Soil microbial communities are crucial to ecosystem functionality, influencing soil fertility and health. Microbial diversity in soil is impacted by various land-use practices and environmental conditions, but the effects on both prokaryotic and eukaryotic communities remain insufficiently understood. This study investigates the influence of different land-use types and soil chemical properties on the composition and diversity of prokaryotic and eukaryotic microbes using next-generation sequencing (NGS). Soil samples were collected from seven distinct locations in South Korea, representing various land uses, including paddy fields, upland fields, forest areas, hydrocarbon- and heavy-metal-contaminated sites, greenhouse soils, and reclaimed tidal soils. Alpha diversity, assessed using Chao1 and Shannon indices, and beta diversity, evaluated through Bray-Curtis dissimilarity and Principal Coordinates Analysis (PCoA), were used to characterize microbial diversity. Soil chemical properties were analyzed, and their relationships with microbial community structure were examined. Results revealed significant variations in both prokaryotic and eukaryotic diversities across different land uses. Soils under conventional agricultural management (paddy and upland fields) showed higher microbial diversity compared to soils with high salinity, contamination, or low suitability for agriculture. Prokaryotic communities were dominated by Proteobacteria, Chloroflexi, Acidobacteria, and Bacteroidetes, with variations in abundance linked to soil condition and quality. Eukaryotic communities predominantly consisted of Opisthokonta, SAR (Stramenopiles, Alveolates and Rhizaria), and Amoebozoa, with distinct abundance patterns across different soils. In conclusion, land-use practices and soil chemical properties significantly influence microbial diversity and community composition. Soils subjected to less stress, e.g., agricultural soils, exhibited higher microbial diversity, while stressed soils, e.g., contaminated and saline soils, showed reduced diversity. These findings emphasize the importance of understanding the interplay between land management and microbial ecology for optimizing soil fertility and health.

Anionic surfactants (AS) are becoming a major emerging contaminant of waters due to their widespread use in household and industrial products. The standard chloroform method for analysis of AS in water relies on chloroform extraction of a methylene blue active substance (MBAS), which contains ion pairs between methylene blue (MB) molecules (positively charged) and AS. Due to the poor extractability of chloroform, the procedure is complicated, time-consuming, and subject to anionic interferences. A mixture of methyl isobutyl ketone (MIBK)–1,2-dichloroethane (DCE) at a 3:1 ratio of MIBK:DCE proved to be a robust solvent for AS extraction for a wide range of samples under various chemical conditions. The objectives of this research were to set the washing protocol to eliminate the anionic interferences in the MIBK-DCE extraction and to develop a new simplified analytical method for AS analysis using the MIBK-DCE (3:1) extractant. The suitability of the proposed MIBK-DCE method was validated based on quality control and assurance criteria, such as selectivity, accuracy, precision, method detection limit (MDL), limit of quantification (LOQ), and sensitivity. Various water samples, such as freshwater, wastewater, and seawater, were used for the method development and validation. Interferences by inorganic and organic anions were evident in the reference chloroform method but were eliminated in the MIBK-DCE procedure with a two-step process that consisted of washing with a carbonate/bicarbonate solution at pH 9.2 and a mixture of silver sulfate (Ag₂SO₄) and potassium alum (AlK(SO₄)₂). The simplified MIBK-DCE method for sodium dodecyl sulfate (SDS) analysis consisted of (i) sample pre-treatment, (ii) MIBK-DCE extraction, (iii) washing and filtration, and (iv) absorbance measurement. The MIBK-DCE method was accurate, precise, selective, and sensitive for AS analysis and showed MDL of 0.0001 mg/L, LOQ of 0.0005 mg/L, relative standard deviation (RSD) of 0.1%, and recovery of 99.0%. All these criteria were superior to those of the chloroform method. Sensitivity analysis showed highly significant correlations in AS analyses between the MIBK-DCE and chloroform methods for domestic wastewater, industrial wastewater, and seawater. The MIBK-DCE method is simple, rapid, robust, reproducible, and convenient, when compared to the chloroform method. Results demonstrate that the simplified MIBK-DCE method can be employed for AS analysis in a wide range of environmental waters including seawater.

A significant quantity of biologically produced sulfur (BPS) is generated as a by-product of chemical and biological desulfurization processes applied to landfill gas treatment. The beneficial upcycling of BPS has seen limited use in the environmental context. The effectiveness and underlying mechanism of BPS as an adsorbent for removing Hg²⁺ from both solution and wastewater were elucidated based on experiments encompassing surface characterization, adsorption isotherms, kinetics, and thermodynamics. The BPS exhibited remarkable efficacy in removing Hg²⁺ from solution, with the Langmuir model accurately describing the adsorption process and showing a maximum adsorption capacity of 244 mg g⁻¹. Surface analysis through X-ray photoelectron spectroscopy and scanning electron microscopy revealed that Hg²⁺ complexed with sulfide on BPS surfaces, forming stable HgS. The adsorbed Hg was strongly retained in BPS, with less than 0.2% of the adsorbed Hg desorbed by strong acids. Adsorption kinetics followed the double-exponential first-order model, showing an initial rapid adsorption phase wherein 75% of the initial Hg²⁺ was removed within 5 min, followed by a slower adsorption rate. The thermodynamic parameters suggested that adsorption of Hg²⁺ by BPS was a spontaneous and endothermic process. Additionally, BPS effectively removed Hg²⁺ from wastewater, showing preference for Hg over other co-existing metals. These findings underscore the potential of BPS as an effective adsorbent for Hg²⁺ removal from wastewater.

The combination of lime immobilization of metals and soil dressing has been a prevalent practice in Korea for remediating metal-contaminated arable soils. However, there have been limited reports on whether this method effectively sustains soil health after remediation, particularly in arable soils. This study undertook a comparative assessment of the soil health index (SHI) across metal-contaminated arable lands, arable soils remediated with lime immobilization and soil dressing, and uncontaminated soils. A total 389 soil samples were collected from these sites and analyzed for nineteen indicators encompassing physical, chemical, and biological properties. To assess soil health, these indicators were screened using principal component analysis, yielding five minimum data set (MDS) indicators: total nitrogen, clay content, dehydrogenase activity, bacterial colony-forming units, and available phosphorus. Among these MDS indicators, total nitrogen exhibited the highest value as the principal component contributing to soil health assessment. Scores of the MDS indicators exhibited significant correlation with those of total data set indicators, affirming the appropriateness of the soil health assessment adopted in this study. The SHI of the remediated arable soils (0.48) surpassed those of the contaminated soils (0.47) and were statistically comparable to those of the uncontaminated forest (0.51) and upland (0.51) soils. The health of the contaminated soils demonstrated a high dependence on soil properties rather than metal concentrations. These findings underscore the robustness of the combined immobilization and soil dressing method for sustaining the health of contaminated arable soils post-remediation.