Contaminated Soil Samples Research Articles

Voltammetric Sensor Based on Titania Nanoparticles Synthesized with Aloe vera Extract for the Quantification of Dithiophosphates in Industrial and Environmental Samples

In this work, TiO2 spherical nanoparticles with a mean diameter of 10.08 nm (SD = 4.54 nm) were synthesized using Aloe vera extract. Rutile, brookite, and anatase crystalline phases were identified. The surface morphology of a carbon paste electrode does not change in the presence of nanoparticles; however, the surface chemical composition does. The voltammetric response to dicresyl dithiophosphate was higher when the electrode was modified with TiO2 nanoparticles. After an electrochemical response study from pH 1.0 to 12.0, pH 7.0 was selected for the electroanalysis. The electroactive area of the modified sensor was 0.036 cm2, while it was 0.026 cm2 for the bare electrode. The oxidation process showed mixed adsorption-diffusion control. The charge transfer resistance of the modified sensor (530.1 Ω, SD = 4.08 Ω) was much lower than that of the bare electrode (4298 Ω, SD = 8.53 Ω). The linear quantitative range by square wave voltammetry was from 5 to 150 μmol/L, with a limit of detection of 1.89 μmol/L and a limit of quantification of 6.26 μmol/L under optimal pulse parameters of 50 Hz frequency, 1 mV step potential, and 25 mV pulse amplitude. The sensor response was repeatable and reproducible over 30 days. The results on real flotation and synthetically contaminated soil samples were statistically equivalent to those obtained by UV-vis spectrophotometry. A dithiocarbamate showed an interfering effect on the sensor response to dithiophosphate.

Coding smell patterns of crude oil by the electronic nose: A soil pollution case

In our study, we leveraged an electronic nose to detect the patterns of crude oils and their mixtures, sourced from the oil fields from neighboring regions in pursuit of the task of environmental impact evaluation. The temporal dynamics of oil-related patterns acquired by an electronic nose was tracked to identify the influence of high or low emissions of volatiles that depend on the oil composition. Analyzing the oils by Fourier-transform IR-spectroscopy and GC×GC-MS, we confirmed the correlation between sensor responses and the oil compositions, significantly dependent on the ratio of aromatic compounds/alkanes. Using pattern recognition techniques, Random Forest classifier enabled good accuracy of classification of oil samples and contaminated soils underscoring a high-resolution distinction between the response data. Applying these principles to determine the oil origin, we observed that the studied oil samples and contaminated soil samples corroborate with the dynamic changes in odor patterns based only on volatile and semivolatile compounds. Crude oils from the border of two oil fields facilitate a change in the odor pattern to remain one of the fields depending on the weathering time. These proposed intelligent multisensor systems show great promise as a tool for estimating oil-contaminated soils, thereby potentially enhancing environmental monitoring practices.

Evaluation of Physicochemical Parameters, Total Bacteria Count and some Heavy Metal Levels in Soil from Automobile Workshop Activities at Nnewi Local Government Area, Anambra State, Nigeria

Disposal of used motor oil and chemical substances on land leads to loss in soil quality by minimal abundance and variety of microorganisms in soil. The objective of this paper was to evalaute the physicochemical parameters, total bacteria count and some heavy metal levels in soil from automobile workshop activities at Nnewi Local Government Area, Anambra State, Nigeria. Using field survey and appropriate standard laboratory analyses, the results showed that the control uncontaminated soil samples recorded high bacteria count (6.9 x106 cfu/g). The available soil nitrogen(9.0), soil nutrients nitrate (15.10) and phosphorous (17.3) all recorded appropriate values when compared with WHO standard. The acidity of the soil using pH value as an indicator showed that the uncontaminated control soil samples were acceptable for crops also the Ec values. The heavy metals analysed indicates that the control soil samples were also moderate in heavy metals accumulation when compared with the contaminated soil samples particularly Cd, Pb (0.08) and Hg (0.01) while Cd was not detectable. These findings have shown that automobile activities can denature soil properties which could lead to soil infertility. The automobile activities has to be controled by the concerned agencies in Nigeria. Environmental education should be encouraged to reduce effects of anthropogenic activities on soil quality in the study area.

Isolation, Characterization and Evaluation of Pseudomonas aeruginosa in the Biodegradation of Propanil Contaminated Rice Farms

Propanil are herbicide commonly used on rice farm for the control of weeds and pests. Like other herbicides, tendencies to persists in the soil and impact on the microbial flora of rice farm soils does exists although study finds that propanil is not recalcitrant. This work aimed to isolate, characterize, and evaluate Pseudomonas aeruginosa from Enugu propanil contaminated rice farm. A total of nine [9], contaminated soil samples {three each from Nenwe, Ugbawka and Akpuoga-Nike} were collected and analyzed for presence of P.aeruginosa. The average total count were 3.8x106 [Ugbawka], 3.5x106 (Nenwe) and 2.8x106 (Akpuoga-Nike). Out of nine samples collected, 7 samples were positive for P.aeruginosa. Nine soil samples yielded 13 Pseudomonas aeruginosa isolates. Out of 13 P.aeruginosa isolated 4(30.8%) from Nenwe, 6(46.1%) from Ugbawka and 3(23.1%) from Akpuoga –Nike soil samples. P.aeruginosa were more in Ugbawka followed by Nenwe. The ability to utilize propanil was tested with other isolates based on their growth. It was observed that Pseudomonas aeruginosa and mixed culture showed heavy growth in mineral salt propanil media than in the media without propanil. The results of molecular identification revealed that Pseudomonas aeruginosa from two different strains utilized propanil heavily than other isolates. The result of the varying concentration of propanil showed that Pseudomonas aeruginosa (S1) had increased growth with increase in concentration of propanil from 0.8 at 1ml to 1.2 at 2ml. S2 showed 0.3 at 1ml to 1.0 at 2ml and mixed culture showed 0.6 at 1ml to 0.9 at 2ml. The result showed that P.aeruginosa is an efficient propanil degrader. Application of P.aeruginosa through fertilizer or soil amendment could be used to manage propanil pollution in the agricultural system.

Hg2+ removal characteristics of a strain of mercury-tolerant bacteria screened from heavy metal-contaminated soil in a molybdenum-lead mining area.

In this study, the mercury-tolerant strain LTC105 was isolated from a contaminated soil sample collected from a molybdenum-lead mine in Luanchuan County, Henan Province, China. The strain was shown to be highly resistant to mercury, with a minimum inhibitory concentration (MIC) of 32 mg·L-1. After a 24-h incubation in LB medium with 10 mg·L-1 Hg2+, the removal, adsorption, and volatilization rates of Hg2+ were 97.37%, 7.3%, and 90.07%, respectively, indicating that the strain had significant influence on mercury removal. Based on the results of Fourier infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), the investigation revealed that the primary function of LTC105 was to encourage the volatilization of mercury. The LTC105 strain also showed strong tolerance to heavy metals such as Mn2+, Zn2+, and Pb2+. According to the results of the soil incubation test, the total mercury removal rate of the LTC105 inoculation increased by 16.34% when the initial mercury concentration of the soil was 100 mg·L-1 and by 62.28% when the initial mercury concentration of the soil was 50 mg·kg-1. These findings indicate that LTC105 has certain bioremediation ability for Hg-contaminated soil and is a suitable candidate strain for microbial remediation of heavy metal-contaminated soil in mining areas.

Evaluation of biofilm formation by bacteria isolated from engine oil-contaminated soil and exploring its bioremediation potential in vitro

This study investigated the biofilm-forming ability of bacteria isolated from engine oil-contaminated soil and assessed their potential for bioremediation. Fifteen engine oil contaminated soil samples were collected and inoculated into Bushnell-Haas (BH) broth supplemented with 2 % engine oil. After incubation, bacterial colonies were isolated and identified using 16s RNA sequencing. The tube adherence test also known as Christensen method and modified microtiter plate quantification of biofilm formation by Stepanović et al. (2000) [1], was used to study bacterial biofilm as tube test and the microtiter-plate test are the most frequently used techniques for quantifying biofilm formation was used to study bacterial biofilm. Both quantitative (OD measurements) and qualitative (visual observation) methods were employed, classifying the six isolates into three categories: strong, moderate, and low biofilm producers. Among the 6 bacterial isolates, Stutzerimonas stutzeri exhibited the highest biofilm-forming ability.Oil degradation capacity of the isolates were tested individually as monocultures and co-cultures with other isolates. Results showed that the co-culture of Stutzerimonas stutzeri and Klebsiella quasipneumoniae showed significantly higher oil degradation compared to their monoculture and other co-cultures, suggesting synergistic interactions between the two bacterial species.However, Stutzerimonas stutzeri alone exhibited good oil degradation potential and is more useful for bioremediation but Klebsiella quasipneumoniae's rare pathogenicity, may not be suitable for field application. This study highlights biofilm-forming bacteria, particularly Stutzerimonas stutzeri, as a potential solution for bioremediating engine oil-contaminated sites.

Sulfate-reducing consortium HQ23 stabilizes metal(loid)s and activates biological N-fixation in mixed heavy metal-contaminated soil

Sulfate-reducing bacteria (SRB) are used in the remediation of mine pollution; however, the mechanism of stabilizing multiple heavy metal(loid)s by the SRB consortium under low oxygen conditions needs further study. Indigenous microflora were extracted from non-ferrous metal-contaminated soil co-inoculated with enriched SRB consortium and assembled as the HQ23 consortium. The presence of Desulfovibrio (SRB) in HQ23 was confirmed by 16S rRNA sequencing and qPCR. The effects of culture media, dissolved oxygen (DO), SO42¯, and pH on the HQ23 growth rate, and the SO42¯-reducing activity were examined. Data indicates that the HQ23 sustained SRB function under low DO conditions (3.67 ± 0.1 mg/L), but the SRB activity was inhibited at high DO content (5.75 ± 0.39 mg/L). The HQ23 can grow from pH 5 to pH 9 and can decrease mobile or bioavailable Cr, Cu, and Zn concentrations in contaminated soil samples. FTIR revealed that Cu and Cr adsorbed to similar binding sites on bacteria, likely decreasing bacterial Cu toxicity. Increased abundances of DSV (marker for Desulfovibrio) and nifH (N-fixation) genes were observed, as well as an accumulation of nitrate-N content in soils suggesting that HQ23 stimulates the biological N-fixation in soils. This study strongly supports the future application of SRB for the bioremediation of heavy metal-polluted sites.

Exploring the diversity and functional profile of microbial communities of Brazilian soils with high salinity and oil contamination

Environmental pollution associated with the petroleum industry is a major problem worldwide. Microbial degradation is extremely important whether in the extractive process or in bioremediation of contaminants. Assessing the local microbiota and its potential for degradation is crucial for implementing effective bioremediation strategies. Herein, contaminated soil samples of onshore oil fields from a semiarid region in the Northeast of Brazil were investigated using metagenomics and metataxonomics. These soils exhibited hydrocarbon contamination and high salinity indices, while a control sample was collected from an uncontaminated area. The shotgun analysis revealed the predominance of Actinomycetota and Pseudomonadota, while 16S rRNA gene amplicon analysis of the samples showed Actinomycetota, Bacillota, and Pseudomonadota as the most abundant. The Archaea domain phylotypes were assigned to Thermoproteota and Methanobacteriota. Functional analysis and metabolic profile of the soil microbiomes exhibited a broader metabolic repertoire in the uncontaminated soil, while degradation pathways and surfactant biosynthesis presented higher values in the contaminated soils, where degradation pathways of xenobiotic and aromatic compounds were also present. Biosurfactant synthetic pathways were abundant, with predominance of lipopeptides. The present work uncovers several microbial drivers of oil degradation and mechanisms of adaptation to high salinity, which are pivotal traits for sustainable soil recovery strategies.

The preparation and properties of carbon-coated fibers as solid-phase microextraction adsorbents for the determination of triacetone triperoxide in soil samples with fast and sensitive analysis using ion mobility spectrometry

Carbon-coated fibers include carbon activated/polydimethylsiloxane (CA/PDMS), graphene/ polydimethylsiloxane (Gr/PDMS), graphene quantum dots/ polydimethylsiloxane (GQD/PDMS), carbon nano-onions/polydimethylsiloxane (CNO/PDMS) and MXene/polydimethylsiloxane (MXene/PDMS) were prepared by sol–gel method, characterized by SEM, EDX and FT-IR techniques and were used by the headspace solid-phase microextraction coupled with ion mobility spectrometry (HS-SPME-IMS) method for extraction and determination of triacetone triperoxide (TATP). According to the results, MXene/PDMS was selected as the best sorbent. A response surface methodology based on a Box Behnken design (BBD) method was used to optimize critical experimental variables. Under optimal extraction conditions, the calibration graph was linear in the 50 to 1000 ng mL−1 (R2 > 0.998). Also, the detection limit and the relative standard deviations (RSDs, n = 6) were 15.1 ng mL−1 and 2.68 %, respectively. Finally, the HS-SPME-IMS method was successfully used to analyze TATP in contaminated soil samples. To check the matrix effect and the accuracy of the process, the analyte addition technique was applied (added: 50–1000 ng mL−1; determined: 48–1015 ng mL−1). The desired relative recoveries were obtained in the range of 95.3 to 104.1 %.

A novel calibration method for portable X-ray fluorescence analysis of printed circuit boards.

Printed circuit boards (PCBs) are the most complex and valuable component of electronic devices, but only 34% of them are recycled in an environmentally sound manner. Improving the recycling rate and efficiency requires a fast, reliable and uncostly analytical method. Although the X-ray fluorescence (XRF) shows high potential, it is often unreliable. In this study, we propose a novel XRF methodology for the elemental analysis of PCBs, using the certified reference material (CRM) to decrease uncertainty and enhance accuracy. The results show significant improvement in robustness and accuracy of portable XRF(pXRF) analyses for elements Cu, Pb, Ni, As and Au, with a relative average inaccuracy of approximately 5% compared to referenced values. The methodology validation carried out by comparing pXRF and inductively coupled plasma mass spectroscopy analyses of personal computer motherboard samples shows no statistically significant difference for elements Cu, Cr and Ag. The study shows that the calibration of pXRF by CRMs enables the necessary analysis of PCBs in an efficient and reliable manner and could be also be applied to different types of PCBs and other electronic components, batteries or contaminated soil samples.

Impact of Industrial Solid Waste on Soil Geotechnical Properties

In this study, the issue of industrial solid waste-contaminated soil and its consequences on various geotechnical parameters is examined. Soil health and geotechnical properties are affected by the global discharge of pollutants from chemical industries, including water, air, oil, and solids. Herein, the specific issue of soil contamination in Peshawar, Pakistan, is discussed. The goals of this study included examining variations in the Atterberg limits, direct shear strength, sieving analysis, consolidation behavior, and unconfined compression strength in contaminated soil samples. The process entailed analyzing soil samples taken from polluted sites in a laboratory. In contrast to uncontaminated soil, the results showed that contaminated soil deviated from the standard grading and exhibited lower liquid and plastic limits, higher moisture content, and lower specific gravity. Interestingly, the unconfined compression strength of the polluted soil was higher, indicating complicated interactions between the contaminants. Overall, this study highlights the need to understand and efficiently mitigate such human impacts by highlighting the extensive alterations in soil properties caused by industrial waste pollution.

Polycyclic Aromatic Hydrocarbon (PAHs) Levels in Treated Spent Engine Oil Contaminated Soil from Automechanic Workshop Site in Wukari, Nigeria

Spent engine oil contaminated soil samples were collected and divided into three portions along with uncontaminated soil sample collected 10 meters away from the contaminated site. Two of the contaminated soil samples were treated with 0.5M NaOH and heat at 2500C respectively. All the samples were extracted with appropriate solvents using sonication, cleaned up and then analyzed with gas chromatograph coupled to flame ionization detector. The results show that total PAHs concentration of contaminated soil sample was 333.6820 mg/kg, contaminated soil sample treated with 0.5M NaOH, 104.8540 mg/kg, contaminated soil sample treated with heat at 2500C was 180.0905 mg/kg and the uncontaminated soil sample, 0.7084 mg/kg. The results showed that Wukari mechanic village is contaminated with PAHs through indiscriminate disposal of spent engine oil. Furthermore, treatment with 0.5M NaOH was a more effective means of remediation relative to treatment with heat at 250oC for two hours. The study will be an appropriate guide for the artisans following enlightenment about the possible threat that contact with PAH contaminated soils could have on their health.

Phenotypic and genetic characterization of a lipolytic Ralstonia mannitolilytica isolate from petroleum-contaminated soil in Iraq.

Lipases play a crucial role in various industrial applications, and microbial lipases, particularly those from bacteria, possess significant properties. With increasing concerns about the environmental and health impacts of hydrocarbons from pipelines and refineries, there is a growing need to mitigate the risks associated with these compounds. In this study, 40 bacterial isolates were recovered from contaminated soil samples collected from multiple refineries across Iraq. Using the Vitek system, bacterial isolates were identified up to the species level, revealing that only 12 isolates exhibited lipase-producing capabilities. Among the lipase-producing isolates, Ralstonia mannitolilytica demonstrated the highest extracellular lipase activity, as determined by an olive oil plate assay supplemented with rhodamine B. Confirmation of the species identity was achieved through 16S rRNA gene sequencing, with the obtained sequence deposited under accession number LC772176.1. Further sequence analysis revealed single nucleotide polymorphisms (SNPs) in the genome of Ralstonia mannitolilytica strain H230303-10_N19_7x_R2 (CP011257.1, positions 1,311,102 and 1,311,457). Additionally, the presence of the lipase gene was confirmed through amplification and sequencing using a thermocycler PCR. Sequence analysis of the gene, aligned using Geneious Prime software, identified SNPs (CP010799, CP049132, AY364601, CP011257, and CP023537), and a phylogenetic tree was constructed based on genetic characterization. Our findings highlight the potential of Ralstonia mannitolilytica as a promising candidate for lipase production and contribute to our understanding of its genetic diversity and biotechnological applications in hydrocarbon degradation and industrial processes.

Silver Nanoparticle-Decorated Carbon Fiber Microelectrode for Imidacloprid Insecticide Analysis

The electrocatalytic activity of silver towards imidacloprid reduction was demonstrated at both macro- and nano-scales. Coupled with the advantages of microscopic electrodes, this has led to the development of a highly-sensitive and selective electrochemical sensor for imidacloprid detection. This sensor utilizes silver nanoparticle-decorated carbon fiber microelectrodes (AgNPs/CF) fabricated through a single-step electrodeposition. Employing AgNPs/CF, the linear range, sensitivity, and limit of detection (3SB/m) were determined to be 0.0–0.40 mM, 2.98 × 10−8 ± 0.10 × 10−8 A mM−1, and 60.4 nM, respectively. The sensor was successfully applied to detect imidacloprid directly in various water samples without the need for sample preparation, demonstrating ca. 100% recoveries. Moreover, the sensor was applied to analyze imidacloprid release from contaminated soil samples, revealing Langmuir characteristics of the desorption process.

Using L. minor and C. elegans to assess the ecotoxicity of real-life contaminated soil samples and their remediation by clay- and carbon-based sorbents

Toxic substances, such as polycyclic aromatic hydrocarbons (PAHs) and heavy metals, can accumulate in soil, posing a risk to human health and the environment. To reduce the risk of exposure, rapid identification and remediation of potentially hazardous soils is necessary. Adsorption of contaminants by activated carbons and clay materials is commonly utilized to decrease the bioavailability of chemicals in soil and environmental toxicity in vitro, and this study aims to determine their efficacy in real-life soil samples. Two ecotoxicological models (Lemna minor and Caenorhabditis elegans) were used to test residential soil samples, known to contain an average of 5.3, 262, and 9.6 ppm of PAHs, lead, and mercury, for potential toxicity. Toxicity testing of these soils indicated that 86% and 58% of soils caused ≤50% inhibition of growth and survival of L. minor and C. elegans, respectively. Importantly, 3 soil samples caused ≥90% inhibition of growth in both models, and the toxicity was positively correlated with levels of heavy metals. These toxic soil samples were prioritized for remediation using activated carbon and SM-Tyrosine sorbents, which have been shown to immobilize PAHs and heavy metals, respectively. The inclusion of low levels of SM-Tyrosine protected the growth and survival of L. minor and C. elegans by 83% and 78%, respectively from the polluted soil samples while activated carbon offered no significant protection. These results also indicated that heavy metals were the driver of toxicity in the samples. Results from this study demonstrate that adsorption technologies are effective strategies for remediating complex, real-life soil samples contaminated with hazardous pollutants and protecting natural soil and groundwater resources and habitats. The results highlight the applicability of these ecotoxicological models as rapid screening tools for monitoring soil quality and verifying the efficacy of remediation practices.

Self-Assembled Organic Aerogel and Sponges for Rapid and Effective Absorption of Oil from Oil- Contaminated Soil Samples

Crude oil spills pose significant risks to both marine ecosystems and human populations. Traditional remediation techniques have their limitations, prompting the exploration of innovative approaches. This study introduces a novel method involving the synthesis of a self-assembled sponge and organic aerogel. These materials were further modified using hexamethyldisilazane (HMDS) and dodecyltrimethoxysilane (DTMS) to impart hydrophobic properties. Characterization via SEM examination and FTIR spectroscopy revealed distinctive features, including bands at approximately 1050 cm-1 and 790 cm-1, indicative of alkyl side chain stretching by Si-O-C and C-H, respectively, enhancing the hydrophobicity of the materials. The SEM images depicted a random rough surface with abundant pores, facilitating oil adsorption from contaminated samples. Notably, after seven cycles of use with contaminated soil samples, the organic aerogel exhibited exceptional oil removal capacity, achieving 100% efficiency according to the Sears method. This innovative sponge and organic aerogel-based approach represents a promising advancement in environmental remediation, offering a highly efficient and sustainable solution for oil spill cleanup.

Temporal and spatial patterns of Trichuris trichiura eggs: a potential threat to human health in Pakistan.

This study investigates the presence of Trichuris trichiura eggs in soil samples collected from urban areas in Lahore, Pakistan. A total of 3600 soil samples were collected over two years from Lahore's urban regions. The detection of helminth eggs in these samples was performed using sodium hypochlorite (NaOCl) as a diagnostic technique. The study reveals an overall prevalence rate of T. trichiura at 0.97 % (35 out of 3600) in the contaminated soil samples from Lahore's slum areas. When analyzing the data by geographical areas, the study found the highest prevalence of T. trichiura in Allama Iqbal Town (1.83 %, 11 out of 600), followed by Samanabad (1.16 %, 7 out of 600), Wapda Town (1.00 %, 6 out of 600), Gulberg (1.00 %, 6 out of 600), and Cantt (0.50 %, 3 out of 600). Conversely, Valencia Town had the lowest prevalence rate at 0.33 % (2 out of 600). However, these variations in prevalence rates were not statistically significant (p = 0.117). Prevalence rates of T. trichiura's eggs varied significantly across different sampling seasons (p>0.001). In autumn, a total of 900 soil samples were collected, with 19 samples (2.11 %) testing positive for T. trichiura. This rate was notably higher compared to the prevalence rates observed in winter, spring, and summer, which were 0.66 %, 0.22 %, and 0.88 %, respectively. Regarding the sampling months, the study observed a significantly higher prevalence during September (3.33 %, 10 out of 300), followed by October (2.33 %, 7 out of 300), and August (1.33 %, 4 out of 300). Prevalence rates gradually decreased in other months, ranging from 1 % to 0.33 % (3 to 1 out of 300), with no parasite detection in March (0 %, 0 out of 300) (p < 0.001). This research underscores soil contamination due to fecal waste and highlights public unawareness of parasite biology, driven by open defecation practices.

Green and sustainable practices for an energy plant cultivation on naturally contaminated versus spiked soils. The impact of ageing soil pollution in the circular economy framework

Silybum marianum L. Gaertn. or milk thistle is an energy-produced weed that has been shown to be tolerant of heavy metal-contaminated soils. In the present study, its cultivation was studied in soils laboratory-spiked (artificial) with Cu and Zn solutions. Meanwhile, plant growing on naturally contaminated soils of Mediterranean regions, both urban and rural, was investigated. The metal concentrations spiked in artificial polluted soils were estimated to be roughly equivalent to those in naturally contaminated soils. Plants grown in artificially contaminated soils incorporated the metal added to the soils more rapidly and in higher proportions. The contamination of soil samples was carried out using different chemical reagents, salts containing the metals with oxidation number II, highlighting the fact that the reagent containing the metal is crucial regarding artificial soil pollution. Statistically significant differences were observed between the individual pollution patterns, as far as plant metals uptake concern. It was also found that the aged, contaminated soils transfer lower levels of metals to the plants. Therefore, aging or weathering of contamination alters toxicity levels in the soil environment by determining transport and uptake into the soil-to-plant system. Eventually, from the present research, it emerged the fact that in urban soils that have aged perennial pollution, the uptake of metals by plants is probably lower than in rural ones. Furthermore, with proper management, it is possible to grow plants, with low nutrient requirements, in urban soils by adopting smart, green and eco-friendly techniques, enhancing sustainable cultivation in the framework of circular economy.

Effect of Agro-Waste on Bioremediation of Soil Polluted with Spent Hydrocarbon in Keffi, Nasarawa State, Nigeria

Petroleum hydrocarbon is a major environmental pollutant throughout the world. This study was aimed at the effect of agro-wastes on bioremediation of soil polluted with spent hydrocarbon in Keffi. Hydrocarbon contaminated soils were collected from three (3) different auto mechanic workshops in Keffi, Nasarawa State Nigeria. The agro wastes used as stimulants were corncobs, fruits peels and melon shells. The hydrocarbon utilization was determined using gravimetric analysis. The hydrocarbon utilization bacteria were isolated and identified using standard microbiological method. The hydrogen ions (pH) of the contaminated soil sample were 4.5. pH of corncobs (CB) was 6.2, melon shells (MS) was 5.6 and fruits peels (FP) was 7.6. The value of total nitrogen for contaminated soil was 0.45 %, when amended with CB was 6.2%, MS was 1.26% and FP was 3.56%. Organic carbon in contaminated soil prior to study was 5.80 %, when amended with CB was 9.03%, MS was 7.55% and FP was 10.12%. The Phosphorous in contaminated soil was 8.41 mg/kg, when amended with CB was 13.40 mg/kg, MS was11.82mg/kg and FP was 15.61 mg/kg. Effect of time in reduction of hydrocarbon from contaminated soil amended with CB recorded highest after 40days (44.98 mg/kg) and the least (10.31 mg/kg) after 10days. Contaminated soil amended with CB the highest reduction was at 30 ℃ (48.92 mg/kg) and the least was at 35℃ (19.21mg/kg). From FP the highest reduction was at 30℃ (48.04 mg/kg). The highest degrading bacteria count was recorded from Keffi garage mechanic workshop (4.04 x106 cfu g/ml) and the lowest was from pyanko road mechanic workshop (1.18 x106 cfu g/ml). The highest bacteria isolated from none amended contaminated soil was Flavobacterium sp (33.3 %) and the lowest was Bacillus subtilis and Proteus sp (33.3%). From amended soil with CB the highest were Corynebacteria spp and Flavobacterium sp (100%) and the lowest were Bacillus subtilis, Pseudomonas flourescens, and Proteus sp (66.6%). From contaminated soil amended with MS the highest bacteria isolated were Flavobacterium sp and Corynebacteria sp (33.3%) and the lowest were Pseudomonas flourescens and Proteus sp (33.3 %). From contaminated soil amended with FP the highest bacteria isolated were Pseudomonas flourescens and Proteus sp (100%) and the lowest were Bacillus subtilis, Flavobacterium sp and Corynebacteria sp (66.6%). It is recommended that the environmental agencies in the country give consideration to agricultural waste products for bioremediation of hydrocarbon polluted soil in Nigeria

Assessment of hydrophobic properties of oil-contaminated soils using the «Water Spot» method

The aim of the study was to assess the hydrophobicity degree of oil-contaminated soils using the Water Spot method. Location and time of the study. The study was carried out in 2024 in laboratory conditions with typical chernozem and gray forest soil. Methods. The sieved (2 mm, air-dried and milled soil samples were amended with oil in amounts needed to established the chosen concentration (0, 0,2, 0,5, 1, 3 and 5% on the mass basis). Then hexane and distilled water were added to reduce oil viscosity and increase soil moisture, respectively. After two days of incubating soil, sodium fluorescein solution was added onto the sample surface to visualize spot boundaries. The images were taken in a dark place under the ultraviolet light. To determine the effectiveness of chitosan (as a natural sorbent), a second series of experiments was performed in the same setup, but with chitosan addition, followed with two days incubation. Sodium fluorescein was then applied, and the area of the resulting spot was imaged. The resulted images were processed using the CorelDRAW software and the Microsoft Excel analysis package. Results. Oil contamination of soils usually disturbs the water regime. Increase in petroleum products content from 0,5 to 5% leads to decrease in absorbency and the area of the water spot on the soil surface. After treating the contaminated soil samples with 0,1% chitosan solution, the water spot area increased on average by 43% on the gray forest soil, and by 6% on typical chernozem. With a twofold increase in the concentration of chitosan solution, the water spot area increased on the gray forest soil by an average of 48% and by 46% on typical chernozem. Thus chitosan solution can be used as a sorbent when soil is contaminated with oil products. Conclusions. The water spot method is reproducible, simple, and can be used to assess soil contamination with petroleum products. The results show that with an increase in the degree of pollution, a decrease in the area of the water spot on the soil is observed.