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

Temporal variability in trace metal solubility in a paddy soil not reflected in uptake by rice (Oryza sativa L.)

Alternating flooding and drainage conditions have a strong influence on redox chemistry and the solubility of trace metals in paddy soils. However, current knowledge of how the effects of water management on trace metal solubility are linked to trace metal uptake by rice plants over time is still limited. Here, a field-contaminated paddy soil was subjected to two flooding and drainage cycles in a pot experiment with two rice plant cultivars, exhibiting either high or low Cd accumulation characteristics. Flooding led to a strong vertical gradient in the redox potential (Eh). The pH and Mn, Fe, and dissolved organic carbon concentrations increased with decreasing Eh and vice versa. During flooding, trace metal solubility decreased markedly, probably due to sulfide mineral precipitation. Despite its low solubility, the Cd content in rice grains exceeded the food quality standards for both cultivars. Trace metal contents in different rice plant tissues (roots, stem, and leaves) increased at a constant rate during the first flooding and drainage cycle but decreased after reaching a maximum during the second cycle. As such, the high temporal variability in trace metal solubility was not reflected in trace metal uptake by rice plants over time. This might be due to the presence of aerobic conditions and a consequent higher trace metal solubility near the root surface, even during flooding. Trace metal solubility in the rhizosphere should be considered when linking water management to trace metal uptake by rice over time

Study on methodological aspects regarding limit values for pollutants in aggregates in the context of the possible development of end-of-waste criteria under the EU Waste Framework Directive

This report provides a methodology proposal for establishing limit values for pollutants in waste-derived aggregates with a view of using such aggregates in a wide variety of construction projects, as part of possible end-of-waste criteria for aggregates in accordance with Article 6 of the Waste Framework Directive (2008/98/EC). More specifically, the study centres on aggregate substances that are subject to leaching and/or release through wear. The report focuses on identifying and assessing the pollution risks of using aggregates derived from waste, on reviewing how the use of aggregates is regulated today in the EU with respect to avoiding pollution, on assessing the need for including limit values for pollutants in end-of-waste criteria, on assessing the suitability of different types of pollutant limit values, on identifying and assessing the different methodological approaches for deriving pollutant limit values and on identifying the most suitable testing approaches and methods, including simplified modes of compliance.JRC.J.5-Sustainable Production and Consumptio

Effects of dissolved organic matter and nitrification on biodegradation of pharmaceuticals in aerobic enrichment cultures

Natural dissolved organic matter (DOM) and nitrification can play an important role in biodegradation of pharmaceutically active compounds (PhACs) in aerobic zones of constructed wetlands (CWs). This study used an enrichment culture originating from CW sediment to study the effect of DOM and nitrification on aerobic biodegradation of seven PhACs. The enriched culture degraded caffeine (CAF), metoprolol (MET), naproxen (NAP), and ibuprofen (IBP) with a consistent biodegradability order of CAF > MET > NAP > IBP. Biodegradation of propranolol, carbamazepine, and diclofenac was insignificant (<15%). CAF biodegradation was inhibited by the easily biodegradable DOM. Conversely, DOM enhanced biodegradation of MET, NAP, and IBP, potentially by contributing more biomass capable of degrading PhACs. Nitrification enhanced biodegradation of NAP and IBP and mineralization of the PhAC mixture as well as less biodegradable DOM, which may result from co-metabolism of ammonia oxidizing bacteria or enhanced heterotrophic microbial activity under nitrification. MET biodegradation was inhibited in the presence of nitrification. DOM and nitrification effects on PhAC biodegradation in CWs gained from this study can be used in strategies to improve CW operation, namely: designing hydraulic retention times based on the biodegradability order of specific PhACs; applying DOM amendment; and introducing consistent ammonium streams to increase removal of PhACs of interest

Sensitivity of labile carbon fractions to tillage and organic matter management and their potential as comprehensive soil quality indicators across pedoclimatic conditions in Europe

Soil quality is defined as the capacity of the soil to perform multiple functions, and can be assessed by measuring soil chemical, physical and biological parameters. Among soil parameters, labile organic carbon is considered to have a primary role in many soil functions related to productivity and environmental resilience. Our study aimed at assessing the suitability of different labile carbon fractions, namely dissolved organic carbon (DOC), hydrophilic DOC (Hy-DOC), permanganate oxidizable carbon (POXC, also referred to as Active Carbon), hot water extractable carbon (HWEC) and particulate organic matter carbon (POMC) as soil quality indicators in agricultural systems. To do so, we tested their sensitivity to two agricultural management factors (tillage and organic matter input) in 10 European long-term field experiments (LTEs), and we assessed the correlation of the different labile carbon fractions with physical, chemical and biological soil quality indicators linked to soil functions. We found that reduced tillage and high organic matter input increase concentrations of labile carbon fractions in soil compared to conventional tillage and low organic matter addition, respectively. POXC and POMC were the most sensitive fractions to both tillage and fertilization across the 10 European LTEs. In addition, POXC was the labile carbon fraction most positively correlated with soil chemical (total organic carbon, total nitrogen, and cation exchange capacity), physical (water stable aggregates, water holding capacity, bulk density) and biological soil quality indicators (microbial biomass carbon and nitrogen, and soil respiration). We conclude that POXC represents a labile carbon fraction sensitive to soil management and that is the most informative about total soil organic matter, nutrients, soil structure, and microbial pools and activity, parameters commonly used as indicators of various soil functions, such as C sequestration, nutrient cycling, soil structure formation and soil as a habitat for biodiversity. Moreover, POXC measurement is relatively cheap, fast and easy. Therefore, we suggest measuring POXC as the labile carbon fraction in soil quality assessment schemes in addition to other valuable soil quality indicators.</p

From 13C-lignin to 13C-mycelium: Agaricus bisporus uses polymeric lignin as a carbon source

Plant biomass conversion by saprotrophic fungi plays a pivotal role in terrestrial carbon (C) cycling. The general consensus is that fungi metabolize carbohydrates, while lignin is only degraded and mineralized to CO2. Recent research, however, demonstrated fungal conversion of 13C-monoaromatic compounds into proteinogenic amino acids. To unambiguously prove that polymeric lignin is not merely degraded, but also metabolized, carefully isolated 13C-labeled lignin served as substrate for Agaricus bisporus, the world's most consumed mushroom. The fungus formed a dense mycelial network, secreted lignin-active enzymes, depolymerized, and removed lignin. With a lignin carbon use efficiency of 0.14 (g/g) and fungal biomass enrichment in 13C, we demonstrate that A. bisporus assimilated and further metabolized lignin when offered as C-source. Amino acids were high in 13C-enrichment, while fungal-derived carbohydrates, fatty acids, and ergosterol showed traces of 13C. These results hint at lignin conversion via aromatic ring-cleaved intermediates to central metabolites, underlining lignin's metabolic value for fungi

Geochemical Multisurface Modeling of Reactive Zinc Speciation in Compost as Influenced by Extraction Conditions

Knowledge on organic matter (OM) concentration and composition is of major importance for predicting Zn speciation and bioavailability in soils, especially for low-Zn soils. However, comprehensive knowledge on the effect of soil-like organic amendments such as compost on metal speciation is limited. For the first time, multisurface modeling is applied on compost to study the effect of solid and dissolved OM composition on the speciation of reactive Zn as influenced by conditions applied in frequently used extractions to estimate Zn bioavailability. First, compost OM composition was determined by fractionation in operationally defined humic, fulvic, and hydrophilic acid pools under various extraction conditions, and subsequently, Zn speciation was modeled using the generic non-ideal competitive adsorption-Donnan (NICA-Donnan) model in addition to adsorption to hydrous ferric oxide (HFO) and clay. The results show a strong effect of extraction conditions on OM concentration and composition and related dissolved Zn speciation. Model predictions show that Zn in solution is mainly bound to dissolved humic acids. Analysis of deviations between measured and modeled Zn concentrations reveal specific limitations of the current generic model parameters, particularly with regard to Zn binding to OM at low concentrations and Ca-Zn competition, that is, typical conditions that occur in low-Zn soils

Gebruik van ijzerwater en fulvozuur als ijzermeststof - laboratoriumtesten

Bij de productie van drinkwater uit grondwater worden grote hoeveelheden ijzerslib geproduceerd. Dit rapport bevat resultaten van lab-experimenten die een eerste verkenning vormen naar de mogelijkheden om ijzerslib, al dan niet in combinatie met fulvozuur, te gebruiken als ijzermeststof in de land- en tuinbouw