmed that anaerobic process proceed mainly through consumption of sugars which represent a readily available energy source for microbial activity. FTIR spectra of pig slurry showed bands indicative of proteins and carbohydrates. A drop of aliphatic structures and a decrease of polysaccharides was observed after the anaerobic process along with the increase of the peak in the aromatic region. The composted substrate showed an increase of aromatic and a relative decrease of polysaccharides. EEM spectra provided tryptophan:fulvic-like fluorescence ratios which increased from fresh substrate to digestate because of the OM decompostion. Composted substrate presented the lowest ratio due to the humification process.

Hybrid solid anaerobic digestion batch: biomethane production and mass recovery from the organic fraction of solid waste.

An experimental apparatus was constructed to perform hybrid solid anaerobic digestion batch processing of the organic fraction of municipal solid waste. The preliminary process was carried out with a high total solids concentration of about 33% w w(-1) and with an initial organic load of about 340 kg VS kg(-1). The fresh organic fraction to inoculum ratio used to enhance the anaerobic process start-up was 0.910 kg VS kg VS(-1). The process was conducted by spreading the percolate on top of the mixture. The percolate was stored in a separate section of the apparatus with a mean hydraulic retention time of about 1 day. During the process, acetate, butyrate and propionate in the percolate reached concentrations ranging from 3000 to 11 000 mg L(-1). In spite of these high concentrations, the biomethane produced from both the solid and the percolate was quite high, at about 210 NL kg VS(-1). The digestate obtained at the end of the run showed rather good features for being classified as an organic fertilizer according to Italian law. However, a residual phytotoxicity level was detected by a standardized test showing a germination index of about 50%.

Greenhouse gas (GHG) emissions from soils amended with digestate derived from anaerobic treatment of food waste.

RATIONALE: The application of organic materials to agricultural lands is considered good practice to improve soil organic matter content and recycle nutrients for crop growth. The anaerobic treatment of food waste may have environmental benefits, particularly with regard to greenhouse gases (GHGs) mitigation and enhancement of carbon sequestration. METHODS: This work presents the results from a field experiment to evaluate CO(2) , CH(4) and N(2) O emissions from grassland amended with digestate produced by anaerobic fermentation of food waste. Experimental plots, located close to Rothamsted Research-North Wyke, were established using a randomized block design with three replicates and two treatments, added digestate (DG) and the unamended control (CNT). The digestate was applied on three occasions at an equivalent rate of 80 kg N ha(-1) . RESULTS: The application of digestate led to an increase in CO(2) emissions, especially after the 2(nd) application (74.1 kg CO(2) -C ha(-1) day(-1) ) compared with the CNT soil (36.4 kg CO(2) -C ha(-1) day(-1) ), whereas DG treatment did not affect the overall CH(4) and N(2) O emissions. The total grass yield harvested on a dry matter basis was greater in the DG treated plots (0.565 kg m(-2) ) than in the CNT plots (0.282 kg m(-2) ), as was the (15) N content in the harvest collected from the DG plots. CONCLUSIONS: The results suggest that the digestate can be applied to agricultural land as a fertilizer to grow crops. Our study was conducted in an exceptionally dry growing season, so conclusions about the effect of digestate on GHG emissions should take this into account, and further field trials conducted under more typical growing seasons are needed.

Carbon deposition in soil rhizosphere following amendments with compost and its soluble fractions, as evaluated by combined soil-plant rhizobox and reporter gene systems.

We determined the organic carbon released by roots of maize plants (Zea mays L.) when grown in soils amended with compost and its soluble fractions. In rhizobox systems, soil and roots are separated from the soil of a lower compartment by a nylon membrane. Treatments are applied to the upper compartment, while in the lower compartment luminescent biosensors measure the bioavailable organic carbon released by roots (rhizodeposition). The rhizobox-plants systems were amended with a compost (COM), its water extract (TEA), the hydrophobic (HoDOM) and hydrophilic (HiDOM) fractions of the dissolved organic matter (DOM) extracted from the compost. After root development, the lower untreated compartments were sampled and sliced into thin layers. The bioavailable organic carbon in each layer was assessed with the lux-marked biosensor Pseudomonas fluorescens 10586 pUCD607, and compared with total organic carbon (TOC) analyses. The TOC values ranged between 8.4 and 9.6 g kg(-1) and did not show any significant differences between bulk and rhizosphere soil samples in any treatment. Conversely, the biosensor detected significant differences in available C compounds for rhizosphere soils amended with various organic materials. Concentrations of available organic compounds in the first 2 mm of soil rhizosphere were 1.69 (control), 1.09 (COM), 2.87 (HiDOM), 4.73 (HoDOM) and 2.14 (TEA)micromol Cg(-1) soil g(-1) roots. The applied rhizobox-biosensor integrated method was successful in detecting and quantifying effects of organic amendments on organic carbon released by maize plant roots. This approach may become important in assessing the carbon cycle in agricultural soils and soil-atmosphere compartments.

Molecular characterization of a compost and its water-soluble fractions.

A sequential chemical fractionation was applied to a compost, with its dissolved organic matter (DOM) extracted in water and separated in hydrophilic (HiDOM) and hydrophobic (HoDOM) components and a water extract, following oxidation of compost suspension with an oxygen flux (TEA). The components sequentially isolated by mild extractions and hydrolyses as structurally unbound (SU), weakly bound (WB), and strongly bound (SB) to the matrix of the bulk compost and its water-soluble fractions were identified in their molecular structure. The bulk compost was rich with components derived from both aromatic (phenolic compounds) and aliphatic (long-chain fatty acids, hydroxy acids, diacids, and alcohols) structures of suberins, whereas components derived from cutins were especially extracted from TEA, HoDOM, and HiDOM. The TEA sample also yielded a significant amount of oxidized products that was dominated by dehydroabietic acids. The fractionation sequence highlighted the different intermolecular interactions that bound the isolated molecular components to the compost complex matrix. While a significant part of the bulk compost was still present as a solid residue at the end of the sequential fractionation, all water-soluble fractions were almost completely hydrolyzed. These results indicate that the water-soluble components of compost may be readily separated from the compost matrix and contribute to the environmental dynamics of natural organic matter.

Transformation of a landfill covering amended with municipal waste compost, Perugia, Italy.

This research deals with the transformation of an anthropomorphous landfill covering composed of a fill soil mixed with mechanically separated municipal waste compost. The study site was a municipal landfill near Perugia, Italy. Throughout the years, waste disposal in the landfill was performed by burial in horizontal layers, each one representing a yearly disposal. The external front of the landfill thus represented the yearly disposal over a 10-yr period starting in 1993. Temporal changes in the anthropomorphous soil over this period were studied by examining and describing soil profiles, and by collecting and analyzing soil samples from the 1993, 1994, 1997, and 2001 disposals. The samples were subjected to a series of physical, chemical, and biochemical analyses. The results obtained suggest that over a 10-yr period the top layer gained a pedological structure (subangular blocky and/or crumb) giving rise to an A horizon. Improved soil structure was confirmed by an increase in macroporosity, particularly for pores larger than 50 microm, measured by image analysis of soil thin sections. Total extractable carbon showed an increase in the content of humic substances, evidenced by parameters of humification. Enzymatic activities in the A and C1 horizons were also indicative of soil evolution and may serve as a valid indicator for monitoring the evolution of anthropogenic soils containing municipal waste compost.

Changes in the chemical characteristics of water-extractable organic matter during composting and their influence on compost stability and maturity.

Composting is the biochemical transformation of waste organic matter by microorganisms whose metabolism occurs in the water-soluble phase. Therefore, a study of the changes occurring in compost dissolved organic matter can be useful for assessing its stability and maturity. In light of the variety of parameters generally utilized to study composting processes, this work aims at identifying the major chemical processes that occur in solution and their influence on the attainment of stability and maturity with composting time. Compost stability, assessed by means of respirometric analysis which determined oxygen demand as a result of mineralization of the compost's organic matter, and compost maturity evaluated with Lepidium sativum L. seed bioassays, were found to be highly related to the nature and content of water-soluble organic matter. Moreover, fractionation of the water-extractable organic carbon showed that the ratio of hydrophobic to hydrophilic carbon increased to values greater than unity for stabilized compost. These results together with the analysis for non-cellulosic polysaccharides, phenolic compounds and organic nitrogen within the water extracts, confirmed the influence of solubilization, mineralization and organic matter transformation on the quality of the final compost.

Influence of dissolved organic matter from waste material on the phytotoxicity and environmental fate of triflusulfuron methyl.

Bioassays and chemical analyses were performed to study the effect of hydrophobic dissolved organic matter (HoDOM) extracted from a municipal waste compost (MWC) on the behavior of triflusulfuron methyl in soil and water. Bioassays with oilseed rape showed that HoDOM in culture solution lowered the effective dose 50 of triflusulfuron methyl by up to 4.8 times. Equilibrium dialysis experiments showed that in aqueous solution triflusulfuron methyl was adsorbed to HoDOM (K(OC) of 446.5 mL g(-1)). The half-life in water (pH 7.0) was increased from 52 to 76 days in the presence of HoDOM, but this cannot completely explain its phytotoxicity, as bioassays lasted for 21 days only. On the other hand, the addition of HoDOM to soils did not change the degradative behavior of triflusulfuron methyl. Fluorescein diacetate hydrolysis showed that HoDOM in soil did not significantly influence soil microbial activity, which may explain the above result on degradation in soil. Furthermore, in batch equilibrium experiments on soil, triflusulfuron methyl was only weakly adsorbed and the presence of HoDOM significantly modified the isotherm form. Results suggest that although the addition of exogenous HoDOM from MWC to soil did not influence the herbicide's persistence, its enhanced mobility could be of environmental concern and may deserve further research.

Environmental fate of triasulfuron in soils amended with municipal waste compost.

The amendment of soil with compost may significantly influence the mobility and persistence of pesticides and thus affect their environmental fate. Factors like adsorption, kinetics, and rate of degradation of pesticides could be altered in amended soils. The aim of this study was to determine the effects of the addition of compost made from source-separated municipal waste and green waste, on the fate of triasulfuron [(2-(2-chloroethoxy)-N-[[4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino]carbonyl]benzenesulfonamide], a sulfonylurea herbicide used in postemergence treatment of cereals. Two native soils with low organic matter content were used. A series of analyses was performed to evaluate the adsorption and degradation of the herbicide in soil and in solution after the addition of compost and compost-extracted organic fractions, namely humic acids (HA), fulvic acids (FA), and hydrophobic dissolved organic matter (HoDOM). Results have shown that the adsorption of triasulfuron to soil increases in the presence of compost, and that the HA and HoDOM fractions are mainly responsible for this increase. Hydrophobic dissolved organic matter applied to the soils underwent sorption reactions with the soils, and in the sorbed state, served to increase the adsorption capacity of the soil for triasulfuron. The rate of hydrolysis of triasulfuron in solution was significantly higher at acidic pH and the presence of organic matter fractions extracted from compost also slightly increased the rate of hydrolysis. The rate of degradation in amended and nonamended soils is explained by a two-stage degradation kinetics. During the initial phase, although triasulfuron degradation was rapid with a half-life of approximately 30 d, the presence of compost and HoDOM was found to slightly reduce the rate of degradation with respect to that in nonamended soil.