Chemical Extraction Research Articles

Comprehensive evaluation of bioavailable phosphorus in biochar synthesized by co-pyrolysis of sewage sludge and straw ash

The world's phosphorus (P) resources are gradually depleting. Sewage sludge is an important secondary P resource, and sludge-derived biochar for land use is an effective way to achieve P recovery. However, P in biochar synthesized by direct pyrolysis of sludge usually shows comparatively low bioavailability. In this study, biomass ash from different types of straw was used as an additive for co-pyrolysis with sludge. The distribution of different P fractions in the obtained co-pyrolyzed biochar was investigated. The P bioavailability of the co-pyrolyzed biochar was comprehensively evaluated by three methods, including chemical extraction, diffusive gradients in thin films (DGT) technology and pot experiments. The results indicate that the bioavailable P in co-pyrolyzed biochar is significantly positively correlated with the contents of K, Ca, and Mg elements in straw ash, which facilitate the transformation of P in sludge into forms that are more easily utilized by plants, including monetite (CaHPO4), hydroxyapatite (Ca5(PO4)3OH) and pyrocoproite (K2MgP2O7). Moreover, pot experiments show that the P contents in ryegrass shoots and roots cultivated in co-pyrolyzed biochar-added soils increased by 11.98–114.97 % and 28.90–69.70 %, respectively, compared to the control soil. The DGT technology could better reflect the uptake of P by plants with a Pearson correlation coefficient as high as 0.94. This study provides references for P resource recovery, and the collaborative reutilization of sewage sludge and straw ash.

Genetic and phenotypic validation of whole body fat content measured across production phases of Atlantic salmon using dielectric and near infrared Interactance spectroscopy

Accurate and repeated whole-body fat (WBF) measurements across production phases are important for optimizing feed utilization, reducing production waste, safeguarding fish health, ensuring product quality and improving overall salmon production. However, the chemical extraction (reference) methods for WBF recording, although precise and accurate, are costly, destructive and have limited applicability for repeated measurements on live fish. This study validates two digital phenotyping technologies: Dielectric spectroscopy (DS) and Near-infrared spectroscopy (NIR) against the reference Soxhlet chemical extraction method. DS is a fast and non-destructive commercial fat meter, whereas the specially designed NIR interactance allows deep penetration (up to 10 mm) through the fish skin into the body. Approximately 2800 fish belonging to 35 full sibs fish families were recorded for WBF at mean body weight (BW) of ∼110, 300 and 750 g in parr, pre-smolt and post-smolt phases, respectively. The WBF percentage changed across the studied production phases: with parr having a mean of 11.3 % and coefficient of variation (CV = 11 %), pre-smolt decreasing slightly in both mean 10.9 – 11.1 % and CV (5.5 – 8.8 %) and post-smolt with an increase to 14.9 % and CV (8.5 %). Both methods performed well relative to the reference, with NIR (R2 = 0.77 – 0.91) slightly outperforming the DS (R2 = 0.61 – 0.71). Significantly high genetic estimates for NIR (h2 = 0.57 ± 0.04 – 0.62 ± 0.06) and DS (h2 = 0.38 ± 0.07 – 0.56 ± 0.10) signify the potential use of these digital technologies for improving WBF in future selective breeding. The low genetic correlations (rg = 0.22 ± 0.13 – 0.33 ± 0.14) across fresh and seawater phases raise questions about the generalizability of metabolic, lipid and feed efficiency research conducted in parr and pre-smolt phases in freshwater, to the post-smolt stage in seawater. The study highlighted the unexplored detail of the genetic regulation of WBF as fish undergoes production phases. Overall, these results will add to our understanding of genetic architecture for WBF and pave the way for digital phenotyping technologies to record complex but economically important traits and refine breeding strategies.

The Chemical Structure, Extraction Method, and Biological Activity of Lignin–Carbohydrate Complexes

The Chemical Structure, Extraction Method, and Biological Activity of Lignin–Carbohydrate Complexes

Extraction technology determines the properties of bamboo shoots dietary fiber concentrate and its application in chicken mince gels: Systematic analysis

This study investigated how physical, chemical, and enzymatic extraction technologies affected the physicochemical properties of bamboo shoot insoluble dietary fiber (IDF). Additionally, the effects of IDF extracted by these techniques on the gel properties, water retention, microstructure, and digestibility of chicken mince gels were evaluated. Results showed that IDFs extracted by physical (P-IDF), chemical (C-IDF), and enzymatic (E-IDF) exhibited a typical cellulose polysaccharide structure and strong water and oil retention capabilities, with the highest values reaching 14.18 g/g and 6.74 g/g, respectively. Compared to P-IDF, C-IDF and E-IDF displayed a rougher porous structure and stronger adsorption capacities for glucose (409.91 mg/g and 604.95 mg/g), cholesterol (54.46 mg/g and 64.06 mg/g), sodium cholate, and nitrite. The addition of IDF improved the water retention, water stability, texture, and rheological properties of chicken mince gels, and had no negative effect on the digestion of chicken mince proteins. On the one hand, the hydrophilic groups exposed in IDF absorb water and fill the gel networks, reducing the formation of water channels in the gel and improving water stability. Furthermore, the hydrophilic groups on the glucose unit that makes up the IDF interacts with the proteins through the hydrogen bond and the transformation of protein β-structure to α-structure, promoting the formation of gel network structure and improving gel texture and rheological properties. E-IDF and C-IDF showed better overall gel performances, but E-IDF had better dry matter digestibility, protein digestibility, and gastrointestinal digestive effects. Therefore, IDF prepared by enzymatic hydrolysis is more suitable for chicken mince processing.

304L Austenitic Stainless Steel Corrosion Studies in Neutral Environment in Presence of Sulfite Ions

Abstract This paper examined the influence of the sulfite concentration introduced in the electrolyte added to the neutral solution (1 mol L-1 Na2SO4) on the corrosion process of 304L stainless steel material. 304L. The accelerated effect of sulfite ions under corrosion rate of 304L austenitic stainless steel was demonstrated using electrochemical techniques such as linear sweep voltammetry at a low scan rate −1 mV s−1, the Tafel slope method, chronoamperometry, and electrochemical impedance spectroscopy. Electrochemical studies were conducted using a BioLogic SP150 potentiostat/galvanostat. Stainless steels are the most varied and intricate group among all steels. Among them, 304L austenitic stainless steel is one of the most commonly utilized alloys, prized for its excellent corrosion resistance and strength, hygienic and aesthetic properties, affordability, good formability, and effective weldability. [1-3]. In modern industry, the amount of austenitic stainless steel represents only about 2% of the total steel production manufactured globally. This type of steel is commonly employed in chemical engineering, metal extraction, desalination and wastewater treatment plants, the oil and gas sector, transportation and aerospace industries, the food and beverage sector, as well as in architecture and construction engineering. [1].

Time-dependent redistribution of soil arsenic induced by transformation of iron species during zero-valent iron biochar composites amendment: Effects on the bioaccessibility of As in soils

Zero-valent iron biochar composites (ZVI/BC) are considered as effective amendments for arsenic (As)-contaminated soils. However, the mechanisms of transformation of various soil As species during ZVI/BC amendments remain unclear. This study investigated As transformation in four soils (namely, GX, ZJ, HB, and HN) treated with ZVI/BC for 65 days under two soil moisture conditions, unsaturated and oversaturated. Results showed that the 65-day treatment was divided into two stages based on the variation of labile As content. Within 2 days (stage 1), ZVI/BC addition quickly reduced labile As content by 5.91–90.3 % in soils under unsaturated conditions. During days 2–65 (stage 2), labile As ultimately decreased by 0.06–0.31 mg/kg in GX, ZJ, and HB while increasing by 22.1 mg/kg in HN soil, due to its lower pH value and Fe content. The variations of labile As were attributed to changes in multiple Fe minerals and associated As species. In stage 1, the corrosion of ZVI/BC generated amorphous Fe oxides to immobilize labile As, resulting in the accumulation of meta-stable As. In stage 2, amorphous Fe oxides were transformed into crystalline Fe oxides, resulting in the release and re-precipitation of As along with transformation, thus redistributing immobilized As into labile and stable As, which was evidenced by multiple methods, including chemical extraction, XRD, and TEM-EDX. The elevated soil moisture condition would enhance the corrosion of ZVI/BC in stage 1, further forming a reductive environment to facilitate the transformation of Fe minerals in stage 2. Besides, As bioaccessibility in soils was reduced by 10.8–38.7 % after ZVI/BC treatment in in-vitro gastrointestinal simulations. Overall, our study revealed the time-dependent transformation mechanism of soil As species and associated Fe minerals under different soil moisture with ZVI/BC treatments, and highlighted the effectiveness of ZVI/BC as a long-term amendment for As-contaminated soils.

De novo biosynthesis of β-Arbutin in Komagataella phaffii based on metabolic engineering strategies

Backgroundβ-Arbutin, found in the leaves of bearberry, stands out as one of the globally acknowledged eco-friendly whitening additives in recent years. However, the natural abundance of β-Arbutin is low, and the cost-effectiveness of using chemical synthesis or plant extraction methods is low, which cannot meet the requirements. While modifying the β-Arbutin synthesis pathway of existing strains is a viable option, it is hindered by the limited synthesis capacity of these strains, which hinders further development and application.ResultsIn this study, we established a biosynthetic pathway in Komagataella phaffii for β-Arbutin production with a titer of 1.58 g/L. Through diverse metabolic strategies, including fusion protein construction, enhancing shikimate pathway flux, and augmenting precursor supplies (PEP, E4P, and UDPG), we significantly increased β-Arbutin titer to 4.32 g/L. Further optimization of methanol concentration in shake flasks led to a titer of 6.32 g/L titer after 120 h of fermentation, representing a fourfold increase over the initial titer. In fed-batch fermentation, strain UA3-10 set a record with the highest production to date, reaching 128.6 g/L in a 5 L fermenter.ConclusionsThis is the highest yield in the fermentation tank level of using microbial cell factories for de novo synthesis of β-Arbutin. Applying combinatorial engineering strategies has significantly improved the β-Arbutin yield in K. phaffii and is a promising approach for synthesizing functional products using a microbial cell factory. This study not only advances low-cost fermentation-based production of β-Arbutin but also establishes K. phaffii as a promising chassis cell for synthesizing other aromatic amino acid metabolites.Graphical abstract

A guidance for the enrichment of micropollutants from wastewater by solid-phase extraction before bioanalytical assessment

BackgroundWastewater can contain a complex mixture of organic micropollutants, with both chemical analysis and effect-based methods needed to identify relevant micropollutants and detect mixture effects. Solid-phase extraction (SPE) is commonly used to enrich micropollutants prior to analysis. While the recovery and stability of individual micropollutants by SPE has been well studied, few studies have optimized SPE for effect-based methods. The aim of the current study was to develop and evaluate two standard operating procedures (SOPs) for the enrichment of micropollutants in preparation for chemical analysis and bioanalysis, one covering a broad range of chemicals and the other selective for estrogenic chemicals.ResultsPristine surface water spiked with > 600 micropollutants was used to develop a generic extraction method for micropollutants with a wide range of physiochemical properties, while water spiked with estrogenic chemicals was used to identify a selective extraction method. Three different SPE sorbents were tested, with recoveries of individual chemicals and effect in assays indicative of mutagenicity, estrogenic activity, and fish embryo toxicity assessed. The sorbent HRX at pH 7 was selected for the generic extraction method as it showed the best recovery of both individual chemicals and effect in the bioassays. The sorbent HLB at pH 3 showed optimal recovery of estrogenic chemicals and estrogenic activity. The two optimal SPE methods were applied to spiked and unspiked wastewater effluents, with the concentrations of detected chemicals and observed effects similar to those of previous studies. The long-term storage of both extracts and SPE cartridges for estrogens and estrogenic activity after extraction with the HRX and HLB methods were evaluated, with estrogenic effectiveness close to 100% after 112 days when HLB was used.ConclusionsHRX is recommended for generic extraction, while HLB is optimal for the selective extraction of estrogenic micropollutants. However, if a laboratory only wants to use a single SPE sorbent, HLB can be used for both generic and selective extraction as it yielded similar chemical and effect recovery as HRX for a wide range of micropollutants. This paper is supplemented by the final SOP that includes a variant for generic extraction and one for the extraction of estrogenic chemicals.

Biogeochemical process governing cadmium availability in sediments of typical coastal wetlands driven by drying-wetting alternation

Fluctuations in water levels within coastal wetlands can significantly affect cadmium (Cd) cycling and behavior in sediments. Understanding the effects of drying-wetting cycles on Cd availability and binding mechanisms is crucial. However, information regarding this subject remains limited. This study conducted incubation experiments employing chemical extraction, high-resolution mass spectrometry, and microbiological analysis to investigate the Cd behavior under these conditions. The results from a 40-day anaerobic incubation followed by a 20-day aerobic phase indicated that the drying-wetting cycles triggered fluctuations in physicochemical parameters (e.g., pH, EC, and reactive iron (Fed)), affecting Cd mobility. The mobility of Cd was closely linked to nanozyme activity (R2=0.63), exhibiting a strong correlation with Fed (R2=0.51). This suggested that the drying-wetting cycles induced Fed changes, which regulated the nanozyme activity, thereby affecting Cd availability. The changes in Cd availability were strongly linked to transformations in iron oxides and organic functional groups (carboxylic-OH and aliphatic C-H), whereas the bacterial community composition, particularly Bacilli and Clostridia, notably influenced Cd accessibility. These findings offer valuable insights into the geochemical dynamics of Cd in coastal wetland sediments under alternating drying-wetting cycles, enhancing our understanding of its biogeochemical cycling and potential risks.

EUPHORBIA CERIFERA CERA (CANDELILA) EMOLLIENT PROPERTIES, USES AND EFFECTIVENESS IN SKINCARE PRODUCTS

Candelila wax, derived from Euphorbia cerifera cera, is a natural and sustainable component that has a wide range of uses in cosmetic products. This review article explores the chemical composition, extraction techniques, and attributes of Candelila wax, with a focus on its distinctive qualities that make it highly useful in the cosmetic business. Candelila wax has been extensively studied and researched, and these studies have shown that it is highly useful in skincare. It has been found to provide significant benefits in terms of moisturizing the skin, protecting it, and improving the function of the skin barrier. The emollient and moisturizing qualities of this substance enhance skin hydration, while its film-forming capacity creates a protective barrier against environmental stresses. In addition, the non-comedogenic properties and potential anti-inflammatory effects of Candelila wax make it highly suitable for a range of skin types, including those that are sensitive or prone to acne. The future outlook for Candelila wax in cosmetics entails investigating the potential benefits of combining it with other natural substances, creating new and advanced methods of delivering it, and embracing sustainable methods of sourcing and processing. By conducting meticulously planned clinical trials, the effectiveness and safety of the substance may be verified, thereby establishing robust scientific proof for its use in skincare products. By recognizing the possibilities of Candelila wax, we may explore environmentally responsible and skin-conscious cosmetic procedures that align with the changing tastes of mindful customers. By utilizing the potent properties of this natural substance, the cosmetic industry can lead the path towards a more environmentally friendly and enduring future in the field of skincare products.

Effect of environmental factors on the mechanism of arsenic release from clay layers during natural compaction

Clay layers are presumed sources of original arsenic (As) in the groundwater of underlying aquifers. However, studies have focused less on the release mechanism of As from clay layers compared to well-studied As release from aquifers, especially during the natural compaction process of clay layers and its role in As mobilization. Herein, simulation experiments of the natural compaction of clay layers were performed at different compaction rates and temperatures. Hydrochemistry, parallel chemical extraction, and high-throughput sequencing of the full-length 16S rRNA gene were employed to investigate the release mechanism of As from clay layers during compaction. While the compaction rate and temperature were found to promote the release of As from clay sediments, increasing the compaction rate caused As to enter pore water through reductive dissolution from crystalline iron (hydr)oxides to ferrihydrite and very poorly crystalline goethite; Meanwhile, temperature increment only increased the microbial activity and did not alter the release mechanism of As. When the natural burial rate of clay layers was altered, the compaction rate has greater effect than temperature on As release from clay sediments.. Under natural compaction, the concentration of As transported to the groundwater by clay layers was found to be 43.58–116.70 μg/L. These results suggested that the contribution of the natural compaction of As-rich clay layers to the formation of high As groundwater in aquifers is underestimated.

Physical Cell Disruption Technologies for Intracellular Compound Extraction from Microorganisms

This review focuses on the physical disruption techniques in extracting intracellular compounds, a critical step that significantly impacts yield and purity. Traditional chemical extraction methods, though long-established, face challenges related to cost and environmental sustainability. In response to these limitations, this paper highlights the growing shift towards physical disruption methods—high-pressure homogenization, ultrasonication, milling, and pulsed electric fields—as promising alternatives. These methods are applicable across various cell types, including bacteria, yeast, and algae. Physical disruption techniques achieve relatively high yields without degrading the bioactivity of the compounds. These techniques, utilizing physical forces to break cell membranes, offer promising extraction efficiency, with reduced environmental impacts, making them attractive options for sustainable and effective intracellular compound extraction. High-pressure homogenization is particularly effective for large-scale extracting of bioactive compounds from cultivated microbial cells. Ultrasonication is well-suited for small to medium-scale applications, especially for extracting heat-sensitive compounds. Milling is advantageous for tough-walled cells, while pulsed electric field offers gentle, non-thermal, and highly selective extraction. This review compares the advantages and limitations of each method, emphasizing its potential for recovering various intracellular compounds. Additionally, it identifies key research challenges that need to be addressed to advance the field of physical extractions.

Analysis of mercury fractions in the fine grains of surface sediments in the Changjiang Estuary wetlands using thermodesorption and chemical extraction methods

Analysis of mercury fractions in the fine grains of surface sediments in the Changjiang Estuary wetlands using thermodesorption and chemical extraction methods

Simultaneous rare earth sulfate transformation and carbon dioxide mineralization

The wet metallurgical process route for recovering rare earth elements usually uses sulfuric acid. To obtain marketable individual rare earth products, converting rare earth sulfates to chlorides is essential. Conventional chemical precipitation and solvent extraction methods result in significant amounts of ammonia wastewater and greenhouse gas emissions. Therefore, we propose a novel process that integrates CO2 mineralization with rare earth sulfates transformation. By utilizing a base-catalyzed mechanism with trioctylamine (TOA), CO2 is effectively employed for selective precipitation of more than 95 % of rare earths from magnesium and calcium under optimized conditions. Subsequently, dissolution in hydrochloric acid allows for enrichment of the concentration of rare earths up to 188.3 g/L. The reaction mechanism is examined through Visual MINTEQ simulations and various analytical techniques. This process not only offers a sustainable approach to rare earth sulfates transformation but also contributes to carbon capture, utilization, and sequestration efforts.

Tracking chemical feature releases from plastic food packaging to humans

Humankind are being exposed to a cocktail of chemicals, such as chemicals released from plastic food packaging. It is of great importance to evaluate the prevalence of plastic food packaging-derived chemicals pollution along the flow of food-human. We developed a robust and practical database of 2101 chemical features associated with plastic food packaging that combined data from three sources, 925 of which were acquired from non-target screening of chemical extracts from eight commonly used plastic food packaging materials. In this database, 625 features, especially half of the non-targets, were potential migrants who likely entered our bodies through dietary intake. Biomonitoring analysis of plastic chemical features in foodstuffs or human serum samples showed that approximately 78 % of the 2101 features were detectable and approximately half were non-targets. Of these, 17 plastic chemicals with high detection frequencies (DFs) in the human serum were confirmed to be functional chemical additives. Together, our work indicates that the number of plastic chemicals in our bodies could be far greater than previously recognized, and human exposure to plastic chemicals might pose a potential health risk.

Effect of carboxymethylated chitosan and cellulose acetate on mechanical properties of PLA blends for biomedical applications

Chitin and chitosan are versatile and valuable biomaterials, with chitosan being abundantly found in the exoskeletons of crustaceans, insects, arthropods, and mollusks. The chemical extraction of chitin involves a series of steps, including deproteinization, demineralization, and decolorization. Chitosan is often combined with various polymeric materials, and polymer blending can enhance the mechanical properties of the resulting bioproduct. In this study, composites of poly(lactic acid) (PLA) with chitosan (Ch) and cellulose acetate (CA) were successfully fabricated using extrusion and injection molding techniques. The chitosan content, ranging from 0 to 7.5 wt. %, was incorporated into the PLA matrix to assess the impact of filler content on the mechanical and morphological properties of the composites. The chitosan powder was first alkalized and then etherified to obtain modified chitosan, specifically o-carboxymethylated chitosan (O-CMCh). The addition of chitosan led to a reduction in tensile strength, flexural strength, modulus of elasticity, and impact strength. However, the hardness of the composite improved with the inclusion of chitosan. The mesoporous structure of chitosan was characterized using nitrogen adsorption and desorption measurements. Morphological analysis revealed that the composite containing 3.75 wt. % chitosan exhibited significantly less fracture surface compared to other composites.

Non-destructive estimation of flesh oil content in avocado (Persea americana Mill.) using fluorescence images from 365-nm UV light excitation.

The flesh oil content (OC) is a crucial commercial indicator of avocado maturity and directly correlates with its nutritional quality. To meet export standards and optimize edible characteristics, avocados must be harvested at the appropriate stage of physiological maturity. The significant variability in OC during maturation, without any external morphological indicators, poses a longstanding challenge. Currently, harvesting maturity is optimized through time-consuming, destructive laboratory methods like freeze-drying and chemical extraction, which use representative samples to estimate the maturity of entire orchards. In this study, for the first time, we employed fluorescence imaging of avocado skin using 365-nm UV polarized light excitation to estimate the OC in the 'Bacon' avocado cultivar. We developed a surface fluorescence index that strongly correlates with OC, achieving correlation coefficients up to -0.91. Our non-destructive and rapid approach achieved a cross-validation accuracy with an R2 value of 0.81, enabling the classification of avocados with low and high OC. This pioneering method shows considerable potential for further improvement and refinement. This study lays the groundwork for developing a portable, cost-effective, and real-time method for non-destructive in situ monitoring of avocado OC in the field and its integration into large-scale post-harvest grading systems.

From β-Carotene to Retinoids: A Review of Microbial Production of Vitamin A.

Vitamin A (retinoids) is crucial for human health, with significant demand across the food, pharmaceutical, and animal feed industries. Currently, the market primarily relies on chemical synthesis and natural extraction methods, which face challenges such as low synthesis efficiency and complex extraction processes. Advances in synthetic biology have enabled vitamin A biosynthesis using microbial cell factories, offering a promising and sustainable solution to meet the increasing market demands. This review introduces the key enzymes involved in the biosynthesis of vitamin A from β-carotene, evaluates achievements in vitamin A production using various microbial hosts, and summarizes strategies for optimizing vitamin A biosynthesis. Additionally, we outline the remaining challenges and propose future directions for the biotechnological production of vitamin A.

Technologies of the Integrated Development of Hydrogeothermal Resources of the North Caucasian Region

This paper focuses on the technologies of the integrated development of high-parametric geothermal brines with steam release. They differ from each other depending on initial parameters. Such way of brine utilization will make it possible to transform thermal energy to electrical power along with significant increasing its salinity that contributes to chemical components extraction. The opportunity is considered of this technology application in the Tarumovka geothermal field with electric power generation in steam-turbine and binary power plants, and consequent obtaining valuable mineral components. The geothermal and biogas technologies are given proposing integrated utilization of thermal water for various applications. Such systems make it possible to use resource potential of geothermal well and biomass that will result in improvement of economic and environmental situation in the North Caucasus region.

Impact of climatic seasons on the dynamics of carbon, nitrogen and mercury in soils of Brazilian biomes affected by gold mining

Land use change, especially mining activities, contributes to anthropic CO2 emissions, leading to decreased carbon (C) storage and loss of biodiversity. Artisanal gold mining associated with the use of mercury (Hg) for amalgamation may change soil organic matter (SOM) contents, and the release of Hg into the environment generates serious environmental problems. Changes in soil biogeochemistry due to C loss and seasonal climate fluctuations affect Hg dynamics and can either increase or decrease its availability. Therefore, our objective was to evaluate the impact of mining on SOM and Hg geochemistry in four Brazilian biomes. We evaluated the dynamics of C and Hg in the dry and rainy seasons of mining and pasture areas by combining spectroscopic, thermogravimetric, and chemical extraction. The critical role of SOM in Hg retention and the influence of climatic seasons on C and nitrogen (N) stocks were highlighted, along with the availability of Hg in solution. Key findings indicated a 50 % reduction in soil C stocks in mined areas, exacerbated during dry seasons, which also saw up to a 70 % increase in bioavailable Hg. SOM played a critical role in Hg retention, with Hg availability closely linked to soil C stability. These results highlight the environmental degradation linked to mining and suggest strategies to mitigate these impacts by increasing SOM and immobilizing Hg. Amalgamation of gold directly into ore, as in the Amazon, has generated great soil Hg stocks, while Hg availability appeared to be governed by soil C stability. This information can serve as a basis for choosing strategies to mitigate environmental degradation caused by changes in land use in mining activities to promote increase in SOM and to immobilize Hg contents.