Assessing pollution degree and human health risks from hazardous element distribution in soils near gold mines in a Colombian Andean region: Correlation with phytotoxicity biomarkers.

The assessment of human health risk due to the presence of hazardous elements in the environment is now necessary for environmental management and legislative initiatives. This study aims to determine the contamination by As, Cd, Pb, and Cr in soils near gold mines in three municipalities located in the Andean region of Colombia. One of the main objectives of the study is to explore possible correlations between the Lifetime Cancer Risk (LCR) and phytotoxicity biomarkers using a simple and rapid-response plant model, radish (Raphanus sativus L.). In the municipality of Yalí, Puerto Berrío, and Buriticá, the hazardous elements concentrations ranged from 8.1 to 35.5, 1.7 to 892, and 5.8 to 49.8 for As, 0.1 to 4.6, 0.1 to 65.2, and 0.5 to 18.2 for Cd, 18.5 to 201.3, 13.0 to 1908, and 189 to 2345 for Pb, and 5.4 to 118.4, 65.4 to 301, and 5.4 to 102.3 for Cr, respectively. The results showed that the biomarkers intracellular H2O2 concentration, antioxidant activity, and radicle elongation exhibited significant (P < 0.05) variations associated with the concentration of hazardous elements in the soils. Significant correlations (P < 0.05, r > 0.58) were found between the biomarkers and the LCR for Cd, Pb, and Cr, but not for As. The results using biomarkers reveal that soil pH and organic matter content are important variables that control the bioavailability of these elements in the soil. The use of indicators like LCR alone has limitations and should be accompanied by the use of biomarkers that allow for a better understanding of the biological system's response to exposure to potentially toxic elements. The results obtained show the urgent need to implement public policies to minimize exposure to hazardous substances in areas near gold mining projects.

Combining anaerobic digestion slurry and different biochars to develop a biochar-based slow-release NPK fertilizer.

In this research, we developed a biochar-based fertilizer using biogas slurry and biochar derived from lignocellulosic agro-residues. Biogas slurry was obtained through the anaerobic digestion of the organic fraction of municipal solid waste (fresh vegetable biomass and/or prepared food), while biochars were derived from residues from quinoa, maize, rice, and sugarcane. The biochar-based fertilizers were prepared using an impregnation process, where the biogas slurry was mixed with each of the raw biochars. Subsequently, we characterized the N, P and K concentrations of the obtained biochar-based fertilizers. Additionally, we analyzed their surface properties using SEM/EDS and FTIR and conducted a slow-release test on these biochar-based fertilizers to assess their capability to gradually release nutrients. Lastly, a bioassay using cucumber plants was conducted to determine the N, P, and K bioavailability. Our findings revealed a significant correlation (r > 0.67) between the atomic O/C ratio, H/C ratio, cation exchange capacity, surface area, and the base cations concentration with N, P, and/or K adsorption on biochar. These properties, in turn, were linked to the capability of the biochar-based fertilizer to release nutrients in a controlled manner. The biochar-based fertilizer derived from corn residues showed <15 % release of N, P and K at 24 h. Utilization of these biochar-based fertilizers had a positive impact on the mineral nutrition of cucumber plants, resulting in an average increase of 61 % in N, 32 % in P, and 19 % in K concentrations. Our results underscore the potential of biochar-based fertilizers in controlled nutrient release and enhanced plant nutrition. Integration of biochar and biogas slurry offers a promising and sustainable approach for NPK recovery and fertilizer production in agriculture. This study presents an innovative and sustainable approach combining the use of biochar for NPK recovery from biogas slurry and its use as a biochar-based fertilizer in agriculture.

Phosphorus-Loaded Biochar-Assisted Phytoremediation to Immobilize Cadmium, Chromium, and Lead in Soils.

Soil contamination with heavy metals (HM) poses significant challenges to food security and public health, requiring the exploration of effective remediation strategies. This study aims to evaluate the remediation process of soils contaminated with Cd, Cr, and Pb using Lolium perenne assisted by four types of biochar: (i) activated coffee husk biochar (BAC), (ii) nonactivated biochar coffee husk (BSAC), (iii) activated sugar cane leaf biochar (BAA), and (iv) nonactivated biochar sugar cane leaf (BSAA). Biochar, loaded with phosphorus (P), was applied to soils contaminated with Cd, Cr, and Pb. L. perenne seedlings, averaging 2 cm in height, were planted. The bioavailability of P and heavy metals (HM) was monitored every 15 days until day 45, when the seedlings reached an average height of 25 cm. At day 45, plant harvesting was conducted and stems and roots were separated to determine metal concentrations in both plant parts and the soil. The study shows that the combined application of biochar and L. perenne positively influences the physicochemical properties of the soil, resulting in an elevation of pH and electrical conductivity (EC). The utilization of biochar contributes to an 11.6% enhancement in the retention of HM in plant organs. The achieved bioavailability of heavy metals in the soil was maintained at levels of less than 1 mg/kg. Notably, Pb exhibited a higher metal retention in plants, whereas Cd concentrations were comparatively lower. These findings indicate an increase in metal immobilization efficiencies when phytoremediation is assisted with P-loaded biochar. This comprehensive assessment highlights the potential of biochar-assisted phytoremediation as a promising approach for mitigating heavy metal contamination in soils.

Evaluation of different composting systems on an industrial scale as a contribution to the circular economy and its impact on human health.

Due to the production of volatile organic compounds (VOCs), large-scale composting can cause air pollution and occupational health issues. Due to this, it is necessary to determine if the amount generated poses a health risk to plant workers, which can be a starting point for those in charge of composting plant facilities. As a result, the goal of this work is to conduct a thorough analysis of both the physicochemical features and the VOC generation of three large-scale systems. For ten weeks, the three different composting plants were monitored weekly, and VOC identification and quantification were performed using GC-MS gas chromatography. It has been observed that the biggest risk related with VOC formation occurs between the fourth and fifth weeks, when microbial activity is at its peak. Similarly, it has been demonstrated that xylenes and toluene are the ones that are produced in the greatest quantity. Finally, after ten weeks of processing, it was discovered that the material obtained complies with the regulations for the sale of an amendment.Implications: The evaluation and monitoring of the composting processes at an industrial scale is very important, due to the implications they bring. VOCs are produced by the operation of composting facilities with substantial amounts of solid waste, such as the companies in this study. These may pose a health risk to those working in the plants; thus, it is critical to understand where the VOCs occur in the process in order to maintain workers' occupational health measures. This form of evaluation is rare or nonexistent in Colombia, which is why conducting this type of study is critical, as it will provide crucial input into determining when the highest levels of VOC generation occur. These are the ones that may pose a risk at some point, but with proper occupational safety planning, said risk may be avoided. This work has evaluated three composting systems, with different types of waste and mixtures. According to reports, while composting systems continue to produce VOCs and their generation is unavoidable, the potential risk exists only within the plant. These findings can pave the way for the implementation of public policies that will improve the design and operation of composting plants. There is no specific legislation in Colombia for the design and execution of this sort of technology, which allows the use of organic waste.

Changes in Lolium perenne L. rhizosphere microbiome during phytoremediation of Cd- and Hg-contaminated soils.

The contamination of soil and water by metals such as mercury (Hg) and cadmium (Cd) has been increasing in recent years, because of anthropogenic activities such as mining and agriculture, respectively. In this work, the changes in the rhizosphere microbiome of Lolium perenne L. during the phytoremediation of soils contaminated with Hg and Cd were evaluated. For this, two soil types were sampled, one inoculated with mycorrhizae and one without. The soils were contaminated with Hg and Cd, and L. perenne seeds were sown and harvested after 30 days. To assess changes in the microbiome, DNA isolation tests were performed, for which samples were subjected to two-step PCR amplification with specific 16S rDNA V3-V4 primers (337F and 805R). With mycorrhizae, changes had been found in the absorption processes of metals and a new distribution. While with respect to microorganisms, families such as the Enterobacteriaceae have been shown to have biosorption and efflux effects on metals such as Hg and Cd. Mycorrhizae then improve the efficiency of removal and allow the plant to better distribute the absorbed concentrations. Overall, L. perenne is a species with a high potential for phytoremediation of Cd- and Hg-contaminated soils in the tropics. Inoculation with mycorrhizae modifies the phytoremediation mechanisms of the plant and the composition of microorganisms in the rhizosphere. Mycorrhizal inoculation and changes in the microbiome were associated with increased plant tolerance to Cd and Hg. Microorganism-assisted phytoremediation is an appropriate alternative for L. perenne.

Remediation of Pb-contaminated soil using biochar-based slow-release P fertilizer and biomonitoring employing bioindicators.

Soil contamination by Pb can result from different anthropogenic sources such as lead-based paints, gasoline, pesticides, coal burning, mining, among others. This work aimed to evaluate the potential of P-loaded biochar (Biochar-based slow-release P fertilizer) to remediate a Pb-contaminated soil. In addition, we aim to propose a biomonitoring alternative after soil remediation. First, rice husk-derived biochar was obtained at different temperatures (450, 500, 550, and 600 °C) (raw biochars). Then, part of the resulting material was activated. Later, the raw biochars and activated biochars were immersed in a saturated KH2PO4 solution to produce P-loaded biochars. The ability of materials to immobilize Pb and increase the bioavailability of P in the soil was evaluated by an incubation test. The materials were incorporated into doses of 0.5, 1.0, and 2.0%. After 45 days, soil samples were taken to biomonitor the remediation process using two bioindicators: a phytotoxicity test and enzyme soil activity. Activated P-loaded biochar produced at 500 °C has been found to present the best conditions for soil Pb remediation. This material significantly reduced the bioavailability of Pb and increased the bioavailability of P. The phytotoxicity test and the soil enzymatic activity were significantly correlated with the decrease in bioavailable Pb but not with the increase in bioavailable P. Biomonitoring using the phytotoxicity test is a promising alternative for the evaluation of soils after remediation processes.

Assessment of the application of two amendments (lime and biochar) on the acidification and bioavailability of Ni in a Ni-contaminated agricultural soils of northern Colombia.

Soil acidification and increased bioavailability of Ni are problems that affect agricultural soils. This study aims to compare the effects of both lime and biochar from corn stover in soil acidity correction, improving soil physicochemical properties and soil re-acidification resistance. As well as assesseing the impacts on human health risk caused by bioavailability of nickel. A greenhouse pot experiment was conducted for 30 days to determine the effect of biochar and lime on soil physicochemical properties and nickel bioavailability. Afterwards, a laboratory test was carried out to determine the repercussions of both amendments on soil resistance to re-acidification and re-mobilization of nickel. Human health risk was determined using nickle bioavailable concentration. Overall, the results of this study showed that biochar application significantly reduced soil acidity from 8.2 ± 0.8 meq 100 g-1 to 1.9 ± 0.3 meq 100 g-1, this reduction markedly influenced the bioavailability of nickel, which decreased significantly. Moreover, soil physicochemical properties and soil resistance to acidification were improved. Furthermore, biochar significantly reduced human health risk compared to lime application, even under a re-acidification scenario. It was possible to verify that Ni immobilization in the soil was increased when biochar was used. Soil Ni immobilization is associated with co-precipitation and chemisorption. Hence, it was demonstrated that biochar is more effective than lime in reducing soil acidity and remedying nickel-contaminated agricultural soils.

Reducing cadmium bioaccumulation in Theobroma cacao using biochar: basis for scaling-up to field.

The intake of Cd-enriched food is the main Cd pathway for the nonsmoking population. In some cases, Cd bioaccumulates in edible plant parts which comprise risk to consumers, because of Cd is a harmful heavy metal that can cause potent environmental and health hazards. For instance, Cd enrichment of cacao seeds have led to Cd enrichment of cacao-based products. In Latin America and the Caribbean, Cd bioaccumulation in cacao seeds occurs in different regions with diverse edaphoclimatic conditions, which makes it difficult to select soil remediation alternatives. Limited resources require that potential amendments must be carefully investigated through laboratory and/or greenhouse conditions before scaling up to field experiments. In this study, we evaluated the effectiveness of four biochars: coffee-, quinoa-, and inoculated- and palm-biochar, derived from three feedstocks: coffee husk, quinoa straw, and oil palm residues, respectively. Biochars were applied in two rates (1 and 2% w/w) in two soils, one moderately acidic and one slightly alkaline (Cd-spiked and non-spiked). CCN-51 cacao plants were used for the greenhouse experiment. After 130 days, biometric parameters, the bioavailability of Cd in the soil, and the concentration of Cd and mineral nutrients in the plants were measured. Quinoa biochar at the 2% significantly decreased (P < 0.01), by ∼71%, bioavailable Cd in moderately acidic and slightly alkaline soils, and leaf-Cd by ∼48%. Soil pH, electrical conductivity, and effective cation exchange capacity were significantly (P < 0.01) correlated with bioavailable soil and leaf-Cd. Biochar characteristics, such as ash contents, basic cations content, and surface functional groups could be used as indicators for the selection of biochars to reduce Cd uptake by cacao. Additionally, application of quinoa derived biochar provided P and K, which could increase productivity to offset mitigation costs. Overall, incorporation of quinoa biochar at 2% rate is effective for lowering bioavailable Cd in different soil types which reduces leaf-Cd in cacao plants.

Use of biochar from rice husk pyrolysis: assessment of reactivity in lime pastes.

Biochar has unique properties such as its porous structure, specific surface area, and stable chemical properties. The rice husk is characterized by its high content of silica, and that during the pyrolysis process it generates a considerable amount of biochar that can be used in different processes. The aim of this work is to evaluate several biochars from the pyrolysis process in the reactivity of lime pastes. For this, biochar has been obtained at four different temperatures (450, 500, 550 and 600 °C), and they have been characterized by XRF, XRD, ICP-EOS, and particle size distribution, to determine their phases and their chemical composition. Biochar has been replaced in lime pastes in different proportions (5, 10, 15, 20, 25 and 30%), and exposed to different curing times (1, 3, 7, 14, 28, 56, 90 and 180 days). It has been found that all the replacements show reactivity within the lime pastes and that the percentage of 25% in all the biochar tested could be an adequate replacement.

Assessment of the potential risk of leaching pesticides in agricultural soils: study case Tibasosa, Boyacá, Colombia.

Agricultural soils need monitoring systems to address pesticide risks for humans and the environment. The purpose of this paper was to obtain leaching risk maps of the pesticides imidacloprid, lambda-cyhalothrin, and chlorpyrifos in agricultural soil under an onion (Allium cepa L.) crop in Tibasosa, Boyacá, Colombia. This was obtained by studying the soil types in the area, analyzing the behavior of pollutants in the soil profile, using a delay factor and an attenuation factor to finally include GIS allowing visualization of the areas of greater potential risk in the study area.

Preliminary study of the production of metabolites from in vitro cultures of C. ensiformis.

BACKGROUND: Canavalia ensiformis is a legume native to Central and South America that has historically been a source of protein. Its main proteins, urease, and lectin have been extensively studied and are examples of bioactive compounds. In this work, the effect of pH and light effects on the growth of C. ensiformis were analyzed. Also, the bioactive compounds such as phenols, carotenoids, chlorophyll a/b, and the growth of callus biomass of C. ensiformis from the effect of different types of light treatments (red, blue and mixture) were evaluated. Likewise, the antioxidative activity of C. ensiformis extracts were studied and related to the production of bioactive compounds. For this, a culture of calluses obtained from seeds were carried out. For the light experiments, polypropylene boxes with red, blue, combination (1/3, 3/1 and 1/1 R-B, respectively) lights and white LED were used as control. In each treatment, three glass containers with 25 ml of MS salts containing 0.25 g of fresh callus were seeded. RESULTS: The results have shown that the pH of the culture medium notably affects the increase in callogenic biomass. It shows that the pH of 5.5 shows better results in the callogenic growth of C. ensiformis with an average increase of 1.3051 g (198.04%), regarding the initial weight. It was found that the pH 5.5 and the 1/3 R-B LED combination had higher production of bioactive compounds and better antioxidant activity. At the same time, the red-light treatment was least effective. CONCLUSIONS: It was possible to find the ideal conditions of important growth under conditions of pH and light of C. ensiformis. Likewise, it is evaluated whether the production of compounds of interest, such as phenolic compounds and carotenoids, occurs under these conditions. The highest production of calluses occurs in the 1/3 R-B LED combined light treatment, which showed a significant increase in biomass, followed by B. From this study, it could be demonstrated that C. ensiformis produces compounds such as phenols and carotenoids in vitro culture that are essential for the antioxidant activity of the plant.