Agricultural application of digestates derived from agricultural and municipal organic wastes: a health risk-assessment for heavy metals.

A Human-health Risk Assessment was performed for an agricultural site in North-East Italy undergone digestate application to (i) check the compliance of digestate land spreading with the Italian and European regulations on contaminated agricultural soils and (ii) evaluate how resulting risk estimations can be influenced by the applied modeling assumptions. The assessment estimated the risk related to adults and children intake of Heavy Metals (HM) contained in crops at concentrations estimated by a soil-plant transfer model based on the substance-specific soil-water partition coefficients. Eight different scenarios were investigated, according to different digestate type (from biowaste and agro-industrial byproducts), digestate application techniques and soil background concentrations. Non-risky situations resulted in all scenarios involving digestate application. The totality of calculated non-carcinogenic Hazard Indexes (HI) and carcinogenic total risk (RTOTC) resulted below 0.02 and 3E10-9, respectively. In contrast with the definition, non-carcinogenic risks were associated with the considered soil background concentrations, with HI s up to 1.7 for child receptors, while carcinogenic risk was calculated below the concern threshold (i.e., RTOTC < 10-5). Accordingly, this study highlighted (i) non-concerning situations related with lawful application of digestates and (ii) the need to improve the modeling of bioavailability to plant of HMs background content of soil.

Ecological restoration of a copper polluted vineyard: Long-term impact of farmland abandonment on soil bio-chemical properties and microbial communities.

This study aimed at investigating the degree of interference of high soil copper (Cu) contamination when an old vineyard is converted into a protected area. This study was performed within an intensive agricultural system; it was organized into a two-factorial nested design to analyze the impact of management (conventional vs re-naturalized orchard) and position within each orchard (tree-rows and strips). Chemical and biochemical properties along with bacterial and fungal communities, evaluated with PCR-DGGE starting from total soil DNA, were analyzed. Total Cu was localized in tree rows in the old vineyard at 1000 mg kg(-1) of soil, whereas it did not exceed 80 mg kg(-1) soil in the other treatments. Total organic carbon and all biochemical properties significantly improved in re-naturalized compared to conventionally cultivated site, while no significant differences were observed between tree row and strip. Moreover, a higher extractable carbon-extractable nitrogen (Cext-to-Next) ratio in the re-naturalized (19.3) site than in the conventionally managed site (10.2) indicated a shift of soil system from C-limited to N-limited, confirming a successful ecological restoration. Deep improvement of soil biochemical properties exceeded the negative impact of Cu contamination. A shift of bacterial community composition as well as increased bacterial diversity in Cu contaminated treatment indicated a bacterial response to Cu stress; to the contrary, soil fungi were less susceptible than bacteria, though an overall reduction of fungal DNA was detected. Findings suggest that ecological restoration of highly polluted agricultural soils leads to overcoming the reduction of soil functionalities linked to Cu contamination and opens interesting perspectives for mitigating Cu stress in agricultural soils with strategies based on conservative agriculture.

Foraging for selenium: a comparison between hyperaccumulator and non-accumulator plant species.

Selenium (Se) hyperaccumulators are a unique group of plants that can accumulate this element in their aerial parts at concentrations exceeding 100 mg kgDW-1. These plants actively search for Se in the soil, a phenomenon known as root foraging, reported to date only by few studies. In this study, the effect of localized Se enrichment, in the form of selenite and selenate, was investigated on the root architecture of two Se-hyperaccumulators (Stanleya pinnata and Astragalus bisulcatus) and two non-accumulators (Brassica juncea and Medicago sativa). Rhizoboxes were divided into two halves: one half was filled with control soil while the other with selenate or selenite (30 mg kgDW-1) spiked soil. Seedling were transferred into the interface of the two soils and allowed to grow for three weeks under controlled light and temperature conditions. Staneya pinnata exhibited equal root density in both halves of the rhizobox when grown in control/control and selenite/control soil treatments. However, in the presence of selenate, S. pinnata developed 76% of the roots towards the selenate-enriched half, indicating an active root foraging. In contrast, A. bisulcatus and the non-accumulators B. juncea and M. sativa did not show any preferential distribution of roots. This study revealed that only S. pinnata showed the ability to detect and forage for Se when provided as selenate. Non-accumulators did not show any morphological or Se-accumulation difference associated with the presence of Se in soil in either form.

A non-lethal method to assess element content in the endangered Pinna nobilis.

The fan shell Pinna nobilis is the largest bivalve endemic to the Mediterranean and is actually a strongly endangered species. Due to the biological, ecological, and historical relevance of this species, the research of a non-lethal method to relate the element content in organism's tissues and environment can provide information potentially useful to evaluate environmental pollution and organism physiological status. In this study, a screening on element concentration in the animal growing environment (seawater and sediments) and in four soft tissues (hepatopancreas, gills, mantle, and muscle), and two acellular tissues (calcite shell layer, and byssus) was performed. The comparison among these results was used to assess whether the no-lethal acellular tissue element concentration can be used to reveal the element presence in the environment and soft tissues. Elements, such as B, Ag, As, Mn, Mo, Pb, or Se, showed a possible relationship between their presence in the byssus and soft tissues. In the byssus Cr, Sb, Sn, and V have shown to be mostly related to the environment, more than the soft tissues, and might be used to draw a historical record of the exposure of the organism. The element concentration in the calcite shell layer did not relate with environmental element concentrations. Essential elements, like Cu, Fe, Ni, and Zn, were present in calcite shell layer and byssus and are likely related to their biological activity in the organism. The research also gave an overview on the presence of pollution and on the preferential intake route of the element. In summary, this study, performed on a limited number of specimens of this protected species, indicated that element concentration in the byssus can be applied as non-lethal method to monitor this endangered species and its interaction with the elements in the growing environment.

Fertilizing potential and CO2 emissions following the utilization of fresh and composted food-waste anaerobic digestates.

Wet and dry-batch anaerobic digestion, and composting are common technologies in food waste (FW) management, resulting in different outputs. However, the effects of composting on carbon dioxide (CO2) emissions, nitrogen (N) and phosphorus (P) fertilizing capacity in view of closing nutrient cycle are still poorly investigated. In this work, two FW anaerobic digestates from the wet (D1) and dry-batch process (D2), and their respective composts (C1 and C2) were tested in a soil incubation (84 days at 25 °C) to assess CO2 emissions in comparison with a mixed (animal slurry/energy crop) digestate (BD) and a reference municipal solid waste compost (MSWC). The same products were also tested for the relative P efficiency (RPE) in soil, in comparison with a chemical-P source (30 mg P kg-1). Lastly, the apparent recovery fraction of N (N-ARF) from the five organic products was determined in a pot test with ryegrass (84 days; 300 kg available N ha-1), compared to a chemical fertilizer (NPK). Composting strongly reduced net-CO2 emissions compared to the two digestates (625 vs. 2850 mg CO2 kg-1 soil). Oppositely, composting very modestly influenced RPE that ranged around 100-90% in D1 and C1, and ≈30% in D2 and C2. Moreover, composting did not significantly reduce N-ARF that ranked in descending order as follows: NPK (77.5%) > D1 = BD (17.7%) ≥ C1 (14.7%) > MSWC (3.6%) > D2 (1.2%) > C2 (-3.1%). Composting was shown a reliable strategy for FW digestate management, as it reduces potential CO2 emission without affecting these products' N- and P-fertilizing capacity.

Metal ion removal using waste byssus from aquaculture.

Byssus is a thread-like seafood waste that has a natural high efficiency in anchoring many metal ions thanks to its richness of diverse functional groups. It also has structural stability in extreme chemical, physical and mechanical conditions. The combination of these properties, absent in other waste materials, has novelty suggested its use as matrix for water remediation. Thus, pristine byssus, upon de-metalation, was studied to remove metal ions from ideal solutions at pH 4 and 7, as model chemical systems of industrial and environmental polluted waters, respectively. The byssus matrix's uptake of metal ions was determined by ICP-OES and its surface microstructure investigated by SEM. The results showed that the byssus matrix excellently uptakes metal ions slightly reorganizing its surface micro-structure. As example of its efficiency: 50 mg of byssus absorbed 21.7 mg·g-1 of Cd2+ from a 10 mM solution at pH 7. The adsorption isotherm models of Freundlich and Langmuir were mainly used to describe the system at pH 7 and pH 4, respectively. In conclusion, we showed that the byssus, a waste material that is an environmental issue, has the potential to purify polluted industrial and environmental waters from metal ions.

Current and residual phosphorous availability from compost in a ryegrass pot test.

Compost can provide nitrogen (N) and especially phosphorous (P) available for plant growth, thus representing a potential alternative to chemical P-fertilizers a non-renewable resource. However, little is known about their residual capacity to provide plant-available P. In this study four compost: a green waste compost (GWC), one from anaerobically-digested bio-waste (DC), one from sewage sludge (SSC), and one from bio-waste (BWC), were compared (10 and 20 Mg VS ha-1) in a ryegrass pot test (112 days), for their N- and P-relative mineral fertilizer equivalence (MFE; %) vs. a chemical fertilizer (NPK). After the test period, the exploited treatments were tested for their MFE during an additional ryegrass growth cycle (112 days) in an N-rich environment (N+). After 112 days, the pot test showed that DC and SSC produced dry biomass in the same range as did NPK, attaining the best N-MFE (80-100%) and P-MFE (100-125%), whereas GWC and BWC performed poorly (60-80 and 80-90%; N-MFE and P-MFE). At the end of the first growth cycle, DC and SSC still showed relevant Olsen-P (20-30 mg kg-1). This was reflected in the best ryegrass P-MFE in DC and SSC at the end of the second growth cycle (N+), after 224 days (100-110%), whereas BWC and GWC poorly performed (90-95%). DC and SSC may therefore represent valuable sources of N available for plant nutrition in the short term, and also represent medium-term valuable P sources, alternative to rock phosphate P fertilizers. This promising approach need further field-scale investigation to confirm the medium-long term capacity of composts to be alternative to rock phosphate P fertilizers.

Organic wastes as alternative sources of phosphorus for plant nutrition in a calcareous soil.

Recycled organic wastes (OW) can be a valuable P source; however, their P-fertilising capacity is still poorly known. In this study, we selected three anaerobic digestates [wastewater sludge (D1), winery sludge (D2), and bovine-slurry/energy crops (BD)] and two animal effluents [bovine slurry (BS) and swine slurry (SS)] to test their P-release and P-fertilising capacities via sequential chemical extraction (SCE), X-ray diffraction (XRD), and 31P-nuclear magnetic resonance (31P NMR). Subsequently, the three digestates (30 mg P kg-1 of soil) were compared for the release of Olsen-P during a soil incubation and for plant-P apparent recovery (ARF) in a pot experiment using ryegrass (112 days) in a soil with poorly available-P (Olsen-P < 5 mg kg-1), under a non-limiting N environment. The amount of labile-P (H2O + NaHCO3), as determined from SCE, related well to the Olsen-P following OW addition to the soil. It was shown via 31P NMR spectroscopy that orthophosphate was the leading P-form in highly P-releasing OW. The amount of labile-P, however, was affected by soil adsorption, thereby reducing plant-P uptake. The plant-P ARF (%) showed that the recycled P-sources were clustered in highly (BD and SS: ≈20%), intermediately (D1 and BS: ≈15%), and poorly performing OWs (D2: ≈10%) vs. chemical P-source (P-chem: 20%). Therefore, only BD and SS were effective alternatives to P-chem; however, the other OW can be efficient P-sources in soils with higher Olsen-P. Thus, crop fertilisation can be tailored on a P-basis by SCE as a function of soil adsorption capacity and on an N-basis according to the demand.

Electrofocusing the compost organic matter obtained by coupling SEC-PAGE.

Humic acids (HA)-like extracted from compost at the beginning (t(0)) and after 130 days of composting (t(130)) were fractionated by coupling size exclusion chromatography to polyacrylamide gel electrophoresis (SEC-PAGE). HA-like fractions with the same molecular size (MS) and electrophoretic mobility were pooled and further characterised by analytical polyacrylamide gel electrofocusing (EF) and compared with HA separated from a Typic Chernozem soil. During the composting process all fractions were subjected to quantitative and qualitative modifications: the high MS fraction was degraded, the mid MS fractions were qualitatively changed, the content of low MS fractions increased and changed qualitatively. The main changes in EF pattern of the non fractionated HA-like t(130) were associated to low MS fractions. Such data seem to be reliable for explanation what mechanisms and monitoring of the evolution of the compost organic matter for their agricultural uses.

Evaluation of photochemical properties of compost humic-like materials.

Humic-like acids (HLA) were extracted from compost at the beginning and after 70, 130 and 730 days of maturation in order to be investigated for their ability to induce the transformation of 2,4,6-trimethylphenol under irradiation at 365 nm. The rate of 2,4,6-trimethylphenol phototransformation in the presence of HLA (25 mg l(-1)) varied within HLA 0<

Delivery systems for agriculture: Fe-EDDHSA/CaCO3 hybrid crystals as adjuvants for prevention of iron chlorosis.

Fe-EDDHSA/CaCO3 hybrid crystals are synthesized and tested in vitro to determine their effect in treating iron chlorosis in kiwifruit plants, used as a proof of concept. Under the alkaline conditions provided by the calcareous substrate, plants release protons that dissolve the hybrids and trigger Fe uptake. These CaCO3 hybrids represent a new system for active molecule delivery in agriculture.

Compost-based growing media: influence on growth and nutrient use of bedding plants.

The agronomic performance and the mineral composition and trace element content in Begonia semperflorens "Bellavista F1", Mimulus "Magic x hybridus", Salvia splendens "maestro", and Tagete patula xerecta "Zenith Lemon Yellow", were tested by growing the plants on substrates of white peat and 25-50-75-100% green waste and sewage sludge (80%+20%v/v) compost (CP). A commercial peat medium of black and white peat (2:1v/v) was used as control. At flowering, the agronomic parameters were compared by ANOVA and plant nutritional status was compared by vector analysis. Substrate-species interactions (P<0.001) were evident for all measured parameters. In the 25% CP medium all the species showed an increase or preservation of the studied agronomic parameters. Begonia grown in 25% CP, showed the highest dry weight (DW) and number of flowers. Other treatments were comparable to the control. Mimulus and Salvia showed the highest DW in the 25-50% CP. Mimulus, after a DW increase up to 50% CP, showed the steepest reduction as the CP increased further. Tagete showed no differences in DW up to 50% CP, or in flower number up to 25% CP, compared to the control. The additional increases of CP in the medium showed a DW decrease similar to that of Salvia. Vector analysis showed the use of compost mainly induced a decrease of P concentration in tissues, except for Begonia which remained unchanged. Plant tissues showed a general P reduction due to a dilution effect in the low compost mixtures (25-50%) and a deficiency in the higher CP mixtures. In contrast, an increase of Mg in the aboveground tissues of all species was detectable as compost usage increased, with the exception of Salvia which suffered a Mg deficiency. Vector analysis also highlighted a Ni and partial Fe deficiency in Tagete and Salvia.

TG-DTA, DRIFT and NMR characterisation of humic-like fractions from olive wastes and amended soil.

The purpose of the present study is to investigate, by means of thermogravimetric analysis (TG) and differential thermal analysis (DTA), diffuse reflectance infrared Fourier transform (DRIFT) and 2D nuclear magnetic resonance (NMR) spectroscopies, the structural features of the humic-like fraction (HLF) from olive pulp (OP), its effluents originated from the fermentation processes for hydrogen (EH2) and methane production (ECH4) and humic acid (HA) from soil amended with each of these materials. A considerable structural modification emerged between the HLF, in particular from the ECH4 effluent, which was characterised by a high content of polyphenolic and polypeptidic substances. The short-term amendment trial with OP and EH2 indicated that no chemical or structural changes in soil HA appeared. In contrast, the amendment with ECH4 substantially influenced the chemical and structural composition of soil HA. The structural interpretation performed by 2D NMR indicated the presence of aliphatic and aromatic protons while the sugar-like content and O-CH3 groups decreased with respect to the soil control HA. It emerges from this study that olive wastes contain stabilised humic-like material that may be recycled as an amendment in areas where olive trees are cultivated.

A multivariate approach to the study of the composting process by means of analytical electrofocusing.

Three blends formed by: agro-industrial waste, wastewater sewage sludge, and their mixture, blended with tree pruning as bulking agent, were composted over a 3-month period. During the composting process the blends were monitored for the main physical and chemical characteristics. Electrofocusing (EF) was carried out on the extracted organic matter. The EF profiles were analyzed by principal component analysis (PCA) in order to assess the suitability of EF to evaluate the stabilisation level during the composting process. Throughout the process, the blends showed a general shifting of focused bands, from low to high pH, even though the compost origin affected the EF profiles. If the EF profile is analyzed by dividing it into pH regions, the interpretation of the results can be affected by the origin of compost. A good clustering of compost samples depending on the process time was obtained by analyzing the whole profile by PCA. Analysis of EF results with PCA represents a useful analytical technique to study the evolution and the stabilisation of composted organic matter.

Effect of iron sulphate on the phosphorus speciation from agro-industrial sludge based and sewage sludge based compost.

Composting is considered a suitable process for organic waste management, providing stable products that can be safely utilized as fertilizers, but little is still known about the variation of phosphorous (P) extractability during the stabilization process. In this work, sequential chemical extraction (SCE) with increasing strength extractants (H2O; 0.5M NaHCO3 pH 8.5; 0.1M NaOH, 1M HCl) was applied for P speciation over 56days of composting of either agro-industrial or urban wastewater sludge with green waste treated (AICFe+; SSCFe+) or not (AICFe-; SSCFe-) with FeSO4 (2%v/v). Composting strongly reduced the H2O-P, promoting the organic-P (Po) mineralization from the labile fraction (H2O+NaHCO3 40%), in addition to the increases of NaHCO3- and HCl-extractable inorganic-P (Pi) in both AICFe- and SSCFe- (+20% on average). The FeSO4 treatment did not negatively affect the process, reducing the Po mineralization during composting by increasing the NaOH-P, also protecting this fraction from fixation in the sparingly soluble fraction. The final P fractionation (%) was in AICFe-: NaOH (41)=NaHCO3 (38)>HCl (18)>H2O (3); in AICFe+: NaOH (53)>NaHCO3 (24)=HCl (22)>H2O (2); in SSCFe-: NaOH (46)>NaHCO3 (29)>HCl (21)>H2O (4) and in SSCFe+: NaOH (66)>NaHCO3 (13)>HCl (20)>H2O (1). Composting reduced the more easily leachable fraction (labile-Po), reducing the risk of P loss by increasing the long-term available P fraction (NaOH-P). This was enhanced by the FeSO4 addition. Further investigation into soil behaviour and plant availability of P from this source is needed.

Highly anomalous accumulation rates of C and N recorded by a relic, free-floating peatland in Central Italy.

Floating islands mysteriously moving around on lakes were described by several Latin authors almost two millennia ago. These fascinating ecosystems, known as free-floating mires, have been extensively investigated from ecological, hydrological and management points of view, but there have been no detailed studies of their rates of accumulation of organic matter (OM), organic carbon (OC) and total nitrogen (TN). We have collected a peat core 4 m long from the free-floating island of Posta Fibreno, a relic mire in Central Italy. This is the thickest accumulation of peat ever found in a free-floating mire, yet it has formed during the past seven centuries and represents the greatest accumulation rates, at both decadal and centennial timescale, of OM (0.63 vs. 0.37 kg/m2/yr), OC (0.28 vs. 0.18 kg/m2/yr) and TN (3.7 vs. 6.1 g/m2/yr) ever reported for coeval peatlands. The anomalously high accretion rates, obtained using 14C age dating, were confirmed using 210Pb and 137Cs: these show that the top 2 m of Sphagnum-peat has accumulated in only ~100 years. As an environmental archive, Posta Fibreno offers a temporal resolution which is 10x greater than any terrestrial peat bog, and promises to provide new insight into environmental changes occurring during the Anthropocene.

Photosensitizing properties of protein hydrolysate-based fertilizers.

The use of protein hydrolysate-based fertilizers (PHF) as adjuvant for pesticides or herbicides has been proposed; however, the behaviors of mixtures of PHFs and pesticides under solar light are not known, and various photochemical reactions may occur. The photosensitizing properties of PHFs were investigated in water solutions (0.8 g of total organic carbon L(-1)) within the wavelength range of 300-450 nm, using furfuryl alcohol (FA) as a probe to test the involvement of singlet oxygen and Irgarol 1051 as an example of organic pollutant. Two commercial PHFs and one standard PHF were studied, all of the products being of animal origin. PHFs photosensitize the transformation of FA (10(-4) M), and the kinetics of FA disappearance follows an apparent first-order rate law. Through the use of sodium azide (1 x 10(-3) M) as singlet oxygen scavenger and deuterium oxide (D2O) for increasing the singlet oxygen lifetime it was shown that singlet oxygen contributes largely to the phototransformation of FA. The replacement of water by D2O increases the apparent first-order rate constant 6 times, whereas the addition of sodium azide reduces it by approximately 90%. These results are confirmed using Irgarol 1051 (10(-5) M). The photosensitizing properties of PHFs might be due to pigments naturally present in tissues from which they are extracted or to compounds generated during the production processes.

Humic-like substances extracted from composts can promote the photodegradation of Irgarol 1051 in solar light.

Humic-like substances (HLS) were extracted from a mixture of sewage sludges and trimmings (70-30%, w/w) after different times of composting (0, 70 days and 130 days). HLS were analyzed by elemental analysis, UV-visible and fluorescence spectroscopy and also tested for their ability to photosensitize the degradation of Irgarol. The rate of Irgarol photodegradation in artificial solar light was found to be 2.5- to 4.3-fold higher in the presence of HLS than in buffered Milli-Q water. These results were confirmed by experiments in solar light that evidenced the photodegrading properties of HLS in a more striking way. Using 2-propanol as hydroxyl radical scavenger, we could show that hydroxyl radicals contributed to the photosensitized Irgarol degradation for about 25%. The photodegrading activity of HLS, their absorbance and their emissive properties were all found to increase between 0 and 70 days of composting and to remain quite constant between 70 and 130 days. The degree of humification varied in the same way, linking all these properties to the humification process.

Effect of humic monomers on the adsorption of sulfamethoxazole sulfonamide antibiotic into a high silica zeolite Y: An interdisciplinary study.

The adsorption efficiency of a high silica zeolite Y towards sulfamethoxazole, a sulfonamide antibiotic, was evaluated in the presence of two humic monomers, vanillin and caffeic acid, representative of phenolic compounds usually occurring in water bodies, owing their dimension comparable to those of the zeolite microporosity. In the entire range of investigated pH (5-8), adsorption of vanillin, as a single component, was reversible whereas it was irreversible for sulfamethoxazole. In equimolar ternary mixtures, vanillin coadsorbed with sulfamethoxazole, conversely to what observed for caffeic acid, accordingly to their adsorption kinetics and pKa values. Lower and higher adsorptions were observed for sulfamethoxazole and vanillin, respectively, than what it was observed as single components, clearly revealing guest-guest interactions. An adduct formed through H-bonding between the carbonyl oxygen of vanillin and the heterocycle NH of sulfamethoxazole in amide form was observed in the zeolite pore by combined FTIR and Rietveld analysis, in agreement with Density Functional Theory calculations of the adduct stabilization energies. The formation of similar adducts, able to stabilize other naturally occurring phenolic compounds in the microporosities of hydrophobic sorbents, was proposed.

Relationships between stability, maturity, water-extractable organic matter of municipal sewage sludge composts and soil functionality.

Compost capability of restoring or enhancing soil quality depends on several parameters, such as soil characteristics, compost carbon, nitrogen and other nutrient content, heavy metal occurrence, stability and maturity. This study investigated the possibility of relating compost stability and maturity to water-extractable organic matter (WEOM) properties and amendment effect on soil quality. Three composts from municipal sewage sludge and rice husk (AN, from anaerobic wastewater treatment plants; AE, from aerobic ones; MIX, from both anaerobic and aerobic ones) have been analysed and compared to a traditional green waste compost (GM, from green manure, solid waste and urban sewage sludge). To this aim, WEOMs were characterized through chemical analysis; furthermore, compost stability was evaluated through oxygen uptake rate calculation and maturity was estimated through germination index determination, whereas compost impact on soil fertility was studied, in a lab-scale experiment, through indicators as inorganic nitrogen release, soil microbial biomass carbon, basal respiration rate and fluorescein di-acetate hydrolysis. The obtained results indicated that WEOM characterization could be useful to investigate compost stability (which is related to protein and phenol concentrations) and maturity (related to nitrate/ammonium ratio and degree of aromaticity) and then compost impact on soil functionality. Indeed, compost stability resulted inversely related to soil microbial biomass, basal respiration rate and fluorescein di-acetate hydrolysis when the products were applied to the soil.