Aluminum (Al)‐bearing and iron (Fe)‐bearing minerals, especially short‐range‐ordered (SRO) phases, are thought to protect soil organic C (SOC). However, it remains methodologically challenging to assess the influence of Al vs. Fe minerals or metal complexes. Whereas SRO Al and Fe phases share some properties, Al dissolved by oxalate (Alox) often correlates stronger with SOC than Fe dissolved by oxalate (Feox) or citrate–dithionite (Fecd). To further evaluate these relationships, we analyzed a large North American soil dataset from the National Ecological Observatory Network. A strong relationship between Aloxand SOC (and weaker Feox‐SOC relationship) persisted even after excluding soils rich in SRO minerals (Andisols and Spodosols). Al dissolved by oxalate was strongly correlated with citrate–dithionite‐extractable Al (Alcd; slope = 0.92,
The 2018, subaerial eruption of Kīlauea volcano, Hawaii, resulted in a 5‐km‐long stretch of coastline that actively drained lava into the ocean. Nutrients were added to the surrounding ocean through the dissolution of basaltic rock and thermal upwelling of deep water, thereby fueling a large phytoplankton bloom. Lava‐impacted, surface seawater had high suspended particle loads, and concentrations of chlorophyll, silicic acid, phosphate (Pi), nitrate, and iron that were elevated up to 12, 36, 5, 960, and 1,400 times, respectively, above the background oligotrophic levels. Widespread precipitation of iron oxyhydroxides (Feox) led to extensive scavenging of the dissolved Pipool, similar to what occurs along mid‐ocean ridge hydrothermal systems. This scavenging transformed a “fertilization” event into a Pisink near the coast of the ocean entry; however, nutrient data from outside the bloom suggest that Picould also desorb from the Feoxas it is dispersed into the open ocean. From lava quench experiments, we estimate that the hydration state of the Feoxprecipitate (H2O/Fe) was 5.2–5.7, and that the equilibrium partition coefficient of Piinto Feox(solid/liquid) was 106. In addition,33Piradiotracer incubations were used to differentiate between biotic and abiotic uptake of Piat Kīlauea's ocean entry. These findings are important for understanding modern‐day volcanic fertilization events, modeling nutrient dynamics during major events in Earth history (such as oxygenation of the atmosphere and the formation of large igneous provinces), and predicting the marine response to greater continental weathering in a warming climate.
more » « less- NSF-PAR ID:
- 10367042
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Geochemistry, Geophysics, Geosystems
- Volume:
- 22
- Issue:
- 7
- ISSN:
- 1525-2027
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract R 2 = .69), and discrepancies could be explained (R 2 = .87) by greater dissolution of Al‐substituted Fe phases by citrate–dithionite and greater dissolution of aluminosilicates by oxalate. Aluminum dissolved by oxalate and Alcdwere both strong SOC predictors despite their differing relationships with silicon (Si). Al dissolved by oxalate and Sioxstrongly covaried (R 2 = .79), but Alcdwas inconsistently related to Sicd(R 2 = .18). Similar relationships of Aloxand Alcdwith SOC, despite differences in minerals extracted by oxalate and citrate–dithionite, suggest that Al‐OC complexes (as opposed to aluminosilicate or iron‐bearing minerals) were the best SOC predictor. This raises important questions: do Al‐OC complexes indicate protection from decomposition or simply reflect greater intensity of mineral weathering by organic acids; and, if the latter, then perhaps SOC input is driving Aloxand SOC correlations rather than Al phase composition or abundance. -
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