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

AbstractA liquid digestate (LD) obtained from the anaerobic digestion of mixed organic waste was characterized 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.

Potential of Biochar from Wood Gasification to Retain Endocrine Disrupting Chemicals

In this study, a biochar obtained from poplar wood gasification at a temperature of 850 °C was used to adsorb the xenoestrogens 4-tert-octylphenol (OP) and bisphenol A (BPA) and the herbicide metribuzin from water. Scanning electron microscopy (SEM-EDX) and Fourier-transform infrared (FTIR) spectroscopy were employed to investigate the surface micromorphology and functional groups composition of biochar, respectively. The study of sorption kinetics showed that all compounds achieved the steady state in less than 2 h, according to a pseudo-second order model, which denoted the formation of strong bonds (chemisorption) between biochar and the compounds. Adsorption isotherms data were described by the Henry, Freundlich, Langmuir and Temkin equations. At temperatures of 10 and 30 °C, the equilibrium data of the compounds were generally better described by the Freundlich model, although, in some cases, high correlation coefficients (r ≥ 0.98) were obtained for more than one model. Freundlich constants, K_F, for OP, BPA and metribuzin were, respectively, 218, 138 and 4 L g^-1 at 10 °C and 295, 243 and 225 L g^-1 at 30 °C, indicating a general increase of adsorption at higher temperature. Desorption of all compounds, especially OP and BPA, from biochar was slow and very scarce, denoting an irreversible and hysteretic process. Comparing the results of this study with those reported in the literature, we can conclude that the present biochar has a surprising ability to retain organic compounds almost permanently, thus behaving as an excellent low-cost biosorbent.

Recent Advances on Innovative Materials from Biowaste Recycling for the Removal of Environmental Estrogens from Water and Soil

New technologies have been developed around the world to tackle current emergencies such as biowaste recycling, renewable energy production and reduction of environmental pollution. The thermochemical and biological conversions of waste biomass for bioenergy production release solid coproducts and byproducts, namely biochar (BC), hydrochar (HC) and digestate (DG), which can have important environmental and agricultural applications. Due to their physicochemical properties, these carbon-rich materials can behave as biosorbents of contaminants and be used for both wastewater treatment and soil remediation, representing a valid alternative to more expensive products and sophisticated strategies. The alkylphenols bisphenol A, octylphenol and nonylphenol possess estrogenic activity comparable to that of the human steroid hormones estrone, 17β-estradiol (and synthetic analog 17α-ethinyl estradiol) and estriol. Their ubiquitous presence in ecosystems poses a serious threat to wildlife and humans. Conventional wastewater treatment plants often fail to remove environmental estrogens (EEs). This review aims to focus attention on the urgent need to limit the presence of EEs in the environment through a modern and sustainable approach based on the use of recycled biowaste. Materials such as BC, HC and DG, the last being examined here for the first time as a biosorbent, appear appropriate for the removal of EEs both for their negligible cost and continuously improving performance and because their production contributes to solving other emergencies, such as virtuous management of organic waste, carbon sequestration, bioenergy production and implementation of the circular economy. Characterization of biosorbents, qualitative and quantitative aspects of the adsorption/desorption process and data modeling are examined.

Single and combined use of Cannabis sativa L. and carbon-rich materials for the removal of pesticides and endocrine-disrupting chemicals from water and soil

Hemp (Cannabis sativa L.) seedlings were used to remove from water the fungicide metalaxyl-M and the endocrine disruptor (EDC) bisphenol A (BPA) at concentrations ranging from 2 to 100 μg mL^-1. In 7 days of exposure, despite the phytotoxicity of each compound that reduced elongation and biomass, the seedlings were able to remove between 67 and 94% of metalaxyl-M and between 86 and 95% of BPA. The amounts of metalaxyl-M and BPA extracted from plant dry biomass were in the range of 106-3861 μg g^-1 and 16-101 μg g^-1, respectively, and resulted positively correlated to both the dose of compound added (P ≤ 0.01) and the amount removed by the plants (P ≤ 0.01). Plant uptake and transformation were the main mechanisms involved in the removal of the compounds. In another set of experiments, hemp was used to remove a mixture of two pesticides, metalaxyl-M and metribuzin, and three EDCs, BPA, 17β-estradiol (E2), and 4-tert-octylphenol (OP), at concentrations of 10, 10, 10, 10, and 1 μg g^-1, respectively, from soil column not added and added with 2.5% (w/w) of a green compost (CM) or a wood biochar (BC). In 25 days, plants did not alter considerably the distribution of the compounds along the soil profile and were capable of removing, on average, 12, 11, 10, 9, and 14% of metalaxyl-M, metribuzin, BPA, E2, and OP, respectively. During growth, hemp transformed the compounds and accumulated part of them (except OP) mainly in the shoots. CM and, especially, BC significantly protected the plants from the toxicity of the compounds and enhanced the retention of the latter in soil, contrasting leaching. Thus, the single or synergistic use of hemp and amendments deserves attention being a very low-cost and eco-sustainable strategy to remediate water and soil.

Removal of ochratoxin A from liquid media using novel low-cost biosorbents

Ground shells of almonds (ALM), hazelnuts (HAZ), walnuts (WAL), and chestnuts (CHE), coconut fiber (COC), spent coffee grounds (COF), and clementine peel (CLE) were used to remove ochratoxin A (OTA) from both water and an ethanol/water mixture (14:86, v/v). Other very efficient adsorbents like wood biochar (BC) and hydrochar (HC) and a humic acid (HA) were also adopted as a comparison. In batch experiments, sorption of OTA from water followed the trend BC (100% removed) > HA > CLE > COC > HC > COF > ALM > HAZ > CHE > WAL (8% removed), whereas sorption of OTA from ethanol/water mixture (14:86, v/v) onto only the raw materials was COC (54% removed) > CLE > HAZ > ALM > COF > CHE > WAL (0.4% removed). The desorption of the toxin from all materials in water was rather low. Afterwards, sorption kinetics and isotherms of OTA onto CLE, COC, and COF were performed. The three materials adsorbed OTA in about 2 h according to a pseudo-second-order kinetic model, thus indicating the occurrence of a chemisorption mechanism. Equilibrium sorption data of OTA onto CLE followed preferentially the Freundlich model, whereas those on COC and COF fitted well both Freundlich and Langmuir isotherms (r > 0.996). The values of Freundlich sorption constants, KFads, for CLE, COC, and COF were 313, 202, and 98 L kg-1, respectively. OTA desorption from each of the three materials showed hysteretic effects. Overall findings of this work suggest that raw plant wastes could be effectively used as biosorbents to abate the level of OTA in liquid media.

Wood biochars and vermicomposts from digestate modulate the extent of adsorption-desorption of the fungicide metalaxyl-m in a silty soil

This study aimed to investigate changes in metalaxyl-M sorption-desorption capacity of soil following the addition of two types of amendments. Two biochars (BC) from grapevine pruning residues (BC-G) and spruce wood (BC-S) and two vermicomposts (VC) obtained vermicomposting digestates from a mixture of manure and olive mill wastewater (VC-M) and buffalo manure (VC-B) were used. Using a batch equilibration method, the materials and a silt loam soil non-amended or amended with each material at 2% (w/w) were interacted with the fungicide at a concentration of 2 mg L^-1 for kinetics study and in the range 1-20 mg L^-1 for sorption isotherms. Kinetics results showed that metalaxyl-M onto the amendments and non-amended soil followed preferentially a pseudo-second-order model, thus indicating a chemisorption process. Sorption isotherm data of the product on BC and VC fitted well the Freundlich equation, whereas those on non-amended and amended soil followed preferentially a linear model. The K_Fads values were 995.2, 788.5, 55.2, 52.1, 6.4, 6.0, 3.4, 2.6 and 1.5 L kg^-1 for BC-G, BC-S, VC-M, VC-B, soil-BC-G, soil-BC-S, soil-VC-M, soil-VC-B and non-amended soil, respectively. Product desorption from each soil sample occurred to a lesser extent than sorption. Highly significant correlations (P < 0.005) were found between the values of sorption and desorption constants of all adsorbents and organic C content, thus confirming the prominent role of organic matter in the sorption process of metalaxyl-M.

Multianalytical characterization of biochar and hydrochar produced from waste biomasses for environmental and agricultural applications

Biochar (BC) and hydrochar (HC) are solid by-products obtained from various types of biomasses through the processes of pyrolysis and hydrothermal carbonization, respectively. Both BC and HC represent a sustainable solution for carbon sequestration and can be used as soil amendments or sorbents for organic and inorganic pollutants. However, the properties of BC and HC largely depend on feedstock and production parameters, which significantly affect their proper use. A detailed characterization of these materials is therefore needed to assess their suitability for environmental and/or agricultural applications. In this work, two BC samples and two HC samples were characterized with a multianalytical approach, including total reflection X-ray fluorescence (TXRF) spectroscopy, scanning electron microscopy (SEM), Fourier-transform infrared (FT-IR) spectroscopy, thermogravimetric analyses (TG), and pyrolysis coupled to gas chromatography and mass spectrometry (Py-GC/MS). By comparing BC and HC data, HC showed a higher content of mineral elements, including important plant nutrients and potentially toxic elements. HC produced from solid urban wastes contained also some potentially toxic organic molecules, like chlorinated aromatic compounds. BC samples were characterized by a higher porosity and hydrophobicity than HC, thus being potentially more suitable for the sorption of organic pollutants. HC samples showed a higher content of cellulose and hemicellulose, resulting in a more hydrophilic but less thermally stable material than BC. In conclusion, both BC and HC have interesting properties for environmental and agricultural applications but careful selection of feedstock is needed, especially for HC production.

Phytotoxic metabolites produced by Verticillium dahliae Kleb. in olive wilting: a chemical and spectroscopic approach for their molecular characterisation

Most of the symptoms associated with Verticillium wilt disease in olive cultivation are due to complexes excreted by Verticillium dahliae. In this study chemical and physico-chemical techniques were combined to investigate how the molecular structure of phytotoxins isolated from two pathotypes of Verticillium dahliae, defoliating, D, and non-defoliating, ND, grown on two different media, Verticillium-dahliae-Medium (VdM) and Simulated Xylem-fluid-Medium (SXM), can affect their aggressiveness. Data obtained highlight important structural differences, both in term of elemental composition and in functional groups distribution. Such peculiarities strongly affect their solubility, resulted higher for the phytotoxins from D pathotype. This property likely induces serious modifications of the conformational state of the proteinaceous component, making tyrosine residues accessible to the phosphate ion. A phosphorylation mechanism would thus be promoted, that is going to interfere with the function of the involved proteins in intracellular signalling networks, likely by altering its role in modulating the plant's response.

Comparative assessment of metribuzin sorption efficiency of biochar, hydrochar and vermicompost

In this study, we used two biochars (BC) produced from grapevine pruning residues (BCgv) and red spruce wood (BCrs), two hydrochars (HC) from urban pruning residues (HCup) and the organic fraction of municipal solid wastes (HCuw), and two vermicomposts (VC) obtained vermicomposting digestates from buffalo manure (VCbm) and mixed feedstock (VCmf). Adsorption kinetics and isotherms of metribuzin onto these materials were performed. Sorption kinetics followed preferentially a pseudo-second-order model, thus indicating the occurrence of chemical interactions between the sorbate and the adsorbents. Adsorption constants were calculated using the Freundlich and Langmuir models. Metribuzin sorption data on BCgv and both HC fitted preferentially the Freundlich equation, whereas on the other materials data fitted both isotherms well (r > 0.95). Metribuzin sorption capacity of the materials followed the trend BC > HC > VC. Sorption constants of metribuzin normalised per organic carbon content (K_OC) on BCgv, BCrs, HCup, HCuw, VCbm and VCmf were 561, 383, 251, 214, 102 and 84 L kg^-1, respectively. A significant positive correlation (P = 0.016) was calculated between distribution coefficients (K_d) of all materials and the corresponding organic carbon contents, thus indicating a prominent role of the organic fraction of these materials in the adsorption of metribuzin.

Adsorptive removal of ascertained and suspected endocrine disruptors from aqueous solution using plant-derived materials

The present study deals with the use of low-cost plant-derived materials, namely a biochar, spent coffee grounds, spent tea leaves, and a compost humic acid, for the adsorptive removal from water of two estrogens, 4-tert-octylphenol (OP) and 17-β-estradiol (E2), and two pesticides, carbaryl and fenuron, each spiked at a concentration of 1 mg L^-1. Kinetics and adsorption isotherms have been performed using a batch equilibrium method to measure the sorption capacities of the adsorbents towards the four molecules. Adsorption constants were calculated using the linear, Freundlich, and Langmuir models. Kinetics data obtained evidenced a rapid adsorption of each compound onto both biochar and coffee grounds with the attainment of a steady-state equilibrium in less than 4 h. Significant differences among the adsorbents and the compounds were found regarding the model and the extent of adsorption. In general, the estrogens were adsorbed more quickly and in greater amounts than the less hydrophobic pesticides, following the order: OP > E2 > carbaryl > fenuron. The ranges of Freundlich constants obtained for OP, E2, carbaryl, and fenuron onto the sorbents were 5049-2253, 3385-206, 2491-79, and 822-24 L kg^-1, respectively. The maximum values of constants were obtained for biochar, except for OP that was more adsorbed by spent coffee grounds. Adsorption kinetic data followed a pseudo-second-order model, thus indicating the occurrence of chemical interactions between the compounds and the substrates. The remarkable sorption capacities of all adsorbents towards the four molecules suggest the valuable exploitation of these materials for decontamination purposes, such as the treatment of wastewater before a feasible recycle in soil.

Decontamination activity of ryegrass exudates towards bisphenol A in the absence and presence of dissolved natural organic matter

Bisphenol A (BPA) is an endocrine disruptor compound widespread in terrestrial and aquatic systems of urbanized and industrialized regions. This study evaluated the capacity of ryegrass (Lolium perenne) aqueous exudates to degrade BPA at a concentration of 10 mg L(-1) both in the absence and in the presence of an organic fraction often coexisting with plant exudates, i.e., natural organic matter (NOM), tested at a concentration of 20 mg L(-1). In exudates alone, BPA degradation ceased after one day from the product addition when residual BPA resulted 65% of the initial BPA, whereas in exudates with the addition of NOM the degradation process continued for 4 days when residual BPA resulted 49%. Measurements of peroxidase and laccase activities in exudates suggested a significant involvement of these enzymes in BPA degradation. This finding was further confirmed by the almost complete absence of BPA degradation in aqueous exudates strongly acidified. In some BPA-contaminated exudates, chromatographic analysis revealed the presence of a newly formed compound identified as a BPA oxidation product by Fourier transform - ion cyclotron resonance mass spectrometry analysis. In conclusion, ryegrass exudates possess a relevant decontamination capacity towards BPA which persists and appears to be enhanced by the addition of NOM.

Comparative evaluation of the efficiency of low-cost adsorbents and ligninolytic fungi to remove a combination of xenoestrogens and pesticides from a landfill leachate and abate its phytotoxicity

In this study, two widely available low-cost adsorbents, almond shells and a green compost, and two ligninolytic fungi, Pleurotus ostreatus and Stereum hirsutum, were used to remove organic contaminants from a landfill leachate (LLe) and abate its phytotoxicity. The methodology adopted was based on the occurrence of two simultaneous processes, such as adsorption and bioremoval. The leachate was artificially contaminated with a mixture of the xenoestrogens bisphenol A (BPA), ethynilestadiol (EE2) and 4-n-nonylphenol (NP), the herbicide linuron and the insecticide dimethoate at concentrations of 10, 1, 1, 10 and 10 mg L(-1), respectively. Three adsorption substrates were prepared: potato dextrose agar alone or the same incorporating each adsorbent. The substrates were either not inoculated or inoculated with each fungus, separately, before to be superimposed on LLe. After 2 months, the residual amount of each contaminant, the electrical conductivity, the pH and the content of total phenols were measured in treated LLe. Germination assays using lettuce, ryegrass and radish were performed to evaluate LLe phytotoxicity. The combination substrate+P. ostreatus showed the best results with average removals of 88, 96, 99, 58 and 46% for BPA, EE2, NP, linuron and dimethoate, respectively. The same treatment considerably reduced the phenol content in LLe compared to no treatment. The combination substrate+S. hirsutum produced average removals of 39, 71, 100, 61 and 32% for BPA, EE2, NP, linuron and dimethoate, respectively. Also uninoculated substrates showed relevant adsorption capacities towards the five contaminants. Most treatments significantly reduced LLe phytotoxicity, especially on lettuce. The best results were obtained with the treatment compost+S. hirsutum, which produced root and shoot lengths and seedling biomass of lettuce, respectively, 2.3, 3.3, and 1.9 times those measured in untreated LLe. In general, germination results were negatively correlated with LLe properties like the residual amount of the contaminants, the electrical conductivity and the pH. These results show that the methodology adopted in the study, i.e., combined adsorption/biodegradation, is suitable not only to remove xenobiotic contaminants from the leachate but also to reduce considerably its inhibition on seed germination.

Decontamination of a municipal landfill leachate from endocrine disruptors using a combined sorption/bioremoval approach

Sorption and biodegradation are the main mechanisms for the removal of endocrine disruptor compounds (EDs) from both solid and liquid matrices. There are recent evidences about the capacity of white-rot fungi to decontaminate water systems from phenolic EDs by means of their ligninolytic enzymes. Most of the available studies report the removal of EDs by biodegradation or adsorption separately. This study assessed the simultaneous removal of five EDs—the xenoestrogens bisphenol A (BPA), ethynilestradiol (EE2), and 4-n-nonylphenol (NP), and the herbicide linuron and the insecticide dimethoate—from a municipal landfill leachate (MLL) using a combined sorption/bioremoval approach. The adsorption matrices used were potato dextrose agar alone or added with each of the following adsorbent materials: ground almond shells, a coffee compost, a coconut fiber, and a river sediment. These matrices were either not inoculated or inoculated with the fungus Pleurotus ostreatus and superimposed on the MLL. The residual amount of each ED in the MLL was quantified after 4, 7, 12, and 20 days by HPLC analysis and UV detection. Preliminary experiments showed that (1) all EDs did not degrade significantly in the untreatedMLL for at least 28 days, (2) the mycelial growth of P. ostreatus was largely stimulated by components of the MLL, and (3) the enrichment of potato dextrose agar with any adsorbent material favored the fungal growth for 8 days after inoculation. A prompt relevant disappearance of EDs in the MLL occurred both without and, especially, with fungal activity, with the only exception of the very water soluble dimethoate that was poorly adsorbed and possibly degraded only during the first few days of experiments. An almost complete removal of phenolic EDs, especially EE2 and NP, occurred after 20 days or much earlier and was generally enhanced by the adsorbent materials used. Data obtained indicated that both adsorption and biodegradation mechanisms contribute significantly to MLL decontamination from the EDs studied and that the efficacy of the methodology adopted is directly related to the hydrophobicity of the contaminant.

Removal of a combination of endocrine disruptors from aqueous systems by seedlings of radish and ryegrass

Endocrine disruptors (EDs) are widespread in the environment, especially aquatic systems, and cause dangerous effects on wildlife and humans. This work was aimed to assess the capacity of radish (Raphanus sativus L.) and ryegrass (Lolium perenne L.) seedlings to tolerate and remove two combinations of EDs containing bisphenol A (BPA), 17alpha-ethynilestradiol (EE2), and linuron from four aqueous media: distilled water, a solution of natural organic matter (NOM), a lake water and a river water. Seeds of the two species were germinated in each contaminated medium and, at the end of germination, the seedling growth was evaluated by biometric measurements and residual EDs were quantified by chromatographic analysis. Biometric measurements revealed that the phytotoxicity of the two combinations of EDs depended on the medium used. Radish showed a discrete tolerance in distilled water and lake water but was inhibited in the solution of NOM and river water. Ryegrass was negatively affected mainly in river water. The concentration of each ED appeared significantly reduced in all media in the presence of seedlings of both species, but not in the blanks without plants. In 5 days, radish removed up to 88% of BPA, 100% of EE2 and 42% of linuron, and in 6 days ryegrass removed up to 92% of BPA, 74% of EE2 and 16% of linuron. The considerable removal capacity of radish and ryegrass in all media tested encourages the use of phytoremediation to remove EDs from waters.

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 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.

Removal of bisphenol A by the freshwater green alga Monoraphidium braunii and the role of natural organic matter

Phytoremediation of waters by aquatic organisms such as algae has been recently explored for the removal of organic pollutants possessing endocrine disrupting capacity. Monoraphidium braunii, a green alga known for rapid growth and good tolerance to different natural organic matter (NOM) qualities, was tested in this study for the ability to tolerate and remove the endocrine disruptor bisphenol A at concentrations of 2, 4 and 10mgL(-1), either in NOM-free or NOM-containing media. NOM at concentrations of 2, 5 and 20mgL(-1) of DOC, was added because it may interfere with xenobiotics and modify their effects, modulate algal growth performances or produce a trade-off of both effects. After 2 and 4 days of algal growth, the cell number and size, the maximum quantum yield of photosystem II in the dark or light adapted state, and the chlorophyll a content were recorded in order to evaluate the algal response to bisphenol A. Moreover, the residual bisphenol A was measured in the algal cultures by chromatographic technique. Results indicated that after 2 and 4 days bisphenol A at the lower concentrations was not toxic for alga, whereas at the highest concentration it reduced algal growth and photosynthetic efficiency. The sole NOM and its combinations with bisphenol A at the lower concentrations increased the cell number and the chlorophyll a content of algae. After 4-day growth, good removal efficiency was exerted by M. braunii at concentrations of 2, 4 and 10mgL(-1) removing, respectively, 39%, 48% and 35% of the initial bisphenol A. Lower removal percentages were found after 2-day growth in the different treatments. NOM at any concentration scarcely influenced the bisphenol A removal. On the basis of data obtained, the use of M. braunii could be reasonably recommended for the phytoremediation of aquatic environments from bisphenol A.

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.

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.

The role of humic fractions from soil and compost in controlling the growth in vitro of phytopathogenic and antagonistic soil-borne fungi

The regulation capacity of four humic substance (HS) samples, a soil humic acid (HA) and two HAs and one fulvic acid (FA) isolated from a composting substrate, was evaluated at two concentrations on the growth in vitro of one plant pathogenic, Sclerotinia sclerotiorum, and two antagonistic, Trichoderma viride and T. harzianum, soil-borne fungi. The presence of any HS sample in the growing medium, especially those from the composting substrate, caused a relevant inhibition of the mycelial growth of S. sclerotiorum and a marked stimulation of sclerotial formation that was exhibited as early appearance and numerical increase. On the contrary, the same HS treatments generally did not inhibit the growth of the two Trichoderma species. In particular, T. viride was significantly stimulated by any HS sample at any concentration, with the only exception of HA from fresh-composting substrate, whereas T. harzianum appeared to be stimulated only slightly or not significantly influenced. Only S. sclerotiorum showed evident high correlations of both the extent of the inhibitory action on mycelial growth and the final number of sclerotia with some chemical and functional properties of HS, such as total acidity, COOH group content, and elemental composition.

Phytotoxic, clastogenic and bioaccumulation effects of the environmental endocrine disruptor bisphenol A in various crops grown hydroponically

The effects of the endocrine disruptor bisphenol A (BPA) at concentrations of 10 and 50 mg l(-1) were evaluated on the germination and morphology, micronuclei (MN) content in root tip cells and BPA bioaccumulation of hydroponic seedlings of broad bean (Vicia faba L.), tomato (Lycopersicon esculentum Mill.), durum wheat (Triticum durum Desf.) and lettuce (Lactuca sativa L.) after 6 and 21 days of growth. In general, BPA at any dose used did not inhibit germination and early growth (6 days) of seedlings of the species examined, with the exception of primary root length of tomato which decreased at the higher BPA dose. In contrast, an evident phytotoxicity was induced by BPA in all species after 21 days of growth with evident morphological anomalies and significant reductions of the lengths and fresh and dry weights of shoots and roots of seedlings. With respect to the nutrient medium without seedlings, BPA concentration decreased markedly during the growth period in the presence of broad bean and tomato seedlings, and limitedly in the presence of durum wheat and, especially, lettuce. Further, the presence of BPA measured in roots and shoots of broad bean and tomato after 21-day growth indicated that bioaccumulation of BPA had occurred. The number of MN in broad bean and durum wheat root tip cells increased markedly by treatment with BPA at both concentrations, thus suggesting a potential clastogenic activity of BPA in these species.

Humic acids reduce the genotoxicity of mitomycin C in the human lymphoblastoid cell line TK6

The antimutagenic/desmutagenic activity of a leonardite humic acid (LHA) and a soil humic acid (SHA) was studied in the cultured human lymphoblastoid cell line TK6 treated with mitomycin C (MMC) as reference mutagen by evaluating the induction of micronuclei (MN). Two different concentrations of HA were used, 2.5 and 10 microg/ml, in three different treatments: (1) HA alone (genotoxic test); (2) HA after 2-h pre-incubation with 0.3 microM of MMC (desmutagenic test) and (3) combinations of HA and MMC at 0.3 microM without pre-incubation (antimutagenic test). Neither of the HA used alone did produce genotoxic effects, but both HAs reduced significantly the frequencies of MN induced by MMC, especially in the desmutagenic test. A slight cell-protective effect against the cytotoxicity of MMC was also exhibited by the two HAs in the desmutagenic test. The LHA showed a desmutagenic/antimutagenic activity that was more pronounced than that of SHA, which is possibly related to the higher carboxylic group content and lower phenolic group content of LHA. These results confirm the antigenotoxic action exerted by HAs in human cells, similarly to what has been previously observed in various plant species.

Humic substances can modulate the allelopathic potential of caffeic, ferulic, and salicylic acids for seedlings of lettuce (Lactuca sativa L.) and tomato (Lycopersicon esculentum Mill.)

The capacity of a leonardite humic acid (LHA), a soil humic acid (SHA), and a soil fulvic acid (SFA) in modulating the allelopathic potential of caffeic acid (CA), ferulic acid (FA), and salicylic acid (SA) on seedlings of lettuce (Lactuca sativa L.) and tomato (Lycopersicon esculentum Mill.) was investigated. Lettuce showed a sensitivity greater than that of tomato to CA, FA, and SA phytotoxicity, which was significantly reduced or even suppressed in the presence of SHA or SFA, especially at the highest dose, but not LHA. In general, SFA was slightly more active than SHA, and the efficiency of the action depended on their concentration, the plant species and the organ examined, and the allelochemical. The daily measured residual concentration of CA and FA decreased drastically and that of SA slightly in the presence of germinating seeds of lettuce, which were thus able to absorb and/or enhance the degradation of CA and FA. The adsorption capacity of SHA for the three allelochemicals was small and decreased in the order FA > CA > SA, thus suggesting that adsorption could be a relevant mechanism, but not the only one, involved in the "antiallelopathic" action.

Estrogenic effect of leachates and soil extracts from lysimeters spiked with sewage sludge and reference endocrine disrupters

Several experiments were conducted to evaluate the behavior and performance of some potential endocrine disrupters (ECDs). Two in vitro screening assays, one based on MCF7-cell proliferation (E-screen test) and the other on estrogenic receptor activity [enzyme-linked receptor assay (ELRA)], were used for the tests, which were done in lysimeters 80 cm in diameter with depth of 30 cm (shallow) or 90 cm (deep). A sandy soil was used to fill in all lysimeters, which were spiked on the surface with either: (a) a sewage sludge (SS) at a dose equivalent to 20 tons ha-1; (b) a mixture of reference ECDs, comprising 17 alpha- and 17 beta-estradiol (E2), nonylphenol, octylphenol, and bisphenol A at doses 100 times higher than the maximum concentrations respectively found in the applied SS; or (c) a mixture of ECDs and SS. After percolation of the lysimeters with rain and/or artificial water, five leachates were sampled from each lysimeter during a period of 210 days. Immediately after the lysimeter percolation experiments, four and six soil fractions were dissected from, respectively, the 30-cm and 90-cm lysimeters and extracted by water. Both the leachate and soil extract samples were analyzed for their estrogenicity using the assays indicated above. The E-screen assay was highly sensitive only for some leachate and extract samples but gave no response for most leachates and soil extracts. The results of the ELRA assay suggests a significantly higher estrogenicity of leachate samples from shallow lysimeters compared with that of leachates from deep lysimeters. In contrast, the estrogenic effect measured for soil extracts of shallow lysimeters was lower than that measured for soil extracts of deep lysimeters. The results of the E-screen assay suggests the occurrence of a fast mobilization of applied ECDs and a moderate retardation effect of native ECDs contained in applied SS in the sandy soil used in the lysimeters. In lysimeters spiked with a mixture of SS and ECDs, the washing-out effect of ECDs in the first leachate fraction decreased, but the distribution of ECDs in the lysimeters increased. The relatively high estrogenic impact measured for soil water extracts suggests that the ECDs were mostly associated with water-soluble fractions of organic matter and/or water-suspended fractions of the mineral soil matrix. The application of SS to agricultural and forest fields may determine the immobilization of ECDs in soil or their movement to surface and/or groundwater. Therefore, an endocrine risk of exposure exists for the water and soil organisms.

Aquatic humic substances inhibit clastogenic events in germinating seeds of herbaceous plants

One humic acid (HA) and two fulvic acids (FAs) of aquatic origin have been tested for their capacity to inhibit clastogenic events caused by maleic hydrazide (MH) in germinating seeds of the herbaceous plant species Allium cepa and Vicia faba. Either HA or FA at concentrations of 50 and 500 mg L(-)(1) was interacted with 10 mg L(-)(1) MH for 24 h before addition to the seeds. The evaluation of genotoxic activity was made by counting micronuclei (MN) and aberrant anatelophases (AT) in root tip cells after treatment with HA or FA alone, MH alone, and interacted HA + MH and FA + MH. Regular AT were also counted as an index of mitotic activity. In all cases HA and FA interacted with MH showed an evident anticlastogenic action indicated by the marked reduction of genetic anomalies. In A. cepa, the anticlastogenic effect of HA and FA was more significant for aberrant AT than for MN, whereas the opposite was true in the case of V. faba. The protective effect exhibited for both anomalies by HA was slightly higher than that of the corresponding FA in A. cepa, whereas no significant differences between these HA and FA treatments were observed in the case of V. faba. The two FAs generally showed similar anticlastogenic behaviors with slight quantitative differences observed as a function of the type of anomaly and the plant species. The effects of HA and FA concentration differed depending on the type of anomaly observed, the plant species, and FA origin. In V. faba, cell division, that is, the number of regular AT, was generally depressed by HA and FA at either concentration with respect to the control. In A. cepa, HA and FA produced either stimulating or inhibiting effects on regular AT depending on their nature, origin, and concentration.