Remediation of soils contaminated by fluoride using a fermentation product of seaweed (Eucheuma cottonii)

This study investigated the efficacy of fermented seaweed (Eucheuma cottonii) on the remediation of fluoride-contaminated soil. The soil was amended with either 1.25, 3.0, or 5.0% (w/w) fermented seaweed (FSW), parallel with the controls (0%). The amendment improved the physicochemical properties of the soil particularly pH regulated from strong alkaline (9.3) to neutral (7.0) which is essential for germination, crop growth, and yield. The amount of water soluble-fluoride (Ws-F) dropped from 81.7 ± 3.1 mg/kg to 42.7 ± 2.4, 33.7 ± 1.2, 19.6 ± 0.9, and 12 ± 1.3 mg/kg following 0, 1.25, 3, and 5% amendment dosage, respectively. Most of the Ws-F was converted into exchangeable fluoride (Ex-F) and to fluoride-bound to iron and manganese (Fe/Mn-F). Furthermore, the amendment also enhanced microbial mass and diversity in the soil. The FSW contains organic acids which participate in ionic bonding with the multivalent cations in the soil. The formed compound participates in ion exchange with clay or with anionic adsorption to positively charged clay sites at the edges. This interaction is further essential for enhancing the fluoride holding capacity of the soil. The use of seaweed reduced the bioavailability of fluoride in the agricultural soils and had positive effects on promoting soil fertility. However, further studies to observe its effects on crop performance is of significance

Long-term manure and cropping systems effect on soil water vapour sorption characteristics is controlled by soil texture

Increasing studies indicate that long-term experiments (LTEs) involving manure application and optimal cropping systems can significantly improve soil physicochemical properties, which may also affect the soil water retention curve (WRC) in the wet region (pF 4.2) as well as the associated soil physicochemical properties. To overcome this knowledge gap, we investigated the effect of long-term manure application (24 to 177 years) and different cropping systems (71 to 82 years) on soil organic carbon (SOC) content, WSIs, hysteresis, and specific surface area (SSA). Soil samples were collected from five long-term manure experiments in Sweden, the United Kingdom, Spain, Germany, and Denmark, and two long-term cropping systems experiments in the United Kingdom. The five manure LTEs comprised three soil textures (silty clay, silt loam, and sandy loam) with one to four crops grown in the fields, including wheat, barley, maize, and grass/clover. The cropping system LTEs comprised silt loam and sandy loam including bare fallow (BF), arable rotation, ley–arable rotation, and permanent grass. Results showed that long-term manure application increased SOC content in each site, but it had little effect on the soil WSIs, hysteresis, and SSA in silty clay soils. The changes of soil WSIs, hysteresis, and SSA in silt loam and sandy loam arising from manure application largely depend on the crops grown in the field. For the long-term cropping systems experiments, permanent grass had the most significant effect in increasing SOC content, soil WSIs in silt loam and sandy loam, and hysteresis and SSA in silt loam compared to other treatments. Compared to BF, arable rotation and ley-arable rotation had no effect on SOC and soil WSIs in silt loam, and on hysteresis and SSA in silt loam and sandy loam. Multiple linear regression models including SOC, clay, and silt contents sufficiently explained the variabilities observed in the soil WSIs, hysteresis, and SSA for both manure and cropping systems LTEs

Prediction of the glyphosate sorption coefficient across two loamy agricultural fields

Sorption is considered one of the most important processes controlling pesticide mobility in agricultural soils. Accurate predictions of sorption coefficients are needed for reliable risk assessments of groundwater contamination from pesticides. In this work, we aim to estimate the glyphosate sorption coefficient, Kd, from easily measurable soil properties in two loamy, agricultural fields in Denmark: Estrup and Silstrup. Forty-five soil samples in Estrup and 65 in Silstrup were collected from the surface in a rectangular grid of 15 × 15-m from each field, and selected soil properties and glyphosate sorption coefficients were determined. Multiple linear regression (MLR) analyses were performed using nine geo-referenced soil properties as variables to identify the parameters related with glyphosate sorption. Scenarios considered in the analyses included: (i) each field separately, (ii) both fields together, and (iii) northern and southern sections of the field in Silstrup. Considering correlations with all possible sets of the same nine geo-referenced properties, a best-four set of parameters was identified for each model scenario. The best-four set for the field in Estrup included clay, oxalate-extractable Fe, Olsen P and pH, while the best-four set for Silstrup included clay, OC, Olsen P and EC. When the field in Silstrup was separated in a northern and southern section, the northern section included EC, and oxalate-extractable Fe, Al and P, whereas the southern part included pH, clay, OC and Olsen P. The best-four set for both fields together included clay, sand, pH and EC. Thus, the most common parameters repeated in the best-four sets included clay and pH as also reported previously in the literature, but in general, the composition of the best-four set differed for each scenario, suggesting that different properties control glyphosate sorption in different locations and at different scales of analysis. Better predictions were obtained for the best-four set for the field in Estrup (R2 = 0.87) and for both fields (R2 = 0.70), while the field in Silstrup showed a lower predictability (R2 = 0.36). Possibly, the low predictability for the field in Silstrup originated from opposing gradients in clay and oxalate-extractable Fe across the field. Also, whereas a lower clay content in Estrup may be the limiting variable for glyphosate sorption, the field in Silstrup has a higher clay content not limiting the sorption, but introducing more variability in Kd due to changes in other soil properties

Hydroxyapatite-activated seaweed biochar for enhanced remediation of fluoride contaminated soil at various pH ranges

This study investigated the defluoridation efficiency of hydroxyapatite-activated seaweed (Eucheuma Cottonii) biochar (HSB) at various soil pH ranges (3â-11) while monitoring the impact of contact time (30Â min - 2.5Â h), adsorbent dosage (0.1â-0.5 g) as well as the initial fluoride concentration and compare its performance to its respective seaweed biochar (SB). Activation of SB with the hydroxyapatite lead to a shift in its point-zero-charge (pHPZC) from 6 to 7.4 broadening its defluoridation pH range from a solitary 5 to amid 3 through 11. The fluoride adsorption mechanism was found to follow both Langmuir (R2Â =Â 0.956) and Freundlich (R2Â =Â 0.942) isotherm models with a maximum defluoridation capacity of 3.03 mg/g equivalent to the defluoridation efficiency of 79. This is accounted to the existence of soil ions, SB active sites, and the attached hydroxyapatite, as fluoride adsorption sites each exhibiting a dissimilar fluoride removal mechanism. Therefore, the HSB could be a promising adsorbent for fluoride removal in the fluoride contaminated agricultural soils of inclusive pH ranges

Transporte de fitosanitarios en formulaciones particuladas y granuladas de uso agrícola : mecanismos de filtración y difusión

El uso abusivo de agroquímicos para el control de enfermedades y plagas conlleva su acumulación en los suelos y el aumento del riesgo de contaminación con el consecuente peligro que supone tanto para la salud como para el medio. Existen numerosas formulaciones comerciales en el mercado con distintas características que ayudan a su aplicación y mejoran su eficiencia. El enfoque clásico utilizado para estudiar la movilidad de los pesticidas en el suelo es la interacción del ingrediente activo puro con el suelo. Sin embargo, el tipo de formulación tiene una importancia crucial en el comportamiento y destino final del ingrediente activo en el medio. Conocer los mecanismos que gobiernan el transporte de estos formulados comerciales en medios porosos es de gran importancia a la hora de evaluar su riesgo ambiental, de poder ser implementados en los modelos existentes que predicen el movimiento de los ingredientes activos de los agroquímicos en el suelo y en las aguas subterráneas. Por todo esto, en esta tesis se estudió el transporte dos tipos de formulaciones ampliamente utilizadas en agricultura. En la primera parte se pretende determinar los mecanismos de transporte de partículas coloidales de fungicidas con base cúprica en lechos porosos atendiendo a las condiciones químicas e hidrodinámicas del medio y a las características de las formulaciones comerciales, en especial al tamaño de partícula. En la segunda parte se evalúan los procesos de liberación y difusión de los ingredientes activos de formulaciones granuladas de liberación controlada. Se estudió el efecto que tiene la velocidad de infiltración de agua en un medio poroso en la tasa de liberación del ingrediente activo y los procesos implicados; así como el transporte difusivo del ingrediente activo desde los gránulos al medio cuando no existe movimiento de agua

Feeding Mars: a pilot study growing vegetables using aquaponic effluent fertiliser in simulant and analogue Martian regoliths

The Feeding Mars study was devised as a small, pilot proof of concept study to research the potential for using aquaponic effluents as an additive to regoliths which on Mars and the Moon are devoid of organic material and thus lacking microbes which assist in the delivery of water and nutrients to the plants via their roots. This research investigates aquaponics as a way to potentially produce fish and vegetal products in regoliths on Mars and the Moon as well as in extreme environments on Earth. In order to settle on Mars, settlers will have to grow their own food in systems that are self-perpetuating, with little or no inputs being brought from Earth once these systems have been established. This means that nutrients from the fish water can be used to grow plants in the hydroponic parts of the aquaponic system but also potentially in the Martian regoliths which are treated with effluents taken from aquaponic systems. Once production is established additional nutrients can be sourced from the arisings and waste, both from the fish (that are processed and eaten) and the plants, which can be used as compost to turn the regoliths into soil. In order to have fish in space, there is also the need for the systems to be self-sustaining in the production of fish feed. The key outcomes of the project were that all the species grown (potatoes, tomatoes, dwarf beans, carrots, lettuce, spring onions, chives and basil) indicate the potential to be grown in regoliths with the addition of aquaponic effluents. A significant result was that on the whole the plants that were grown with the addition of aquaponic effluents were greener than those grown in the horticultural soil, indicating that the nutrient supply was adequate. However, a key lesson learned is that germination and thus development of the plants grown in the Mars simulant and analogue was slower than those grown in the horticultural soil. Thus, developing nutrients in the soil before planting is necessary as it is with agriculture and horticulture practices on Earth, where manuring/fertilization occurs before planting. The consequence of this research, and the envisaged research to follow is not only for extra-terrestrial environments. The Earth has its own hostile environments, characterised with regoliths and other unproductive soils, and aquaponic water and aquaponic wastes can readily be envisaged as providing solutions to growing nutritious food in areas where agriculture is not currently viable. The research was undertaken in an exhibition gallery setting at the University of Greenwich in order to encourage public interest and dialogue, which it did

Investigating the effects of fish effluents as organic fertilisers on onion (Allium cepa) yield, soil nutrients, and soil microbiome

Although waste waters from aquaculture farms, known as fish effluents, have been shown to be a viable source of nutrients for crop production, their use is not permitted in organic production under the current European regulatory framework, Council Regulation (EU) 2018/848. In contrast, the use of livestock manure as fertiliser is allowed and indeed encouraged. In this work we tested the effects of two types of fish effluents – filtered and unfiltered fish waters – from an aquaponic system on the yield of onions (Allium cepa) and the soil nutrients and microbiome, compared with a fertilisation regime using composted horse manure. Soil fertility was enhanced by the addition of fish effluents, in particular in the soil treated with unfiltered fish water or sludge, which resulted in the soil with the highest nitrate content. Fertilisation with fish water and aerobically treated fish sludge resulted in higher yields than the manure, performing the best in all growth and yield measurements. The bulb weight and bulb diameter in the onions fertilised with manure were 102.43 g ± 7.26 and 61 mm ± 2.05 respectively, the ones fertilised with filtered fish effluents were 126 g ± 6.64 and 66.52 mm ± 2.17, and the ones fertilised with filtered (fish water) and unfiltered (sludge) fish effluents were 133.32 g ± 6.86 and 67.66 mm ± 1.81. The horse manure significantly affected the microbial community structure of the soil, resulting in a higher species diversity compared with the fish effluents, with the most predominant genus types being Flavobacterium, Pseudarthrobacter, Sphingomonas, Massilia, Nitrososphaera, Pseudomonas and Nocardioides. However, the microbial activity in the soil with fish effluents was also significant, which indicates that the soil treated in this way can be considered a ‘living soil’, as required for organic certification in the EU. Overall, the results confirm the findings of previous studies on the effectiveness of fish effluents as fertilisers, and highlight the superior performance of fish effluents compared with a livestock manure, thus directly questioning the prohibition on using fish effluents in organic agriculture

Improvements in soil physical properties after long-term manure addition depend on soil and crop type

Manure application and crop rotation are common agricultural practices that can alter soil physical properties and affect soil functions. In this study, we assessed the effect of long-term manure fertilization (24 to 126 years) and crop type on soil hydraulic, aggregate and pore structural properties. Samples were collected from three long-term experiments (LTEs) in Sweden (silty clay, SiC), Germany (silt loam, SiL) and Denmark (sandy loam, SL). Measurements included water retention, air permeability and gas diffusivity measured at five matric potentials −3, −5, −10, −30 and −50 kPa, saturated hydraulic conductivity (Ksat), bulk density (ρb), and water-stable aggregates (WSA). The treatments at the three LTEs included various manure rates and crop sequences (winter wheat, maize, spring barley, and grass/clover). Results showed that long-term manure addition reduced ρb by an average of 3–6% for all three sites, and improved soil water retention, plant available water and WSA for most investigated plots. However, increasing manure rates for the SiL and SL sites did not result in further improvements in soil water retention, ρb and water-stable aggregates. The effect of manure on soil pore size distribution, gas transport, and Ksat varied with soil and crop type. Manure increased the porosity of pores 30 µm for wheat and maize plots in the SL site. Manure improved gas transport and Ksat in the wheat plots and decreased these properties in the barley plots regardless of soil texture. The maize plots in the SL site had well developed pore structure, while the pore structure in the SiL site was relatively poor. Grass plots had poorer gas transport than maize plots in the SL site despite the manure addition. The study shows that improvements in soil physical and chemical properties arising from manure application largely depend on the crops grown and the soil texture

Linking litter decomposition to soil physicochemical properties, gas transport, and land use

Litter decomposition is a critical process in carbon cycling, which can be affected by land use. The relationship between litter decomposition and soil properties under different land uses remains unclear. Litter decomposition can be quantified by the Tea Bag Index (TBI), which includes a decomposition rate k and a stabilization factor S. Our objective was to investigate linkages between TBI and soil physicochemical and gas transport properties and land use. We buried three pairs of tea bags in 20 sites (covering cropland, grassland, heathland, and forest land uses) in a transect from the western to the eastern coast of the Jutland peninsula, Denmark. The tea bags were retrieved after 90 d and TBI was determined. Disturbed and undisturbed (100 cm3 soil cores) samples were collected from each site. Thereafter, clay content, organic carbon (OC), bulk density (ρb), pH, electrical conductivity (EC), oxalate-extractable phosphorus (Pox), aluminum (Alox), and iron (Feox) content, soil water content, gas diffusivity (Dp/D0), and air permeability (ka) at −10 kPa were measured. Results showed that grasslands had the highest k and S among four land uses, and agricultural soils (croplands and grasslands) exhibited higher TBI values than seminatural soils (forest and heathland). The prediction of S was better than that of k based on multiple linear regression analysis involving soil physicochemical properties. Clay content and OC were not strong predictors. Including Dp/D0 and ka improved the prediction of S, and finally, the inclusion of land use enhanced the prediction of both k and S. The different trends between two distinct land-use groups can be attributed to pH, Pox, and ρ

3D multifractal characterization of computed tomography images of soils under different tillage management: linking multifractal parameters to physical properties

Multifractal analysis of pore images obtained from X-ray computed tomography (CT) was used to characterize the scaling properties of macropores in soils with different managements and their correspondence with macroscopic physical properties related with the soil functions. We used CT images of twenty undisturbed soil columns to examine the multifractal properties of the pores identified by X-ray computed tomography (CT-Porosity). Multifractal spectra successfully describe the scaling of the pore network in all soil columns. The dimensions and scaling parameters of these spectra correlate with macroscopic magnitudes, namely, CT-Porosity, surface area of the pore walls, tortuosity, and bulk density. We also found strong correlations between the singularity spectra and the topological descriptors of the pore network skeleton: total slab voxels, number of branches per path, number of endpoints and sum of branch length, among others. These correlations show that the complexity of the CT-Porosity can be related quantitatively with physical properties, the organization of the pore skeleton and solute transport