Quantifying Uncertainties in Sequential Chemical Extraction of Soil Phosphorus Using XANES Spectroscopy

Gu, Chunhao; Dam, Than T.N.; Hart, Stephen C.; Turner, Benjamín L.; Chadwick, Oliver A.; Berhe, Asmeret Asefaw; Hu, Yongfeng; Zhu, Mengqiang

doi:10.1021/acs.est.9b05278

Cited by 69 publications

(38 citation statements)

References 64 publications

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“…This procedure isolated four inorganic P pools: anion‐exchange membrane P (P i‐AEM ), an index of bioavailable P; weakly surface‐sorbed inorganic P extracted with sodium bicarbonate (

P_{{i-NaHCO}_{3}}

); strongly surface‐sorbed (Fe‐ and Al‐bound) inorganic P extracted with sodium hydroxide (P i‐NaOH ); and calcium P, often interpreted as apatite but also inclusive of secondary calcium phosphates (Gu et al. 2020), extracted with hydrochloric acid (P i‐HCl ) (Cross and Schlesinger 1995). Three organic P pools were also quantified: water‐extractable organic P (

P_{{o-H}_{2} normalO}

); sodium bicarbonate‐extractable organic P (

P_{{o-NaHCO}_{3}}

), and sodium hydroxide‐extractable organic P (P o‐NaOH ).…”

Section: Methodsmentioning

confidence: 99%

Soil biogeochemistry across Central and South American tropical dry forests

Waring

Guzman

et al. 2021

Ecological Monographs

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The availability of nitrogen (N) and phosphorus (P) controls the flow of carbon (C) among plants, soils, and the atmosphere, thereby shaping terrestrial ecosystem responses to global change. Soil C, N, and P cycles are linked by drivers operating at multiple spatial and temporal scales: landscape‐level variation in macroclimate and soil geochemistry, stand‐scale heterogeneity in forest composition, and microbial community dynamics at the soil pore scale. Yet in many biomes, we do not know at which scales most of the biogeochemical variation emerges, nor which processes drive cross‐scale feedbacks. Here, we examined the drivers and spatial/temporal scales of variation in soil biogeochemistry across four tropical dry forests spanning steep environmental gradients. To do so, we quantified soil C, N, and P pools, extracellular enzyme activities, and microbial community structure across wet and dry seasons in 16 plots located in Colombia, Costa Rica, Mexico, and Puerto Rico. Soil biogeochemistry exhibited marked heterogeneity across the 16 plots, with total organic C, N, and P pools varying fourfold, and inorganic nutrient pools by an order of magnitude. Most soil characteristics changed more across space (i.e., among sites and plots) than over time (between dry and wet season samplings). We observed stoichiometric decoupling among C, N, and P cycles, which may reflect their divergent biogeochemical drivers. Organic C and N pool sizes were positively correlated with the relative abundance of ectomycorrhizal trees and legumes. By contrast, the distribution of soil P pools was driven by soil geochemistry, with larger inorganic P pools in soils with P‐rich parent material. Most earth system models assume that soils within a texture class operate similarly, and ignore subgrid cell variation in soil properties. Here we reveal that soil nutrient pools and fluxes exhibit as much variation among four Neotropical dry forests as is observed across terrestrial ecosystems at the global scale. Soil biogeochemical patterns are driven not only by regional differences in soil parent material and climate, but also by local‐scale variation in plant and microbial communities. Thus, the biogeochemical patterns we observed across the Neotropical dry forest biome challenge representation of soil processes in ecosystem models.

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“…This procedure isolated four inorganic P pools: anion‐exchange membrane P (P i‐AEM ), an index of bioavailable P; weakly surface‐sorbed inorganic P extracted with sodium bicarbonate (

P_{{i-NaHCO}_{3}}

P_{{o-H}_{2} normalO}

); sodium bicarbonate‐extractable organic P (

P_{{o-NaHCO}_{3}}

), and sodium hydroxide‐extractable organic P (P o‐NaOH ).…”

Section: Methodsmentioning

confidence: 99%

Soil biogeochemistry across Central and South American tropical dry forests

Waring

Guzman

et al. 2021

Ecological Monographs

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“…Chemical extraction is more sensitive to small changes in P pools than solid-state spectroscopy. However, these operationally defined P-pools are sometimes inconsistent with those from XANES spectra [10,17]. The pool size of Ca-P evaluated by the modified Hedley method is larger than those evaluated by XANES [10].…”

Section: Introductionmentioning

confidence: 97%

“…The chemical extraction methods [6][7][8] are quite useful to compare relative abundance and availability of P with different solubility on large numbers of samples. However, they are operational methods that have a drawback of producing artifacts in presumed soil P speciation analysis because of the possible redistribution of P among different binding sites during the extraction process [9,10].…”

Section: Introductionmentioning

confidence: 99%

“…However, these operationally defined P-pools are sometimes inconsistent with those from XANES spectra [10,17]. The pool size of Ca-P evaluated by the modified Hedley method is larger than those evaluated by XANES [10]. On the other hand, the pool size of Ca-P evaluated by the Sekiya method [8] was consistent with those evaluated by XANES, while those of Al-P and Fe-P were inconsistent with XANES results [16].…”

Section: Introductionmentioning

confidence: 99%

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Microscale Heterogeneous Distribution and Speciation of Phosphorus in Soils Amended with Mineral Fertilizer and Cattle Manure Compost

et al. 2021

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Global concerns for the sustainability of agriculture have emphasized the need to reduce the use of mineral fertilizer. Although phosphorus (P) is accumulated in farmland soils due to the long-term application of fertilizer, most soil P is not readily available to plants. The chemical speciation of P in soils, which comprise heterogeneous microenvironments, cannot be evaluated with a high degree of specificity using only macroscopic analyses. In this study, we investigated the distribution and speciation of P accumulated in soils by using both macro- and microscopic techniques including chemical extraction, solution and solid-state 31P NMR, bulk- and micro- P K-edge X-ray absorption near edge structure (XANES), and electron probe microanalysis (EPMA). Soil samples were collected from a field in which cabbage was cultivated under three amendment treatments: i) mineral fertilizer (NPK), ii) mineral fertilizer and compost (NPK + compost), and iii) mineral fertilizer plus compost but without nitrogen fertilizer (PK + compost). Macro-scale analyses suggested that accumulated P was predominantly inorganic P and associated with Al-bearing minerals. The repeated application of compost to the soils increased the proportion of P associated with Ca which accounted for 17% in the NPK + compost plot and 40% in the PK + compost plot. At the microscale, hot spots of P were heterogeneously distributed, and P was associated with Fe and Ca in hot spots of the NPK + compost (pH 6) and PK + compost (pH 7) treated samples, respectively. Our results indicate that application of compost contributed to creating diverse microenvironments hosting P in these soils.

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“…The basis of such fractionation analyses is in the differential reactivity of solid substrates to various chemical extractants [14]. Hence, such chemical extraction methods provide only operationally defined P pools and do not directly determine P speciation [15]. Notwithstanding their widespread application, there are various limitations associated with many sequential chemical P extraction schemes, including: (1) the specificity of extracting agents for sedimentary chemical P forms is relative; (2) transformation processes during the extractions between fractions (i.e., P sorption on calcite from calcareous sediments may be extracted in the Fe-oxide CBD extractant step).…”

Section: Introductionmentioning

confidence: 99%

Speciation of Phosphorus from Suspended Sediment Studied by Bulk and Micro-XANES

et al. 2020

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Mobilization, transformation, and bioavailability of fluvial suspended sediment-associated particulate phosphorus (PP) plays a key role in governing the surface water quality of agricultural catchment streams. Knowledge on the molecular P speciation of suspended sediment is valuable in understanding in-stream PP cycling processes. Such information enables the design of appropriate catchment management strategies in order to protect surface water quality and mitigate eutrophication. In this study, we investigated P speciation associated with fluvial suspended sediments from two geologically contrasting agricultural catchments. Sequential chemical P extractions revealed the operationally defined P fractions for the fluvial suspended sediments, with Tintern Abbey (TA) dominated by redox-sensitive P (PCBD), Al, and Fe oxyhydroxides P (PNaOH) and organic P (POrg) while Ballyboughal (BB) primarily composed of acid soluble P (PDetr), redox-sensitive P (PCBD), and loosely sorbed P (PNH4Cl). The dominant calcareous (Ca) elemental characteristic of BB suspended sediment with some concurrent iron (Fe) influences was confirmed by XRF which is consistent with the catchment soil types. Ca-P sedimentary compounds were not detected using bulk P K-edge XANES, and only P K-edge µ-XANES could confirm their presence in BB sediment. Bulk P K-edge XANES is only capable of probing the average speciation and unable to resolve Ca-P as BB spectra is dominated by organic P, which may suggest the underestimation of this P fraction by sequential chemical P extractions. Notably, µ-XANES of Ca K-edge showed consistent results with P K-edge and soil geochemical characteristics of both catchments where Ca-P bonds were detected, together with calcite in BB, while in TA, Ca-P bonds were detected but mostly as organic complexed Ca. For the TA site, Fe-P is detected using bulk P K-edge, which corresponds with its soil geochemical characteristics and sequential chemical P extraction data. Overall, P concentrations were generally lower in TA, which led to difficulties in Fe-P compound detection using µ-XANES of TA. Overall, our study showed that coupling sequential chemical P extractions with progressively more advanced spectroscopic techniques provided more detailed information on P speciation, which can play a role in mobilization, transformation, and bioavailability of fluvial sediment-associated P.

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Quantifying Uncertainties in Sequential Chemical Extraction of Soil Phosphorus Using XANES Spectroscopy

Cited by 69 publications

References 64 publications

Soil biogeochemistry across Central and South American tropical dry forests

Soil biogeochemistry across Central and South American tropical dry forests

Microscale Heterogeneous Distribution and Speciation of Phosphorus in Soils Amended with Mineral Fertilizer and Cattle Manure Compost

Speciation of Phosphorus from Suspended Sediment Studied by Bulk and Micro-XANES

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