Contaminated Soil Research Articles

Exploring the Potential of Crotalaria juncea L. for Phytoremediation: Insights from Gas Exchange, Pigment Quantification, and Growth Measurements under Copper Stress

Soil contamination by trace elements is a worldwide concern that can result from several sources, such as mining, smelting, car traffic exhaust, agriculture plant protection products such as fungicides, and fertilizers. Among the metals involved, copper can cause alterations in the photosynthetic, respiratory, and enzymatic processes of plants, leading to reduced growth of roots and shoots. An alternative to dealing with metals present in the soil is phytoremediation, which consists of using plants to extract or stabilize these elements. The leguminous Crotalaria juncea is widely used as a green manure and may be advantageous due to its capacity for biological nitrogen fixation and biomass accumulation. This research aimed to evaluate the growth and physiological behaviour of C. juncea in copper-contaminated soil and its potential use as a phytoremediation plant. For the fresh and dry mass of shoots and roots, compared with 30 mg.dm−3 of Cu, there was a decrease in values with the increase in concentrations up to a dose of 480 mg.dm−3. The roots were less sensitive to increased Cu concentrations than the shoots. The tolerance index decreased as copper concentrations in the soil increased. From 60 mg.dm−3, its vegetative growth decreased, but C. Juncea was able to tolerate and accumulate copper in the root system, presenting high potential as a phytostabilizing species.

Effects of phosphate fertilization and sulfadiazine on plant growth, root morphology, nitrogen and phosphorus uptake of soybean and maize

Low soil phosphorus (P) availability is a limiting factor for crop production. Application of livestock manure as organic fertilizer can increase soil P availability, but may cause soil contamination with antibiotics such as sulfadiazine (SD), thus adversely affecting plant growth and nutrient uptake. The effects of P (0 and 50 mg kg−1) and SD (0, 1, 10, and 100 mg kg−1) levels on plant growth, root development, and nitrogen (N) and P uptake of maize and soybean were examined in a pot experiment using a loess soil as the test soil. High levels of SD considerably inhibited plant growth of both crops. Both P fertilization and SD negatively affected root development of both crops, especially at higher SD levels. For both crops, the average root diameter and the proportion of thick roots increased with increasing soil SD level. When soil SD level was ≤10 mg kg−1, the effects of P fertilization and SD on plant N and P concentrations, and N:P, N- and P-utilization efficiency were not significant in most cases. The effects of SD on plant N and P nutrition could not be of a great concern when soil SD level was ≤10 mg kg−1. Overall, soil SD pollution could reduce plant biomass and inhibit root development of soybean and maize, with a stronger effect on root development than on plant biomass at a high soil SD level (≥10 mg kg−1). In agricultural production, attention should be paid to soil SD pollution via manure application.

Biocontrol of Aflatoxin-Producing Aspergillus flavus ATCC 22546 by a Non-Aflatoxigenic Aspergillus flavus ATCC 9643

The biological control of Aspergillus flavus and A. parasiticus by non-aflatoxigenic strains has been introduced in cotton- and peanut-cultivating fields and proven successful at reducing aflatoxin (AFB) contamination of crops and agricultural soils. In this study, a non-aflatoxigenic strain, A. flavus ATCC 9643 (ATCC 9643), was evaluated for its ability to competitively inhibit the growth of an aflatoxigenic strain, A. flavus ATCC 22546 (ATCC 22546), and mitigate AFB production in ATCC 22546 during competitive growth. To comparatively analyze the suppressive effect of ATCC 9643 on ATCC 22546, a non-aflatoxigenic strain (A. flavus ATCC 96045, known as AF36) was used as a positive control in some experiments. The two non-aflatoxigenic strains did not produce AFB1 or AFB2 owing to the absence of several AFB biosynthesis-related genes, especially aflK and aflL, which encode versicolorin B synthase and desaturase, respectively. To create a competitive growth environment, ATCC 9643 and ATCC 22546 were co-inoculated into a solid agar medium, and they grew at similar rates when added at a 1:1 ratio. Increasing the inoculum rate of ATCC 9643 (1:1, 1:3, 1:5) dramatically inhibited ATCC 22546 growth, and AFB production was effectively decreased by about 84%, 95%, and 97% by treatment with ATCC 9643. On rice, ATCC 22546 attenuated ATCC 9643 growth only when the rice was submerged in distilled water, whereas agar addition enhanced it. Taken together, ATCC 9643 is a promising candidate biological agent for suppressing aflatoxigenic A. flavus strain growth and alleviating AFB contamination. Further studies on AFB reduction in crop fields, including cotton-cultivation and maize-cultivation fields, are warranted.

Mapping legacy lead: socioeconomic and demographic connections in urban soil contamination in Lafayette, LA

Mapping legacy lead: socioeconomic and demographic connections in urban soil contamination in Lafayette, LA

Advancing on ametrine pesticide detection through surface‐enhanced Raman spectroscopy and Ag colloid: Understanding the pH effect and the adsorption mechanism supported by theoretical calculation

AbstractThe excessive use of pesticides has detrimental effects on the ecosystem, leading to soil contamination and the spread of pollution beyond the targeted areas. Concerns arise regarding the permissible limits of pesticides, typically around 10−8 mol/L. In this study, we employed surface‐enhanced Raman spectroscopy (SERS), a highly sensitive and selective technique, to investigate the behavior of the pesticide ametrine (AMT) on silver colloids. The Ag nanoparticles (AgNPs) exhibited an average size of (26 ± 2) nm and a zeta potential of (−30 ± 1) mV in the absence of AMT, which decreased to (−24 ± 1) mV in the presence of AMT, resulting in mild AgNPs aggregation, with the average diameter of AgNPs increasing to approximately 300 nm. This aggregation is advantageous, as they provide active sites for pesticide detection. Besides, the purification method employed ensured that AMT remained undegraded, and various conformations of AMT were simulated using Ag clusters to study the SERS effect. Comparison with the experimental spectra indicated that the SERS‐4 conformer closely resembled the experimental spectrum, suggesting simultaneous interaction between the Ag surface and the sulfur (S) and nitrogen (N) atoms of the AMT triazine ring. Notably, changes in the AMT molecule were observed with pH variations: at pH below 5, hydroxylation occurred, resulting in an Ag–Cl stretching at 241 cm−1 in the SERS spectra. Conversely, at pH above 5 (pH 6–13), the presence of bands at 230 and 219 cm−1 in the SERS spectra indicate the formation of Ag–N and Ag–S bonds, respectively, between the AMT and the AgNPs. Furthermore, the study successfully detected AMT at pH 7, establishing a limit of detection (LOD) of 1.36 × 10−8 mol/L (3 ppb) based on the SERS spectra. These findings underscore the applicability of the SERS technique in the sensitive and selective detection of AMT, offering a promising approach for monitoring the presence of this pesticide in environmental samples.

Effects and remediation of heavy metals contamination in soil and vegetables from different areas: A review

Heavy metals are non-biodegradable and thus persist in the environment, potentially infiltrating the food chain via crop plants and accumulating in the human body through biomagnification. Due to their toxic nature, heavy metal poisoning poses a severe threat to human health and the environment. Consuming vegetables contaminated with heavy metals can lead to increased accumulation of these metals in the human body. This review discusses the risks of heavy metal contamination in various areas, as reported in some research studies, and the implications for human health. Data obtained from several journals indicated that levels of lead (Pb) and cadmium (Cd) in vegetables were generally within permissible limits, though cadmium concentrations were found to be low in some studies. High concentrations of lead (Pb) can affect metabolic functions, growth, and photosynthetic activities. Cadmium (Cd) levels, which are lower than the permissible limit of 0.2 mg kg−1 set by WHO, can lead to chromosomal aberrations and sister chromatid exchanges in cells. Zinc (Zn) levels were within permissible limits except in lettuce and spinach in some findings. Low zinc content in vegetables impacts human health, plant health, and agricultural productivity. Addressing zinc deficiency requires integrated approaches such as soil management, crop biofortification, and dietary diversification. Ensuring adequate zinc levels is essential for improving public health and achieving sustainable agricultural practices. Addressing heavy metal contamination in vegetables requires a combination of remediation and preventive strategies. Implementing soil and water management practices can mitigate these risks and ensure the safe production of vegetables.

Traversing the prevalence of microplastics in soil-agro ecosystems: Origin, occurrence, and pollutants synergies

The ubiquity of plastics in modern life has made them a significant environmental concern and a marker of the Anthropocene era. The degradation of plastics results in the formation of microplastics (MPs), which measure 5 mm or less. The coexistence of MPs with other pollutants found in sludge, water treatment plant effluents, surface water, and groundwater, shapes the environmental landscape together. Despite extensive investigation, the long-term implications of MPs in soils remain uncertain, underscoring the importance of delving into their transportation and interactions with soil biota and other contaminants. The present article provides a comprehensive overview of MPs contamination in soil, encompassing its sources, prevalence, features, and interactions with soil flora and fauna, heavy metals, and organic compounds. The sources of MPs in soil agroecosystems are mulching, composting, littering, sewage sludge, irrigation water, and fertilizer application. The concentration of MPs reported in plastic mulch, littering, and sewage sludge is 503 ± 2760 items per kg−1, 4483 ± 2315 MPs/kg, and 11,100 ± 570 per/kg. The transport of MPs in soil agroecosystems is due to their horizontal and vertical migration including biotic and abiotic mobility. The article also highlighted the analytical process, which includes sampling planning, collection, purification, extraction, and identification techniques of MPs in soil agroecosystems. The mechanism in the interaction of MPs and organic pollutants includes surface adsorption or adhesion cation bridging, hydrogen bonding, charge transfer, ligand exchange, van der Waals interactions, and ion exchange.

Factors affecting nutrient losses in hay production

AbstractThe primary objective of haymaking is to dry forage adequately to inhibit the growth of undesirable microbes and halt residual plant enzymatic activity that causes nutrient losses. During the field and storage phases of haymaking, the environment, management practices, and other factors influence the extent of dry matter losses. This review discusses these factors and the strategies that have been developed to mitigate nutrient losses. A major emphasis was placed on hay microbiome dynamics, as it has been scarcely studied despite its importance on nutrient losses during storage and harvest, especially under humid conditions. The effects of cutting height, mower type, and swath manipulation on soil contamination were discussed. Also, the impact of environmental conditions and swath manipulation on wilting time was analysed for humid and arid conditions. Special attention was given to design improvements in harvesting equipment to reduce wilting time and field losses. Furthermore, we assessed the nutrient losses during storage caused by microbial and residual plant enzymatic activity resulting from excessive moisture at baling or re‐introduced moisture during storage. The spoilage extent during storage depends on bale moisture, size, density, shape, wrapping, forage type, and storage facilities. A Venn diagram analysis showed that each phase of haymaking process has a unique microbiome and that certain fungal and bacterial genera could be shared across more than one hay production phase. To take corrective actions, hay producers need to be aware of the increased susceptibility to nutrient losses associated with particular field and storage practices, environmental conditions, and forage types.

Layered double hydroxides for simultaneous and long-term immobilization of metal(loid)s in soil under simulated aging

Soil contamination by toxic metals and metalloids poses a grave threat to food security and human well-being. Immobilization serves as an effective method for the remediation of soils contaminated by metal(loid)s. Nevertheless, the ability of soil amendments for simultaneous immobilization of cations and oxyanions, and the long-term effectiveness of immobilization need substantial improvements. In this study, we used a series of layered double hydroxides (LDHs), including Mg-Al LDH and Ca-Al LDH fabricated from pure chemicals, and one waste-derived LDH synthesized using granulated ground blast furnace slag (GGBS), for the immobilization of Cu, Zn, As, and Sb in a historically contaminated soil obscured from a mining-affected region. The LDHs were first subjected to iron (Fe) modification to enhance their short-term immobilization performances toward metal(loid)s. Furthermore, the long-term effectiveness of Fe-modified LDHs was examined via two sets of experiments, including column experiments simulating 2-year water leaching, and accelerated aging experiments simulating 100-year proton attack. It was observed that Fe-modified LDHs, either made from pure chemicals or GGBS, demonstrated promising long-term immobilization performances toward metal(loid)s. Results from this study are encouraging for the future use of LDHs for simultaneous and long-term immobilization of metal(loid)s in soil.

A comprehensive study of source apportionment, spatial distribution, and health risks assessment of heavy metal(loid)s in the surface soils of a semi-arid mining region in Matehuala, Mexico

BackgroundThis study investigates the contamination level, spatial distribution, pollution sources, potential ecological risks, and human health risks associated with heavy metal(loid)s (i.e., arsenic (As), copper (Cu), iron (Fe), manganese (Mn), lead (Pb), and zinc (Zn)) in surface soils within the mining region of Matehuala, located in central Mexico. ObjectivesThe primary objectives are to estimate the contamination level of heavy metal(loid)s, identify pollution sources, assess potential ecological risks, and evaluate human health risks associated with heavy metal(loid) contamination. MethodsSoil samples from the study area were analysed using various indices including Igeo, Cf, PLI, mCd, EF, and PERI to evaluate contamination levels. Source apportionment of heavy metal(loid)s was conducted using the APCS-MLR and PMF receptor models. Spatial distribution patterns were determined using the most efficient interpolation technique among five different approaches. The total carcinogenic risk index (TCR) and total non-carcinogenic index (THI) were used in this study to assess the potential carcinogenic and non-carcinogenic hazards posed by heavy metal(loid)s in surface soil to human health. ResultsThe study reveals a high contamination level of heavy metal(loid)s in the surface soil, posing considerable ecological risks. As was identified as a priority metal for regulatory control measures. Mining and smelting activities were identified as the primary factors influencing heavy metal(loid) distributions. Based on spatial distribution mapping, concentrations were higher in the northern, western, and central regions of the study area. As and Fe were found to pose considerable and moderate ecological risks, respectively. Health risk evaluation indicated significant levels of carcinogenic risks for both adults and children, with higher risks for children. ConclusionThis study highlights the urgent need for monitoring heavy metal(loid) contamination in Matehuala's soils, particularly in regions experiencing strong economic growth, to mitigate potential human health and ecological risks associated with heavy metal(loid) pollution.

Diffusion coefficients of polycyclic aromatic hydrocarbons in supercritical carbon dioxide: A molecular dynamics simulation study

Supercritical carbon dioxide (SC-CO2) extraction technology is an effective way to deal with soil contamination problems. Among them, polycyclic aromatic hydrocarbons (PAHs) are one of the main pollutants in soil. Studying the diffusion coefficients of PAHs in SC-CO2 can help us better understand the mass transfer characteristics during the SC-CO2 extraction process. Molecular dynamics simulation was applied in this work to study the diffusion behavior of PAHs in the SC-CO2 environment. Under different SC-CO2 thermodynamic states (temperature: 313–373 K, pressure: 10–30 MPa) and molecule sizes, the diffusion coefficients of PAHs were calculated. The trend of the interaction energy between PAHs and SC-CO2 molecules as temperature, pressure, and molecule size changed was also investigated. The findings demonstrated that compared to heavy PAHs, light PAHs had a higher diffusion coefficient in SC-CO2. Changes in the system’s temperature and pressure have an important effect on the diffusion coefficients of PAHs in SC-CO2. The high-temperature and low-pressure conditions had a promoting effect on the diffusion behavior of PAHs molecules. The van der Waals energy accounts for the largest proportion of the intermolecular interaction energy, which was about 80 %. It can be concluded that the van der Waals interaction energy played an important impact on the diffusion process of PAHs molecules in SC-CO2.

Comparative transcriptomics provides insight into molecular mechanisms of zinc tolerance in the ectomycorrhizal fungus Suillus luteus.

Zinc (Zn) is a major soil contaminant and high Zn levels can disrupt growth, survival, and reproduction of fungi. Some fungal species evolved Zn tolerance through cell processes mitigating Zn toxicity, though the genes and detailed mechanisms underlying mycorrhizal fungal Zn tolerance remain unexplored. To fill this gap in knowledge, we investigated the gene expression of Zn tolerance in the ectomycorrhizal fungus Suillus luteus. We found that Zn tolerance in this species is mainly a constitutive trait that can also be environmentally dependent. Zinc tolerance in S. luteus is associated with differences in expression of genes involved in metal exclusion and immobilization, as well as recognition and mitigation of metal-induced oxidative stress. Differentially expressed genes were predicted to be involved in transmembrane transport, metal chelation, oxidoreductase activity, and signal transduction. Some of these genes were previously reported as candidates for S. luteus Zn tolerance, while others are reported here for the first time. Our results contribute to understanding the mechanisms of fungal metal tolerance and pave the way for further research on the role of fungal metal tolerance in mycorrhizal associations.

Towards a more realistic approach to the problem of detecting fuel leaks in filling stations: Mixed time windows

The early detection of fuel leaks in filling stations is crucial to minimize environmental risks, such as soil and groundwater contamination. There are some commercial products for fuel leakage detection based on statistical analysis of data from station inventory books. Although they solve the tackled problem, they have some important drawbacks, such as their high price, and issues related to the privacy of station data, which must be shared with the company owning the reconciliation technology.In this work, a solution based on Artificial Intelligence is proposed to address this problem. Machine Learning techniques, specifically two-class supervised classifiers, are applied to data extracted from inventory books of real petrol stations. The classification models used in this paper are trained and tested with real data of days without leaks and simulated data of days with leaks. Thus, the more representative of reality these data are, the better the classifiers will work when implemented in a real filling station. In this sense, the most novel contribution of this paper is the way in which the training sets are constructed to achieve a realistic scenario. These sets are composed of time data windows in which the leak can begin on any day within the window, not necessarily on the first day, as the authors had assumed in a previous contribution. Therefore, they are mixed windows containing a variable number of non-leaking and leaking days.In addition, the design of these data sets complies with the requirements of the current European standard UNE-EN 13160–5. This allows the classifiers to work under even more realistic conditions and thus increase the practical applicability of their results. This work demonstrates that by using two-class classifiers it is possible not only to comply with the standard in terms of the maximum allowable ratio of false positives and false negatives, but also to detect the leak in a shorter time than that established in the norm.

Over 50 years of a field experiment on cropping systems in Bałcyny, Poland: Assessing pesticide residues in soil and crops from the perspective of their field application history

Many agricultural problems can be illustrated and solved through long-term field experiments. Since 1967, an experiment has been conducted in Bałcyny, Poland, to compare continuous cropping with growing crops in crop rotation. The experiment also provides information on the history of chemical crop protection, which may have influenced soil and crop contamination with pesticide residues. In this study, fields of winter rye in continuous cropping (CCrye) and a 5–6-field crop rotation (CRrye) were used as an example to investigate the occurrence of pesticides in soil and grain in the context of previous use of chemical crop protection products. Two levels of crop protection were also examined: herbicide (since the 1972/73 growing season) and fungicide (since 1982/83) application (HF) and control treatment (CT; no herbicides since 1972/73, no fungicides since 1982/83). Insecticides were used only when absolutely necessary. Between 1967 and 2019, 58 different active substances were applied to the fields selected for this study. Soil and grain samples collected in 2019 after rye harvest were analyzed for the presence of 441 and 496 different substances, respectively. Only DDT and its metabolites were detected in soil, even though DDT was not applied to the fields after 1967. The concentration of ΣDDT (sum of all metabolites and isomers) ranged from 038 to 130 µg kg–1 soil and exceeded the limit set in Poland (120 µg kg–1) under CRrye-HF treatment. In winter rye grain, no pesticide residues were found. The results show that long-term rational use of less persistent pesticides does not lead to contamination of the soil or the test cereal grain, but DDT continues to threaten the environment five decades after its probable last use. The study points to the value of comprehensive long-term recording for providing a retrospective assessment of pesticide exposure. Long-term field experiments facilitate this approach.

Microplastic contamination in the agri-food chain: The case of honeybees and beehive products

Microplastics, MPs, plastic fragments with a dimension lower than 5 mm, and microfibers, MFs, synthetic and natural/artificial fibrous fragments with a diameter lower than 50 μm, are ubiquitous pollutants identified in different environmental compartments. In this work the occurrence of MPs and MFs on honeybees, Apis mellifera, and beehive products was evaluated, using Fourier transform infrared microspectroscopy, confirming that MPs and MFs are widely present as air contaminants in all the apiary's areas (high and low urbanized areas) in Southern Italy.Results indicated that independently from the site, both honeybees and honey samples, are contaminated by MFs with non-natural color. The majority of MFs were of natural origin followed by artificial MFs and synthetic MFs. Moreover, the chemical composition of MFs isolated from honeybees reflect that used in synthetic fabrics, leading to the hypothesis that they are released from textile to air where are captured by bees. Results highlight that MFs represent a class of ubiquitous airborne anthropogenic pollutants. The identification of polytetrafluoroethylene, PTFE, MPs in honeybees confirm the recent findings that PTFE MPs are diffuse soil and air contaminants while the identification of polyethylene, PE, based MPs in honey samples, from low density urban sites, could be correlated to the large use of PE in agriculture. In the honey samples, also polycaprolactone, PCL, MPs were identified, mainly in high density urban sites, confirming that biodegradable materials could be further pollutants in the environments. The results indicate that honeybees are contaminated by MPs and MFs during their flights or picking up from the hive components, flowers, from other nest mates, from the clothes of the beekeeper, among others and some of them could be transferred to honey samples that could be also affected by soil contamination.

Reproduction, growth and oxidative stress in earthworm Eisenia andrei exposed to conventional and biodegradable mulching film microplastics

Plastic contamination in agricultural soils has become increasingly evident. Plastic mulching films are widely used in agricultural practices. However, the increased use of biodegradable plastics has, to some extent, replaced their non-degradable counterparts. The fragmentation of plastics generates microplastics (MPs), posing risk to soil functions and organisms. In this study the effects of low-density polyethylene microplastics (PE-MP) and polybutylene adipate terephthalate biodegradable microplastics (PBAT-BD-MP) originating from mulching films on the earthworm Eisenia andrei were studied. The earthworms were exposed to seven concentrations (0, 0.005, 0.05, 0.1, 0.5, 1, and 5 % w/w) based on environmentally relevant levels and worst-case scenarios on soil contamination. Survival, growth, reproduction, and biomarkers for oxidative stress [superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), glutathione S-transferase (GST), glutathione (GSH), and lipid peroxidation (LPO)] were analysed. Additionally, the Integrated Biomarker Response Index (IBR) was calculated to assess the overall oxidative stress status of the earthworms. Results showed that PE-MP exposure slightly decreased the biomass of the earthworms towards higher concentrations, whereas PBAT-BD-MPs induced growth at lower concentrations. MPs did not have a significant effect on Eisenia andrei reproduction; however, a slight negative trend was observed in juvenile production with increasing PE-MP concentrations. Both PE-MP and PBAT-BD-MP affected antioxidant system, PE-MPs with changes in CAT and GR levels and PBAT-BD-MPs inducing effects on SOD and LPO levels. Additionally, both MPs exhibited effects on soil parameters, resulting in increased soil pH and water-holding capacity at 5 % concentration. Changes in soil parameters can further affect soil organisms such as earthworms. This study provides understanding of the ecotoxicological effects of conventional and biodegradable microplastics on the earthworm Eisenia andrei. It also shows that MP particles of both conventional and biodegradable mulching films induce oxidative stress, considered as an early-warning indicator for adverse ecological effects, in environmentally relevant concentrations.

Intensifying Cadmium remediation: the impact of synergy between Crambe abyssinica and plant growth-promoting microorganisms

Cd, a toxic metal, is naturally found in the environment and is exacerbated by human activities such as mining, agriculture, and industrial processes. Its contamination in soils poses serious risks to human health and ecosystems, prompting the need for effective remediation strategies. This study focuses on the use of Crambe abyssinica, an oilseed plant known for its tolerance to adverse environmental conditions, including Cd contamination, for phytoremediation of contaminated soils, associated with bioremediation through plant growth-promoting microorganisms. The study involved growing Crambe in vitro. Methods included seed asepsis, substrate contamination with various Cd concentrations, and inoculation with beneficial microorganisms such as Bradyrhizobium japonicum, Bacillus subtilis along with Bacillus megaterium, Azospirillum. brasilense, Pseudomonas fluorescens, and Trichoderma harzianum. Data such as plant length and root area were measured, and the nutrient and Cd content in the plants were assessed. Results indicated that inoculation with microorganisms significantly enhanced the nutrient content in Crambe plants, even under different Cd concentrations. Notably, A. brasilense and P. fluorescens were particularly effective, not only increasing nutrient uptake but also enhancing Cd accumulation in the plants, which is crucial for phytoremediation. The presence of these microorganisms also led to a significant reduction in the Cd concentration in the substrate, showcasing their potential in bioaugmentation. The study highlights the efficacy of using Crambe abyssinica in conjunction with specific microorganisms for the remediation of Cd-contaminated soils. The synergistic effects of these plant-microorganism interactions not only promote plant growth and health but also enhance the phytoextraction of Cd, offering a sustainable solution to soil contamination. Future research should focus on optimizing these interactions and exploring their applications in larger-scale environmental remediation projects.

Promoting sustainability in the solar industry: bibliometric and systematic analysis of alternatives for the end-of-life of photovoltaic modules

This study conducted bibliometric and systematic analyses of the literature to map the application of life cycle assessment studies on photovoltaic panels, focusing on end-of-life alternatives. Seventy-six articles addressing management strategies, treatment, recycling, and utilization of the panels were examined. The results revealed a significant increase in the number of publications over time, particularly in high-impact journals. Sixteen end-of-life alternatives for the panels were identified, including recycling practices, material recovery, and landfills. All alternatives were analyzed regarding environmental, social, and economic impacts. Understanding the impacts of different end-of-life methods for solar panels is key in supporting government management and the implementation of effective policies and regulations. Additionally, it is necessary to consider the environmental and social effects, as well as ensure the protection of workers involved in related activities and prevent soil, water, and air contamination caused by different types of alternatives, such as dissolution and incineration. To enhance the recycling and recovery of elements from solar panels, scientific advancements and improvements in industrial infrastructure are necessary along with the implementation of a regional logistics approach that minimizes emissions resulting from transportation. The bibliometric analysis indicates that 65% of the studies were published within the last 3 years, and one quarter of the trending keywords of this period is “recycling”. This is particularly relevant to show a major area for research in the solar industry. By means of the systematic analysis, this study compiles and synthetizes the most recent and relevant alternatives for managing end-of-life photovoltaic panels. The comprehensive overview of the impacts associated with these alternatives contributes to the literature and practice of sustainability in the energy sector, providing support for informed decisions directed towards implementation.

Heavy Metal Pollution in Gas Flare-Impacted Soils: An Assessment Using Pollution Indices in Obunagha, Bayelsa State, Nigeria

Gas flaring is the controlled burning of natural gas which occurs as a result of the activities of oil exploration and exploitation using flare stacks. In Nigeria, gas flaring activities is high and it mainly takes place in the Niger Delta region. The aim of this study was to investigate the bioavailability and concentration of heavy metals pollution of gas flare-impacted soils using pollution indices such as contamination factor, geo-accumulation index and pollution load index. Soil samples were collected with soil auger at depths of 0-15 cm from distances of 200 m, 500 m, 1000 m, 2000 m, and 3000 m away from the flaring point. Flame atomic absorption spectrometry was used to assess the presence of the following heavy metals in the soils: cadmium, chromium, nickel, zinc, copper, and manganese. The findings revealed that Fe (90% bioavailability) had the highest bioavailability among the metals tested in the soils, while Cr (45%) had the lowest. The metals bioavailability decreased in the order of Fe>Mn>Cu>Cd>Ni>Zn>Cr. The geo-accumulation index revealed that the soils were practically uncontaminated by Zn and Cu at all distances, moderately polluted by Cd and Ni at 1000 m and 2000 m and strongly polluted with Cd at a distance of 200 m. The Contamination factor results were consistent with the geo-accumulation index results. The pollutant load index (PLI) was found to be high but decreasing (1.37-0.49) as the distance from the flare point increased, indicating that the research region was polluted. In conclusion, the study's overall findings suggested that the soils were contaminated with heavy metals (particularly Cd) as a result of nearby gas flaring. As a result, the area must be appropriately monitored and managed to prevent future soil contamination by heavy metals to a level that is hazardous to human health.

Tracing Soil Contamination from Pre-Roman Slags at the Monte Romero Archaeological Site, Southwest Spain

Soil serves as a repository of human history, preserving artifacts within its horizons. However, the presence of chemically reactive remnants, such as ancient slags, can significantly impact the surrounding soil environment. This paper addresses this scarcely explored issue by focusing on soil contamination arising from pre-Roman slag deposits at the Monte Romero archaeological site in southwest Spain, dating back to the Tartessian period (c. 7th century BC). Through the high-resolution microscopy examination of slag wastes and the trace element analysis of soil samples by ICP-OES, this study evaluated current contamination status using a multi-index approach. The results revealed markedly high levels of Pb (>5000 mg kg−1), Cu (up to 2730 mg kg−1), and As (up to 445 mg kg−1) in the soil compared to a control sample. The identification of secondary complex compounds like Cu arsenates and Pb arsenates/antimonates within slag cavities suggests post-depositional weathering processes, leading to the dispersion of potentially toxic elements into the surrounding soil. Assessments through indices of contamination and potential ecological risk highlighted severe contamination, particularly concerning Ag, Pb, Sb, Cu, and As. This study underscores the importance of addressing potential environmental hazards associated with archaeological sites hosting remnants of metal production.