Garden Compost Research Articles

The Influence of a Practical Remediation Medium on the Relationship of Exchange Reaction in Soil to Hazardous Lead and Inorganic Forms of Nitrogen

Abstract The objective of this research was to analyse soil and garden compost as a remediation medium at the foothill´s locality of the Tribeč Mountains, Southwestern Slovakia, to determine the pH/KCl, Pb, NO3 −-N, NH4 +-N contents in soil and soil affected by compost (the ratio 1 : 1), to evaluate the statistical significance of pH/KCl in relation to Pb and inorganic forms of nitrogen, and to find whether garden compost affects the monitored parameters. The analyses were carried out using Atomic Absorption Spectrometry, and Colorimetric and Potentiometric methods. Ascertained values of exchange reactions in soil ranged from 5.74 to 6.83 and exchange reactions in soil affected by garden compost ranged from 6.78 to 7.98. According to the calculated indices of dependencies, the development of pH/KCl values can be evaluated as moderately dynamic. The obtained results were evaluated statistically using the SAS 9.4 software method by the Spearman‘s correlation coefficient. The results in the observed three-year period showed that NO3 −-N contents in soil had reached 14.73 mg.kg−1, NH4 +-N 9.50 mg.kg−1, Nin 23.05 mg.kg−1, Pb 67.38 mg.kg−1, soil affecting by remediation medium – garden compost (the ratio 1 : 1) showed that NO3 −-N contents had reached 23.93 mg.kg−1, NH4 +-N 26.42 mg.kg−1, Nin 42.63 mg.kg−1, Pb 64.71 mg.kg−1 dry matter. Statistical dependence was high (P <0.01), which was demonstrated for soil pH : soil + compost Pb, soil + compost pH : soil + compost Pb. The garden compost influenced pH/KCl, reduced Pb levels, and increased the proportion of inorganic forms of nitrogen in soil.

Optimizing greywater treatment in green walls: A comparative analysis of recycled substrate materials

The utilization of green walls for on-site greywater treatment in urban buildings has garnered significant attention in recent research, with substrates playing a vital role in treatment performance. The incorporation of recycled materials as substrates not only offers a cost-effective solution for greywater treatment, but also enhances sustainability by repurposing wastes. This study investigates the efficacy of three recycled substrates: alum sludge, garden compost, and a mixture of perlite-coconut fiber in three green wall systems for greywater treatment. Each substrate was allocated to a three-pot column. Comparative analysis revealed alum sludge (C3) and the coconut fiber-perlite mix (C1) achieving the highest chemical oxygen demand (COD) removal at 89.45 ± 2.92 % and 89.34 ± 2.47 %, respectively, with garden compost (C2) recording 67.98 ± 7.45 %. For total nitrogen (TN) removal, C2 achieved the lowest efficiency (49.27 ± 9.39 %), while C1 demonstrated 83.79 ± 10.45 %. Notably, C3 exhibited superior total phosphorus (TP) removal at 94.86 ± 1.87 %, compared to 52.07 ± 17.88 % for C1 and 24.90 ± 30.95 % for C2. Our findings demonstrate that substrate selection is crucial for optimizing both pollutant removal and plant health in green walls. The coconut fiber mix emerged as the most effective substrate, supporting robust plant growth and superior pollutant removal, particularly for nitrogen removal. In contrast, garden compost proved unsuitable, with minimal plant survival post-greywater introduction. Alum sludge showed significant promise, particularly for TP removal, reinforcing its effectiveness in green walls. These insights underscore the importance of substrate optimization in greywater treatment systems in urban environments.

Enhancing Azo Dye Mineralization and Bioelectricity Generation through Biocathode-Microbial Fuel Cell Integration with Aerobic Bioreactor

This study explores the efficient decolorization and complete mineralization of the diazo dye Evans blue, using an integrated aerobic bioreactor system coupled with a double-chamber microbial fuel cell (DCMFC) including a bio-cathode and acetate as a cosubstrate. The research addresses the environmental challenges posed by dye-laden industrial effluents, focusing on achieving high decolorization efficiency and understanding the microbial communities involved. The study utilized mixed strains of actinomycetes, isolated from garden compost, to treat initial dye concentrations of 100 mg/L and 200 mg/L. Decolorization efficiency and microbial community composition were evaluated using 16S rRNA sequencing, and electrochemical impedance spectroscopy (EIS) was used to assess anode and DCMFC resistance. The results demonstrated decolorization efficiencies ranging from 90 ± 2% to 98 ± 1.9% for 100 mg/L and from 79 ± 2% to 87% ± 1% for 200 mg/L. An anode resistance of 12.48 Ω indicated a well-developed biofilm and enhanced electron transfer. The microbial community analysis revealed a significant presence of Pseudomonadota (45.5% in dye-acclimated cultures and 32% in inoculum cultures), with key genera including Actinomarinicola (13.75%), Thermochromatium (4.82%), and Geobacter (4.52%). This study highlights the potential of the integrated DCMFC–aerobic system, utilizing mixed actinomycetes strains, for the effective treatment of industrial dye effluents, offering both environmental and bioenergy benefits.

Formulation and efficacy testing of vermi-tea based liquid organic fertilizers on green-amaranth (<em>Amaranthus viridis</em> L.) for home gardens

Sudden food shortage due to strict green agriculture policy, economic crisis, COVID pandemic situation instruct the importance of home level organic production of good quality fruits and vegetables. Therefore, an experiment was conducted to test the efficacy of organic liquid fertilizers formulated from fish, livestock’s and plant wastes on leafy vegetable green Amaranth to promote home gardening. The liquid fertilizer was tested on Amaranth grown separately in vemicompost and garden compost. The 7 kg capacity pots were filled with two media (medium 1: vemicompost; medium 2: garden compost) and arranged in CRD with four replicates with each medium. Five plants of green-amaranth per pot were planted and treated with fish emulsion + vermi-tea (1:4=T1), cow urine + vermi-tea (1:4=T2), three leaves [Neem+ Giliricidia+ Candle bush] solution + vermi tea (3:1=T3), vermi tea (T4) and control (T5) at the rate of 50 mL/pot on 2nd, 4th and 6th week after planting. Agronomic and yield data were collected and subjected to ANOVA using SAS. Tukey's HSD multiple comparison test and PROC CORR was used to determine the best treatment combination at P <0.05. The results revealed that there was significant difference in N, P and K content of the treatments tested. The plant height, leaf area, number of leaves, root shoot ratio was significantly higher in fish emulsion + vermi-tea (1:4) [T1] and cow urine + vermi-tea [T2] at 8th weeks after planting in vermi-compost medium. There was strong and positive correlation (R2 > 0.8) among yield parameters, and root: shoot ratio with N, P K content of the liquid fertilizers tested in vermi-compost medium. Therefore, this investigation concludes that the fish emulsion + vermi-tea (1:4) and cow urine + vermi-tea (1:4) are good combination to use as liquid fertilizer at the rate of 50mL/Pot to get best yield in vermi-compost medium.

Set up of a Microbial Fuel Cell for the Treatment of a Garden Compost Leachate: Impact of the External Polarizing Electric Resistance Upon the Chemical Oxygen Demand Removal

Microbial fuel cells (MFCs) are new and growing renewable energy devices. They transform chemical products into electricity with the help of microorganisms (enzymes, bacteria, microbes, etc.) acting as biocatalysts. They are nowadays displaying technological development since they concomitant simultaneously the wastewater treatment and the electric power generation. These two novelties incite researchers in the field, the utilization of this promising technology. As a matter of fact, a bioelectrochemical fuel cell has been elaborated and set up for garden compost leachate treatment. Following a previous study on the microbial anode formed from wastewater under the application of an electric potential either positive or negative by using chronoamperometry. In this work, we propose the simple method of connecting the two electrodes (anode and cathode) by electrical resistance, to flow a current. The impact of the polarizing electric load on the achievement of the MFC has therefore been studied. Moreover, the chemical oxygen demand (COD) removal for the MFC running for 7 days has been also investigated. It decreased and showed simultaneously an increase in the cell voltage. Thus, the effects of the external load on the current and power generation, as well as on pollutant removal, have been studied by modifying each time the external load. The external polarizing resistance (EPR) was increased from 1 to 10 kΩ, to assess the pollutant decay of the organic matter contained in the wastes. As a result of this, the voltage was increased, whilst the current was decreased, with increasing values of the EPR. The results have been discussed with respect to the type and the predominant microorganisms (electrogenic/fermentative) being involved during the generation of the electric current. This new technology is very promising for converting waste into electricity by offering a way to clean up the polluted environment.

Organic amendments from recycled waste promote short-term carbon sequestration of restored soils in drylands

Soils are considered as a major reservoir for terrestrial carbon and it can act as a source or sink depending upon the land management activities. In semi-arid areas, the natural recovery of soils degraded by mining activities is complicated. A possible solution to recover soil quality and functionality, plant cover and carbon sequestration capacity could be the application of organic amendments. This work focuses on a restoration carried out in 2018 by applying with different composted organic amendments (stabilized sludge, gardening and greenhouse waste) in a limestone quarry under semi-arid climate (SE Spain). The objective was to evaluate the effects of different organic amendments on net CO2 exchange in two microcosms: soil-Stipa tenacissima and soil-spontaneous vegetation. Soil physical and chemical properties, environmental and ecological variables and their interrelationship were studied in amended and unamended soils. The results obtained under soil-forming factors in the study area showed an increase in soil organic carbon and nitrogen content, improved moisture and plant growth, and plant canopy development in amended soils. Soil moisture, soil temperature and plant cover significantly influenced net CO2 exchange. In general, microcosms with S. tenacissima showed higher carbon sequestration rates than soils with only spontaneous plant cover. Soils treated with a vegetable-only amendments showed higher plant cover and CO2 fixation rates after significant rainfall. On the other hand, the plots treated with sludge compost presented more soil respiration than photosynthesis, especially in the wet seasons. Soils with sludge and greenhouse compost mixed had higher CO2 fixation rates than soils restored with a mixture of sludge and garden compost. Soils with greenhouse waste compost showed CO2 fixation in the microcosm with plants in all campaigns, being the best treatment to promote atmospheric CO2 sequestration in soil restoration.

Effects of Repeated Application of Organic Soil Amendments on Horticultural Soil Physicochemical Properties, Nitrogen Budget and Yield

Application of organic amendments to soil is commonplace in domestic gardening. However, a vast array of materials could be labelled as ‘compost’ by retailers and suppliers. We investigated six different amendments currently used, or available for use, in horticulture: composted bark, composted bracken, spent mushroom compost, composted horse manure, garden waste compost (at two different application rates), and peat. Using a controlled field experiment, we examined the physicochemical differences between the amendments, the subsequent effects on soil characteristics, and resultant yield and biometrics of Lavatera trimiestris. Amended soils resulted in a significantly different multivariate soil environment and N budget when compared to the unamended control. However, the effect on yield and plant biometrics (number of flowers, plant height, etc.) depended on the amendment used. Application of garden compost resulted in up to a five-fold increase in yield. However, there was no significant difference in yields in soils amended with composted bark or peat, when compared to the unamended control. This has implications, as there is increasing pressure to remove peat from products available to domestic gardeners. The variability in the different amendments investigated in our research, in addition to the variable effects on plant growth parameters, suggests that repeated use of a single amendment may not be best practise for gardeners.

Plant parasitic nematodes, substrates or grass species as reasons for poor reestablishment of a sand‐based putting green after winter kill

AbstractIn 2018–2019, establishment problems were encountered, after reseeding creeping bentgrass (Agrostis stolonifera) on a sand‐based putting green after ice encasement at the NIBIO Turfgrass Research Center, Norway. Seeds germinated, but the seedlings attained a purple color and died in large patches. Replacement of the top 3 cm layer with new sand amended with Sphagnum peat or garden compost did not solve the problem. To explain this phenomenon, we (1) analyzed the original substrate for nematodes in patches with and without reestablishment failure; and (2) conducted a factorial pot trial with creeping bentgrass and Chewings fescue (Festuca rubra ssp. commutata) seeded on different substrates, some of them in layers, and with and without phosphorus (P) fertilization. The nematode counts showed six times more stubby‐root nematodes and two times more spiral nematodes and needle nematodes in the patches with dead seedlings than in the patches with healthy seedings. In the pot trial, the fastest and slowest reestablishment was observed with new sand amended with garden compost and in the two treatments that included the original substrate, respectively. Replacement of the top 3 cm of the old substrate with new garden compost resulted in stagnation of bentgrass seedlings from four weeks after seeding, while fescue seedlings were unaffected. We conclude that the failure to reestablish creeping bentgrass was primarily due to nematodes, which are likely to be more critical for seedlings than for established turf. The green was later reestablished successfully with a 100 % red fescue seed blend.

Soil amendments from recycled waste differently affect CO₂ soil emissions in restored mining soils under semiarid conditions

Drylands affected by serious disturbances such as mining activities lose their vegetation cover and organic soil horizons, becoming CO2 emissions sources. Applications of organic amendments could be a good restoration solution that favours vegetation establishment and soil carbon sequestration; however, they are also associated with CO₂ emissions. Experimental plots with different organic amendments (sewage sludge, garden and greenhouse vegetable composts, and mixtures of both) and unamended soils were installed in a quarry in southeast Spain. The aim of this study was: i) to evaluate the magnitude and changes of in situ CO₂ emission from each experimental plot during a year and a half, and ii) to assess the effects of several physical–chemical (total organic carbon, total nitrogen, water retention, pH and electrical conductivity) and environmental parameters (moisture and temperature) in CO2 emissions. The results showed an initial CO2 emission (priming effect), produced from all restored plots just after the application of the organic amendment, which was significantly higher (P < 0.05) in soils with sewage sludge and their mixtures in comparison to vegetable compost. Garden compost had low emission rates, similar to soils without amendment and showed lower CO2 emission rates than the rest of the restoration treatments. Nevertheless, CO2 emissions decreased in each field campaign over time, showing that all restored soils had lower emissions than natural soils at the end of the sampled period. The different composition of organic amendments had a different effect on soil CO2 emissions. DistLM analysis showed that soil properties such as total organic carbon, total nitrogen, pH and soil moisture, associated with rainfall periods, strongly influenced CO₂ emissions, whereas temperature did not affect the CO2 flow. In conclusion, the compost from plant remains could serve better as treatment to restore degraded soils in drylands than sewage sludge because of its lower CO2 emissions and concomitant effect on climate warming and carbon balance.

Leaching and surface runoff after fall application of fungicides on putting greens

AbstractMany greenkeepers and authorities are concerned about the environmental risks resulting from pesticide use on golf courses. We studied leaching and surface runoff of fungicides and metabolites for two winter seasons after fall application of boscalid, pyraclostrobin, prothioconazole, trifloxystrobin, and fludioxonil in field lysimeters at NIBIO Landvik, Norway. The applications were made on creeping bentgrass greens (5% slope) that had been established from seed or sod (26‐mm mat) on USGA‐specification. root zones amended with Sphagnum peat or garden compost, both with 0.3–0.4% organic carbon in the root zone. The proportions of the winter precipitation recovered as surface and drainage water varied from 3 and 91% in 2016–2017 to 33 and 55% in 2017–2018 due to differences in soil freezing, rainfall intensity, and snow and ice cover. Detections of fungicides and their metabolites in drainage water were mostly within the environmental risk limits (ERLs) for aquatic organisms. In contrast, concentrations in surface runoff exceeded ERLs by up to 1,000 times. Greens established from sod usually had higher fungicide losses in surface runoff but lower losses in drainage water than greens established from seed. Presumably because of higher microbial activity and a higher pH that made prothioconazole‐desthio more polar, fungicide and metabolite losses in drainage water were usually higher from greens containing compost that from greens containing peat. Leaching of fungicides and metabolites occurred even from frozen greens. The results are discussed in a practical context aiming for reduced environmental risks from spraying fungicides against turfgrass winter diseases.

Platinum Nanoarrays Directly Grown onto a 3D-Carbon Felt Electrode as a Bifunctional Material for Garden Compost Microbial Fuel Cell

The practical implementation of air-breathing microbial fuel cell (MFC) is critically linked to the development of efficient materials as cathode and electrochemically active biofilm-based anode. In this contribution, we demonstrate the feasibility by decorating a 3D carbon felt electrode with Pt nanoarrays (CF@Pt) as a bifunctional electrode material as efficient garden compost bioanode and air-breathing cathode. Half-cell electrochemical characterizations reveal that the onset potential of the anode reaction negatively shifts of about 800 mV to reach −0.4 V vs Ag/AgCl after the growth of the biofilm onto CF@Pt. The investigation before and after the biofilm formation shows that Pt nanoarrays act as excellent electron relays, reducing significantly the charge transfer resistance. For MFC application (with a proton exchange membrane), the use of CF@Pt as bioanode’ scaffold and CF@Pt air-cathode enables a drastically enhanced power density of Pmax = 292.3 mW m−2, and a high short-circuit current density jsc = 1.9 A m−2.

Fabrication and Performance of a Microbial Fuel Cell: Utilization of Modified Nafion Membrane with Carbon Powder as Separator and Bio-Anode

A Microbial Fuel Cell (MFC) was conceived by using garden soil as a source to culture. It was then utilized as a bio-catalyst to decompose waste organic matter, reduce pollution from the soil, and produce energies. The MFC was composed of a bio-anode inoculated with a mixture of garden compost leachate and an abiotic stainless steel cathode. Besides, the bio-anode consisted of a Nafion membrane modified with carbon. The microorganisms agglomerated under polarization and formed electroactive bio-film onto bio-anode. In the preliminary test of MFC, potassium hexacyanoferrate has been utilized as catholyte, to enhance the reduction of proton and electrons resulting in a higher voltage. However, this electrolyte is toxic and oxidized rapidly, thus substituted by the hydrochloric acid. The results showed that the MFC with modified Nafion, gave relatively high current-density 379 mA/m2 in two days, whereas the conventional biofuel cell without modification attained the current-density 292 mA/m2 in four days. Nevertheless, both cells yielded almost the same current density of 20 mA/m2 during 60 days. Although it has been used for a long time, the modified Nafion has not been corroded and preserved its physicochemical properties.

Ethanol toxicity in a dog due to gin‐soaked sloe berry (Prunus spinosa) ingestion

AbstractA 10‐month‐old male Labrador retriever was presented for acute onset altered mentation and inability to walk. The dog was presented with a modified glasgow coma scale (MGCS) of 12 with tachycardia (148 bpm) and hypothermia (37°C). The dog had been normal the previous night then found semi‐comatose at the following morning. Investigations included haematology, biochemistry, C‐reactive protein, magnetic resonance imaging, urine toxicology and cerebrospinal fluid analysis. Ten hours after being found the dog passed faeces containing a significant volume of berries. The owner later determined that 750 g of sloe berries soaked in gin were missing from the garden compost heap. Serum ethanol concentrations measured approximately 20 hours after the suspected consumption were 310 mgD/L. The dog was treated with intralipid, intravenous fluid therapy and paracetamol. He was neurologically normal (MGCS = 0) 24 hours later, following diagnosis and treatment. Differential diagnosis and management of the comatose dog and management of ethanol toxicity are discussed.

Treatment of fruit waste leachate using microbial fuel cell: Preservation of agricultural environment

A microbial fuel cell (MFC) was conceived to low electric power production in parallel to valorization of industrial wastes and environment preservation. It consisted of two compartments separated by polymer Nafion membrane, platinum grid as cathode catalyst and graphite rod inoculated with fruit leachate as bio-anode. Owing to its bio-compatibity with bacterial inoculum and chemical stability, Graphite Carbon (GC) was tested as carrier of biofilm using fruit waste inoculum. The maximum power density harvested with this electrode was about 20 mW.m−2 much greater than that obtained previously with a garden compost inoculum (i.e. 7 mW.m−2). The difference between the two values may be attributed to the bacterial nature of inoculum utilized. Impressively, upon the addition of 6 mL of fuel (sucrose), the soft porous graphite felt GF yielded voltage (260 mV) which was significantly higher than that of the hard smooth solid GC (i.e. 140 mV). This result makes in evidence the effect of adsorption of the electro-active biofilm onto the surface of the electrode. We ascribe therefore the enhanced power density to a more uniform spread out of the electro-active biofilm within the GF matrix, as verified by higher conductivity obtained with four probe method. The results reported herein highlight the importance of assessing the bio-catalytic activity towards the oxidation of the organic substrate to yield renewable low energy. The experimental data and the differences between the bio-anodes GC and GF were discussed in term of electrochemical techniques such as cyclic voltammetry, impedance spectroscopy and four-probe conductivity. Whatever the nature of the bio-anodes, the overall bacterial colonization still yields low values of clean electric energy compared to highly polluted energy obtained with an alkaline fuel cell.

Impact of novel materials on alkalinity movement down acid soil profiles when combined with lime

Subsurface soil acidity in conjunction with aluminium (Al3+) toxicity is a major limitation to agricultural production globally. The conventional use of surface-applied lime is often insufficient at correcting subsurface acidity; therefore, new practices and ameliorants are required. This 3-month leaching experiment investigated whether animal wastes and other novel ameliorants in combination with lime could improve alkalinity movement, leading to greater amelioration of acid subsurface soil layers compared with lime alone. Five ameliorants (mature dairy compost, vegetable garden compost, poultry litter, potassium humate and gypsum) were added at a rate of 18 mg dry matter g−1 to the topsoil layer either without or with lime (target pH 5.5). All ameliorants with lime improved alkalinity movement below the amended layer (0–10 cm), with pH increases of 0.03–0.10 units at 1 month and 0.02–0.20 units at 3 months. In comparison, the Al3+ concentrations in 10–12-cm and 12–15-cm layers were significantly decreased by 2–5.5 μg g−1. With lime, the improvements in alkalinity movement with ameliorants were in the order of gypsum > vegetable garden compost > potassium humate > poultry litter > mature dairy compost. Without lime, each amendment increased soil pH in the subsoil, with their effectiveness decreasing in the order of poultry litter > vegetable garden compost > mature dairy compost > gypsum > potassium humate. Some organic amendments are effective in addressing subsoil acidity. When combined with lime, their additive effects are limited.

Monitoring of mechanical performances of flax non-woven biocomposites during a home compost degradation

Non-woven composites reinforced with plant fibers are widely used in the automotive and construction sectors. The vast majority is composed of petroleum-based, non-compostable polyolefins, which are no longer a viable solution in an environmental context where the end-of-life management of industrial products is becoming a major societal issue. Here, fully green composites are produced by reinforcing three bio-based and biodegradable matrices – poly-(hydroxyalkanoate) (PHA), poly-(butylene-succinate) (PBS) and poly-(lactide) (PLA) – with non-woven flax fiber preforms. Notably, their mechanical performance was observed to be at least equivalent to the industry reference – poly-(propylene) (PP) reinforced non-woven flax. These composites were then buried in an instrumented garden compost, and the evolution in microstructure and mechanical properties was studied over a period of six months. Microtomography studies revealed that evolution in composite microstructure principally depended on the polymer matrix: surface degradation was predominant for PBS and PHA biocomposites, whereas rapid fiber-matrix interface degradation in the core was observed for PLA biocomposites. Interestingly, even after six months in the compost, all composites exhibit tensile strengths of at least 50% of their initial value. Moreover, the strength reduction in biodegradable composites was of the same magnitude as the industry reference, flax/PP composite. These results demonstrate the potential of biocomposites in resolving the ‘biodegradation paradox’: flax composites with biopolymers like PLA, PHA and PBS can be designed to have adequate mechanical performance for industrial products, even after ageing in harsh conditions, and yet offer an alternative end-of-life route to the typical incineration (with or without energy recovery).

Experimental manipulation of selfish genetic elements links genes to microbial community function.

Microbial communities underpin the Earth's biological and geochemical processes, but their complexity hampers understanding. Motivated by the challenge of diversity and the need to forge ways of capturing dynamical behaviour connecting genes to function, biologically independent experimental communities comprising hundreds of microbial genera were established from garden compost and propagated on nitrogen-limited minimal medium with cellulose (paper) as sole carbon source. After 1 year of bi-weekly transfer, communities retained hundreds of genera. To connect genes to function, we used a simple experimental manipulation that involved the periodic collection of selfish genetic elements (SGEs) from separate communities, followed by pooling and redistribution across communities. The treatment was predicted to promote amplification and dissemination of SGEs and thus horizontal gene transfer. Confirmation came from comparative metagenomics, which showed the substantive movement of ecologically significant genes whose dynamic across space and time could be followed. Enrichment of genes implicated in nitrogen metabolism, and particularly ammonification, prompted biochemical assays that revealed a measurable impact on community function. Our simple experimental strategy offers a conceptually new approach for unravelling dynamical processes affecting microbial community function.This article is part of the theme issue ‘Conceptual challenges in microbial community ecology’.

A Comparison of Physical Soil Organic Matter Fractionation Methods for Amended Soils

Selecting a suitable physical fractionation method, to investigate soil organic matter dynamics, from the plethora that are available is a difficult task. Using five different physical fractionation methods, on soils either nontreated or with a history of amendment with a range of exogenous organic matter inputs (Irish moss peat; composted horse manure; garden compost) and a resulting range of carbon contents (6.8 to 22.2%), we show that method selection had a significant impact on both the total C recovered and the distribution of the recovered C between unprotected, physically protected, or chemically protected conceptual pools. These between-method differences most likely resulted from the following: (i) variation in the methodological fractions obtained (i.e., distinguishing between aggregate size classes); (ii) their subsequent designation to conceptual pools (e.g., protected versus unprotected); and (iii) the procedures used in sample pretreatment and subsequent aggregate dispersion and fractionation steps. The performance of each method also varied depending on the amendment in question. The findings emphasise the need for an understanding of the nature of the soil samples under investigation, and the stabilisation mechanism of interest, both prior to method selection and when comparing and interpreting findings from literature studies using different fractionation methods.

The effect of the selected remediation medium on the cadmium bioavailability in the selected ecosystem in the Southwestern locality of Slovakia

Abstract Soil is a sensitive ecological factor. Biodegradable materials from the environment can also be used to deal with serious ecological problems. Soil affecting by remediation medium - garden compost - was analysed for toxic cadmium (Cd) in terms of environmental protection. The objective of this research was to analyse soil and compost at foothill locality of the Tribeč Mountains (Southwestern Slovakia) in the years 2015−2017 to determine Cd contents in soil and compost, pH and to assess Cd bioavailability. The analyses were carried out using the Atomic Absorption Spectrometry with seven-step Selective Sequential Extraction methods. The results obtained were evaluated statistically using the SAS 9.4 software method by Spearman’s correlation coefficient. The results showed that Cd contents in soil had reached 2.96 mg kg−1 and soil with compost (the ratio 1:1) 2.71 mg kg−1 dry matter. Cd contents in the soil exceeded maximum allowed limit of 196%. And deceased by 25% after adding compost. The pH in soil with compost varied from 6.78 to 7.98. The pH prevented the mobility of Cd about 8.3% in average. Statistical dependence was high, which was demonstrated for relationship between Cd in soil, pH and compost. Available Cd forms in soil were 53.3% and soil with compost were 45% in average. The garden compost as a remediation medium reduced Cd bioavailability.

Determining the possibility of using selected composts to remove aqueous solutions from zinc ions in concentrations of up to 1000 mg.L-1

The high sorption capacity of compost indicates that it can be a cheap alternative to the currently used sorbents, also in the case of heavy metals. The sorption of zinc from aqueous solutions with the use of the selected compost types not meeting standards was carried out in accordance with the batch method in the constant contact conditions of a liquid (100 mL) and a solid (5,0 g) when the concentrations of Zn2+ were 100, 250, 500, 750 and 1000 mg·L-1. The efficiency of the process decreased with an increasing Zn2+ concentration and was strongly dependent on the quality of the compost and the composition of the initial compost mixture. For the highest concentration of zinc, the best efficiency (nearly 70%) was obtained in case of the commercial compost, while the lowest one (only 25%) in the case of the compost made only from green waste and prepared in a garden compost bin. The experimental results were described using the Freundlich isotherms and the obtained equation parameters show the adsorption process. It was found that compost can serve as an efficient sorbent with regard to zinc ions.