The liquid by-product of biogas production: characterisation and impact on soil fungi.

ABSTRACTA liquid digestate (LD) obtained from the anaerobic digestion of mixed organic waste was characterised and tested on the fungi Pleurotus eryngii, Irpex lacteus and Trametes versicolor. Aqueous mixtures of LD at doses of 0.5, 1 and 2% (v/v) were tested directly or after interaction with 5% (w/v) biochar (BC-LD) and/or 100 mg L-1 soil humic acid (HA-BC-LD and HA-LD). Total luminescence (TL) analysis of LD showed the presence of fluorophores typical of scarcely aromatic matter, while the Fourier transform infrared (FTIR) spectrum evidenced absorption bands typical of labile and non-condensed material. Some spectroscopic variations of the LD sample were observed after its interaction with the other materials. All LD treatments markedly promoted hyphal extension of P. eryngii whose growth rate increased up to 38% at the highest LD dose. The LD alone had no influence on the other fungi, whose growth was stimulated by some combinations of LD with the other materials. In facts, the growth rate of I. lacteus increased in BC-LD 1 and BC-LD 2 (P ≤ 0.05) and in all treatments with HA (up to 6% in HA-LD 2, P ≤ 0.01), while the growth of T. versicolor was promoted by HA-BC-LD 2 treatment (P ≤ 0.05) and slightly inhibited by all BC-LD combinations (up to 7% by BC-LD 1, P ≤ 0.05). The overall results obtained encourage the addition of LD to the soil and suggest a possible use of this material as substrate ingredient for the cultivation of edible mushrooms such as P. eryngii.

Uptake of different pharmaceuticals in soil and mycorrhizal artichokes from wastewater.

The irrigation with treated wastewater is among the main anthropogenic sources for the release of pharmaceuticals (PhACs) into the soils and their translocation into crops, with possible toxic and adverse effects on humans. The arbuscular mycorrhizal fungi (AMF) can be employed for the reduction of organic soil pollutants, even if their efficiency depends on the mycorrhizal fungi, the plant colonized, and the type and concentration of the contaminant. This study aimed to evaluate the uptake of PhACs from wastewaters of different qualities used for the irrigation of mycorrhizal artichoke plants, the presence in their edible parts and the role of the arbuscular mycorrhizal fungi. The research was carried out on artichoke plants not inoculated and inoculated with two different AMF and irrigated with treated wastewater (TW), groundwater (GW) or GW spiked with different and selected PhACs (SGW). The inocula were a crude inoculum of Septoglomus viscosum (MSE) and a commercial inoculum of Glomus intraradices and Glomus mosseae (MSY). The results of the present study showed that carbamazepine and fluconazole were found in the artichoke only with SGW irrigation. The mycorrhizal plants showed a reduction of the pharmaceutical's uptake, and within the AMF, MSE was more effective in preventing their absorption and translocation.

Use of constructed wetlands to prevent overloading of wastewater treatment plants.

The fluctuation in the number of people in tourist areas affects the wastewater quality and quantity. Constructed wetlands (CWs) aim to simulate physical, chemical, and biological processes occurring in natural environments for wastewater treatment and are considered a sustainable system. The current study aimed at evaluating the effectiveness of in-vessel CWs for supporting the wastewaters treatment plants in periods of overloading. Such approach can be quickly implementable, economic, and the CWs can be fast regenerated in the framework of sustainable good practices. Three pilot scale CWs were prepared in as many containers layering 10 cm of gravel, 60 cm of sand and 10 cm of gravel, and placing pieces of giant reed rhizomes in the upper layers. The bottom of each CW had a tap, and CWs were irrigated with a real municipal sewage three times a week. Before each new irrigation, the tap was opened, and the effluent collected for determining gross parameters, elemental composition, and contaminants of emerging concern (CECs). CWs significantly reduced almost all gross parameters considered and half the CECs, except for a couple of metabolites of corresponding parental compounds. With regards to the potentially toxic elements, all reduced their concentration from the influents to the effluents. The results of this study were promising and highlighted good efficiency of constructed wetlands as pre-treatment of real municipal sewage to reduce the overloading of the wastewater treatment plant.

Effects of different pioneer and exotic species on the changes of degraded soils.

Soil degradation resulting from deforestation contributes to a dramatic decline in soil quality whose restoration must go through reforestation with pioneer species. We investigated the effects of cypress and black locust, pioneer but exotic species, on soil chemical properties and microbial and enzymatic activities of two marginal soils. The sampling sites were Lama Giulia and Locone lake in the Murge plateau of the Apulia Region, Italy. The soils at Lama Giulia presented a silty loam texture, while at Locone Lake site were sandy, and most likely due to the different texture, the former exhibited higher organic C, N, P and micronutrients contents than Locone Lake under black locust reforestation, despite the latter was reforested earlier. In addition, the higher microbial entropy and turnover of Locone Lake's soils suggested a less conservative soil state than Lama Giulia's soils. The effects of black locust reforestation at Lama Giulia on almost all soil parameters considered did not differ from those of the corresponding pasture, confirming the more conservative soil state in that site and suggesting that the time of reforestation was not enough to get differences between the reforested and not reforested soil. The soils reforested with cypress showed the significantly highest SOC, N, dissolved organic C and microbial biomass C content. In addition, it presented also the numerically largest dehydrogenase, phosphatase and ß-glucosidase activities, soluble carbohydrates, and phenolic compounds content. These results may be ascribed to the longer litter deposition occurred in cypress soils.

Influence of crop rotation, tillage and fertilization on chemical and spectroscopic characteristics of humic acids.

The changes in soil organic matter composition induced by anthropogenic factors is a topic of great interest for the soil scientists. The objective of this work was to identify possible structural changes in humic molecules caused by a 2-year rotation of durum wheat with faba bean, lasted for a decade, and conducted with different agricultural practices in a Mediterranean soil. Humic acids (HA) were extracted at three depths (0-30, 30-60 and 60-90 cm) from a Mediterranean soil subjected to different tillage (no tillage, minimum tillage and conventional tillage), crops (faba bean and wheat), and fertilization. The changes in HA quality were assessed by several chemical (ash, yield and elemental analysis) and spectroscopic techniques (solid-state 13C nuclear magnetic resonance, Fourier transform infrared and fluorescence). The results suggest that the different agronomic practices strongly affected the quality of HA. Smaller but more aromatic molecules were observed with depth, while the fertilization induced the formation of simpler and less aromatic molecules due to the enhanced decomposition processes. Under no tillage, more stable humic molecules were observed due to the less soil aeration, while under conventional tillage larger and more aromatic molecules were obtained. Compared to wheat, more aromatic and more oxidized but less complex molecules were observed after faba bean crop. The inorganic fertilization accelerates the decomposition of organic substances rather than their stabilization. At the end of each crop cycle, humic matter of different quality was isolated and this confirms the importance of the rotation practice to guarantee a diversification of the soil organic matter with time. Finally, no tillage induces the formation of more stable humic matter.

Minimum tillage and organic fertilization for the sustainable management of Brassica carinata A. (Braun) in the Mediterranean environment.

In recent years, the massive exploitation of agricultural land intended to meet growing food demand has led to a reduction in soil fertility through the depletion of nutrients and organic matter. To implement sustainable agriculture, it is necessary to reduce soil tillage and use residual biomasses that are easily available in the region as soil amendments. Furthermore, it is important to test these residual biomasses in order to exclude a possible increase of heavy metals in soils due to the incorporation of the aforementioned biomasses. The current study aimed to evaluate the effects on soil fertility and health following the application of organic fertilizers combined with different soil tillage practices and the agronomic response of Brassica carinata A. (Braun). The soil tillage treatments consisted of conventional (CT) and minimum tillage (MT), whereas the fertilization treatments were mineral fertilizer (Nmin), municipal solid waste compost (Ncomp), mixed compost and mineral fertilizer (Nmix), and sewage sludge (Nss). These treatments were compared with an unfertilized control (N0). The Ncomp and Nss treatments enhanced soil fertility, increasing the organic carbon and available phosphorus concentrations compared with N0 and Nmin, whereas no significant difference was showed between the soil tillage treatments in terms of soil fertility. In addition, Nss did not show any significant difference compared to Nmin in terms of crop biomass, whereas this parameter appeared higher in CT compared with MT. A principal component analysis showed that the concentrations of toxic elements applied by the organic amendments did not change the dynamic equilibrium of the soil-plant system. Over the short term, the replacement of CT and Nmin with MT and Nss can be achieved, thus guaranteeing the sustainable cultivation of Brassica, without significant changes in heavy metal concentration in soil.

Posidonia oceanica (L.) based compost as substrate for potted basil production.

BACKGROUND: Peat is the main component of growing media but is also a non-renewable resource; therefore European policy strongly encourages the use of peat alternatives such as compost. Posidonia is a Mediterranean seagrass that produces very conspicuous onshore deposits that can be composted. In this study, a commercial green compost and a Posidonia residue-based compost were tested in order to assess their potential use as substitutes or complements to peat. RESULTS: All macro and micro-element concentrations of the substrates were positively and significantly related to the percentage of composts in the growing media. Plant grown on peat showed higher content of P, Ca, K, Na, Cu, Mn, Zn and Fe, and a slightly higher biomass production in comparison to compost-based growing media. In contrast, plants grown on compost-based substrates showed lower uptake of Cd and Cr than peat. CONCLUSION: The results indicate that both composts can be used as a complement to the peat for substrate preparation, especially at a rate of 30%. The Posidonia-based compost showed better productive results in comparison to the green one. Basil grown on the two compost-based media showed reduced absorption level of potentially toxic metals in comparison to peat.

Ptaquiloside in Pteridium aquilinum subsp. aquilinum and corresponding soils from the South of Italy: influence of physical and chemical features of soils on its occurrence.

The bracken fern Pteridium aquilinum (L.) Kuhn, one of the most common plant species on Earth, produces a wide range of secondary metabolites including the norsesquiterpene glucoside ptaquiloside (PTA). Several studies are present in literature about eco-toxicological aspects related to PTA, whereas results about the effect of growth conditions and soil properties on the production and mobility of PTA are sometimes conflicting and further investigations are needed. The aim of the present work is to investigate the occurrence and possible fate of PTA in soils showing different physical and chemical features, and collected in several areas of the South of Italy. The PTA content was determined in both soil and fern samples by GC-MS; both the extraction protocol and recovery were previously tested through incubation studies. Soils samples were also characterized from the physical and chemical points of view in order to correlate the possible influence of soil parameters on PTA production and occurrence. PTA concentration in P. aquilinum fern seemed to be significantly affected by the availability of nutrients (mainly P) and soil pH. At the same time, PTA concentration in soil samples was always undetectable, independent of the PTA concentration in the corresponding Pteridium samples and pedo-climatic conditions. This seems to suggest the degradation of the PTA by indigenous soil microbial community, whereas incubation studies underlined a certain affinity of PTA for both organic colloids and clay/silt particles.

Chemical and spectroscopic characteristics of humic acids and dissolved organic matter along two Alfisol profiles.

The aim of this study was to elucidate the heterogeneous structural and functional composition of humic acids (HAs) and dissolved organic matter (DOM) isolated from two Alfisol profiles with different soil texture, in order to develop a better understanding of the organic matter dynamics. Soil samples were collected at different depths from three (Ap, 2AB and 2Bt) and eight (A1, A2, A3, E1, E2, 2Bt1, 2Bt2 and 2Bt3) soil horizons of two Alfisols located in the south (PR1) and north (PR2) of Italy, with a clay texture and a silt loam to loam ones, respectively. Chemical and spectroscopic methods were used to characterize the HAs and the DOM isolated from different soil horizons, including Ultraviolet-Visible (UV-Vis), Fourier Transform Infrared (FTIR), and Fluorescence spectroscopies. The HAs and the DOM isolated from the two Alfisols apparently showed significant differences in their compositional, structural and functional characteristics. In particular, the HAs isolated from the PR1 featured a higher degree of humification and molecular complexity with respect to those isolated from the PR2. On the contrary, the DOM samples isolated from the PR2 showed a more marked aromatic character and polycondensation degree. Both the HAs and the DOM obtained from the PR1 presented a greater qualitative homogeneity with respect to those obtained from the PR2. These results could be reasonably ascribed to the different texture and horizons of the two Alfisols, and to a greater pedogenesis occurred in the PR1.

Comparative assessment of three ligninolytic fungi for removal of phenolic endocrine disruptors from freshwaters and sediments.

Bisphenol A (BPA) and 4-n-nonylphenol (NP) are two endocrine disruptor compounds dangerous to animals, especially aquatics, and humans. They can be leached from urban and industrial wastes and contaminate the environment. White rot fungi produce ligninolytic enzymes capable of biodegrading aromatic contaminants, including some endocrine disruptors. This investigation has evaluated the potential of three fungal species, Trametes versicolor, Stereum hirsutum and Pleurotus ostreatus, to remove BPA at a concentration of 4.6 mg L(-1) from two freshwaters, a lake and a river, and both BPA and NP each at a concentration of 10 mg kg(-1) from the corresponding sediments. A comparative assessment of mycelial growth during biodecontamination showed that, in general, the maximum fungal hyphae elongation was observed with T. versicolor in freshwaters and with P. ostreatus in sediments. The fungi T. versicolor and P. ostreatus exhibited a similar capacity for removing BPA from the two freshwaters, whereas S. hirsutum was much more effective in the decontamination of lake water than river water. A significant disappearance of both BPA and NP was shown in the two sediments inoculated with each fungus, especially of BPA in the lake sediment and of NP in the river sediment. The most effective removal of the two contaminants from sediments occurred during the first seven days after fungal inoculation.

Biodecontamination of aqueous substrates from bisphenol A by ligninolytic fungi.

Bisphenol A (BPA) is an endocrine disruptor compound of health concern in natural systems. In this study, BPA removal from solid and aqueous matrices by ligninolytic fungi was investigated. Three white rot fungi, Trametes versicolor (TRA), Stereum hirsutum (STE) and Pleurotus ostreatus (PLE) were evaluated for their capacity to remove BPA added at concentrations of 4.6 and 46 mg L(-1) from potato dextrose agar (PDA) growth medium and at 4.6 mg L(-1) from aqueous solutions. Further, the inhibition of mycelial growth exerted by BPA was evaluated in the experiments with PDA. Results obtained showed that BPA was toxic for TRA and STE only at the higher concentration in PDA. However, the efficiency of the three fungi for BPA removal was significant at either doses, with TRA showing the maximum removal efficiency. In the experiments in aqueous solutions BPA was removed efficiently only by TRA after 7 days and STE after 10 days.

Biodecontamination of water from bisphenol A using ligninolytic fungi and the modulation role of humic acids.

Bisphenol A (BPA) is an endocrine disruptor compound (EDC) of xenobiotic origin occurring in natural waters and wastewaters, especially in the most industrialized and urbanized areas. Recent investigations report the use of ligninolytic fungi for the removal of aromatic contaminants, including some EDCs, from different matrices. Humic acids (HA) are widely spread in all natural systems and their presence is ascertained to interfere with microbial growth and activity. The objective of this study was to assess the capacity of three ligninolytic fungi, Trametes versicolor, Stereum hirsutum and Pleurotus ostreatus, to remove BPA at the concentration of 4.6 mg L(-1) from water. Fungal growth on potato dextrose agar (PDA), in the absence and in the presence of a leonardite HA or a green compost HA, was evaluated during the biodecontamination process. The methodological approach adopted in this study excluded the presence of the mycelium in the contaminated water. Results obtained evidenced a relevant removal of BPA by any fungus when PDA only was used as growing medium. The addition of leonardite HA and compost HA stimulated the mycelial growth of any fungus, especially T. versicolor, and significantly enhanced the removal of the contaminant from water by, respectively, T. versicolor only and T. versicolor and S. hirsutum.

Potential of various herbaceous species to remove the endocrine disruptor bisphenol A from aqueous media.

Several different plants are capable of removing and detoxifying the endocrine disruptor bisphenol A from water starting with initial concentrations of 4.6 mg L(-1) and 46 mg L(-1). Bisphenol A seems to be glycosylated, transformed to polar compounds, and bound as residue by five forage grasses, fescue, couch grass, perennial ryegrass, Siberian wheatgrass, and white clover, and three horticultural species, cucumber, marrow plant, and radish. Septic and axenic testing established that microbial degradation is possible for fescue and radish, and perennial ryegrass exudates seemed to contain enzymatic activity that transforms bisphenol A, but this activity is evidently deactivated by microorganisms. Although the grasses tested were more effective than the horticultural species, the optimal species of plants best suited for phytoremediation of bisphenol A was not determined. The limited plant testing during 16d does not define how nor which phytoremediation practices can be applied, but the removal efficiency and evident transformation of bisphenol A justify further feasibility, pilot, and treatability testing of different wastewaters.