Changes In Speciation Research Articles

Effects of a short‐term Mediterranean diet on mental health, cognition and cerebral blood flow in UK adults: MediMood study protocol

AbstractBackgroundDementias and mental health disorders (i.e. depression, anxiety) are significant public health challenges. Chronic consumption of a Mediterranean diet (MD) has been associated with lower incident dementia, improved cognitive performance, and reduced brain atrophy. Yet, short‐term studies and randomised clinical trials (RCT) are lacking. Our systematic review of RCTs showed that in only four available studies, a MD can improve attention, alertness and contentment in up to 10 days (1). In a controlled efficacy study with all foods provided, we aim to explore postprandial, 24‐h and 5 days impacts of a MD and a Western diet (WD) on mood, anxiety and cognition, cerebral blood flow as assessed by MRI.MethodMediMood is an efficacy crossover RCT. Individuals (n = 25) over 18 years with mild to moderate anxiety and/or depression will complete a 5‐day MD and a 5‐day WD intervention with a 4‐week wash‐out period, with foods, meal plans and instructions provided. Biological samples (blood, urine, faeces) will be collected. The primary outcomes are mood and anxiety assessed using Bond‐Lader and POMS questionnaires. Secondary outcomes include cognitive outcomes assessed through computerised neuropsychology tests, brain perfusion assessed by MRI, select cardiometabolic and inflammatory biomarkers, ketones, brain‐derived neurotrophic factor, several hormones (e.g. serotonin, dopamine), gut microbiome speciation, sleep quality and behaviour change. The assessment time points during each arm are baseline (day 1 morning), postprandial (post day 1 lunch), 24‐h (day 2 morning) and day 6 morning.ResultNAConclusionThis will be the first well‐controlled RCT examining the acute and short‐term impacts of a MD and a WD on mental health and cognition in a targeted risk group. MediMood considers interfaces between sleep quality and the gut‐brain axis as modifiable determinants of mental health. We expect the findings to provide novel insights in efficacy of a MD on daily and short‐term well‐being in those with existing mild‐moderate mental health difficulties and to provide an initial mechanistic understanding of any observed benefits. Funding:Medical Research Council (MRC, UK), NuBrain Consortium (MR/T001852/1); Turkish Government personal PhD scholarship

Desorption kinetic and sequential extraction of Pb and Zn in a contaminated soil amended with phosphate, lime, biochar, and biosolids.

The mining and metallurgical industry sector activities often release potential toxic elements (PTE) surrounding exploitation area. We evaluated the addition of phosphate and lime using the dosage of 0.5:1, 1:1, and 2:1 molar ratio of PO43- and CO32- to the sum of PTE, respectively, and also, biochar and biosolids using the dosage of 2.5, 5, and 10% (m:m) to immobilize PTE in contaminated forest soil (Pb (270mgkg-1) and Zn (858mgkg-1)) near an abandoned mine site in Brazil. The desorption by stirred flow kinetics revealed that 15% of the total Zn and 12% Pb contents are mobile before any amendment application. Phosphate amendment decreased Pb desorption but increased Zn desorption. Biochar and biosolids immobilize high amounts of Zn and Pb because of their high cation exchange capacities and alkaline properties; however, 20% biosolid dose increased Pb desorption. X-ray absorption spectroscopy suggested Zn-kerolite as the major species in the contaminated soil, likely from mine dust. The change in Zn speciation after soil amendment addition indicated that biochar and lime kept a high proportion of Zn-Al species, whereas phosphate and biosolids led to more Zn-Fe species. Our results pointed out that lime might reduce both Pb and Zn mobilities; however, field trials are crucial to confirm the immobilization efficiency of lime and other amendments over long term.

Al and Mn speciation changes during the pre-oxidation with potassium permanganate and coagulation removing natural organic matter and its membrane fouling behavior

In this study, we systematically explore coagulation behavior, ultrafiltration membrane fouling behavior and the mechanism involved in during the process of pre-oxidation of potassium permanganate and coagulation of aluminum chloride at different condition to treat model pollutants (humic acid, HA) and natural water. The KMnO4 pre-oxidation significantly enhances flocs formation, and for HA artificial water the flocs size increases from 82 to 122 μm at pH 5.5, from 63 to 185 μm at pH 7.0 and from 0 to 75 μm at pH 8.5, respectively, as for natural water it increases from 72 to 139 μm. The enhanced coagulation at pH 5.5 is attributed to the increased polymeric Al speciation after pre-oxidation along with the generated Mn2+ damaging the electric double layer structure. And for pH 8.5 it is mainly caused by the in-situ MnO2 as combination nuclei during pre-oxidation. Besides, for pH 7.0, the combined effect of in-situ MnO2 and the increased polymeric Al speciation both contribute to improvement of the coagulation. What's more, the enhanced Al coagulation by pre-oxidation of KMnO4 also helps alleviate the membrane fouling for both HA artificial water and natural water, and a much rougher surface with larger flocs forms after KMnO4-aided Al coagulation filtration. This study provides an alternative perspective on the mechanism of pre-oxidation coagulation process.

Changes in arsenic mobility and speciation across a 2000-year-old paddy soil chronosequence

Rice accumulates arsenic (As) when cultivated under flooded conditions in paddy soils threatening rice yield or its safety for human consumption, depending on As speciation. During long-term paddy use, repeated redox cycles systematically alter soil biogeochemistry and microbiology. In the present study, incubation experiments from a 2000-year-old paddy soil chronosequence revealed that As mobilization and speciation also change with paddy soil age. Younger paddies (≤100 years) showed the highest total As mobilization, with speciation dominated by carcinogenic inorganic oxyarsenic species and highly mobile inorganic thioarsenates. Inorganic thioarsenates formed by a high availability of reduced sulfur (S) due to low concentrations of reducible iron (Fe) and soil organic carbon (SOC). Long-term paddy use (>100 years) resulted in higher microbial activity and SOC, increasing the share of phytotoxic methylated As. Methylated oxyarsenic species are precursors for cytotoxic methylated thioarsenates. Methylated thioarsenates formed in soils of all ages being limited either by the availability of methylated As in young soils or that of reduced-S in older ones. The present study shows that via a linkage of As to the biogeochemistry of Fe, S, and C, paddy soil age can influence the kind and the extent of threat that As poses for rice cultivation.

Migration characteristics of chlorine during pyrolysis of municipal solid waste pellets

The migration process of chlorine during municipal solid waste (MSW) pellets pyrolysis was studied in a fixed bed reactor. Distribution and speciation changes of chlorine at different pyrolysis temperatures were determined by ion chromatography (IC) and X-ray photoelectron spectroscopy (XPS) analyses. Results showed that chlorine was mainly distributed in pyrolysis char (42.36–65.29 %) and gas (26.66–35.03 %) after MSW pellets pyrolysis. With the temperature increasing, chlorine in char and tar was enriched due to the increase of chlorine release and the decrease of product yields, with chlorine concentration increasing to 3498 ppm and 1415 ppm at 800 °C, respectively. Results of chlorine forms analysis indicated that most of the organic-Cl in MSW was released into the volatiles during pyrolysis due to the dissociation of CCl. Inorganic-Cl became the dominant form of chlorine in char after pyrolysis, with the proportion increasing from 46.69 % (raw) to 61.22 % (500 °C), which also suggested that part of organic-Cl was converted into the inorganic-Cl. Notably, the proportions of inorganic-Cl decreased at >600 °C due to the migration of inorganic. In addition, the pyrolysis release behavior of chlorine was affected by the pore structure of char, which could be inhibited by the unprosperous pores in char, especially at low temperatures (<600 °C). These findings provided a reference for the chlorine regulation of MSW pyrolytic products.

Exploring congruent diversification histories with flexibility and parsimony

Abstract Using phylogenies of present‐day species to estimate diversification rate trajectories—speciation and extinction rates over time—is a challenging task due to non‐identifiability issues. Given a phylogeny, there exists an infinite set of trajectories that result in the same likelihood; this set has been coined a congruence class. Previous work has developed approaches for sampling trajectories within a given congruence class, with the aim to assess the extent to which congruent scenarios can vary from one another. Based on this sampling approach, it has been suggested that rapid changes in speciation or extinction rates are conserved across the class. Reaching such conclusions requires to sample the broadest possible set of distinct trajectories. We introduce a new method for exploring congruence classes that we implement in the R package CRABS. Whereas existing methods constrain either the speciation rate or the extinction rate trajectory, ours provides more flexibility by sampling congruent speciation and extinction rate trajectories simultaneously. This allows covering a more representative set of distinct diversification rate trajectories. We also implement a filtering step that allows selecting the most parsimonious trajectories within a class. We demonstrate the utility of our new sampling strategy using a simulated scenario. Next, we apply our approach to the study of mammalian diversification history. We show that rapid changes in speciation and extinction rates need not be conserved across a congruence class, but that selecting the most parsimonious trajectories shrinks the class to concordant scenarios. Our approach opens new avenues both to truly explore the myriad of potential diversification histories consistent with a given phylogeny, embracing the uncertainty inherent to phylogenetic diversification models, and to select among these different histories. This should help refining our inference of diversification trajectories from extant data.

Kinetics, stoichiometry, and mechanism of arsenopyrite-water interaction under anoxic conditions

Arsenopyrite dissolution is an important source of arsenic’s environmental occurrence and is well-studied under oxidative conditions. However, little is known of anoxic leaching of arsenopyrite by water, though it is probably one of the dominant abiotic processes controlling arsenic mobility in oxygen-limited environments such as groundwaters and paddy fields. The present study attempts to probe the mechanism of arsenopyrite-water interaction in anoxic environment through examining the pH dependence of dissolution kinetics and stoichiometry, as well as speciation changes both on the surface and in solution. Batch and flow-through experiments were first carried out to measure dissolution rates and the results showed alkaline pH mildly encourages As release. Furthermore, the dissolution was found to be near stoichiometric with respect to As and S but not with Fe/As or Fe/S, and the non-stoichiometry exhibited a negative dependence on pH. Combining speciation analyses that revealed the presence of H2O2, SO42− and S2O32− in solutions and a positive correlation of surface species Fe(III)-O, S(-II), and As(I), As(III), As(V), and As(-III) to solution pH, we interpreted the anoxic dissolution behavior of arsenopyrite through a mechanism that combines surface complexation and interfacial redox reactions. The kinetic measurements came to be concerning as data indicates arsenopyrite dissolution in anoxic environment can lead to water having arsenic concentrations above the 10 ppb WHO guideline value in one day at the experimental conditions. The observed H2O2 production indicated the dissolution is associated with or initiated by electron transfer despite the anoxic condition, further suggesting that a more comprehensive theory other than surface complexation model may be needed to better understand the geochemical behavior of As and possibly S in the context of sulfide mineral–water interactions.

Diversification dynamics of a common deep-sea octocoral family linked to the Paleocene-Eocene thermal maximum

The deep-sea has experienced dramatic changes in physical and chemical variables in the geological past. However, little is known about how deep-sea species richness responded to such changes over time and space. Here, we studied the diversification dynamics of one of the most diverse octocorallian families inhabiting deep sea benthonic environments worldwide and sustaining highly diverse ecosystems, Primnoidae. A newly dated species-level phylogeny was constructed to infer their ancestral geographic locations and dispersal rates initially. Then, we tested whether their global and regional (the Southern Ocean) diversification dynamics were mediated by dispersal rate and abiotic factors as changes in ocean geochemistry. Finally, we tested whether primnoids showed changes in speciation and extinction at discrete time points. Our results suggested primnoids likely originated in the southwestern Pacific Ocean during the Lower Cretaceous ∼112 Ma, with further dispersal after the physical separation of continental landmasses along the late Mesozoic and Cenozoic. Only the speciation rate of the Southern Ocean primnoids showed a significant correlation to ocean chemistry. Moreover, the Paleocene-Eocene thermal maximum marked a significant increase in the diversification of primnoids at global and regional scales. Our results provide new perspectives on the macroevolutionary and biogeographic patterns of an ecologically important benthic organism typically found in deep-sea environments.

Tracing the source and transport of Hg during pedogenesis in strongly weathered tropical soil using Hg isotopes

Soil is one of the largest reservoirs and re-emission sources of mercury (Hg) on Earth’s surface. The accumulation and remobilization of Hg during pedogenesis affect how Hg is transported from terrestrial to aquatic environment and biota, but these processes are poorly understood. Here we present Hg concentration and isotope ratios of soil and bedrock samples from a latosol profile formed through intense weathering of Cenozoic basalts in Zhanjiang, Guangdong Province, China, to trace the sources, transport and transformation processes of Hg during pedogenesis, and to gain insights on the potential impact of tropical soils on global Hg cycling. The entire soil profile shows negative δ202Hg (−2.97‰ ± 0.08‰ to −2.54‰ ± 0.08‰) and negative Δ199Hg (−0.68‰ ± 0.04‰ to −0.43‰ ± 0.04‰), with a gradual downward positive shift of Δ199Hg below 35 cm. An isotopic mixing model based on Δ199Hg suggests a dominant Hg input from atmospheric Hg (HgAtm) and limited contribution (<36%) of geogenic Hg (HgGeo) from the bedrock. The strongly negative Δ199Hg throughout the latosol profile suggests that HgAtm was likely subject to substantial photoreduction on soil surface and migrated downward after incorporation into soils. Moreover, there is a distinct positive shift of δ202Hg alongside a rapid decrease of HgGeo from the bedrock to the weakly weathered basalt, indicating a substantial loss of HgGeo with the preferential release of lighter isotopes during the initial weathering, likely due to the dissolution of primary minerals. In addition, the δ202Hg shows a negative correlation with soil pH at some horizons, attributable to the isotopic fractionation during Hg(II) speciation change in soil solution and the selective complexation/adsorption of different Hg(II) species onto mineral surfaces, which are affected by surface charge properties and thus soil pH. Overall, our results provide direct evidence for the accumulation and downward migration of HgAtm in tropical soils during pedogenesis, as well as the loss of HgGeo during the weathering of bedrock, which may serve as an underappreciated source of Hg in tropical regions and have a potential impact on the Hg isotope signatures in aquatic environments.

Antimony and arsenic behaviour in lead/zinc mine tailings during storage under vegetation cover

The high-volume, fine grained tailings produced from Pb/Zn ore processing need to be carefully managed. Metalloid elements, As and Sb, are present in tailings at ∼800 and ∼80 mg kg−1 respectively, and in neutral pH leachates at 5–50 μg L−1. Despite these relatively low leachate concentrations, As and Sb can cause regulatory concern due to their high toxicity and propensity for bioaccumulation. As and Sb mobility in tailings are controlled by their chemical speciation and associations with mineral phases. Changes in As and Sb speciation were, therefore, determined in depth profile samples taken from an active tailings management facility during waste storage up to 8 years since deposition. At this site, primarily to prevent dust formation, a vegetation cover was established by addition of organic compost to surface layers and seeding grasses. Over time a robust vegetation cover was established consisting of perennial grasses, clovers, and after 8 years, small trees and shrubs. The surface layer of the tailings also became progressively more oxidised over time producing a substrate more suitable for plant growth enabling the establishment of beneficial vegetation cover and the development of a thin soil-like surface layer. As and Sb were both present in predominately reduced 3+ forms in freshly deposited tailings but were converted to oxidised 5+ forms in older samples. Oxidation of Fe(II) in pyrite also occurred, producing increased amounts of weak acid leachable Fe(III)-oxides in the tailings. Sorption of As to neoformed iron oxides in leachate drains reduced concentrations in leachates to below regulatory limits, but Sb sorption was relatively ineffective resulting in higher Sb concentration in site drainage waters, which may require specific treatments to reduce Sb concentrations prior to discharge.

Synergistic mechanism of iron manganese supported biochar for arsenic remediation and enzyme activity in contaminated soil

This study prepared and characterized bamboo-derived biochar loaded with different ratios of iron and manganese; evaluated its remediation performance in arsenic-contaminated soil by studying the changes in various environmental factors, arsenic speciation, and arsenic leaching amount in the soil after adding different materials; proposed the optimal ratio and mechanism of iron–manganese removal of arsenic; and explained the multivariate relationship between enzyme activity and soil environmental factors based on biological information. Treatment with Fe–Mn-modified biochar increased the organic matter, cation exchange capacity, and N, P, K, and other nutrient contents. During the remediation process, O-containing functional groups such as Mn–O/As and Fe–O/As were formed on the surface of the biochar, promoting the transformation of As from the mobile fraction to the residual fraction and reducing the phytotoxicity of As, and the remediation ability for As was superior to that of Fe-modified biochar. Mn is indispensable in the FeMn-BC synergistic remediation of As, as it can increase the adsorption sites and the number of functional groups for trace metals on the surface of biochar. In addition to electrostatic attraction, the synergistic mechanism of ferromanganese-modified biochar for arsenic mainly involves redox and complexation. Mn oxidizes As(Ⅲ) to more inert As(V). In this reaction process, Mn(Ⅳ) is reduced to Mn(Ⅲ) and Mn(II), promoting the formation of Fe(Ⅲ) and the conversion of As into Fe–As complexes, while As is fixed due to the formation of ternary surface complexes. Moreover, the effect of adding Fe–Mn-modified biochar on soil enzyme activity was correlated with changes in soil environmental factors; catalase was correlated with soil pH; neutral phosphatase was correlated with soil organic matter; urease was correlated with ammonia nitrogen, and sucrase activity was not significant. This study highlights the potential value of FM1:3-BC as a remediation agent in arsenic-contaminated neutral soils.

Mixed nitrate and metal contamination influences operational speciation of toxic and essential elements

Environmental contamination constrains microbial communities impacting diversity and total metabolic activity. The former S-3 Ponds contamination site at Oak Ridge Reservation (ORR), TN, has elevated concentrations of nitric acid and multiple metals from decades of processing nuclear material. To determine the nature of the metal contamination in the sediment, a three-step sequential chemical extraction (BCR) was performed on sediment segments from a core located upgradient (EB271, non-contaminated) and one downgradient (EB106, contaminated) of the S-3 Ponds. The resulting exchangeable, reducing, and oxidizing fractions were analyzed for 18 different elements. Comparison of the two cores revealed changes in operational speciation for several elements caused by the contamination. Those present from the S-3 Ponds, including Al, U, Co, Cu, Ni, and Cd, were not only elevated in concentration in the EB106 core but were also operationally more available with increased mobility in the acidic environment. Other elements, including Mg, Ca, P, V, As, and Mo, were less operationally available in EB106 having decreased concentrations in the exchangeable fraction. The bioavailability of essential macro nutrients Mg, Ca, and P from the two types of sediment was determined using three metal-tolerant bacteria previously isolated from ORR. Mg and Ca were available from both sediments for all three strains; however, P was not bioavailable from either sediment for any strain. The decreased operational speciation of P in contaminated ORR sediment may increase the dependence of the microbial community on other pools of P or select for microorganisms with increased P scavenging capabilities. Hence, the microbial community at the former S-3 Ponds contamination site may be constrained not only by increased toxic metal concentrations but also by the availability of essential elements, including P.

X-ray Absorption Spectroscopy as a Process Analytical Technology: Reaction Studies for the Manufacture of Sulfonate-Stabilized Calcium Carbonate Particles.

Process analytical technologies are widely used to inform process control by identifying relationships between reagents and products. Here, we present a novel process analytical technology system for operando XAS on multiphase multicomponent synthesis processes based on the combination of a conventional lab-scale agitated reactor with a liquid-jet cell. The preparation of sulfonate-stabilized CaCO3 particles from polyphasic Ca(OH)2 dispersions was monitored in real time by Ca K-edge XAS to identify changes in Ca speciation in the bulk solution/dispersion as a function of time and process conditions. Linear combination fitting of the spectra quantitatively resolved composition changes from the initial conversion of Ca(OH)2 to the Ca(R-SO3)2 surfactant to the ultimate formation of nCaCO3·mCa(R- SO3)2 particles. The system provides a novel tool with strong chemical specificity for probing multiphase synthesis processes at a molecular level, providing an avenue to establishing the relationships between critical quality attributes of a process and the quality and performance of the product.

Adsorption/desorption of mercury (II) by artificially weathered microplastics: Kinetics, isotherms, and influencing factors

While both mercury (Hg) and microplastics (MPs) are well-studied global pollutants, comparatively little is known about the interactions between them and the mobilization of Hg from MPs into organisms. We examined the affinity of Hg(II) to artificially weathered MPs, including polyamide (w-PA), polyethylene (w-PE), polyethylene terephthalate (w-PET), polyester fibers (w-PEST), polyvinyl chloride (w-PVC), and polylactic acid (w-PLA), along with crumb rubber (CR) and PE collected from a wastewater treatment plant (WWTP-PE). WWTP-PE, CR, and w-PEST had particularly high Hg(II) affinities, which can be attributed to electrostatic interaction and pore filling. The adsorption followed a pseudo-second-order kinetic process and fitted the Freundlich model, suggesting multi-step (mass transfer and intraparticle diffusion) and heterogeneous adsorptions. Hydrochemical conditions (pH, dissolved organic matter (DOM), salinity and co-existent metal ions) all impacted Hg-MP behavior. Changes in Hg speciation and MP surface properties contributed to the different Hg(II) adsorption capacities for the MPs. Weathering of MPs generally increased the adsorption of Hg(II) onto MPs, but CR, PET and PEST did not follow this trend. Less than 3% of adsorbed Hg(II) was mobilized from the MPs in freshwater, but that increased up to 73% under simulated avian digestive conditions, suggesting increased bioavailability of Hg(II) from ingested MPs. Overall, weathered MPs adsorb and retain Hg(II) under environmentally relevant conditions but desorb much of it in simulated avian digestion fluid, suggesting that birds that ingest MPs may have increased Hg(II) exposure.

Species-dependent uptake of gadolinium in Chlamydomonas reinhardtii algae

Single cell-inductively coupled plasma-mass spectrometry (sc-ICP-MS) was used in this study as a valuable tool to assess the species-dependent uptake of metallopharmaceuticals into algal cells. Chlamydomonas reinhardtii algae were incubated for 24 h with four Gadolinium-based contrast agents (GBCAs) and GdCl3. A species dependency towards the uptake of the tested Gd species was observed. Using single cell-ICP-MS, a Gd signal corresponding to single cell events was detected for GdCl3 and the linear GBCAs Omniscan® (Gadodiamide, Gd-DTPA-BMA) and Magnevist® (Gadodiamide, Gd-DTPA). For the macrocyclic complexes Dotarem® (Gadoteric acid, Gd-DOTA) and Gadovist® (Gadobutrol, Gd-BT-DO3A), no such Gd signal was visible. Total Gd analysis via ICP-MS confirmed the presence of Gd in the cells only after incubation with GdCl3 and the linear GBCAs, while only small amounts of Gd were detected for the incubations with macrocyclic GBCAs. Furthermore, the results showed that more Gd is bound to cell structures or macromolecules, while smaller amounts are present in the lysate. Using hydrophilic interaction liquid chromatography (HILIC)-ICP-MS, the soluble Gd species in the lysate were analyzed to determine if the initial Gd complexes were still intact. Surprisingly, no intact GBCAs were detected in the lysates of any incubation solution, possibly due to a change in Gd speciation. Further research is needed to assess which Gd species are present in the lysate, while “free” Gd ions or adducts with cell constituents are the most likely explanation. This study highlights the need for species-dependent investigation of elements in aquatic organisms. Moreover, the uptake of linear GBCAs and their species alteration raises the question of a potential accumulation of Gd in the food chain.

Simultaneous enhancement of soil properties along with water-holding and restriction of Pb–Cd mobility in a soil-plant system by the addition of a phosphorus-modified biochar to the soil

Soil quality deterioration and heavy metal contamination have greatly limited soil productivity in mining areas. As soil is a complex system with various properties and interactions, it is imperative to conduct a comprehensive investigation to understand the amendment's mechanisms at work in the soil in mining areas as well as effective ways to address its deteriorating quality. In this study, a potassium dihydrogen phosphate-modified maize straw-cow dung biochar (PBC) was applied as a soil amendment. Various physicochemical properties of the soil including organic matter, total nitrogen, available phosphorus, and pore characteristics were analyzed. This study also assessed soil-saturated water content and soil moisture characteristic curve. Lettuce biomass was measured and changes in various speciation of Pb and Cd in the soil, and the accumulation of Pb and Cd in lettuce were examined. Results showed that the addition of PBC increased soil organic matter, total nitrogen, and available phosphorus while reducing soil bulk density, it also increased soil porosity, saturated water content, and capillary water capacity. Soil structure analysis using CT scanning revealed that 3% PBC increased the macrospores volume fraction while 5% PBC made the pores more uniform. Lettuce biomass increased by 53.3%. 5% PBC resulted in a 56.79% and 38.30% reduction in Pb and a 44.56% and 16.60% reduction in Cd in roots and shoots of lettuce respectively. PBC facilitated the transformation of Pb and Cd from unstable fractions to stable fractions through complexation and precipitation. Overall, the addition of PBC effectively improved soil nutrients, porosity, and water-holding capacity, promoted plant growth, immobilized Pb and Cd, as well as reduced the bioavailability in contaminated-soil from mining areas. This study provides an effective strategy and a new perspective for the remediation of Pb–Cd-contaminated soils.

Cadmium speciation in cacao beans changes during a fermentation-like incubation

Cadmium (Cd) concentrations in cacao often exceed food limits. Recently, it was shown that cacao bean fermentation enhances Cd solubility, opening potential for Cd mitigation in cacao products. This study was set-up to identify changes in Cd speciation during fermentation. X-Ray absorption spectroscopy (XAS) complemented with speciation calculations, were used on samples collected from high and low Cd farms, that were subjected to a fermentation-like incubation that reached high temperatures (>45 °C) and acidic pH (<5). Incubation decreased nib Cd concentration up to a factor 1.5 and changed Cd complexation in high Cd beans from sulphur to oxygen ligands, likely due to pH changes. In beans with lower Cd concentrations, Cd was complexed before and after incubation with oxygen-ligands. A combination of pH changes and/or phytate breakdown may explain the migration of Cd outward from the nib. XAS and speciation calculations proved complimentary techniques and indicated similar speciation changes during fermentation.

Unexpected Cu and Zn speciation patterns in the broiler feed-animal-excreta system revealed by XAS spectroscopy

Trace minerals such as copper (Cu) and zinc (Zn) are animal nutrition supplements necessary for livestock health and breeding performance, yet they also have environmental impacts via animal excretion. Here we investigated changes in Cu and Zn speciation from the feed additive to the broiler excreta stages. The aim of this study was to assess whether different Cu and Zn feed additives induce different Cu and Zn speciation patterns, and to determine the extent to which this speciation is preserved throughout the feed-animal-excreta system. Synchrotron-based X-ray absorption spectroscopy (XAS) was used for this investigation. The principal findings were: (i) in feed, Cu and Zn speciation changed rapidly from the feed additive signature (Cu and Zn oxides or Cu and Zn sulfates) to Cu and Zn organic complexes (Cu phytate and Zn phytate). (ii) in the digestive tract, we showed that Cu and Zn phytate were major Cu and Zn species; Cu sulfide and Zn amorphous phosphate species were detected but remained minor species. (iii) in fresh excreta, Cu sulfide and Zn amorphous phosphate were major species. These results should help to: (i) enhance the design of future research studies comparing different feed additive performances; (ii) assess Cu and Zn bioavailability in the digestive tract; (iii) gain further insight into the fate of Cu and Zn in cultivated soils when poultry manure is used as fertilizer.

Changed mercury speciation in clouds driven by changing cloud water chemistry and impacts on photoreduction: Field evidence at Mt. Tai in eastern China

Chemical speciation of mercury (Hg) in clouds largely determines the photochemistry of Hg in the atmosphere and consequently influences Hg deposition on the surface through precipitation. Cloud water chemistry has notably changed over the last decade in response to global changes, however, the effects on Hg speciation remain poorly understood. During summer 2021, we collected sixty cloud water samples at Mt. Tai in eastern China and compared the cloud chemistry and Hg speciation with our previous findings during summer 2015. The results showed that although there were no statistically significant differences in the concentrations of total Hg (THg), dissolved Hg (DHg), and particulate Hg (PHg), there was a distinct shift in DHg species from the predominated Hg-DOM (78.6% in 2015 campaign) to the more homogeneously distributed Hg(OH)2 (28.4% in 2021 campaign), HgBr2 (26.5%), Hg-DOM (17.3%) and HgBrOH (17.0%). Changes in cloud water chemistry, particularly the significant increase in pH values to 6.49 ± 0.27 and unexpectedly high levels of bromide ions (Br−, 0.19 ± 0.22 mg L−1), were found to drive the changing of Hg speciation by enhancing Hg(II) hydrolysis and binding by Br−. Elevated Br− originating primarily from the continent likely caused noticeable differences in the dominating DHg species between cloud water sourced from marine and continental regions. The changes in chemical speciation of DHg were estimated to result in a 2.6-fold decrease in Hg(II) photoreduction rate between 2015 and 2021 campaigns (0.178 ± 0.054 h−1 vs. 0.067 ± 0.027 h−1), implying a shortened lifetime of atmospheric Hg and increased ecological risks associated with Hg wet deposition.

Carbon Sequestration Strategies in Soil Using Biochar: Advances, Challenges, and Opportunities.

Biochar, a carbon (C)-rich material obtained from the thermochemical conversion of biomass under oxygen-limited environments, has been proposed as one of the most promising materials for C sequestration and climate mitigation in soil. The C sequestration contribution of biochar hinges not only on its fused aromatic structure but also on its abiotic and biotic reactions with soil components across its entire life cycle in the environment. For instance, minerals and microorganisms can deeply participate in the mineralization or complexation of the labile (soluble and easily decomposable) and even recalcitrant fractions of biochar, thereby profoundly affecting C cycling and sequestration in soil. Here we identify five key issues closely related to the application of biochar for C sequestration in soil and review its outstanding advances. Specifically, the terms use of biochar, pyrochar, and hydrochar, the stability of biochar in soil, the effect of biochar on the flux and speciation changes of C in soil, the emission of nitrogen-containing greenhouse gases induced by biochar production and soil application, and the application barriers of biochar in soil are expounded. By elaborating on these critical issues, we discuss the challenges and knowledge gaps that hinder our understanding and application of biochar for C sequestration in soil and provide outlooks for future research directions. We suggest that combining the mechanistic understanding of biochar-to-soil interactions and long-term field studies, while considering the influence of multiple factors and processes, is essential to bridge these knowledge gaps. Further, the standards for biochar production and soil application should be widely implemented, and the threshold values of biochar application in soil should be urgently developed. Also needed are comprehensive and prospective life cycle assessments that are not restricted to soil C sequestration and account for the contributions of contamination remediation, soil quality improvement, and vegetation C sequestration to accurately reflect the total benefits of biochar on C sequestration in soil.