Olive Mill Wastewater Application Research Articles

The Short-Term Effect of Olive Mill Wastewater Application on Humic Acid in Subsurface Soil Layers of the Arid Region of Tunisia

ABSTRACT Few studies have assessed the changes in soil quality based on humic acids (HA) in relation to the fresh olive mill wastewater (OMW) application. Qualitative changes to soil organic matter (SOM) under the application of OMW in real conditions have been little investigated. To make a contribution in this context, an experimental field was established in an arid Tunisian area, which included a control soil, a soil treated with 10 L m˗ 2 OMW and another amended with 10 kg m˗ 2 manure. Soil samples were collected from soil depths: 0–20 cm, 20–40 cm and 40–60 cm on the first day of OMW and manure application (day 0) and after 4 months (120 days). Results revealed that soil treated with OMW had the highest SOM content (1.42 ± 0.13%), cation exchange capacity (CEC) (3.03 ± 0.51 (cmol(c) kg−1)) and soil pH value. OMW mineralization supplied soluble ions which enhanced the electrical conductivity (EC) (1.44 ± 0.34 dS m−1). Infrared (IR) spectroscopy showed higher aliphatic, aromatic and phenolic groups in OMW amended soil than the manured soil for initial and final dates. Spreading OMW on soils provides a favorable environment for improving soil humic acids (HAs), recycling organic matter (OM) and enhancing soil properties by transferring aromatic and aliphatic structures into deeper horizons, which in turn increased the sequestration of soil organic carbon (SOC).

Comparative life cycle assessment of anaerobic digestion, lagoon evaporation, and direct land application of olive mill wastewater

Olive mill wastewater is a prominent waste stream in the Mediterranean countries, with its uncontrolled disposal in water recipients causing significant environmental issues. Anaerobic digestion has been extensively studied for the treatment of various agricultural waste streams. The scope of the present study was the environmental evaluation of the anaerobic digestion of three-phase olive mill wastewater for energy production in an anaerobic bioreactor. Regarding the environmental assessment of the process, the results indicate a lead in the proposed process compared with the baseline scenarios. Moreover, several environmental issues in terrestrial acidification and water eutrophication midpoint categories were exhibited by the digestate utilization. The implementation of the anaerobic digestion method averts an overall environmental damage of 5 mPt per 1000 kg of waste treated. For this reason, the implementation of the proposed method could be a sustainable alternative for wastewater treatment in olive oil production regions, aiming to circular economy.

Potential Use of Olive Mill Wastewater Spreading in Olive Orchards for Improving Soil Fertility and Olive Oil Quality Under Semi-Arid Environment

ABSTRACT In Tunisia, olive growing and olive oil production represent a key element of the agricultural and economic sectors. Furthermore, olive producing areas are mostly located in semi-arid and arid regions with low water availability. On the other hand, olive oil industry generates high liquid effluent volumes (olive mill wastewater (OMW)) that represent a major environmental concern, and therefore must be appropriately managed. Accordingly, spreading OMW on agricultural lands in water scare areas may help to sustain dry lands productivity. In this study, we investigated the long-term effects of OMW spreading to an olive orchard in a semi-arid region. Physicochemical and biological properties of soil as well as olive oil quality were monitored. OMW was applied, after the end of the olive milling season, at annual dose of 50 m3 ha−1 y−1 every 2 years. The findings revealed that the OMW application increased soil water content. Moreover, OMW positively affected soil fertility, and increased, soil organic matter and biological activity. The overall results of this study indicate that OMW spreading at doses of 50 m3 ha−1 y−1 in a semi-arid region improves soil physicochemical properties and does not have a negative impact on olive oil quality. Additionally, direct spreading of OMW, if applied every 2 years, could be a sustainable practice in olive orchards under semi-arid environments.

Short-term Effects of Applying Olive Mill Waste on Turfgrass

The reuse of wastes in agriculture and landscape is often viewed as one way to conserve existing resources. Among the organic waste materials produced by agricultural activities, olive mill wastes derived from the olive oil extraction process may represent a suitable soil amendment. This study evaluated the effect of olive mill wastewater (OMW) application on turfgrass growth and quality and on soil electrical conductivity and pH. Olive mill wastewater at different doses (0, 3.0, and 6.0 L/m2) was applied on a sodded turfgrass grown in clay loamy soil, identically irrigated with fresh water, and without any chemical fertilizer application. The results revealed that OMW application had a positive effect on the tested turfgrass, improving visual quality and increasing the dry weight of the clipping yield, in proportion to doses applied. An increase in electrical conductivity was observed in wastewater-irrigated soil while OMW did not remarkably change the initial soil pH.

Use of Microbially Treated Olive Mill Wastewaters as Soil Organic Amendments; Their Short-Term Effects on the Soil Nematode Community

Managing olive mill wastewater (OMW) is a major environmental problem. We followed two methods for OMW bioremediation: one with the white-rot fungus Pleurotus ostreatus alone and one with the fungus plus the microalga Chlorella vulgaris. To evaluate the potential use of both final products as soil amendments, in a pot experiment, we applied treated OMW to soil cultivated with Lactuca sativa, and we studied their short-term effects on the soil nematode community in terms of trophic and functional structure, metabolic footprint, genera composition, and interaction networks. We also applied non-treated OMW and simply water (control). The addition of non-treated OMW significantly reduced the abundance of all nematodes, and the network of interactions was the most fragmented and the least robust against future disturbance. The effect on trophic group abundances was similar but less pronounced when OMW was previously detoxified either by the fungus alone or by its combination with the alga. In the latter case, the phytoparasites were suppressed but the bacterivorous nematodes were not affected. However, the most cohesive and robust nematode network was formed in the soil that received the fungal-treated OMW. None of our OMW applications significantly changed community composition, none improved the already degraded status of the soil food web—which is attributed to the sandy texture of our soil—and none affected the growth of lettuce plants, perhaps because of the short duration of the experiment (30 days). Thus, our future research will aim to estimate the long-term impact of OMW.

Comparing the Response of Growth and Physiologic Variables of Onion to Olive Mill Wastewater Application and Arbuscular Mycorrhizal Fungi Inoculation

Comparing the Response of Growth and Physiologic Variables of Onion to Olive Mill Wastewater Application and Arbuscular Mycorrhizal Fungi Inoculation

Combined management of olive mill wastewater and compost in olive grove: Effects on soil chemical properties at different layers depth

The effects of combined agronomic application of olive mill wastewater (OMW) with compost were evaluated in an olive field (Tunisia). Four treatments were used. The first plot was spread by 50 m3 ha−1 of OMW, the second treated with 5 T ha−1 of compost, the third amended by both (50 m3 ha−1 + 5 T ha−1), and the fourth, used as a control. After ten days of organic amendment, the soil upper layers presented the highest organic matter (OM), total nitrogen, available phosphorus, exchangeable potassium and sodium contents, with the highest values noted for the mixed treatment. Also, this treatment exhibited the most important soil phenolic concentrations accumulation. All organic fertilizing treatments produced significant increase in the total alkali-extractable humic carbon (HEC), humic acid carbon (HAC) and fulvic acid carbon (FAC) concentrations, especially with OMW and compost applied simultaneously.

Effect of Olive Mill Wastewater on the composition of the essential oil of bergamot-mint under semi-arid climate

In this work, we investigate the changes in Mentha aquatica var. citrata (bergamot-mint) characteristics and essential oil composition regarding the modification of the amended dose of Olive Mill Wastewater (OMW) in pots at three different doses; D1 = 9 ml/100 g, D2 = 22.5 ml/100 g and D3 = 54 ml/100 g of soil, seven months before plantation of bergamot-mint cuttings. OMW application didn’t affect plant biomass production (leaves, stems, roots) and chlorophylls in the leaf, while the amount of leaf phenols showed a dose dependent increase. Bergamot-mint essential oil major compound is linalool acetate for control, trans-pulegol when OMW is applied at 9 ml/100 g, isopulegyl acetate when OMW is applied at 22.5 ml/100 g, and verbenone when OMW is applied at 54 ml/100 g. When OMW was applied to soil at doses D1, D2 and D3, some of bergamot-mint essential oil compounds such as decanone, citronellol, piperitone epoxide, guaiacol acetate, methyl cinnamate and citronellyl propanoate, totally disappeared. OMW spreading at 9 ml/100 g allowed appearance of menthone in Mentha aquatica var. citrata essential oil while menthol and terpineol appeared only when OMW was applied at the high dose 54 ml/100 g.

Effect of Olive Mill Wastewater of in the Control of Olive Verticillium Wilt Caused by Verticillium dahlia Kleb

Muhrez, K.A., M.Z. Tawil and B. Barhoum. 2021. Effect of Olive Mill Wastewater of in the Control of Olive Verticillium Wilt Caused by Verticillium dahlia Kleb. Arab Journal of Plant Protection, 39(4): 273-280. https://doi.org/10.22268/AJPP-39.4.273280 This research aimed to evaluate the application of olive mill wastewater in controlling Verticillium dahliae the causal agent of olive wilt disease on olive trees. This study was carried out on 2 years old olive local variety (Khderi) plants planted in pots after it has been artificial inoculated with V. dahliae, and severity was recorded within 90 days. Olive mill wastewater (omww) efficacy was estimated at the end of the experiment. Severity was increased from 8.89% before treatment to 28.89% 60 days after treatment, and decreased to 13.33% 90 days after treatment with omww 450 ml/l. Disease severity increased from 11.11% before treatment to 37.78% 60 days after treatment and decreased to 35.56% 90 days after treatment with omww 300 ml/l. Whereas, disease severity increased from 17.78% before treatment to 40% 90 days after treatment with azoxystrobin compared to the inoculated control where disease severity increased from 13.33% before treatment to 100% 90 days after treatment. Omww 450 ml/l had the highest efficacy of 80% followed by azoxystrobin 70%, and omww 300 ml/l 57.33%. It can be concluded that olive mill wastewater has a potential application as a bio-fungicide for the control of olive verticillium wilt disease. Keywords: Olive mill waste waters, Verticillium dahlia, olive, Fungicide.

ENHANCEMENT OF TOMATO ROOT-KNOT NEMATODES CONTROL USING A NOVEL BIOLOGICAL TREATMENT IN NORTH SINAI

This study focuses on using olive mill waste water (OMWW) as a novel biological treatment to decrease plant diseases while improving food quality. Root-knot nematode Meloidogyne is considered one of the main tomato diseases in North Sinai. The current study aimed to evaluate the efficiency of diffracting olive mill waste waters concentrations compared with the nematicide Oxamylon on Tomato Root-knot. OMWW was applied daily to tomato plants growing in sandy loam soil for three months. Represented five different concentration of OMWW (0%, 25%, 50%, 75%, and 100%) used for irrigation during the experiment. The positive control treatment was treated with Oxamyl at recommended dose. The negative control was watered only with tap water (0%). The results showed that mortality rates of M. incognita were significantly affected by concentrations. All treatments were superior to the untreated control in reducing nematode, except for OMWWs at 100 %, which was equivalent to the control treatment. The largest drop in root galling numbers Oxamyl was achieved (75.73%) was followed by 50% at (73.81%), 75% (68.01%), and 25% (39.67%). The highest reductions rated were recorded with the 50%and 75% concentrations used of OMWW. Overall, in the effort of efficient biological treatments was achieved for root knot control measures in tomato, the OMWW application may be used as one factor of integrated root-knot nematode management.

Impact of olive mill wastewater (OMW) on the soil hydraulic and solute transport properties

The Mediterranean area concentrates the world’s largest production area of olive oil. The olive oil industry represents, in this basin, one of the leading sectors of the agri-food economy. Olive mill water (OMW) is the principal waste effluent produced by the olive oil industry. Due to its high pollution load, this aqueous by-product cannot be directly disposed of in domestic wastewater treatment plants (especially those with a biological treatment unit). Untreated OMW is currently used for agronomic purposes in several countries, mainly because it is rich in valuable plant nutrients. However, OMW is characterized by toxic phenols, high organic matter, high salinity, suspended solids and several other components that may have possible negative effects on chemical and physical soil properties, as well as soil biological activities. In the present research, we focused on the effects of OMW application on transport and hydraulic soil properties. Three distinct soils from a pedological point of view were selected and a series of laboratory steady-state miscible flow tests were conducted under saturated conditions, on both OMW-treated and -untreated soil columns. Tests were conducted on disturbed and undisturbed soil columns. The approach proposed by Kachanoski, based on soil impedance (Z) measurements via the time domain reflectometry (TDR) technique, was used to monitor the leaching experiments. The breakthrough curves (BTCs) exhibited different shapes that allowed the repercussions of OMW applications on soil transport behaviour to be distinguished. Several additional tests conducted on OMW-treated and -untreated soil cores to determine water retention curves (SWRCs) and saturated hydraulic conductivity Ks allowed us to infer the probable mechanisms involved in soil hydrological behaviour changes under OMW treatments. The results show that when OMW leaches into the soil immediately after its disposal there is little effect on the evaluated hydraulic and hydrodispersive properties. By contrast, we demonstrated that a short incubation period (i.e. a short contact time between OMW and soil) of 10 days is enough to exert a great influence on all the values determined (e.g. soil pore velocity v and Ks reduced by up to one order of magnitude). These effects were especially evident in undisturbed soil samples.Graphic

Toward Balancing the Pros and Cons of Spreading Olive Mill Wastewater in Irrigated Olive Orchards

The controlled application of olive mill wastewater (OMW) as a by-product of the olive oil extraction process is widespread in olive oil-producing countries. Therefore, a sustainable approach necessarily targets the positive effects of soil resilience between successive annual applications to exclude possible accumulations of negative consequences. To investigate this, we applied 50, 100, 100 with tillage and 150 m3 OMW ha−1 y−1 for five consecutive seasons to an olive orchard in a semi-arid region and monitored various soil physicochemical and biological properties. OMW increased soil water content with concentration of total phenols, cations, and anions as well as various biological and soil organic matter indices. Soil hydrophobicity, as measured by water drop penetration time (WDPT), was found to be predominantly in the uppermost layer (0–3 and 3–10 cm). OMW positively affected soil biology, increased the activity and abundance of soil arthropods, and served as a food source for bacteria and fungi. Subsequent shallow tillage reduced the extent of OMW-induced changes and could provide a simple means of OMW dilution and effect minimization. Despite potentially higher leaching risks, an OMW dose of 50–100 m3 ha−1 applied every two years followed by tillage could be a cost-effective and feasible strategy for OMW recycling.

Short-term effects of olive oil mill wastewater application on soil water repellency

Land spreading of olive mill wastewater (OMW) allows a cheap and environmentally sound effluent disposal. However, this practice requires suitable application protocols, in order to avoid negative effects on soil hydrological properties, such as the increase of soil water repellency (SWR). The effects of OMW land spreading on SWR, mainly evaluated in the long term, have been rarely measured few days or weeks after land spreading. To this purpose, this study has evaluated the short-term effects of OMW land spreading on SWR of olive groves (with silt, loam or silty clay loam soil texture) using the Water Drop Penetration Test (WDPT) at laboratory scale. SWR significantly (p < 0.001) varied with the soil texture and depth (surface layer or 10-cm depth) as well as the treatment (land spreading of OMW or fresh water, FW) and time elapsed from land application. More specifically, SWR was significantly higher (p < 0.001) in the topsoil than the sub-surface layer. Compared to the soils irrigated with FW, a two-fold WDPT (thus a slightly higher SWR) was found after OMW application in both soil layers, regardless of the texture. However, this weak SWR disappears just after 2weeks from land spreading, and the hydrophobicity of the soils treated with OMW and FW becomes very similar. Moreover, the topsoil and sub-surface layer showed the same SWR after 4weeks. The high coefficients of determination (r2 >0.86) in the linear regressions between WDPT and OM content of soils proved the clear influence of the organic compounds on SWR, which decreases with OM, as expected. Overall, OMW land spreading has not significantly changed SWR, at least under the limited hydraulic and organic loads adopted in this study, and less noticeably on loam or silty clay loam soil compared to sandy loam texture. However, this practice is more viable in spring or autumn, since in these seasons the risk of groundwater contamination is particularly reduced.

Controlled Land Application of Olive Mill Wastewater (OMW): Enhance Soil Indices and Barley Growth Performance in Arid Environments

Olive oil industry generates a considerable amount of olive mill wastewater (OMW) each year, which increases the difficulties for successful processing and disposing. A possible and potential alternative is controlled application of OMW into the land. In these two fields’ experiments, we investigated a sustainable controlled land application of OMW to enhance soil properties and improve barley production under rainfed conditions. OMW was spread at five application rates (20, 40, 60, 80, and 120 m3 ha−1) in addition to the control at two sites, Rabba and Ghweer. The physicochemical characterizations of OMW were determined throughout the season. Physicochemical properties of soil were measured after 2 weeks of OMW spreading after planting and after barley harvest. Leaf nutrient content as well as other growth performance has been measured. The results of this study showed no harmful effect of OMW application for all application rates on growth parameters of barley as well as soil properties at both locations. Under all application rates, OMW has increased soil organic matter and nutrient contents, which could reduce the use of chemical fertilizer. There was a significant increase in barley growth in OMW treatments for dry weight (DM) (14 and 22%), biological yield (BYLD) (49 and 34%), grain yield (GYLD) (41 and 47%), and straw yield (SYLD) (55 and 31%) at Rabba and Ghweer sites, respectively. The results exhibited the benefit of controlled application of OMW. However, long-term effect of OMW application needs more study, and local legislative is necessary.

Spreading raw olive mill wastewater is compatible with the growth and the beneficial functions of the earthworm Octodrilus complanatus

Recycling Olive Mill Wastewater (OMW) by its application on agricultural land is considered to be a sustainable practice for soil enrichment and waste management, and recent legislation permits large scale OMW recycling in Mediterranean countries. Therefore, studies on the effects of OMW application on earthworms under experimental conditions that closely resemble those occurring in the field are urgently required to facilitate the safe and ecologically friendly use of OMW at large scale. In this study, the effects of three-phase OMW liquid on the survival and growth of the earthworm Octodrilus complanatus (Dugès, 1828), commonly present in olive groves, were assessed. The liquid was applied at a rate i) equal to the maximum authorized by Greek legislation for olive groves fertilization (80 m3 ha−1) and ii) half of this amount (40 m3 ha−1). The effects were tested in an indoor experiment conducted in plastic containers. The results showed no adverse effect on the survival of the earthworms over a period of 56 days post-treatment, at both application doses. The growth of earthworms, as estimated by their body weight change at 28 or 56 days post-treatment, was not negatively affected; instead, there was a relative increase seen at the higher dose (80 m3 ha−1), although the difference between the treatments was not significant. Qualitative observations indicated feeding of earthworms on the OMW liquids. Organic matter decomposition was not affected and there was no significant alteration in the soil properties, except the electrical conductivity that was increased at the higher level of OMW application. Therefore, the application of OMW liquids at the doses recommended by the legislation does not affect the survival and growth of the earthworms and is compatible with their activities to promote organic matter decomposition.

A study of olive mill wastewaters obtained from different treatment processes effects on chemical and microbial properties of a Typic Xerofluvent soil and wheat yield

This study was carried out to investigate the potential for the usability of treated olive mill wastewater (OMW) as an organic amendment in agricultural soils under Mediterranean climate conditions. OMW was treated by two different treatment processes as economical (E-OMW) and advanced (A-OMW). The treated OMWs and raw OMW (R-OMW) were applied to a loamy soil at a rate of 100 m3 ha-1 year-1 for 2 years. Soils were sampled 15 days and about 5 months (at harvest) after OMW application for chemical and microbial analyses in each year. The total concentrations of N, P, Cu, Zn, and phenol of R-OMW decreased after both treatment processes while salinity (EC) and the total amounts of K, Na, and Ca increased. The applications of OMW caused changes in soil chemical (pH, EC, Pext, Kext) and microbial (microbial biomass-C (MB-C), microbial biomass-N (MB-N), basal soil respiration (BSR), N-mineralization (N-min)) characteristics (P < 0.05). In the second year of the experiment, initial samplings showed that the values of soil pH and EC increased significantly under all OMW applications compared to the control. High Pext concentrations were determined in soils amended with R-OMW, while there were high Kext concentrations in soils amended with the treated OMWs. The increases determined in MB-C and MB-N at all sampling times resulted in high MB-C/TOC and MB-N/TN ratios in soils amended with the treated OMWs. The wheat grain yield over the 2-year period showed that the application of the treated OMWs had a positive effect. It was determined that no negative effects occurred for either soil properties or wheat growth with the treated OMW applied at rates of up to 100 m3 ha-1. The addition of treated OMW after removal of its phenolic components may be considered as a good option for evaluating this waste in countries where OMW causes serious environmental pollution.

Effects of combination of tillage with olive mill wastewater on soil organic carbon groups in arid soils

Soil fertility in arid areas is poor due to the climatic conditions, weak natural biomass and inappropriate agricultural practices. Soil fertility can be determined by asses the chemical composition of soil organic carbon (SOC) and soil organic matter (SOM) quantity in different systems of soil management. To identify efficient field management practices for enhanced soil fertility in arid regions, the impact of combination tillage with olive mill wastewater as compared to native vegetation were studied for more than 20 years of field experiment. Soil samples were collected from three field management treatments and three replicates for each treatment localized in Chaâl area in southern Tunisia. Field experiment includes uncultivated soil (NC) for more than 80 years (since 1936), with native vegetation, cultivated and tilled soil (CT1) and tilled soil with addition of 5 l.m−2 of olive mill wastewater (CT2). Soil properties were assessed and principal component analysis (PCA) was executed. In addition, structural functional carbon groups were investigated using MIR spectroscopy. The results showed that NC had the highest significant values of moisture content, soil organic matter, and exchangeable cations. This is likely to be due to the role of humified organic matter with colloidal properties. Significant reduction in pH and cation exchange capacity values were found in CT2 conversely to CT1. Olive mill wastewater mineralization provided soluble ions increasing electrical conductivity. MIR analyzes determined higher absorbance of aromatic/aliphatic C in NC and CT2 more than in CT1. Long-term using olive mill wastewater application improved soil carbon groups, which lead to the SOC stabilization for long-term sequestration in arid climates.

Microbiological and Chemical Modifications of Soil Cultivated with Grapevine Following Agronomic Application of Olive Mill Wastewater

The reuse of olive mill wastewater (OMW) by spreading on agricultural land is subject to a long-time debate since they supply to agricultural land both substances of undoubted positive influence on fertility and compounds that may adversely alter its chemical, physical and microbiological characteristics and/or cause negative effects on crops. In this study different amounts of OMW from 3-phases centrifugal decanter were spread in February on soil cultivated with grapevine in a research-farm located in central Italy for 11 consecutive years, with the aim to verify the long term effect on grape production, physico-chemical and microbiological characteristics of soil. In particular, the effect of the OMW spread in the largest amount (50 L m−2) was an increase of the weight of the grape-brunches and total grapes production and, in addition, an improvement of the soil characteristics due to the increase of the content of the organic reducing substances with humic-like properties. Moreover, it was also ascertained that in the short-medium period (2–8 months) the respiratory activity of the micro-organisms of the soil parcels, treated with different amount of OMW, was higher than that of the soil control parcels. The results obtained demonstrated that the controlled spreading of OMW helps to increase both the grapes crop and the fertility of the soil, recycling the organic matter and mineral nutrients, in this way allowing to reduce, or avoid, the use of chemical fertilisers.

Change and spatial variability of soil organic matter humification after long-term tillage and olive mill wastewater application in arid regions

The changes of soil organic matter (SOM) humification induced by long-term combination of tillage and olive mill wastewater (OMW) application compared to natural and cultivated soil have been little investigated. This study aimed to compare effects of no cultivation with natural vegetation soil (NC), tillage (CT1) for 80 years and combination of tillage with OMW application (CT2) for 20 years on SOM humification degree. Fluorescence spectroscopy and UV-visible ratios (E4/E6 and CHA/CFA) were used to study soil humic acids (HAs). The SOM and humification distribution was determined for the whole field area using the Inverse Distance Weighting method. Results showed that SOM content, fluorescence emission area and E4/E6 and CHA/CFA ratios were higher in NC. Tillage reduced SOM amount, molecular size, aromatic condensation and humification degree as shown by the strong correlation between fluorescence area and CHA/CFA ratio in CT1 conversely to E4/E6. Contradictory results between fluorescence emission area and E4/E6 ratio found in NC and CT1 indicated that E4/E6 ratio was not a reliable indicator of SOM humification degree. The SOM amount, CHA/CFA ratio and emission fluorescence area increased conversely to E4/E6 ratio in CT2. This revealed a greatly humified organic matter and aromatic structure condensation with tillage and OMW application. Spatial distribution showed a progressive increase of SOM and CHA/CFA from north-west to south-east linked to the positive relationship between CHA/CFA ratio and SOM amount independent of soil management practices. Soil amended with OMW provided a favourable environment for the development of HAs which improved soil quality. The UV-visible ratio CHA/CFA with fluorescence emission area can be used as parameters to investigate SOM humification degree.

Single and combined effect of chelating, reductive agents, and agro-industrial by-product treatments on As, Pb, and Zn mobility in a mine-affected soil over time.

Application of chelating and reductive agents in soils can increase the availability of potentially toxic elements facilitating their uptake by plants. This study discusses the effect of single or combined EDTA (E), sodium dithionite (SD), and olive mill wastewater (OMW) treatments on As, Pb, and Zn mobility over time in a heavily contaminated mine-affected soil. Soil samples were incubated for 1, 3, 7, 15, 30, 60, and 90days and at each incubation time the easily mobilizable fraction obtained by (NH4)2SO4 (for As) and CH3COOH (for Pb/Zn). The results showed that the highest availability of As (mean value 41mgkg-1) was observed for the EDTA treatment followed by E+OMW (mean value 32mgkg-1) and E+SD+OMW (mean value 27mgkg-1). For Pb and Zn, significantly higher available concentrations were obtained by the EDTA and E+OMW treatments (mean values 2532mgkg-1 and 1427mgkg-1 for Pb and Zn respectively) followed by the E+SD (mean value 2259 and 1333mgkg-1 for Pb and Zn) and E+SD+OMW treatments (mean value 2388 and 1340mgkg-1 for Pb and Zn). Moreover, the incubated for 90days soil samples subjected to two different sequential extraction protocols (SEPs): Wenzel (for As) and BCR (for Pb, Zn, Fe, and Mn). The results showed that As, Pb, and Zn mobility was mainly regulated by the amorphous Fe oxides. Our findings suggest that OMW application in soils should focus more attention since when combined with other amendments produced contradictory results.