Yuji Arai

University of Illinois, Urbana-Champaign | UIUC · Department of Natural Resources and Environmental Sciences

Residence time effects on phase transformation of silver nanoparticles (AgNPs) (15-50 nm, with and without polyvinylpyrrolidone (PVP) coating) were investigated in reducing soils using experimental geochemistry and synchrotron-based x-ray techniques. After 30 days of anaerobic incubation, a substantial fraction of PVP-coated AgNPs (15 nm) were tran...

Mineralizable macronutrients (e.g. C, N, P, and S) are sorbed readily (i.e. adsorption and precipitation) in clays and clay minerals. Phosphorus (P) is one of the limiting macronutrients in soils because both phosphate and organic P undergo chemisorption in soil minerals. Furthermore, phosphatases that mineralize the organic P species tend to parti...

Natural occurring ferrihydrite (Fh) nanoparticles have varying degrees of crystallinity, but how Fh crystallinity affects its transformation behavior remains elusive. Here, we investigated the Fe(II)-catalyzed transformation of Fh with different degrees of crystallinity (i.e., Fh-2h, Fh-12h, and Fh-85C). X-ray diffraction patterns of Fh-2h, Fh-12h,...

With the increasing demand for P fertilizer for world food production, the use of soil organic P fraction via mineralization could become an important P resource in agricultural soils. However, the predominant organic P species, phytic acid, has been considered rather recalcitrant to mineralization due to its active interaction with dissolved metal...

In soils and rhizospheres, iron (oxyhydr)oxides and oxyanions like carbonate and phosphate occur ubiquitously and their interaction have important implications for nutrients and metals cycling. An elevated activity of carbonate in soils and sediments (e.g., pCO2, ∼2%) above current atmospheric CO2 (∼0.04%) is observed. The level of agronomic soil t...

As one of the most abundant organic phosphorus (P) species in soils, phytic acid could serve as a mineralizable P reservoir in soils and sediments. It has been widely acknowledged that the adsorption of phytic acid to soil minerals retards P mineralization in soils. However, the adsorption mechanisms of phytic acid in the minerals are not clearly u...

Legacy effects of P in agricultural soils have been highlighted in recent literature. However, co-accumulation and release of organic P (Po) have often been ignored in current agro-environmental assessments. The mineralizable Po fraction has a potential to increase the activity of phosphate in pore water, increasing fertility or degrading water qua...

Myo-inositol hexakisphosphate (myo-IHP) is one of the most common soil organic phosphorus (P) species in soil. Its retention in soil is often competed by phosphate, making bioavailability of P species difficult. In this study, the adsorption mechanism of myo-IHP at the amorphous aluminum (oxyhydr)oxide (AAH)-water interface was investigated at pH 6...

Phosphorus (P) loss from intensively managed agricultural soils is a well-known environmental issue in the world because of its negative impact on aquatic environments (e.g., eutrophication and hypoxia). Most soil P chemistry research focused on the accumulation of phosphate or total P(TP) in soils and sediments. However, coaccumulation of an organ...

Transformation of metastable Fe(III) oxyhydroxides is a prominent process in natural environments and can be significantly accelerated by the coexisting aqueous Fe(II) (Fe(II)aq). Recent evidence points to the solution mass transfer of labile Fe(III) (Fe(III)labile) as the primary intermediate species of general importance. However, a mechanistic a...

Sorption processes at the mineral–water interface are fundamental to the chemical functioning of soils, and impact the biogeochemical cycling of both trace and major elements in soil and sediment environments. Surface complexation reactions control the solubility, and hence bioavailability and mobility, of trace elements and may promote electron tr...

Phytic acid (myo-inositol hexaphosphate, IHP) is a dominant form of organic phosphate (OP) in organic carbon-rich surface soil. The IHP impact on Fe (oxyhydr)oxide transport is critical for iron and phosphorus (bio)geochemical processes in iron and phosphorus rich soil and subsurface systems. Three typical Fe (oxyhydr)oxides (ferrihydrite, hematite...

As an essential component of enzymes, higher N availability from agricultural runoff to forest soils may boost the activity of phosphatase, increasing the bioavailability of phosphate. The objective of this study was to evaluate P mineralization rates in temperate floodplain soils as a function of inorganic N species (i.e., ammonium and nitrate) an...

A mineralizable phosphorus (P) fraction in soils has not been considered in the current agronomic soil P test. Organic P might be a potential source of bioavailable P under the influence of specific soil conditions such as N input. In this laboratory incubation study, the effects of urea (0.1‐0.3 g of N kg–1 soil) on P mineralization was investigat...

Legacy phosphorus (P) has accelerated the subsurface transport of colloidal P (CP) in intensively managed agricultural soils in the Midwestern U.S. Because of its high P sorption capacity and mobility, understanding the depth sequence distribution of mobile CP and its speciation in the soil profile is critical in assessing total P(TP) loss to prote...

While the effects of carbon on soil nitrogen (N) cycle have been extensively studied, it is not clearly understood how co-existing macronutrients, such as phosphorus (P), affect the N cycle in agroecosystems. In this study, P amendment effects on nitrification in a fertile agricultural soil were investigated under a typical N-P amendment rate. In a...

As phosphorus (P) losses from Midwestern crop fields degrade water quality in downstream water bodies, the assessment of natural P immobilization in floodplain soils is imperative to reduce P input to the Gulf of Mexico. While the organic C:P ratio of soil is widely accepted as an important indicator of P immobilization, roles of the quality/type o...

An elevated activity of (bi)carbonate in soils and sediments (pCO2, ∼2%) above current atmospheric CO2 (∼0.04%) could influence the iron cycling in mineral-water interfacial chemistry. However, the impact of (bi)carbonate on mineral transformation is unclear. Here, a model short range-ordered iron oxyhydroxide, two-line ferrihydrite, was used to ev...

Tile drainage waters carry considerable loads of phosphorus (P) from agricultural fields to rivers and streams in the Midwestern U.S. An innovative and economical approach to monitor dissolved reactive P (DRP) flux in tile waters is needed to understand the extent of P loss in field-scale. In this study, a passive sampling technique was developed u...

Nutrient losses from Mississippi watersheds degrade downstream water bodies. As forested floodplains intercept agricultural drainage waters, a limiting nutrient like phosphorus (P) could potentially be sequestered in forest soils, reducing P loss to the Gulf of Mexico. Thus far, the role of temperate deciduous floodplain soils for P has not been ex...

Subsurface storm flow of phosphorus (P), including particulate P, has been recently discussed as an important P transport path in contrast to typical surface runoff events. However, P speciation, and P concentration during storm events has not been extensively investigated; therefore, its contribution to the water quality is not clearly understood....

Phosphorus (P) is one of the essential macronutrients for agricultural production. Accelerated crop production to meet the global food demand has led to the accumulation of P in agriculture soils through over-use of fertilizers. Phosphorus loss to the aquatic environment through surface runoff and subsurface transport is known to contribute to the...

The process of phosphate desorption from soils is difficult to measure using stirred batch techniques because of the accumulation of desorbed ions in a bathing solution. To accurately measure the apparent rate coefficient of phosphate desorption from soils, it is necessary to remove the desorbed ions. In this study, a novel hybrid (i.e., iron oxide...

Phytic acid is a common phosphate monoester that is present in soils due to the deposition of plant derived materials. Thus far, its interaction with dissolved Fe and Fe minerals has not been as extensively investigated as phosphate although it is expected be highly reactive due to its multiple phosphate functional groups. In this study, the effect...

Excessive phosphorus (P) loss from soil to water bodies is known to cause negative impacts in the aquatic ecosystem. Along with dissolved reactive P, colloidal P has been of the interest in the agroecosystem research because of its mobility in surface runoff and subsurface flow in soil. The physicochemical characteristics (i.e., high adsorption cap...

Ferrihydrite (Fh) is generally associated with dissolved organic matter (DOM) in natural environments due to a strong sorption affinity at circumneutral pH and its high specific surface area. In suboxic conditions, aqueous Fe(II) (Fe(II)aq) can catalyze transformation of Fh into more stable crystalline Fe(III) phases, but how DOM influences the tra...

Aqueous Fe(II) (Fe(II)aq) effectively magnifies the reducibility of magnetite towards environmental substances. In natural magnetite, isomorphous substitution by foreign metals is ubiquitous, and Zn2+ and Co2+ have been reported to positively improve the reducing capacity of magnetite coupled with Fe(II)aq. Though most metal ions significantly alte...

In addition to surface runoff, subsurface P loss through tile lines in agricultural lands has been receiving attention in the last decade. It is not clearly understood how this strong ligand, phosphate, is distributed in subsoils (up to 180 cm) and contributing to the subsurface P loss. It was hypothesized that subsurface accumulation of labile P a...

The growing use of nano titanium dioxide (TiO2) in consumer and agricultural products has accelerated its introduction into terrestrial environments, where its impact has not been documented extensively. TiO2 toxicity arises primarily from its ability to photochemically generate reactive oxygen species (ROS), including hydrogen peroxide (H2O2). Whi...

Precipitation of hydroxyapatite, is one of the important geochemical processes controlling the concentration of phosphorus (P) in alkaline soils, though its formation at below neutral pH is not clearly understood. In this study, the precipitation of hydroxyapatite at pH 5.8 and 6.8 was investigated under the environmentally relevant Ca/P molar rati...

Biochar has attracted widespread attention due to its high carbon (C) content, abundant surface functional groups and porous structure. Numerous studies have shown that biochar has beneficial effects on the soil phosphorus (P) cycle. This article reviewed the current literatures on biochar and the effects of biochar amendments on the soil P cycle....

Phytic acid, as the dominant organic phosphorus species in soils, always preferentially adsorbs on Fe/Al minerals. In this study, adsorption mechanisms of phytic acid at the ferrihydrite-water interface were investigated as a function of pH using batch adsorption experiment, zeta potential measurements, in-situ P K-edge X-ray absorption near edge s...

The potential agricultural use of metal nanoparticles (NPs) for slow-release micronutrient fertilizers is beginning to be investigated by both industry and regulatory agencies. However, the impact of such NPs on soil biogeochemical cycles is not clearly understood. In this study, the impact of commercially-available copper NPs on soil nitrification...

The potential agricultural use of metal nanoparticles (NPs) for slow-release micronutrient fertilizers is beginning to be investigated by both industry and regulatory agencies. However, the impact of such NPs on soil biogeochemical cycles is not clearly understood. In this study, impacts of a commercially-available copper NPs on the soil nitrificat...

Converting swine manure to biochar is an effective way to recycle valuable nutrients, but there are few reports on its feasibility as a phosphorus (P) source. The objective of this study was to clarify the unique nature, including P speciation, of manure biochar products under various pyrolysis temperatures. We used solution ³¹P nuclear magnetic re...

A chemical extraction of soil organic- and poly‑phosphorus (P) with a 0.25 M NaOH +0.05 M ethylenediaminetetraacetic acid (EDTA) solution is the most widely accepted method for ³¹P NMR measurements. The chemical preservation is often questioned because of inconsistent extraction time (4–16 h) among researchers. In this study, the effect of extracti...

It became increasingly important to regulate phosphorus (P) loss from P-rich agricultural fields because of accelerated eutrophication and hypoxia in freshwater and coastal marine systems in the world. Understanding the P stabilization mechanisms in soils, such as mineralization and immobilization, will help in adopting good agricultural management...

Manure biochar (MB) is recognized a beneficial material for absorbing heavy metals from soil and alleviating soil degradation. However, the addition effects of MB on the phospholipid fatty acid (PLFA) concentrations and their linkage to heavy metal accumulation in rice are poorly understood. A microcosm incubation experiment was conducted to study...

Soil test phosphorus (STP) (Bray P-1, Mehlich III) was developed to predict the plant available P in agricultural soils in the USA. The acidic STP extracting solutions were intended to extract phosphate from alkaline earth metal-based solubility products and or adsorbed species on amorphous metal hydroxides or phyllosilicates in soils. However, the...

Reduced sulfur species in ground-granulated blast furnace slag (GGBFS) play an important role in immobilizing radionuclide contaminants in caustic cement-GGBFS mixtures via reductive precipitation reaction. However, sulfur (S) speciation and its stability in GGBFS have not been clearly understood. In this study, S speciation of GGBSF in alkaline ra...

Ceria (CeO2) has received much attention in the global nanotechnology market due to its useful industrial applications. Because of its release to the environment, chemical fate of ceria nanoparticles (NPs) becomes important in protecting the agricultural and food systems. Using experimental biogeochemistry and synchrotron-based X-ray techniques, fa...

Technetium-99 (⁹⁹Tc) is a radioactive isotope with a half-life of 2.13 × 10⁵ year. ⁹⁹Tc is a major radionuclide contaminant of concern for the world. Therefore, detailed understanding of ⁹⁹Tc environmental chemistry is important for protecting human and ecological health. Here, we review the aqueous geochemistry of ⁹⁹Tc, focusing on chemical proper...

Reducing cementitious materials (RCMs) are presently being developed for the long-term, subsurface disposal of low-level radioactive waste within the United States Department of Energy complex. Slag is included in the formulation of the RCM to facilitate the reductive precipitation of redox-sensitive radionuclides, particularly ⁹⁹Tc. Using Re(VII)O...

Soil chemistry, the study of the chemical processes in soils, is affected by soil composition and biological and physicochemical processes. Although traditionally the field of soil chemistry has dealt with soil fertility, modern soil chemistry covers both agronomic and environmental aspect such as soil–water interfacial reactions of nutrients, meta...

Core Ideas Original ascorbic acid methods are sensitive in STP solutions at phosphate <2 mg L ⁻¹ . New optimum wavelengths for the Dick and Tabatabai method in STP extraction solutions. A new optimum wavelength of 888 nm for Asher's methods is recommended. Phosphate spectrophotometric methods are valuable in agro‐environmental research because of...

Technetium(Tc)-99 is one of major risk drivers in low level radioactive liquid waste at the U.S. Department of Energy sites. Cementitious waste technology (CWT) has been considered immobilizing pertechnetate, Tc(VII)O4⁻, in brine and alkaline waste solutions, as Tc(IV) oxides and/or sulfides with the use of reducing agents like slag. In this study,...

Background: Reductive precipitation of hexavalent chromium (Cr(VI)) with magnetite is a well-known Cr(VI) remediation method to improve water quality. The rapid (<a few hr) reduction of soluble Cr(VI) to insoluble Cr(III) species by Fe(II) in magnetite has been the primary focus of the Cr(VI) removal process in the past. However, the contribution...

2-pyridyl thiourea and methyl-2-pyridyl ketoxime based perrhenate, Re(VII), UV-vis spectrophotometric methods were evaluated in nitrate and bicarbonate solutions ranging from 0.001 M to 0.5 M. Standard curves at [Re]=2.5–50 mg L−1 for the Re(IV)-thiourea and the Re ketoxime complexes were constructed at 405 nm and 490 nm, respectively. Detection of...

Metal hydroxides (e.g. ferrihydrite) present in geomedia play significant roles in regulating the environmental mobilities of arsenate (As(V)) and inorganic phosphate (Pi) because of their high adsorption affinities for these oxyanions. In this study, results are presented of experiments aimed at determining individual and competitive adsorption/de...

Cement waste form (CWF) technology is among the leading approaches to disposing of metals and liquid low-level nuclear waste in the United States. One such material, saltstone, includes slag, fly ash and Portland cement to enhance the immobilization of contaminants (e.g., Cr, (99)Tc) in alkaline liquid wastes. To evaluate the stability of such redo...

Cerium is the most abundant of rare-earth metals found in the Earth's crust. Several Ce-carbonate, -phosphate, -silicate, and -(hydr)oxide minerals have been historically mined and processed for pharmaceutical uses and industrial applications. Of all Ce minerals, cerium dioxide has received much attention in the global nanotechnology market due to...

Iodine is a trace halide found in the environment. A majority of global iodine budget resides in ocean while lithosphere and pedosphere contain the rest limiting the bio-availability of iodine in terrestrial environment. Iodine cycles involve the multivalence state chemical speciation at the air-water-sediment interfaces. The mobility and reactivit...

To investigate the effect of P surface loading on the structure of surface complexes formed at the goethite/water interface, goethite was reacted with orthophosphate at P concentrations of 0.1, 0.2, and 0.8 mmol L-1 at pH 4.5 for 5 days. The P concentrations were chosen to ensure that P loadings at the surface would allow one to follow the transiti...

Two aqueous PuIV-desferrioxamine B (DFOB) complexes were characterized by one- and two-dimensional NMR techniques and an unexpected dimeric PuIVDFOB-di-μ-(O/OH)-PuIVDFOB complex was identified. Both “Curie” and “anti-Curie” behavior were observed for the dimeric species, yet the monomeric species only showed “anti-Curie” behavior. Diffusion ordered...

A large increase in commercial and home use of silver nanoparticle (AgNP) products and technologies has raised concerns about their impact on environmental health. While several sources cite soils and sediments as the predominant sink for AgNPs in natural environments, few studies contribute to risk assessment of AgNPs in terrestrial environments....

Cerium (Ce)-based compounds, such as CeO2 nanoparticles (NPs), have received much attention in the last several years due to their popular applications in industrial and commercial uses. Understanding the impact of CeO2 NPs on nutrient cycles, a subchronic toxicity study of CeO2 NPs on soil-denitrification process was performed as a function of par...

The release of silver (Ag) nanoparticles (NPs) from the use of consumer products to the environment has raised concern about the risk to ecosystems because of its unpredictable toxicological impact to microorganisms in terrestrial environment. In this study, the impact of Ag chemical speciation (Ag(+) and Ag-NPs [50-nm uncoated and 15-nm polyvinylp...

Metal hydroxides (e.g. ferrihydrite) present in geomedia play significant roles in regulating the environmental mobilities of arsenate (As(V)) and inorganic phosphate (Pi) because of their high adsorption affinities for these oxyanions. In this study, results are presented of experiments aimed at determining individual and competitive adsorption/de...

The environmental fate of actinides is greatly influenced by interfacial reactions, including adsorption onto solid surfaces where the adsorption of trivalent and tetravalent actinides is generally a very strong and potentially irreversible reaction. Changes in the primary hydration sphere of the actinide during inner-sphere adsorption could greatl...

Cerium-based compounds such as CeO2 nanoparticles (NP) have received much attention in the last several years due to their popular applications in industrial and commercial uses. There is a growing concern about the environmental fate of released CeO2 NPs, particularly their unintended impact in aquatic and terrestrial environments. To understand t...

Colloid (typically < 1 μm) facilitated phosphorus (P) transport in agricultural soils has received much research attention in recent decades due to the possibility of a mobile solid form of P, which may increase P runoff in some soils. The existing literature reports inconsistent results of colloidal P release as a percentage of total P in soil sol...

Eutrophication caused by phosphorus (P) rich leachate from sandy soils has been one of the major agro-environmental issues in the world. In predicting P bioavailability in soils, P reactivity in soil clay fractions (e.g., iron oxyhydroxides) has been a major focus of soil chemistry research in the past. However, the role of sand fraction has been r...

Silver, Ag, is a metallic element that has been valued for its use in currency, jewelry, photoprocessing, electronics, and in the medical field. In the past decade, there have been many advances in the field of nanotechnology, including the use of silver and other metal nanoparticles. Silver nanoparticles are currently one of the most common metal...

The toxicity of silver nanoparticles to bacteria, while frequently demonstrated in laboratory settings, has not been well established within environmental media. This study investigates the effect of three different silver nanoparticles (35-60nm, uncoated and coated with 0.3% polyvinylpyrrolidone) at various concentrations (1, 10, or 100mg/L) on th...

The effects of dissolved calcium (Ca) on arsenate (As(V)) reactivity and surface speciation at the kaolinite-water interface were studied as a function of pH using pseudo-equilibrium adsorption/ desorption experiments and extended X-ray absorption fine-structure spectroscopy (EXAFS) analyses. The EXAFS analyses indicated that As(V) tetrahedral mole...

Understanding uranium (U) sorption processes in permeable reactive barriers (PRB) are critical in modeling reactive transport for evaluating PRB performance at the Fry Canyon demonstration site in Utah, USA. To gain insight into the U sequestration mechanism in the amorphous ferric oxyhydroxide (AFO)-coated gravel PRB, U(VI) sorption processes on f...

Environmental contamination of lead (Pb) in soils and sediments poses serious threats to human and ecological health. The objective of this study is to investigate the effect of seasonal dove sports hunting activities on Pb contamination in acid forest soils. A grid sampling method was used to investigate the spatial distribution of Pb contaminatio...

Methylated forms of arsenic (As), monomethylarsenate (MMA), and dimethylarsenate (DMA) have historically been used as herbicides and pesticides. Because of their large application to agriculture fields and the toxicity of MMA and DMA, the persistency of these compounds in the environment is of great concern. MMA and DMA sorption and desorption were...

Methylated forms of arsenic (As), monomethylarsenate (MMA) and dimethylarsenate (DMA), have historically been used as herbicides and pesticides. Because of their large application to agriculture fields and the toxicity of MMA and DMA, the distribution, speciation, and sorption of methylated As to soils requires investigation. Monomethylarsenate and...

High levels of U (up to 5570μg/L) have been discovered in well waters near Simpsonville, South Carolina, USA. In order to characterize the mineralogical source of the U and possible structural controls on its presence, a deep (214m) well was cored adjacent to one of the enriched wells. The highest gamma-ray emissions in the recovered core occur in...

Labile P is a well-recognized nonpoint source pollutant in agroecosystems. Predicting the fate and transport of P in watershed systems is critical in protecting water quality. In this case study, we investigated the role of soil nanoparticles in P release in South Carolina agricultural soils. Batch desorption experiments were coupled with scanning...

Understanding in situ metalloid surface speciation on mineral surfaces is critical to predicting the bioavailability in surface and subsurface environments. In this study, Mo K-edge X-ray absorption spectroscopy (XAS) was used to elucidate Mo(VI) surface speciation at the goethite-water interface. Effects of pH and loading levels were investigated....

The influence of parasitoids and soil compaction on pupation behavior of blow flies was examined in a host–parasitoid system involving Lucilia sericata (Meigen) (Diptera: Calliphoridae) and Nasonia vitripennis (Walker) (Hymenoptera: Pteromalidae). Larvae of L. sericata were introduced to containers with soil of different compaction levels, with or...

IntroductionGeogenic OccurrenceSources of Soil ContaminationChemical Behavior in SoilsRisks from Arsenic and Antimony in SoilsConclusions and Future Research NeedsReferences

The hymenopteran parasitoid Nasonia vitripennis (Pteromalidae) has long been used to control the green bottle fly Lucilia sericata (Diptera: Calliphoridae) in many locations worldwide. This interaction has traditionally occurred in an agricultural setting where L. sericata is regarded as a pest of humans and livestock. This symbiotic relationship a...

Understanding in situ metal surface speciation on mineral surfaces is critical to predicting the natural attenuation of metals in the subsurface environment. In this study, we have demonstrated the novel Ni K-edge X-ray absorption spectroscopy (XAS) measurements needed to understand Ni(ll) surface speciation in three synthetic iron oxyhydroxides (f...

Macroscopic‐ to more recent molecular scale investigations have enhanced our knowledge of soil phosphorus (P) chemistry, including the retention/release mechanisms in soils and soil components. Phosphate uptake on metal (oxy)hydroxide and phyllosilicate mineral surfaces and in soils generally increases with decreasing pH. Rapid adsorption kinetics...

Uranium (U) solid-state speciation in vadose zone sediments collected beneath the former North Process Pond (NPP) in the 300 Area of the Hanford site (Washington) was investigated using multi-scale techniques. In 30 day batch experiments, only a small fraction of total U (approximately 7.4%) was released to artificial groundwater solutions equilibr...

Np(V) surface speciation on hematite surfaces at pH 7-9 under pC2 = 10(-3.45) atm was investigated using X-ray absorption spectroscopy (XAS). In situ XAS analyses suggest that bis-carbonato inner-sphere and tris-carbonato outer-sphere ternary surface species coexist at the hematite-water interface at pH 7-8.8, and the fraction of outer-sphere speci...

Guadalupe Reservoir (GUA), California, and Lahontan Reservoir (LAH), Nevada, U.S. are both affected either directly or indirectly by the legacy of gold and silver mining in the Sierra Nevada during the nineteenth century. Analysis of total mercury in fish from these lentic systems consistently indicate elevated concentrations (>1 microg x g(-1) wet...

Macro- and molecular-scale knowledge of uranyl (U(VI)) partitioning reactions with soil/sediment mineral components is important in predicting U(VI) transport processes in the vadose zone and aquifers. In this study, U(VI) reactivity and surface speciation on a poorly crystalline aluminosilicate mineral, synthetic imogolite, were investigated using...