Aqueous Soil Extracts Research Articles

Decrease in radiocesium adsorption of illite induced by soil organic matter: Quantity or quality?

Organic matter blocks highly selective frayed edge sites on clay minerals and reduces radiocaesium adsorption. The effects of different soil organic matter on Cs adsorption on illite have been investigated. The quantity and quality of soil organic matter was varied by extracting from three contrasting soils and varying extraction conditions. Extracted organic matter was quantified, and analysed using UV and fluorescent spectroscopy. Cs adsorption was markedly lower in soil aqueous extracts, than in simple electrolyte solution at the same ionic strength (IS). Part of the decrease was attributed to soluble soil potassium. After correction for ionic strength and potassium, the relative distribution coefficient of Cs, KdIS,K, decreased with increasing dissolved organic carbon (DOC) concentration. The correlation between KdIS,K and DOC was largely unchanged by taking into account any of the measured spectral parameters. We find no evidence that molecular size and composition of organic coatings determine their effect on the Cs adsorption properties of illite.

Антибиотик ципрофлоксацин в водных и почвенных средах: реакция микроводорослей

Pharmaceuticals and antibiotics in the environment are of increasing concern due to the impact on representatives of all links in the food chain of natural ecosystems. The effect of the widespread antibiotic ciprofloxacin (Cip) on the green protococcal microalgae Scenedesmus quadricauda and Chlorella vulgaris in water and aqueous soil extracts (artificial standard soil, technosoil, soddy-podzolic soil) was studied in model experiments. Fluorescent parameters were assessed by two different methods (Fluorat 02-5M and Water-PAM devices). The phenomenon of hormesis was observed at low antibiotic concentrations of 5 and 10 mg/L. A decrease in the photosynthetic activity of algae was recorded at an increase of Cip content from 20 to 50 mg/L. A comparison was made of the median (average effective) concentration of the EC50 antibiotic, which suppresses the fluorescent characteristics of microalgae by 50% on 3 days of exposure in different media. The decrease in the toxicity of the studied dose of Cip (300 mg/L) in a number of studied objects can be represented as follows: water > technosoil > artificial standard soil > soddy-podzolic soil. It reflects the percentage of inhibition of the test function relative to the control (samples without antibiotic) by 91.5, 80.0, 62.5, and 60.0% respectively. In the soil matrix, the inhibitory effect of the antibiotic is less pronounced (by 10–30%), probably due to the protective properties of humic substances that adsorb the antibiotic or its metabolites.

Ability for vegetation and spore formation of <i>Bacillus anthracis</i> strains with different phenotypical properties under soil simulating conditions

Introduction. The study of the ability of Bacillus anthracis strains with different phenotypic properties to spore germination, reproduction and sporulation on a medium based on an aqueous soil extract can help assess the significance of these processes in the formation and maintenance of soil anthrax foci.
 Aim. The analysis of individual characteristics of the development of a vegetative culture of anthrax pathogen strains with different phenotypes in a soil medium model.
 Materials and methods. On a group of anthrax microbe strains with different plasmid composition and virulence, the possibility of spore germination, reproduction of bacilli and, at least in some of them, productive spore formation on the soil medium was studied.
 Results. Three variants of culture development of B. anthracis strains were identified: 1 spores remain intact, not germinating; 2 after germination of spores, bacilli are formed, which multiply with different intensity, passing into involutional forms without spore formation; 3 the passage of a complete physiological cycle "sporebacillusspore". The presence of 2% blood in the soil environment contributed to the germination of spores and reproduction of the culture, but inhibited the process of sporulation during the observation period of 3 days. No correlation was found between a certain phenotype of the studied strains of B. anthracis and the ability to germinate and vegetate on soil media.
 Conclusion. The data obtained that only 17% of CFU gives rise to the formation of colonies on the soil medium suggest the heterogeneity of the properties of the population of the studied strains. Isolation of such cultures and their further detailed study will make it possible to identify the most significant complexes of biological properties for the realization of a complete physiological cycle under soil-simulating conditions.

Biodegradation of Amphipathic Fluorinated Peptides Reveals a New Bacterial Defluorinating Activity and a New Source of Natural Organofluorine Compounds.

Three peptides comprising mono-, di-, and tri-fluoroethylglycine (MfeGly, DfeGly, and TfeGly) residues alternating with lysine were digested by readily available proteases (elastase, bromelain, trypsin, and proteinase K). The degree of degradation depended on the enzyme employed and the extent of fluorination. Incubation of the peptides with a microbial consortium from garden soil resulted in degradation, yielding fluoride ions. Further biodegradation studies conducted with the individual fluorinated amino acids demonstrated that the degree of defluorination followed the sequence MfeGly > DfeGly > TfeGly. Enrichment of the soil bacteria employing MfeGly as a sole carbon and energy source resulted in the isolation of a bacterium, which was identified as Serratia liquefaciens. Cell-free extracts of this bacterium enzymatically defluorinated MfeGly, yielding fluoride ion and homoserine. In silico analysis of the genome revealed the presence of a gene that putatively codes for a dehalogenase. However, the low overall homology to known enzymes suggests a potentially new hydrolase that can degrade monofluorinated compounds. 19F NMR analysis of aqueous soil extracts revealed the unexpected presence of trifluoroacetate, fluoride ion, and fluoroacetate. Growth of the soil consortium in tryptone soya broth supplemented with fluoride ions resulted in fluoroacetate production; thus, bacteria in the soil produce and degrade organofluorine compounds.

A New Method for the Quantitative Determination of Sulfate Ions in Aqueous Extracts from Soils and in Aqueous Media, and Analytical Equipment for Its Implementation

A method and the necessary analytical equipment for the mass quantitative determination of sulfate ions in aqueous extracts from soils and in aqueous media is proposed, consisting in the fact that a known amount of 2-aqueous barium chloride with hydrogen chloride is added to the aliquot of the analyzed sample in the form of an aqueous solution. The resulting insoluble barium sulfate compound reduces the initial concentration of barium chloride. The amount of barium chloride remaining in the solution is determined on the specially designed flame spectrophotometric analyzer. This allows you to calculate the amount of sulfate ions associated with barium, which is automatically performed by the device program. The range of reliably determined concentrations of sulfate ions by the proposed method in water samples ranged from 10 to 100 mg/dm³. The range of reliably determined concentrations of sulfate ions in aqueous extracts from soils ranged from 0.2 to 2.4 C_(1/2SO4) mol/dm³ (from 10 to 115 mg/dm³). Higher concentrations of sulfate ions must be diluted multiple times with distilled water. The method makes it possible to determine the concentration of sulfate ions in aqueous soil extracts, freshwater reservoirs and rivers, underground sources, tap water, sediments contaminated with sulfuric acid emissions from industrial enterprises. The method is quite simple, accurate and productive. The method is certified by the State Ural Research Institute of Metrology (MVI-66373620-007-2018) and approved by the Federal Agency for technical regulation and Metrology (Rosstandart), as a standard method under No. 253.0080/RA. RU.311866/2019. Patent No. 2681855 of the Russian Federal Service for Intellectual Property with priority dated September 15, 2017 was obtained for the method for determining sulfur in the form of a sulfate ion in an aqueous extract from soils and the equipment necessary for this. Detailed methods for determining sulfate ions in these objects are published in the open press in the book: "Determination of agrochemical and chemical parameters of soils, plants and aquatic environments using flow-decade analysis technology" edited by Academician of the Russian Academy of Sciences R. F. Baibekov.

Development of SiO2-coumarin fluorescent nanohybrid and its application for Cu(II) sensing in aqueous extracts of roadside soil

A SiO2-coumarin nanohybrid was investigated for its Cu(II) sensing performance in aqueous media, and in comparison with the Cu(II)-selective coumarin used alone. Fluorescence of both coumarin itself and the nanohybrid, λex/λem 435/481 nm, was selectively quenched by Cu(II) when tested against a range of multivalent cations. The nanohybrid had enhanced Cu(II) sensing properties when compared to the coumarin including (i) improved limit of detection from μM-level (0.48 μM) of Cu(II) using coumarin alone to nM-level (0.033 μM) and (ii) an extended linear detection range of 0.033–260 μM (0.0005–4.1 mg/mL) Cu(II) compared to 0.48–55 μM for the coumarin itself. The lower limit of detection and extended range were achieved with a smaller amount of coumarin and no traces of organic solvents used to help coumarin dissolution. Characterization suggested that under applied test conditions at pH = 5, SiO2 nanoparticles with negative surface charges adsorbed coumarin and then (when present) Cu(II) ions. The SiO2-coumarin nanohybrid was then applied for the determination of Cu(II) levels in aqueous soil extracts reaching over 94% recovery rates when used against the standard soil analysis method by inductively coupled plasma mass spectrometry (ICP-MS).Graphical

Bioluminescent-Inhibition-Based Biosensor for Full-Profile Soil Contamination Assessment.

A bioluminescent-enzyme-inhibition-based assay was applied to predict the potential toxicity of the full profile of the following soil samples: agricultural grassland, 10-year fallow land (treated with remediation processes for 10 years) and uncontaminated (virgin) land. This assay specifically detects the influence of aqueous soil extracts from soils on the activity of a coupled enzyme system of luminescent bacteria: NAD(P)H:FMN-oxidoreductase + luciferase (Red + Luc). It was shown that the inhibitory effect of the full-profile soil samples on the Red + Luc system decreased with depth for the 10-year fallow-land and virgin-land samples, which correlated with a decrease in the humic organic matter content in the soils. The inhibitory effect of the agricultural grassland on the Red + Luc enzyme system activity was more complex and involved the presence of the humic organic matter content, as well as the presence of pollutants in the whole-soil profile. However, if the interfering effect of humic organic substances on the Red + Luc system’s activity is taken into account during full-profile soil toxicity assessments, it might help to detect pollutant mobility and its leaching into the subsoil layer. Thus, this bioluminescent method, due to the technical simplicity, rapid response time and high sensitivity, has the potential to be developed as a biological part of the inhibition-based assay and/or biosensors for the preventive tracing of potential full-profile soil contamination.

Interactive effects of allelopathy and arbuscular mycorrhizal fungi on the competition between the invasive species Bidens alba and its native congener Bidens biternata

AbstractAllelopathy is an invasion driver, and arbuscular mycorrhizal fungi (AMF) also play an important role in plant invasion. However, little is known about their interactive effects on plant invasion mechanisms. In this study, we have investigated the interactive effects of allelopathy and AMF on competition between the exotic invasive species, Bidens alba, and its native congener, Bidens biternata. A two‐factor (allelopathy, AMF) common garden experiment was conducted using sterilised soil with or without AMF inoculation and with or without activated carbon (AC) addition. The results showed that both AC and AMF had significant effects on the relative yield (RY) of invasive species and competitive aggressivity (AG) between invasive and native species. Both AC and AMF exerted interactive effects on the AG. Activated carbon significantly reduced AG (0.86 vs 0.15%) without AMF, while it had no significant effects on AG with AMF. Moreover, AC significantly reduced the mycorrhizal dependency of the native species (108.06% vs 23.62%) but did not affect the invasive species. The AMF increased the variety of organic compounds in the aqueous extracts of the rhizosphere soil of invasive species, regardless of the competition. Overall, allelopathy significantly increased the mycorrhizal dependency of the native species, while it promoted the competitive ability of the invader regardless of AMF inoculation. Conversely, AMF reduced the facilitation of allelopathy in the AG of the invasive species. These results suggest that AMF play a critical role in improving the resistance of the native species to the invader by mediating allelopathy.

Organic matter in aqueous soil extracts: Prediction of compositional attributes from bulk soil mid-IR spectra using partial least square regressions

Water-extractable organic matter (WEOM) is labile and a key component of soil organic matter. Thus, the prediction of soil WEOM concentration and composition-related characteristics is of great interest. The main objective of this study was to model and predict dissolved organic C (DOC) concentration and WEOM composition-related attributes of aqueous soil extracts using mid-infrared (IR) spectra of bulk soils coupled with partial least square (PLS) regression. Absorbance of UV light at 254 nm (Abs254), considered proportional to the concentration of aromatic substances in soil extracts, and light emission intensities proportional to concentrations of some components controlling WEOM fluorescence, were used as composition-related attributes of the soil extracts. The DOC-normalized Abs254 and emission intensities were used as composition-related attributes of WEOM. Application of PLS regressions for predicting spectroscopy-based composition-related attributes of aqueous soil extracts, using bulk soil IR spectra, is novel. Mid-IR spectra were determined for 216 soil samples collected from different (i) Israeli climate regions (Mediterranean and Semi-arid), (ii) types of land use (field crops, orchard and non-cultivated land), (iii) two depths (0–10 and 30–60 cm), (iv) sampling seasons (Fall and Spring). Prediction of DOC concentrations in the soil extracts was of limited and variable success evaluated by the coefficient of determination and slope of the linear regression of predicted vs measured values, with some soil subsets yielding no satisfactory predictions. However, Abs254 and emission intensities of fluorescent humic-like components were predicted more successfully than DOC concentrations, suggesting that WEOM aromatic and fluorescent components are better presented in soil IR spectra compared to WEOM aliphatic substances. Yet, prediction of the specific UV absorbance (SUVA), using bulk soil IR spectra, was less successful than prediction of Abs254. Prediction of DOC-normalized emission intensities of fluorescent components (analogous to SUVA in fluorescence spectroscopy) was not successful. The differences between the success of predicting extract properties, i.e., Abs254 and fluorescence emission intensities, and the prediction of DOC-normalized derivatives, suggest that concentrations of aromatic (fluorescent) components in soil extracts are better predicted using PLS regression analysis of bulk soil mid-IR spectra than the WEOM composition.

Parallel artificial liquid membrane extraction of organophosphorus nerve agent degradation products from environmental samples

An emerging miniaturized high-throughput microextraction technique named Parallel artificial liquid membrane extraction (PALME) was, for the first time, investigated for the extraction of polar alkyl methylphosphonic acids (AMPAs) that are the degradation products of organophosphorus nerve agents. The effect of the key-parameters of the extraction method (nature of the membrane, of the extraction solvent, of the pH values of both donor and acceptor phases, agitation speed, extraction time, temperature and ionic strength) on the extraction recoveries was studied in spiked pure water samples. This led to extraction recoveries in the range of 25–102% for the 5 targeted analytes from water with enrichment factors in the range of 4.50–42.75.The developed PALME-LC-MS/MS method was first evaluated with spiked pure water. LOQs (S/N ≥ 10) were in the range of 0.009–1.141 ng mL−1, linearity above 0.9973 for all the AMPAs and with RSD values below 11%. This method was then applied on simulated waste water, river water and aqueous soil extracts. The achieved LOQs were in the range of 0.011–1.210, 0.013–1.196 and 0.016–6.810 ng mL−1, respectively. A detailed comparison of the performances of this PALME method with those of a previously developed hollow fiber liquid-phase microextraction methods already applied to AMPAs was done thus allowing to demonstrate the easy transfer of methods from HF-LPME to PALME. Moreover, the high-throughput potential of PALME was revealed since 192 samples were processed in parallel during 120 min (37.5 s/sample).

Impact of Oxyfluorfen 23.5% EC on Soil Microorganisms Carbon and Nitrogen Transformations

Oxyfluorfen widely using in paddy field and unknowingly polluting the soil. The present study soil microorganism’s carbon and nitrogen transformation test was conducted in loamy sand soil, the experiment conducted as per Organization for Economic Co-operation and Development (OECD) Guideline 216 and 217. The application of oxyfluorfen 23.5% EC applied dose rates T0-Control, T1-100 g a.i/ha (active ingredient/hectare) and T2-1000g a.i/ha soil dry weight. The test concentrations were one and ten times the recommended field application rate. After application of the soil boxes were incubated at 20°C in dark conditions. The soil samples were collected at 0 (within the 6 hours), 7, 14, and 28 days after imposing the treatment. Carbon transformation (short-term respiration) was determined by amended the glucose to soil samples. Short-term respiration was calculated based on oxygen consumption (BOD) during the experiment. Soil nitrification was determined by measuring the NO3- contents of aqueous soil extracts using calibrated ion-sensitive electrodes and the Orion expandable ion analyzer. The deviation in respiration rates and nitrification compared to controls after applying the test item after 28 days 2.8 % and 7.0 % for the; -3.12% and -7.18% for the respiration rates and nitrification respectively T1 and T2 test concentrations. There was no significant variation between the treatment and control samples.

Liquid Chromatographic Determination of Trace Bioavailable Neonicotinoids in Soil with Dispersive Liquid-Liquid Microextraction and Its Application for Experimental Monitoring.

Dispersive liquid-liquid microextraction (DLLME) was applied to extract bioavailable neonicotinoids involved in the uptake from soil through roots to plants. To quantitatively extract bioavailable neonicotinoids with the proposed DLLME, 3.5 mL of dichloromethane (extractant)/acetonitrile (dispersive solvent) (6:1, v/v) was injected into 5 mL of aqueous soil extracts in which 1 g of sodium chloride was previously dissolved. The separated dichloromethane phase after sonication and centrifugation was evaporated, reconstituted with a mobile phase, and determined with high-performance liquid chromatography. The established method showed sufficient analytical performance to quantify the amount remaining in soil in trace amounts. In a pilot trial conducted in the field, the changes in the concentrations of bioavailable neonicotinoids were confirmed using the method. After showing rapid degradation in soil, degradation of clothianidin and imidacloprid slowed after about 100 days of treatment, but it continued to be detected at around 0.02-0.05 μg/g-dried weight until 1097 days. This result suggests that once these neonicotinoids are treated in soil, they might remain for long periods, which supports the possibilities of crop contamination and exposure to pollinators.

Effect of Chlorides from Chemical De-Icing Agents on Soil Contamination Depending on the Distance from Road and its Effects on Living Organisms

Abstract The article deals with the contamination of soil in the vicinity of the D1 motorway caused by the application of chemical de-icing agents in winter. In the selected area, during a period of one year (from October 2017 to October 2018), soil samples were regularly collected once a month at five different distances from the road. Chloride concentrations in aqueous extracts of the soil were monitored and the degree of toxicity was established for the selected living organisms. The resulting chloride load was evaluated with respect to the precipitation activity and the amount of de-icing salt applied in the area. The highest concentrations of chlorides were found at a distance of 2 m from the road. At the distance of 20 m from the road, the concentration of chlorides in the soil was approaching the chloride concentration found in the referential background set for the selected locality. The concentrations of chlorides at the first three measured distances from the road corresponded to the quantity of de-icing salt applied and the precipitation activity recorded during the relevant months. The maximum concentrations were reached in April 2018. Ecotoxicological testing of aqueous extracts of soil did not confirm any significant toxicity to the selected living organisms. From the tested organisms, the white mustard was identified to be the most sensitive to this type of toxicity; the increased toxicity was observed only for aqueous extracts of soil samples collected at distances dI (0 m) and dII (1 m), thus, it could have been related to the increased concentration of chlorides during the relevant period.

Garlic Allelochemical Diallyl Disulfide Alleviates Autotoxicity in the Root Exudates Caused by Long-Term Continuous Cropping of Tomato.

Continuous cropping obstacles seriously affect the sustainable production of tomatoes (Solanum lycopersicum L.). Researchers have found that intercropping with garlic (Allium sativum L.) could alleviate tomato continuous cropping obstacles. Diallyl disulfide (DADS) is the main allelochemical in garlic. However, the mechanism of DADS in alleviating tomato continuous cropping obstacles is still unknown. In this research, aqueous extracts of tomato continuous cropping soil were used to simulate the continuous cropping condition of tomato. Our results showed that DADS increased root activity and chlorophyll content and improved the activity of antioxidant enzymes (superoxide dismutase (SOD), peroxidase (POD), and phenylalanine ammonia-lyase (PAL)) and the metabolism of nonenzymatic antioxidants (glutathione (GSH) and oxidized glutathione (GSSG)) in tomato plants. DADS treatment reduced the content of fatty acid esters in tomato root exudates (e.g., palmitate methyl ester, palmitoleic acid methyl ester, oleic acid methyl ester) and increased the level of substances such as dibutyl phthalate and 2,2'-methylenebis(6-tert-butyl-4-methylphenol). The higher concentrations of palmitate methyl ester inhibited tomato hypocotyl growth, while oleic acid methyl ester inhibited tomato root growth. Moreover, the application of DADS significantly inhibited the secretion of these esters in the root exudates. Therefore, it suggests that DADS may increase tomato resistance and promote tomato plant growth by increasing root activity and photosynthetic capacity and development to reduce autotoxicity of tomato.

Dynamic analysis on weeds inhibition and phenolic acids of allelopathic rice in field test

ABSTRACT Weed suppression of allelopathic rice PI312777 (PI) and non-allelopathic rice Lemont (LE) at 3-, 5-, and 7-leaf stages were studied in field test. The results showed that inhibitory effect of rice rhizosphere soil (IR1), the soil aqueous extracts (IR2), and the mixture of phenolic acids of the soil extracts (IR3) were IR1 > IR2 > IR3. The same trend was observed in the content of total phenols (Ctp) and the phenolic acids (Cpa) in the soil aqueous extract. The qRT-PCR results showed that six genes related to biosynthesis of phenolic acids in rice leaves and roots of PI were up-regulated and the up-regulated multiplies were increased as leaf stage increased. However, four genes were up-regulated and two genes were down-regulated in rice leaves and roots of LE. The regulated multiplies were smaller in LE than that in PI. The correlation analysis showed that IR1, IR2, IR3, Ctp, and Cpa were positively correlated. There results indicated that rice allelopathic potential was enhanced in response of paddy weeds, which accompanied by up-regulation of genes in rice leaves and roots related to metabolism pathway of phenolic compounds and increase of phenolic allelochemicals in rice rhizosphere soil.

Soil water solutes reduce the critical micelle concentration of quaternary ammonium compounds

Quaternary alkyl ammonium compounds (QAACs) are produced in large quantities for use as surfactants and disinfectants and also found in soils, sediments, and surface waters, where they are potentially involved in the selection of antibiotic resistance genes. Micelle formation influences fate and effects of QAACs. The critical micelle concentration (CMC) of six homologs of benzylalkylammonium chlorides (BAC) was determined in deionized water, 0.01 M CaCl2 solution, and aqueous soil extracts, using both spectrofluorometric and tensiometric methods. Additionally, eight organic model compounds were employed at concentrations of 15 mg C L−1 as background solutes in order to test the effect of dissolved organic carbon (DOC) on CMCs. Results found CMCs decreased with an increasing length of the alkyl chain from 188 mM for BAC-C8 to 0.1 mM for BAC-C18. Both methods yielded similar results for measurements in water and CaCl2 solution; however, the spectrofluorescence method did not work for soil extracts due to fluorescence quenching phenomena. In soil extracts, CMCs of BAC-C12 were reduced below 3.7 mM, while the CMC reduction in soil extracts was less pronounced for BAC-C16. Besides ionic strength, molecular structures of BACs and dissolved organic compounds also affected the CMC. The number of carboxyl groups and small molecular weights of the DOC model compounds reduced the CMCs of BAC-C12 and BAC-C16 at pH 6. This study highlights that CMCs can be surpassed in soil solution, pore waters of sediments, or other natural waters even at (small) concentrations of QAACs typically found in the environment.

Trace level detection and identification of tabun in aqueous media by derivatization and liquid chromatography tandem mass spectrometry analysis

A highly sensitive method for the detection and identification of the G-nerve agent tabun (GA) was developed. 2-[(Dimethylamino)methyl]phenol (2-DMAMP), which was recently developed for the derivatization of GB, GD and GF, was also found to be efficient for the derivatization of GA. The optimized derivatization procedure in an aqueous medium was the addition of 2-DMAMP followed by 5 min of stirring at ambient temperature and subsequent LC-ESI(+)-MS/MS analysis. Derivatized GA was more stable than intact GA, and with detection nearly two orders of magnitude more sensitive. Its ESI-MS/MS spectrum shows two major product ions at m/z 242 and m/z 214. The developed method is more sensitive than any other LC-MS or GC-MS-based method and clearly demonstrates the new concept of “freezing the clock” for determining reactive GA in an aqueous medium, with a limit of detection (LOD) of 10 pg/mL in drinking water. The derivatization reaction efficiencies were evaluated with aqueous extracts of soil, asphalt, cloth, formica and linoleum spiked with GA and found to be similar to that with drinking water. The method was also found to be useful for enhancing the sensitivity of the detection method for other members of the GA family, namely, the GA hydrolysis product (O-ethyl phosphorylcyanidate) obtained under acidic conditions and the diethylamino analog of GA, which both possess a good leaving group (e.g., CN−). The method is appropriate for routine use for verification and evaluation of contamination in cases where trace level detection is required.

PBAT biodegradable mulch films: Study of ecotoxicological impacts using Allium cepa, Lactuca sativa and HepG2/C3A cell culture

Biodegradable mulch films are an alternative to polyethylene films used in agriculture for weed control, improving crop productivity. This change could minimize the residue production and costs related to the final disposal. Nevertheless, the environmental safety of these biodegradable products is scarcely investigated. In this work, samples of poly(butylene adipate-co-terephthalate)-PBAT mulch films, with and without UV stabilizer additives, were prepared. Aqueous extracts of soil samples, where mulch films were disposed, were investigated using bioassays with Lactuca sativa, Allium cepa, and cell culture HepG2/C3A. As PBAT is expected to suffer photodegradation and biodegradation, soil samples mixed with films before and after these processes were evaluated. Soil aqueous extracts promoted root grown (mainly hypocotyl) of L. sativa, probably due to presence of nutrients. So, to evaluate toxicity potential, in this case it was necessary to use aqueous extract prepared with soil instead of ultrapure water as the control. After doing this analysis it was observed that no adverse impacts due to PBAT films occurred. No chromosomal abnormalities were observed in A. cepa bioassay for any of tested samples. The absence of genotoxic potential was confirmed by comet assay and micronucleus test using human hepatocarcinoma cell line HepG2/C3A. These results showed that the soil did not induce damage to the tested organisms, before and after degradation of PBAT films.

Measuring the influence of environmental conditions on dissolved organic matter biodegradability and optical properties: a combined field and laboratory study

Fluorescence spectroscopy is a common tool to assess optical dissolved organic matter (DOM) and a number of characteristics, including DOM biodegradability, have been inferred from these analyses. However, recent findings on soil and DOM dynamics emphasize the importance of ecosystem-scale factors, such as physical separation of substrate from soil microbial communities and soil physiochemical cycles driving DOM stability. We apply this principle to soil derived DOM and hypothesize that optical properties can only supply information on biodegradability when evaluated in the larger ecosystem because substrate composition and the activity/abundance of the microbial community ultimately drive DOM degradation. To evaluate biodegradability in this context, we assessed aqueous soil extracts for water extractable organic carbon (WEOC) content, biodegradability, microbial biomass and DOM characteristics using fluorescence spectroscopy across a range of environmental conditions (covariant with season and land use) in northern Vermont, USA. Our results indicate that changes in environmental conditions affect composition, quantity, and biodegradability of DOM. WEOC concentrations were highest in the fall and lowest in the summer, while no significant differences were found between land covers; however, DOM biodegradability was significantly higher in the agricultural site across seasons. Despite a shift in utilized substrate from less aromatic DOM in summer to more aromatic DOM in winter, biodegradability was similar for all seasons. The only exception was cold temperature incubations where microbial activity was depressed, and processing was slowed. These results provide examples on how fluorescence based metrics can be combined with context relevant environmental parameters to evaluate bioavailability in the context of the larger ecosystem.

Fast Optical Sensing of Metals: A Case Study of Cu2+ Assessment in Soils

In this paper we report an application of a novel porphyrin ligand, Zn(II)TPP-BPI-crown (ZnPC), functionalized with two dibenzo-crown-ether moieties as cation-sensitive ionophore. The test on the optical response of ZnPC ligand inside PVC-based polymeric membranes towards different cations (Na+, K+, Li+, Ca2+, Mg2+, Co2+, Cd2+, Pb2+, Zn2+, Cu2+ and NH4+) were performed. The influence of the lipophilic site functionalization on the ZnPC optode response was investigated. The visibly (naked eye) observed color change of sensing material from green to red demonstrated the suitability of the ZnPC-based optodes to perform fast monitoring of Cu(II) ions in the concentration range between 6.6 × 10−7 and 2.4 × 10−2 mol l−1, with a low detection limit (estimated by s/n = 3 method) of 0.03 mg l−1, which is lower than WHO guideline value of 2 mg l−1 for natural waters. The membranes with the best composition were deposited onto paper support and employed for the express analysis of copper(II) ion in aqueous soil extracts. The results obtained were in a good agreement with a standard ASS method, thus suggesting the utility of developed sensors for aims of express environmental monitoring.