Relationship between heavy metals and minerals extracted from soil clay by standard and novel acid extraction procedures

Strontium isotope signature of the PGI lemons Limone Costa d'Amalfi and Limone di Sorrento, and of the orchard soils from Sorrento peninsula

The Limone Costa d'Amalfi and Limone di Sorrento lemons from the Sorrento Peninsula have Protected Geographical Indication (PGI) and are subject to origin fraud. The 87Sr/86Sr ratio (SrIR) signature of lemons and soils was investigated to verify its reliability to trace the PGI lemons and to highlight environmental factors responsible of the lemon SrIRs. The SrIR ranges of each PGI lemon were not discriminating as they overlapped with each other and some non-PGI lemon SrIRs fell within these ranges. The lemon SrIRs were generally not correlated with bulk and bioavailable soil SrIRs, rather, they were the result of plant Sr uptake with different SrIRs depending on interaction between water supplied to soil and soil with different chemical and physical characteristics. The study of lemon SrIRs and the causes of their origin and variability provides a reliable forecast reference for the other PGI agri-food products in the study area.

Integrated environmental assessment of iron ore tailings in floodplain soils and plants after the Fundão Dam disaster in Brazil

Previous studies of the Doce River basin (Brazil) seem to be contradictory regarding the contamination of soils with potentially harmful elements (PHE). This research aimed to perform an integrated assessment of PHE in the soil-plant-tailing system from the area most affected by the iron waste after the Fundão Dam disaster in 2015. Different fractions of PHE (exchangeable, nonexchangeable, reducible, and pseudo-total) were determined on deposited iron waste (DIW), soil waste mixture (SWM), and control soil (CS) samples. Total contents of PHE in Poaceae were also determined, and Allium cepa bioassays were performed to determine DIW and CS cytotoxicity and/or genotoxicity to plants. The Fe and Mn contaminations were the only ones related to the deposition of DIW on floodplains, and other harmful element content (such as As, Hg, Ni, Cd, Cr, and Pb) was not found above baseline values for soils. In addition, a significant part of the Fe and Mn in DIW is readily available or subject to acidification and prolonged flood reduction processes. The high available content of Fe favored its excessive accumulation by Brachiaria. The DIW chemical conditions reduced biological functions of A. cepa under a controlled environment. However, more drastic effects, such as genetic damage, were not seen. The postdisaster action of covering DIW with CS resulted in undesirable enrichment of Pb on the floodplain soils. The integrated results allow the conclusion that the iron waste is not a time bomb for PHE contamination of soils between the Fundão and Risoleta Neves Hydroelectric Dam (~100 km away from Fundão). Integr Environ Assess Manag 2024;20:117-132. © 2023 SETAC.

Soil Properties Correlate with Microbial Community Structure in Qatari Arid Soils

This is the first detailed characterization of the microbiota and chemistry of different arid habitats from the State of Qatar. Analysis of bacterial 16S rRNA gene sequences showed that in aggregate, the dominant microbial phyla were Actinobacteria (32.3%), Proteobacteria (24.8%), Firmicutes (20.7%), Bacteroidetes (6.3%), and Chloroflexi (3.6%), though individual soils varied widely in the relative abundances of these and other phyla. Alpha diversity measured using feature richness (operational taxonomic units [OTUs]), Shannon's entropy, and Faith's phylogenetic diversity (PD) varied significantly between habitats (P = 0.016, P = 0.016, and P = 0.015, respectively). Sand, clay, and silt were significantly correlated with microbial diversity. Highly significant negative correlations were also seen at the class level between both classes Actinobacteria and Thermoleophilia (phylum Actinobacteria) and total sodium (R = -0.82 and P = 0.001 and R = -0.86, P = 0.000, respectively) and slowly available sodium (R = -0.81 and P = 0.001 and R = -0.8 and P = 0.002, respectively). Additionally, class Actinobacteria also showed significant negative correlation with sodium/calcium ratio (R = -0.81 and P = 0.001). More work is needed to understand if there is a causal relationship between these soil chemical parameters and the relative abundances of these bacteria. IMPORTANCE Soil microbes perform a multitude of essential biological functions, including organic matter decomposition, nutrient cycling, and soil structure preservation. Qatar is one of the most hostile and fragile arid environments on earth and is expected to face a disproportionate impact of climate change in the coming years. Thus, it is critical to establish a baseline understanding of microbial community composition and to assess how soil edaphic factors correlate with microbial community composition in this region. Although some previous studies have quantified culturable microbes in specific Qatari habitats, this approach has serious limitations, as in environmental samples, approximately only 0.5% of cells are culturable. Hence, this method vastly underestimates natural diversity within these habitats. Our study is the first to systematically characterize the chemistry and total microbiota associated with different habitats present in the State of Qatar.

The classic aqua regia and EPA 3051A methods can mislead environmental assessments and certifications: Potentially harmful elements resorption in short-range order materials

EPA 3051A and Aqua Regia (AR) are widely adopted by global environmental agencies to assess soil quality in relation to potentially harmful elements (PHE). However, previous study has shown the formation of large amounts of short-range order materials (SRO) in the residues of these extractions. Residues obtained from the 3051A and AR were recovered from filter papers. To characterize the SRO in these residues, sequential extractions were performed with 0.2 mol L^-1 ammonium oxalate (AO) and 0.5 mol L^-1 NaOH. On average (n = 15), the 3051A and AR residues contained 37% and 60% of SRO, respectively. The largest amounts of SRO formed in the AR residue was in sample 5 (99% of SRO). The main component of the SRO was Al₂O₃-AO, Fe₂O₃-AO and SiO₂-NaOH. The formation of SRO and PHE resorption levels were random and highly dependent on the mineralogy of the soil clay fraction. Soils rich in smectites, which are more common in temperate regions, formed larger amounts of SRO. The association of Pb with the SRO was more pronounced in the 3051A residue than in the AR residue. If SRO was not extracted after 3051A, in sample 7, for example, 595 mg kg^-1 of Pb (10.2%) would have not been accounted. The maximum PHE resorptions in SRO were (%): Pb - 10; Cu - 470; Ba - 280; As - 21. The underestimation of PHE contents due to resorption mechanisms may lead an environmental agency to certify the use of an area contaminated with PHE.

Adsorption of glyphosate on Brazilian subtropical soils rich in iron and aluminum oxides

We investigated the adsorption of glyphosate onto five subtropical soils of Paraná and São Paulo states, Brazil, a region of intense agricultural activities, aiming at the determination of kinetic and isotherm adsorption parameters which enable the evaluation of the potential leaching of the herbicide. The adsorption was fast, being described by the pseudo-second order and intraparticle diffusion models, thus suggesting that mixed mechanisms are involved. The Oxisol containing the highest concentrations of metal oxides (209.5 g kg-1 Fe2O3 and 160.2 g kg-1 Al2O3) was the sample with the highest rate constant, indicating the adsorption sites are readily available. All the soils are rich in aluminum and iron oxides, explaining the Freundlich coefficients (KF) between 642 and 1360 mg1-1/n kg-1 L1/n, which are higher than most of the coefficients described for other soils around the world. The maximum desorption (15% of the adsorbed amount) was observed for the Oxisol. For the other soils, desorption ranged from 2 to 7%. These results suggest that the leaching of free glyphosate to nearby surface and groundwaters is unlikely unless excessive doses are used. The adsorption parameters are useful for managing the right doses applied to the crops, thus avoiding contamination of adjacent areas.