Arsenic is ubiquitous in soil and water environments and is consistently at the top of the Agency... more Arsenic is ubiquitous in soil and water environments and is consistently at the top of the Agency for Toxic Substances Disease Registry (ATSDR) substance priority list. It has been shown to induce toxicity even at low levels of exposure. One of the major routes of exposure to arsenic is through drinking water. This review presents current information related to the distribution of arsenic in the environment, the resultant impacts on human health, especially related to diabetes, which is one of the most prevalent chronic diseases, regulation of arsenic in drinking water, and approaches for treatment of arsenic in drinking water for both public utilities and private wells. Taken together, this information points out the existing challenges to understanding both the complex health impacts of arsenic and to implementing the treatment strategies needed to effectively reduce arsenic exposure at different scales.
Critical zone science seeks to develop mechanistic theories that describe critical zone structure... more Critical zone science seeks to develop mechanistic theories that describe critical zone structure, function, and long-term evolution. One postulate is that hydrogeochemical controls on critical zone evolution can be inferred from solute discharges measured down-gradient of reactive flow paths. These flow paths have variable lengths, interfacial compositions, and residence times, and their mixing is reflected in concentration-discharge (C-Q) relations. Motivation for this special section originates from a U.S. Critical Zone Observatories workshop that was held at the University of New Hampshire, 20-22 July 2015. The workshop focused on resolving mechanistic CZ controls over surface water chemical dynamics across the full range of lithogenic (e.g., nonhydrolyzing and hydrolyzing cations and oxyanions) and bioactive solutes (e.g., organic and inorganic forms of C, N, P, and S), including dissolved and colloidal species that may cooccur for a given element. Papers submitted to this special section on ''concentration-discharge relations in the critical zone'' include those from authors who attended the workshop, as well as others who responded to the open solicitation. Submissions were invited that utilized information pertaining to internal, integrated catchment function (relations between hydrology, biogeochemistry, and landscape structure) to help illuminate controls on observed C-Q relations. Plain Language Summary This article introduces the special section of Water Resources Research entitled ''Concentration-Discharge Relations in the Critical Zone''.
Decomposition of soil organic matter (SOM) can be stimulated by fresh organic matter input, a phe... more Decomposition of soil organic matter (SOM) can be stimulated by fresh organic matter input, a phenomenon known as the ‘priming effect’. Despite its global importance, the relationship of the priming effect to mineral weathering and nutrient release remains unclear. Here we show close linkages between mineral weathering in the critical zone and primed decomposition of SOM. Intensified mineral weathering and rock-derived nutrient release are generally coupled with primed SOM decomposition resulting from “triggered” microbial activity. Fluxes of organic matter products decomposed via priming are linearly correlated with weathering congruency. Weathering congruency influences the formation of organo-mineral associations, thereby modulating the accessibility of organic matter to microbial decomposers and, thus, the priming effect. Our study links weathering with primed SOM decomposition, which plays a key role in controlling soil C dynamics in space and time. These connections represent ...
Understanding the temporal effects of organic matter input and water influx on metal lability and... more Understanding the temporal effects of organic matter input and water influx on metal lability and translocation is critical to evaluate the success of the phytostabilization of metalliferous mine tailings. Trends of metal lability, e.g., V, Cr, Mn, Co, Ni, Cu, Zn, and Pb, were investigated for three years following a direct-planting phytostabilization trial at a Superfund mine tailings site in semi-arid central Arizona, USA. Unamended tailings were characterized by high concentrations (mmol kg−1) of Fe (2100), S (3100), As (41), Zn (39), and Pb (11), where As and Pb greatly exceeded non-residential soil remediation levels established by Arizona. Phytostabilization treatments included a no-compost control, 100 g kg−1 compost with seed, and 200 g kg−1 compost with and without seed to the top 20 cm of the tailings profile. All plots received supplemental irrigation, effectively doubling the mean annual precipitation. Tailings cores up to 90 cm were collected at the time of planting and...
Abiotic transformation of anthropogenic compounds by redox-active metal oxides affects contaminan... more Abiotic transformation of anthropogenic compounds by redox-active metal oxides affects contaminant fate in soil. The capacity of birnessite and ferrihydrite to oxidize the insensitive munitions compound, 2,4-dinitroanisol (DNAN), and its amine-containing daughter products, 2-methoxy-5-nitro aniline (MENA) and 2,4-diaminoanisole (DAAN), was studied in stirred reactors at controlled pH (7.0). Aqueous suspensions were reacted at metal oxide solid to solution mass ratios (SSR) of 0.15, 1.5 and 15 g kg and solutions were analyzed after 0-3 h by high performance liquid chromatography coupled with photodiode array or mass spectrometry detection. Results indicate that DNAN was resistant to oxidation by birnessite and ferrihydrite. Ferrihydrite did not oxidize MENA, but MENA was susceptible to rapid oxidation by birnessite, with nitrogen largely mineralized to nitrite. This is the first report on mineralization of nonphenolic aromatics and the release of mineralized N from aromatic amines fo...
Assessment of ecosystem services—the benefits society receives from ecosystems—can be improved by... more Assessment of ecosystem services—the benefits society receives from ecosystems—can be improved by including broader spatial and temporal scales of geosciences perspectives.
Environmental pollution (Barking, Essex : 1987), Jan 5, 2018
The emerging insensitive munitions compound (IMC) 3-nitro-1,2,4-triazole-5-one (NTO) is currently... more The emerging insensitive munitions compound (IMC) 3-nitro-1,2,4-triazole-5-one (NTO) is currently being used to replace conventional explosives such as 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX), but the environmental fate of this increasingly widespread IMC remains poorly understood. Upon release from unexploded solid phase ordinances, NTO exhibits high aqueous solubility and, hence, potential mobilization to groundwater. Adsorption and abiotic transformation at metal oxide surfaces are possible mechanisms for natural attenuation. Here, the reactions at ferrihydrite and birnessite surfaces of NTO and its biotransformation product, 3-amino-1, 2, 4-triazol-5-one (ATO), were studied in stirred batch reactor systems at controlled pH (7.0). The study was carried out at metal oxide solid to solution ratios (SSR) of 0.15, 1.5 and 15 g kg. The samples were collected at various time intervals up to 3 h after reaction initiation, and analyzed using HPLC with photodiode array and mass spect...
Metal(loid)-contamination of the environment due to anthropogenic activities is a global problem.... more Metal(loid)-contamination of the environment due to anthropogenic activities is a global problem. Understanding the fate of contaminants requires elucidation of biotic and abiotic factors that influence metal(loid) speciation from molecular to field scales. Improved methods are needed to assess micro-scale processes, such as those occurring at biogeochemical interfaces between plant tissues, microbial cells, and metal(loid)s. Here we present an advanced method that combines fluorescence in situ hybridization (FISH) with synchrotron-based multiple-energy micro-focused X-ray fluorescence microprobe imaging (ME μXRF) to examine colocalization of bacteria and metal(loid)s on root surfaces of plants used to phytostabilize metalliferous mine tailings. Bacteria were visualized on a small root section using SytoBC nucleic acid stain and FISH probes targeting the domain Bacteria and a specific group (Alphaproteobacteria, Gammaproteobacteria, or Actinobacteria). The same root region was then ...
The rare earth elements (REE) are of increasing importance in a variety of science and economic f... more The rare earth elements (REE) are of increasing importance in a variety of science and economic fields, including (bio)geosciences, paleoecology, astrobiology, and mining. Despite their great promise, REE fractionation in early plant-microbe-rock systems has largely remained elusive. We tested the hypothesis that REE mass-partitioning during the incipient weathering of basalt, rhyolite, granite and schist depends on the activity of microbes, plant, and arbuscular mycorrhiza. Pore-water element abundances reflected a rapid transition from abiotic to biotic weathering, the latter associated with lower aqueous loss and higher uptake. Abiotic dissolution contributed 38.6+/-19% to total denudation. Microbes incremented denudation, particularly in rhyolite, this effect associating with decreased bioavailable solid fractions in this rock. Total mobilization (aqueous+uptake) was ten times greater in planted treatments compared to abiotic control, REE masses in plant generally exceeding thos...
An Inceptisol A-horizon from Hawaii was subjected to a series of reduction-oxidation cycles-14 d ... more An Inceptisol A-horizon from Hawaii was subjected to a series of reduction-oxidation cycles-14 d cycle length over a 56 d duration-across the ''soil-Fe'' [Fe(OH) 3 .Fe 2+ (aq) , log K o = 15.74] equilibrium in triplicate redox-stat reactors. Each reducing event simulated the flush of organic C and diminished O 2 that accompanies a rainfall-induced leaching of bioavailable reductants from the forest floor into mineral soil. The soil contained considerable amounts of short-range ordered (SRO) minerals (e.g., nano-goethite and allophane) and organic matter (11% org-C). Room temperature and cryogenic 57 Fe Mö ssbauer spectroscopy showed that the iron-bearing minerals were dominated by nano-to micro-scale goethite, and that ferrihydrite was not present. Over the four full cycles, fluctuations in E h (from 200 to 700 mV) and pFe 2+ (from 2.5 to 5.5) were inversely correlated with those of pH (5.5 to 4). Here, we focus on the solubility dynamics of the framework elements (Si, Fe, Ti, and Al) that constitute 35% of the oxygen-free soil dry mass. Intra-cycle oscillations in dissolved (<3 kDa) metals peaked during the reduction half-cycles. Similar intra-cycle oscillations were observed in the HCl and acid ammonium oxalate (AAO) extractable pools. The cumulative response of soil solids during multiple redox oscillations included: (1) a decrease in most HCl and AAO extractable metals and (2) a transformation of SRO Fe (as nano-goethite) to micro-crystalline goethite and micro-crystalline hematite. This may be the first direct demonstration that Fe oxide crystallinity increases during redox oscillationsan a priori unexpected result.
In redox-dynamic soils, iron reduction-oxidation events may initiate wide shifts in the concentra... more In redox-dynamic soils, iron reduction-oxidation events may initiate wide shifts in the concentration of colloidal and dissolved material because of either Fe mineral dissolution or pH shifts associated with Fe oxidation state changes. This can have profound effects on the mobilization of organic and metal constituents. We conducted laboratory studies of colloid dynamics in a Hawaiian soil subjected to four consecutive 14-day reduction-oxidation cycles across the "soil-Fe" (Fe(OH) 3)/(Fe 2+ (aq)) equilibrium. Size fractionated samples were isolated by differential centrifugation and characterized based on analysis of the framework and trace elements (Si, C, Fe, Ti, Al, Zr, Nb, La, and U). Intracycle oscillations in all colloidal (3 kDa to 160 nm) elements peaked during the reduction half-cycles, mobilizing 10% of total soil Ti and from 1-5% of total soil Zr, Nb, La, and U at peak dispersion. Colloid dynamics were dependent on pH shifts accompanying the redox oscillations rather than the fluctuating solubility of Fe oxides. TEM/EDS and massbalance calculations suggest a carbon-based colloid matrix with zones of metal enrichment. The cumulative effects of four redox cycles included an apparent increase in colloid stability. Proton production/consumption associated with Feredox cycling has important implications for mobilization colloid-borne trace elements and sorbed contaminants.
We studied the influence of tree species on soil carbon and nitrogen (N) dynamics in a common gar... more We studied the influence of tree species on soil carbon and nitrogen (N) dynamics in a common garden of replicated monocultures of fourteen angiosperm and gymnosperm, broadleaf and nee
Environmental contextThere is a growing need to understand how insensitive munitions compounds be... more Environmental contextThere is a growing need to understand how insensitive munitions compounds behave in natural environments, particularly in soils, where non-combusted residues accumulate. Here, we tested the ability of sulfate green rust, a naturally occurring mineral, to transform munitions compounds by reacting with the mineral surface. Our results show that both the munitions compounds and the mineral structures are transformed in an oxidation–reduction reaction that alters the compounds’ environmental fates. Abiotic transformation of contaminants by redox-active mineral surfaces plays an important role in the fate and behaviour of pollutants in soils and sediments. However, there is very little information on such transformations for the insensitive munitions compounds (IMCs), 3-nitro-1,2,4-triazol-5-one (NTO) and 2,4-dinitroanisole (DNAN), developed in recent years to replace the traditional munition compounds in explosive mixtures. We tested the ability of sulfate green rus...
At Earth's surface, a complex suite of chemical, biological, and physical processes combines... more At Earth's surface, a complex suite of chemical, biological, and physical processes combines to produce soil from bedrock within the zone that extends from the outer limits of vegetation to the lower limits of groundwater (the Critical Zone). This weathering engine transforms primary minerals, provides nutrients to nourish ecosystems and human society, mediates the transport of toxic components within the biosphere, creates water flow paths that shape and weaken bedrock, and contributes to the evolution of landscapes at all ...
Arsenic is ubiquitous in soil and water environments and is consistently at the top of the Agency... more Arsenic is ubiquitous in soil and water environments and is consistently at the top of the Agency for Toxic Substances Disease Registry (ATSDR) substance priority list. It has been shown to induce toxicity even at low levels of exposure. One of the major routes of exposure to arsenic is through drinking water. This review presents current information related to the distribution of arsenic in the environment, the resultant impacts on human health, especially related to diabetes, which is one of the most prevalent chronic diseases, regulation of arsenic in drinking water, and approaches for treatment of arsenic in drinking water for both public utilities and private wells. Taken together, this information points out the existing challenges to understanding both the complex health impacts of arsenic and to implementing the treatment strategies needed to effectively reduce arsenic exposure at different scales.
Critical zone science seeks to develop mechanistic theories that describe critical zone structure... more Critical zone science seeks to develop mechanistic theories that describe critical zone structure, function, and long-term evolution. One postulate is that hydrogeochemical controls on critical zone evolution can be inferred from solute discharges measured down-gradient of reactive flow paths. These flow paths have variable lengths, interfacial compositions, and residence times, and their mixing is reflected in concentration-discharge (C-Q) relations. Motivation for this special section originates from a U.S. Critical Zone Observatories workshop that was held at the University of New Hampshire, 20-22 July 2015. The workshop focused on resolving mechanistic CZ controls over surface water chemical dynamics across the full range of lithogenic (e.g., nonhydrolyzing and hydrolyzing cations and oxyanions) and bioactive solutes (e.g., organic and inorganic forms of C, N, P, and S), including dissolved and colloidal species that may cooccur for a given element. Papers submitted to this special section on ''concentration-discharge relations in the critical zone'' include those from authors who attended the workshop, as well as others who responded to the open solicitation. Submissions were invited that utilized information pertaining to internal, integrated catchment function (relations between hydrology, biogeochemistry, and landscape structure) to help illuminate controls on observed C-Q relations. Plain Language Summary This article introduces the special section of Water Resources Research entitled ''Concentration-Discharge Relations in the Critical Zone''.
Decomposition of soil organic matter (SOM) can be stimulated by fresh organic matter input, a phe... more Decomposition of soil organic matter (SOM) can be stimulated by fresh organic matter input, a phenomenon known as the ‘priming effect’. Despite its global importance, the relationship of the priming effect to mineral weathering and nutrient release remains unclear. Here we show close linkages between mineral weathering in the critical zone and primed decomposition of SOM. Intensified mineral weathering and rock-derived nutrient release are generally coupled with primed SOM decomposition resulting from “triggered” microbial activity. Fluxes of organic matter products decomposed via priming are linearly correlated with weathering congruency. Weathering congruency influences the formation of organo-mineral associations, thereby modulating the accessibility of organic matter to microbial decomposers and, thus, the priming effect. Our study links weathering with primed SOM decomposition, which plays a key role in controlling soil C dynamics in space and time. These connections represent ...
Understanding the temporal effects of organic matter input and water influx on metal lability and... more Understanding the temporal effects of organic matter input and water influx on metal lability and translocation is critical to evaluate the success of the phytostabilization of metalliferous mine tailings. Trends of metal lability, e.g., V, Cr, Mn, Co, Ni, Cu, Zn, and Pb, were investigated for three years following a direct-planting phytostabilization trial at a Superfund mine tailings site in semi-arid central Arizona, USA. Unamended tailings were characterized by high concentrations (mmol kg−1) of Fe (2100), S (3100), As (41), Zn (39), and Pb (11), where As and Pb greatly exceeded non-residential soil remediation levels established by Arizona. Phytostabilization treatments included a no-compost control, 100 g kg−1 compost with seed, and 200 g kg−1 compost with and without seed to the top 20 cm of the tailings profile. All plots received supplemental irrigation, effectively doubling the mean annual precipitation. Tailings cores up to 90 cm were collected at the time of planting and...
Abiotic transformation of anthropogenic compounds by redox-active metal oxides affects contaminan... more Abiotic transformation of anthropogenic compounds by redox-active metal oxides affects contaminant fate in soil. The capacity of birnessite and ferrihydrite to oxidize the insensitive munitions compound, 2,4-dinitroanisol (DNAN), and its amine-containing daughter products, 2-methoxy-5-nitro aniline (MENA) and 2,4-diaminoanisole (DAAN), was studied in stirred reactors at controlled pH (7.0). Aqueous suspensions were reacted at metal oxide solid to solution mass ratios (SSR) of 0.15, 1.5 and 15 g kg and solutions were analyzed after 0-3 h by high performance liquid chromatography coupled with photodiode array or mass spectrometry detection. Results indicate that DNAN was resistant to oxidation by birnessite and ferrihydrite. Ferrihydrite did not oxidize MENA, but MENA was susceptible to rapid oxidation by birnessite, with nitrogen largely mineralized to nitrite. This is the first report on mineralization of nonphenolic aromatics and the release of mineralized N from aromatic amines fo...
Assessment of ecosystem services—the benefits society receives from ecosystems—can be improved by... more Assessment of ecosystem services—the benefits society receives from ecosystems—can be improved by including broader spatial and temporal scales of geosciences perspectives.
Environmental pollution (Barking, Essex : 1987), Jan 5, 2018
The emerging insensitive munitions compound (IMC) 3-nitro-1,2,4-triazole-5-one (NTO) is currently... more The emerging insensitive munitions compound (IMC) 3-nitro-1,2,4-triazole-5-one (NTO) is currently being used to replace conventional explosives such as 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX), but the environmental fate of this increasingly widespread IMC remains poorly understood. Upon release from unexploded solid phase ordinances, NTO exhibits high aqueous solubility and, hence, potential mobilization to groundwater. Adsorption and abiotic transformation at metal oxide surfaces are possible mechanisms for natural attenuation. Here, the reactions at ferrihydrite and birnessite surfaces of NTO and its biotransformation product, 3-amino-1, 2, 4-triazol-5-one (ATO), were studied in stirred batch reactor systems at controlled pH (7.0). The study was carried out at metal oxide solid to solution ratios (SSR) of 0.15, 1.5 and 15 g kg. The samples were collected at various time intervals up to 3 h after reaction initiation, and analyzed using HPLC with photodiode array and mass spect...
Metal(loid)-contamination of the environment due to anthropogenic activities is a global problem.... more Metal(loid)-contamination of the environment due to anthropogenic activities is a global problem. Understanding the fate of contaminants requires elucidation of biotic and abiotic factors that influence metal(loid) speciation from molecular to field scales. Improved methods are needed to assess micro-scale processes, such as those occurring at biogeochemical interfaces between plant tissues, microbial cells, and metal(loid)s. Here we present an advanced method that combines fluorescence in situ hybridization (FISH) with synchrotron-based multiple-energy micro-focused X-ray fluorescence microprobe imaging (ME μXRF) to examine colocalization of bacteria and metal(loid)s on root surfaces of plants used to phytostabilize metalliferous mine tailings. Bacteria were visualized on a small root section using SytoBC nucleic acid stain and FISH probes targeting the domain Bacteria and a specific group (Alphaproteobacteria, Gammaproteobacteria, or Actinobacteria). The same root region was then ...
The rare earth elements (REE) are of increasing importance in a variety of science and economic f... more The rare earth elements (REE) are of increasing importance in a variety of science and economic fields, including (bio)geosciences, paleoecology, astrobiology, and mining. Despite their great promise, REE fractionation in early plant-microbe-rock systems has largely remained elusive. We tested the hypothesis that REE mass-partitioning during the incipient weathering of basalt, rhyolite, granite and schist depends on the activity of microbes, plant, and arbuscular mycorrhiza. Pore-water element abundances reflected a rapid transition from abiotic to biotic weathering, the latter associated with lower aqueous loss and higher uptake. Abiotic dissolution contributed 38.6+/-19% to total denudation. Microbes incremented denudation, particularly in rhyolite, this effect associating with decreased bioavailable solid fractions in this rock. Total mobilization (aqueous+uptake) was ten times greater in planted treatments compared to abiotic control, REE masses in plant generally exceeding thos...
An Inceptisol A-horizon from Hawaii was subjected to a series of reduction-oxidation cycles-14 d ... more An Inceptisol A-horizon from Hawaii was subjected to a series of reduction-oxidation cycles-14 d cycle length over a 56 d duration-across the ''soil-Fe'' [Fe(OH) 3 .Fe 2+ (aq) , log K o = 15.74] equilibrium in triplicate redox-stat reactors. Each reducing event simulated the flush of organic C and diminished O 2 that accompanies a rainfall-induced leaching of bioavailable reductants from the forest floor into mineral soil. The soil contained considerable amounts of short-range ordered (SRO) minerals (e.g., nano-goethite and allophane) and organic matter (11% org-C). Room temperature and cryogenic 57 Fe Mö ssbauer spectroscopy showed that the iron-bearing minerals were dominated by nano-to micro-scale goethite, and that ferrihydrite was not present. Over the four full cycles, fluctuations in E h (from 200 to 700 mV) and pFe 2+ (from 2.5 to 5.5) were inversely correlated with those of pH (5.5 to 4). Here, we focus on the solubility dynamics of the framework elements (Si, Fe, Ti, and Al) that constitute 35% of the oxygen-free soil dry mass. Intra-cycle oscillations in dissolved (<3 kDa) metals peaked during the reduction half-cycles. Similar intra-cycle oscillations were observed in the HCl and acid ammonium oxalate (AAO) extractable pools. The cumulative response of soil solids during multiple redox oscillations included: (1) a decrease in most HCl and AAO extractable metals and (2) a transformation of SRO Fe (as nano-goethite) to micro-crystalline goethite and micro-crystalline hematite. This may be the first direct demonstration that Fe oxide crystallinity increases during redox oscillationsan a priori unexpected result.
In redox-dynamic soils, iron reduction-oxidation events may initiate wide shifts in the concentra... more In redox-dynamic soils, iron reduction-oxidation events may initiate wide shifts in the concentration of colloidal and dissolved material because of either Fe mineral dissolution or pH shifts associated with Fe oxidation state changes. This can have profound effects on the mobilization of organic and metal constituents. We conducted laboratory studies of colloid dynamics in a Hawaiian soil subjected to four consecutive 14-day reduction-oxidation cycles across the "soil-Fe" (Fe(OH) 3)/(Fe 2+ (aq)) equilibrium. Size fractionated samples were isolated by differential centrifugation and characterized based on analysis of the framework and trace elements (Si, C, Fe, Ti, Al, Zr, Nb, La, and U). Intracycle oscillations in all colloidal (3 kDa to 160 nm) elements peaked during the reduction half-cycles, mobilizing 10% of total soil Ti and from 1-5% of total soil Zr, Nb, La, and U at peak dispersion. Colloid dynamics were dependent on pH shifts accompanying the redox oscillations rather than the fluctuating solubility of Fe oxides. TEM/EDS and massbalance calculations suggest a carbon-based colloid matrix with zones of metal enrichment. The cumulative effects of four redox cycles included an apparent increase in colloid stability. Proton production/consumption associated with Feredox cycling has important implications for mobilization colloid-borne trace elements and sorbed contaminants.
We studied the influence of tree species on soil carbon and nitrogen (N) dynamics in a common gar... more We studied the influence of tree species on soil carbon and nitrogen (N) dynamics in a common garden of replicated monocultures of fourteen angiosperm and gymnosperm, broadleaf and nee
Environmental contextThere is a growing need to understand how insensitive munitions compounds be... more Environmental contextThere is a growing need to understand how insensitive munitions compounds behave in natural environments, particularly in soils, where non-combusted residues accumulate. Here, we tested the ability of sulfate green rust, a naturally occurring mineral, to transform munitions compounds by reacting with the mineral surface. Our results show that both the munitions compounds and the mineral structures are transformed in an oxidation–reduction reaction that alters the compounds’ environmental fates. Abiotic transformation of contaminants by redox-active mineral surfaces plays an important role in the fate and behaviour of pollutants in soils and sediments. However, there is very little information on such transformations for the insensitive munitions compounds (IMCs), 3-nitro-1,2,4-triazol-5-one (NTO) and 2,4-dinitroanisole (DNAN), developed in recent years to replace the traditional munition compounds in explosive mixtures. We tested the ability of sulfate green rus...
At Earth's surface, a complex suite of chemical, biological, and physical processes combines... more At Earth's surface, a complex suite of chemical, biological, and physical processes combines to produce soil from bedrock within the zone that extends from the outer limits of vegetation to the lower limits of groundwater (the Critical Zone). This weathering engine transforms primary minerals, provides nutrients to nourish ecosystems and human society, mediates the transport of toxic components within the biosphere, creates water flow paths that shape and weaken bedrock, and contributes to the evolution of landscapes at all ...
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Papers by Jon Chorover