Boron adsorption to ferrihydrite with implications for surface speciation in soils: Experiments and modeling

The adsorption and desorption of boric acid onto reactive materials such as metal (hydr)oxides and natural organic matter are generally considered to be controlling processes for the leaching and bioavailability of boron (B). We studied the interaction of B with ferrihydrite (Fh), a nanosized iron (hydr)oxide omnipresent in soil systems, using batch adsorption experiments at different pH values and in the presence of phosphate as a competing anion. Surface speciation of B was described with a recently developed multisite ion complexation (MUSIC) and charge distribution (CD) approach. To gain insight into the B adsorption behavior in whole-soil systems, and in the relative contribution of Fh in particular, the pH-dependent B speciation was evaluated for soils with representative amounts of ferrihydrite, goethite, and organic matter. The pH-dependent B adsorption envelope of ferrihydrite is bell-shaped with a maximum around pH 8–9. In agreement with spectroscopy, modeling suggests formation of a trigonal bidentate complex and an additional outer-sphere complex at low to neutral pH values. At high pH, a tetrahedral bidentate surface species becomes important. In the presence of phosphate, B adsorption decreases strongly and only formation of the outer-sphere surface complex is relevant. The pH-dependent B adsorption to Fh is rather similar to that of goethite. Multisurface modeling predicts that ferrihydrite may dominate the B binding in soils at low to neutral pH and that the relative contribution of humic material increases significantly at neutral and alkaline pH conditions. This study identifies ferrihydrite and natural organic matter (i.e., humic substances) as the major constituents that control the B adsorption in topsoils.The Dutch Research Council/[Grant N°14688]/NWO/Países BajosUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Agroalimentarias::Centro de Investigaciones Agronómicas (CIA

Modeling arsenic in European topsoils with a coupled semiparametric (GAMLSS-RF) model for censored data

Arsenic (As) is a versatile heavy metalloid trace element extensively used in industrial applications. As is carcinogen, poses health risks through both inhalation and ingestion, and is associated with an increased risk of liver, kidney, lung, and bladder tumors. In the agricultural context, the repeated application of arsenical products leads to elevated soil concentrations, which are also affected by environmental and management variables. Since exposure to As poses risks, effective assessment tools to support environmental and health policies are needed. However, the most comprehensive soil As data available, the Land Use/Cover Area frame statistical Survey (LUCAS) database, contains severe limitations due to high detection limits. Although within International Or- ganization for Standardization standards, the detection limits preclude the adoption of standard methodologies for data analysis. The present work focused on developing a new method to model As contamination in European soils using LUCAS soil samples. We introduce the GAMLSS-RF model, a novel approach that couples Random Forests with Generalized Additive Models for Location, Scale, and Shape. The semiparametric model can capture non-linear interactions among input variables while accommodating censored and non-censored observations and can be calibrated to include information from other campaign databases. After fitting and validating a spatial model, we produced European-scale As concentration maps at a 250 m spatial resolution and evaluated the patterns against reference values (i.e., two action levels and a background concentration). We found a significant variability of As concentration across the continent, with lower concentrations in Northern countries and higher concentrations in Portugal, Spain, Austria, France and Belgium. By overcoming limitations in existing databases and methodologies, the present approach provides an alternative way to handle highly censored data. The model also consists of a valuable probabilistic tool for assessing As contamination risks in soils, contributing to informed policy-making for environmental and health protection

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Environmental availability of micronutrients in tropical soils

Trace elements such as zinc (Zn), copper (Cu) and boron (B), are important micronutrients for crop production. Their bioavailability is essential to crops yield quantity and quality in tropical soils from Sub-Saharan Africa (SSA). Blanket fertilizer recommendations including only macronutrients are most common practice in SSA. Alternatively, science-based approaches have been developed for formulating site-specific fertilizer recommendations. Such science-based approaches could be extended to account for micronutrients, based on the knowledge about the processes that affect their availability for plant uptake.Micronutrient bioavailability depends partly on the soil micronutrient status, and in particular on the labile, reactive or potentially available pool that is distributed over the solid and solution phase, through sorption/desorption and precipitation/dissolution. A fraction of this labile pool is present in the soil solution and is therefore directly available for plant uptake. Together, the soluble and potential available pool represent the soil micronutrient environmental availability.The aim of this thesis was to gain insight in the soil chemical processes that control the solid-solution partitioning of Zn, Cu, and B in tropical soils from SSA, and to use this knowledge to develop accessible tools for predicting the soluble concentrations of these micronutrients. This was done using geochemical multi-surface models and partition relations.Geochemical multi-surface models require input data about the amount of reactive surfaces and their corresponding reactivity for ion adsorption. The metal (hydr)oxides and soil organic matter have been previously identified as the most important reactive surfaces for micronutrient adsorption in soils. The first objective of this thesis was therefore to better understand the reactivity of metal (hydr)oxides and soil organic matter in tropical soils from SSA. Soils from the humid tropics are often intensively weathered, resulting in a high abundance of metal (hydr)oxides. These metal (hydr)oxides are mainly present as well-crystallized metal (hydr)oxides while the contribution of oxide nanoparticles (i.e. ferrihydrite-like materials) may be relatively small on a mass basis. Nevertheless, we have shown in this thesis that irrespective of weathering stage, ferrihydrite is a good model oxide to describe the surface reactivity of the natural metal (hydr)oxides in soils. With regard to the soil organic matter content, our results showed that in soils, the mean particle size of the natural oxide fraction explains the organic carbon content found in soils, irrespective of origin, land use and soil depth. According to these results, soil organic carbon is predominantly stored in primary organo-oxide aggregates that are additionally organized by association with larger mineral particles.In addition to the amount and reactivity of the adsorption surfaces, geochemical multi-surface models also require well-parameterized models to describe the ion adsorption processes to these surfaces. Since ferrihydrite was identified as the best proxy for the natural metal (hydr)oxides in tropical soils, the second objective of this thesis was to use a consistent modeling approach for describing the adsorption of Zn, Cu and B to ferrihydrite with the Charge Distribution model in combination with a Multi Site Ion Complexation model.The third objective of this thesis was to apply a multi-surface model for calculating the solid-solution partitioning of Zn, Cu, and B in tropical soils, and to translate these results in easily accessible prediction tools in the form of partition relations.First, the chemical speciation of B in soils was studied with a geochemical multi-surface model that included B adsorption to dissolved and solid organic matter, ferrihydrite, and clay mineral edges. This was done for five temperate and five tropical. In addition, the performance of previously proposed extraction methods for measuring reactive B were evaluated, since this information is needed as input variable for multi-surface modeling calculations. Based on modeling calculations, the reactive B in soils corresponded best to the B measured in a 0.05 M KH2PO4 (pH 4.5) extraction. In general, the multi-surface modeling showed that 68% or more of reactive boron was present in the solution phase for the soils in this study and that the adsorption was dominated by oxides in the tropical soils, while organic matter was the main adsorbent in the temperate soils. When changing the soil pH, B concentration was found to decrease with increasing pH, and both experimental data and modelling suggested that this effect is mainly due to increased binding of B to organic matter.Next, the solid-solution partitioning of Zn, Cu and B was studied for 172 soils from Burundi, Rwanda and Kenya, using extensive soil characterization in combination with multi-surface modelling and two types of Freundlich-like partition relations. The results showed that the generic multi-surface model applied to these tropical soils performs similarly for Zn and Cu as in previous studies on temperate and contaminated soils. The Zn and Cu speciation was dominated by adsorption to soil organic matter, with an increased importance of metal (hydr)oxides with increasing pH. Given its generally low concentrations in these soils, dissolved organic matter was found to be important only for the solution speciation of Cu. The observed and modeled solid-solution partitioning of Cu and B was found to be rather constant among soils, and the soluble concentration was consistently mainly controlled by the reactive concentration. The solid-solution partitioning of Zn was strongly related to the soil pH. The partition relations in which the soluble concentration was optimized, resulted in an average overestimation for the lowest observed concentrations, and an underestimation for highest concentrations of all three elements. Partition relations in which the Zn solid-solution partitioning was optimized, resulted in more robust predictions since the prediction error was not related to the actual measured concentration.Overall, this thesis delivered valuable information on the micronutrient soil status in SSA, and knowledge on the processes that control soil micronutrient availability. Based on this knowledge, a low-cost and reliable method was developed for predicting soluble micronutrient concentrations, based on partition and transfer relations. This method can be used for testing soils for Zn, Cu and B availability and for making regional and national soil maps showing micronutrient availability. The soil micronutrient information obtained by these methods, can be used in future work for establishing micronutrient fertilizer recommendation systems. &nbsp

Boron speciation and extractability in temperate and tropical soils : A multi-surface modeling approach

Boron is an essential micronutrient for plants, but can also be toxic when present in excess in the soil solution. A multi-surface geochemical model was used to assess the important processes that affect the distribution of the geochemically reactive B in soils over the solution and solid phase. The multi-surface model was based on the adsorption of B on dissolved and solid humic acids, representing reactive organic matter, ferrihydrite, representing the Fe and Al (hydr)oxides, and clay mineral edges. In addition, the performance of previously proposed extraction methods for measuring reactive B was evaluated. Based on B measured in 0.01 M CaCl2 soil extracts (7–85 μmol kg−1 soil), we calculated the reactive boron concentration for 5 temperate and 5 tropical soils (8–106 μmol kg−1 soil). We found that extractions with 0.43 M HNO3 or with 0.2 M mannitol + 0.1 M triethanolamine buffer extract on average 240 and 177% of the reactive B predicted by the model, thus releasing additional B that is assumed to be not or only very slowly available for exchange with the soil solution. Reactive B calculated by the model corresponded best to the B measured in a 0.05 M KH2PO4 (pH 4.5) extraction. In general, the multi-surface modeling showed that 68% or more of reactive boron was present in the solution phase for the soils in this study and that the adsorption was dominated by oxides in the tropical soils, while solid organic matter was the main adsorbent in the temperate soils. When changing the soil pH(CaCl2), B concentration was found to decrease with increasing pH, and both experimental data and modelling suggests that this effect is mainly due to increased binding of B to organic matter.</p

Spatial assessment of topsoil zinc concentrations in Europe

International audienc

Impact of landslides on soil characteristics: implications for estimating their age

The slopes of Mount Elgon, a complex volcano at the border between Uganda and Kenya, are frequently affected by landslides with disastrous effects on the livelihood of its population. Since local people greatly depend on the land for crop production, this paper examines if and how fast physico-chemical characteristics in landslide scars recover. A chronosequence of 18 landslides covering a period of 103 years was sampled in order to explore differences between topsoil inside and outside landslide scars. For each landslide, two topsoil samples were taken within the landslide and two in nearby undisturbed soils to compare their physico-chemical characteristics. Samples inside the landslides were located at the transition zone between the depletion and accumulation zone, which is situated at the contact line between the plan concave and plan convex section of the landslide. No differences were found for available phosphorus, Ca2+, Mg2+ content or for the fine earth texture. Recent landslides had however lower content of soil organic carbon (OC) and K+, and higher content of rock fragments and Na+ than the adjacent soils. Soil OC content increased significantly with age and reached levels of the corresponding undisturbed soils after ca. 60 years. Older landslides had even higher OC contents than soils adjacent to the landslide. Hence landslide scars act as local carbon sink. We suggest that the occurrence of rock fragments in the topsoil is a useful indicator for mapping past landslides. Moreover, the difference in soil OC content between landslide scars and adjacent soil could be used for estimating the age of landslides in data-poor regions.status: publishe

Soil characteristics of landslides on Mount Elgon (Uganda): implications for estimating their

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Solid-solution partitioning of micronutrients Zn, Cu and B in tropical soils : Mechanistic and empirical models

Trace elements such as zinc (Zn), copper (Cu) and boron (B) are important micronutrients for crop production. Their bioavailability is essential to crops yield quantity and quality in many tropical soils. Nutrient bioavailability depends partly on the soil nutrient status, and in particular on the reactive and soluble fractions. Adsorption/desorption and precipitation/dissolution processes control the partitioning of the reactive pool over the solid and solution phase. However, so far the solid-solution partitioning of trace elements has mostly been studied in temperate and often contaminated soils. We studied, therefore, the solid-solution partitioning of Zn, Cu and B for 172 soils from Burundi, Rwanda and Kenya, using extensive soil characterization in combination with multi-surface modelling and two types of empirical Freundlich type partition relations. Our aim was to enhance the understanding of the soil chemical processes that control the solid-solution partitioning of the three micronutrients in these soils from the tropics with a multi-surface model, and to use this knowledge as benchmark to develop partition relations that require less input data and are more convenient tools for predicting the concentration in solution based on existing soil data. We show that the generic multi-surface model applied to these tropical soils performs similarly for Zn and Cu as in previous studies on temperate and contaminated soils. The Zn and Cu speciation was dominated by adsorption to soil organic matter, with an increased importance of metal (hydr)oxides with increasing pH. Given its generally low concentrations in these soils, dissolved organic matter was found to be important only for the solution speciation of Cu. The adsorption of B was mainly to metal (hydr)oxides at low pH, and with increasing pH soil organic matter became more important. The multi-surface model overestimated the dissolved B concentration for most soil samples, which we attributed to an inaccurate estimation of reactive B. Interestingly, the variation in observed and modeled solid-solution partitioning expressed as Kd of Cu and B among the soils was relatively small (∼1 log L kg−1), and the concentration in solution was consistently mainly controlled by the reactive concentration. Generally, the optimized partition relations resulted in a smaller prediction error compared to the multi-surface models. The partition relations in which the concentration in solution was optimized, resulted generally in an overestimation for the lowest observed concentrations, and an underestimation for highest concentrations of all three elements. Partition relations with optimized Freundlich parameters Kf and n resulted in more robust predictions since the prediction error was not related to the actual measured concentration. The partition relations from this study are easy-to-use tools for predicting the dissolved concentrations of Zn, Cu and B in soils from the tropics with low contents of these micronutrients and can therefore enhance the use of current existing soil information data for Sub-Saharan Africa

Are trait emotional competencies and heart rate variability linked to mental health of coronary heart disease patients?

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