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1. Fractionation and environmental assessment of legacy phosphorus from acidic, organic, and calcareous soils

   https://doi.org/10.1007/s10533-026-01335-x  

   Mahmud, Md Anik; Bai, Xue; Fisher, Caroline Buchanan; Lee, Shin-Ah; Moreira, Geisianny; Rabbany, Abul; Morrison, Elise; Muenich, Rebecca; Gatiboni, Luke; Mclamore, Eric S; et al (June 2026, Biogeochemistry)

   Phosphorus (P) is essential for plant growth, but excessive and continuous application of P fertilizers and animal manure has led to the accumulation of legacy phosphorus (legacy-P) in soils. While legacy-P presents a potential resource to support future agricultural demands, limited understanding of its chemical forms across different soil types hinders its sustainable management. This study aimed to characterize the chemical nature and storage potential of legacy-P in three contrasting soil types: acidic, organic, and calcareous. Key soil properties—including pH, organic matter, total P, Mehlich-3 P, and concentrations of aluminum (Al), calcium (Ca), iron (Fe), and magnesium (Mg)—were evaluated alongside P fractionation using a modified Hedley method. Furthermore, the soil P saturation ratio (PSR) was calculated to evaluate the relative saturation of soil sorption sites with P. Results showed considerable variability in Mehlich-3 P across soil types, ranging from 7–62% of total P in acidic soils, 1–8% in organic soils, and 3–47% in calcareous soils. Acidic soils were dominated by humic/fulvic-bound P (> 42%), organic soils by recalcitrant residual P (> 62%), and calcareous soils by Ca/Mg-bound P (> 69%), highlighting the influence of soil chemistry on P stability. Despite considerable variation among soil types in P fractionations, PSR results suggested that Ca/Mg-associated minerals play a greater role in retaining legacy P in organic and calcareous soils than Al- and Fe-associated minerals. In acidic soils, both mineral groups contributed similarly to P retention. 

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2. Relict soil evidence for post-Miocene aridification in the Atacama Desert of South America

   https://doi.org/10.1130/B37356.1  

   Amundson, Ronald; Heimsath, Arjun; Jungers, Matt; Balan, Simona; Ebeling, Angela; Nishiizumi, Kunihiko; Ewing, Stephanie; Shuster, David; Caffee, Marc W; Pfeiffer, Marco; et al (July 2024, Geological Society of America Bulletin)

   Abstract Deep exposures of soil profiles on Miocene or Mio-Pliocene alluvial deposits were studied along a 500 km N-S transect in the Atacama Desert. These ancient deposits, with excellent surface preservation, now stand many meters above a broad incised Plio-Pleistocene alluvial terrain. Total geochemical analyses and mass balance calculations allowed the establishment of elemental gains, losses, and redistribution in the soils. From north to south (presently hyperarid to arid), the ancient soils reveal an increase in losses of rock-forming elements (Si, Al, Fe, K, Mg). Additionally, rare earth elements (REE) show losses with increasing southerly latitude and systematic patterns with soil depth. Some REEs appear to be unique chemical tracers of exogenous dust and aerosol additions to the soils. The removal of major elements and REEs is impossible in the present climate (one of salt and dust accumulation), revealing that for a significant period following the deposition of the alluvium, soils were exposed to rainfall, chemical weathering, and mass loss—with a geographical pattern that mirrors the present rainfall gradient in the region. Following the cessation of weathering, the pre-weathered soils have undergone enormous dust and salt accumulations, with the rates and types of salt accumulation consistent with latitude: (1) carbonate in the south and (2) sulfate, chlorides, and nitrates to the north. The quantity, and apparent rates, of salt accumulation have a strong latitudinal trend. Isotopes of sulfate have predictable depth patterns based on isotope fractionation via vertical reaction and transport. The relict hyperarid soils are geochemically similar to buried Miocene soils (ca. 10–9 Ma) in the region, but they differ from older Miocene soils, which formed in more humid conditions. The overall soil record for the Atacama Desert appears to be the product of changes in Pacific Ocean sea surface temperatures over time, and resulting changes in rainfall. The mid-Miocene was relatively humid based on buried soil chemistry and evidence of fluvial activity. The mid to late Miocene cooling (ca. 10–5.5 Ma) appears to have aridified the region based on paleosol soil chemistry. Pliocene to earliest Pleistocene conditions caused weathering of the relict soils examined here, and regional fluvial activity. Since the earliest Pleistocene, the region has largely experienced the accumulation of salts and, except for smaller scale oscillations (glacial-interglacial), has experienced protracted hyperaridity. 

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3. Gradients of geochemical change in relic charcoal hearth soils, Northwestern Connecticut, USA

   https://doi.org/https://doi.org/10.1016/j.catena.2020.104991  

   Donovan, S. (February 2021, Catena)

   null (Ed.)

   Relic charcoal hearths (RCHs) have produced distinct legacy effects in forest soils around the world. Recently, LiDAR imagery has revealed thousands of 18th–early 20th century RCHs in Litchfield County, Connecticut, USA; however, the effects of RCHs on a landscape-scale are not well-documented, particularly fine-scale heterogeneity within RCHs and surrounding soils. This study examines the long-term impacts of charcoal production by measuring RCH soil chemical and physical properties from three perspectives: (1) compared to adjacent reference sites (RSadj), (2) laterally at systematic distances away from the RCH center, and (3) vertically within the RCH soil profile. Mean charcoal abundance was greater in RCH sites than RSadj (p < 0.01). Soil organic carbon (SOC), total C, and extractable Ca2+, Mg2+, Na+ were greater in RCH sites as compared to RSadj (p < 0.01), and available phosphorus (p < 0.01), K+, and trace elements (Mo, Ag, Hg, and Se) were lower (p < 0.05). In vertical profiles, many RCHs had 2 charcoal-rich layers within the anthropic epipedon, demonstrating multiple episodes of charcoal production. Peaks in SOC, C:N, Ca2+, Mg2+ corresponded with charcoal-rich layers. Systematic transect sampling across the RCH boundary identified charcoal fragments in soils at distances up to 25 m beyond the RCH boundary, increasing the surface-level (0–15 cm) area of impact for an individual RCH by more than 30×, from a 5-m radius (RCH area = 78.5 m2) to a 30-m radius (total area of impact = 2826 m2). These findings capture fine-scale variations within and among RCH and reference sites and contribute to estimating the total area of forest soils impacted by historical charcoal production. 

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4. Soil physical and chemical properties of gypsum & non-gypsum soils from the Chihuahuan and Mojave Deserts in 2023

   https://doi.org/10.6073/pasta/01123dd2785f8ff3cb314a837d3bb6fd  

   Gobbie, Katelyn G; Pietrasiak, Nicole; Drenovsky, Rebecca E (January 2024, Environmental Data Initiative)

   This dataset contains data for soil physical and chemical properties of gypsum and non-gypsum soils in the northern Chihuahuan and eastern Mojave Deserts. Data were obtained from 20 study sites total, 10 located on soils derived from gypsum parent material and 10 located on soils derived from non-gypsum parent materials. Sites were grouped into 10 pairs, in which every gypsum site was partnered with a non-gypsum site located in the same region. Apart from soil type, partnered-site characteristics (topography, climate, elevation, slope, aspect, and presence of biocrusts) were held relatively constant. Site info and characteristics data can be accessed at knb-lter-jrn.210616001. Soil physical properties included: percent gravel, percent < 2mm fraction, soil aggregate stability, and soil compaction. Soil chemical properties were: percent gypsum content, pH, EC, and soil soluble concentrations of calcium, magnesium, potassium, sulfur, and phosphorus. The resulting soil data was used to understand physical and chemical differences between gypsum and non-gypsum soils and to examine how biocrust community types and moss species abundance and composition were associated with the measured soil variables. This study and dataset are complete. 

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5. Godzilla mineral dust and La Soufrière volcanic ash fallout immediately stimulate marine microbial phosphate uptake

   https://doi.org/10.3389/fmars.2023.1308689  

   Elliott, Hope Elizabeth; Popendorf, Kimberly J; Blades, Edmund; Royer, Haley M; Pollier, Clément_G L; Oehlert, Amanda M; Kukkadapu, Ravi; Ault, Andrew; Gaston, Cassandra J (January 2024, Frontiers in Marine Science)

   During the “Godzilla” dust storm of June 2020, unusually high fluxes of mineral dust traveled across the Atlantic from the Sahara Desert, reaching the Caribbean Basin, Gulf Coast, and southeastern United States. Additionally, an eruption of the La Soufrière volcano on St. Vincent in April 2021 generated substantial ashfall in the southeastern Caribbean. While many studies have analyzed mineral dust’s ability to relieve nutrient limitation of phosphorus (P) in the P-stressed North Atlantic, less is known about the impact of extreme events and other natural aerosols on fluxes of P into seawater and from seawater into marine microbial cells. We quantified P and iron (Fe) content in mineral dust from the Godzilla dust storm and volcanic ash from the La Soufrière eruption collected at Ragged Point, Barbados. We also performed seawater incubations to assess the marine microbial response to aerosol deposition. Using environmentally-relevant concentrations of atmospheric particles for within the ocean’s mixed layer allowed us to draw realistic conclusions about how these deposition events impacted P cycling in situ. Volcanic ash has lower P content than mineral dust, and P in volcanic ash is far less soluble (~1%) than assumed in current atmospheric deposition models. Adding mineral dust and the volcanic ash leachate in concentrations representing different deposition scenarios increased soluble reactive phosphorus (SRP) concentrations in coastal seawater by ~7-32 nM. Phosphate uptake rate was stimulated in coastal seawater after either mineral dust or volcanic ash deposition at aerosol concentrations relevant to the Godzilla dust event, with ash eliciting the fastest uptake rate. Furthermore, high concentrations of both the mineral dust and volcanic ash led to slightly elevated alkaline phosphatase activity (APA) compared to the relevant controls, indicating higher potential for use of dissolved organic phosphorus (DOP) as a P source. Quantifying these aerosols’ impacts on P cycling is a significant step towards achieving a better understanding of their potential roles in relieving nutrient limitation and fueling the biological carbon pump. 

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