Linking organic matter deposition and iron mineral transformations to groundwater arsenic levels in the Mekong delta, Cambodia

2008 ◽  
Vol 23 (11) ◽  
pp. 3088-3098 ◽  
Author(s):  
Andrew N. Quicksall ◽  
Benjamin C. Bostick ◽  
M.L. Sampson
Keyword(s):  
Organic Matter ◽  
Mekong Delta ◽  
Iron Mineral ◽  
Groundwater Arsenic ◽  
Mineral Transformations

scholarly journals Associations between inorganic arsenic in rice and groundwater arsenic in the Mekong Delta

Chemosphere ◽  
2021 ◽  
Vol 265 ◽  
pp. 129092
Author(s):  
Matthew C. Reid ◽  
Maria P. Asta ◽  
Lily Falk ◽  
Scott C. Maguffin ◽  
Vu Hoai Cong Pham ◽  
...  
Keyword(s):  
Mekong Delta ◽  
Inorganic Arsenic ◽  
Groundwater Arsenic

Fe(II)-catalyzed transformation of Fe (hydr)oxides in particle-size soil organic matter fractions from amended agricultural soils

2020 ◽  
Author(s):  
Beatrice Giannetta ◽  
Ramona Balint ◽  
Daniel Said-Pullicino ◽  
César Plaza ◽  
Maria Martin ◽  
...  
Keyword(s):  
Particle Size ◽  
Organic Matter ◽  
Soil Organic Matter ◽  
Agricultural Soils ◽  
Solid Phase ◽  
Organic Amendments ◽  
Fine Sand ◽  
Organic C ◽  
Amended Soils ◽  
Mineral Transformations

<p>Redox-driven changes in Fe crystallinity and speciation may affect soil organic matter (SOM) stabilization and carbon (C) turnover, with consequent influence on global terrestrial soil organic carbon (SOC) cycling.<span> </span>Under reducing conditions, increasing concentrations of Fe(II) released in solution from the reductive dissolution of Fe (hydr)oxides may accelerate ferrihydrite transformation, although our understanding of the influence of SOM on these transformations is still lacking.<span> </span></p><p>Here, we evaluated abiotic Fe(II)-catalyzed mineralogical changes in Fe (hydr)oxides in bulk soils and size-fractionated SOM pools (for comparison, fine silt plus clay, FSi+Cl, and fine sand, FSa) of an agricultural soil, unamended or amended with biochar, municipal solid waste compost, and a combination of both.<span> </span></p><p>FSa fractions showed the most significant Fe(II)-catalyzed ferrihydrite transformations with the consequent production of well-ordered Fe oxides irrespective of soil amendment, with the only exception being the compost-amended soils. In contrast, poorly crystalline ferrihydrite still constituted <em>ca. </em>45% of the FSi+Cl fractions of amended soils, confirming the that the higher SOM content in this fraction inhibits atom exchange between aqueous Fe(II) and the solid phase. Building on our knowledge of Fe(II)-catalyzed mineralogical changes in simple systems, our results evidenced that the mechanisms of abiotic Fe mineral transformations in bulk soils depend on Fe mineralogy, organic C content and quality, and organo-mineral associations that exist across particle-size SOM pools. Our results underline that in the fine fractions the increase in SOM due to organic amendments can contribute to limiting abiotic Fe(II)-catalyzed ferrihydrite transformation, while coarser particle-size fractions represent an understudied pool of SOM subjected to Fe mineral transformations.<span> </span></p>

scholarly journals Vivianite formation in ferruginous sediments from Lake Towuti, Indonesia

2019 ◽  
Author(s):  
Aurèle Vuillemin ◽  
André Friese ◽  
Richard Wirth ◽  
Jan A. Schuessler ◽  
Anja M. Schleicher ◽  
...  
Keyword(s):  
Sediment Cores ◽  
Iron Phosphate ◽  
Microbial Reduction ◽  
Water Geochemistry ◽  
Continuous Growth ◽  
Iron Mineral ◽  
Reducing Conditions ◽  
Pore Water Geochemistry ◽  
Mineral Transformations ◽  
Lake Towuti

Abstract. Ferruginous lacustrine systems, such as Lake Towuti, Indonesia, can experience restricted primary production due to phosphorus trapping by hydrous ferric iron (oxyhydr)oxides that reduce P concentrations in the water column. The oceans were also ferruginous during the Archean, so understanding the dynamics of phosphorus in modern-day ferruginous analogues may shed light on the marine biogeochemical cycling that dominated much of Earth's history. Here we report the presence of large crystals (> 5 mm) and nodules (> 5 cm) of vivianite – a ferrous iron phosphate – in sediment cores from Lake Towuti, and address the processes of phosphorus retention and iron mineral transformations during diagenesis in ferruginous sediments. Core scans together with analyses of bulk sediment and pore water geochemistry document a 30 m long interval consisting of beds of sideritic and non-sideritic clays and diatomaceous oozes containing diagenetic vivianites. High-resolution imaging of vivianite revealed continuous growth of crystals from tabular to rosette habits that eventually form large (up to 7 cm) vivianite nodules in the sediment. Mineral inclusions like millerite and siderite reflect antecedent diagenetic mineral formation that is related to microbial reduction of iron and sulfate. This implies the formation and growth of vivianite crystals under reducing conditions during diagenesis. Negative ð56Fe values of vivianite indicated reductive dissolution of ferric oxides as the source of Fe in the vivianites with incorporation of microbially fractionated light Fe2+ into the crystals. The size and growth history of the nodules indicate that, after formation, continued growth of vivianite may constitute a significant sink for P in these sediments.

scholarly journals Rice husk and melaleuca biochar additions reduce soil CH4 and N2O emissions and increase soil organic matter and nutrient availability

F1000Research ◽  
2021 ◽  
Vol 10 ◽  
pp. 1128
Author(s):  
Nam Tran Sy ◽  
Thao Huynh Van ◽  
Chiem Nguyen Huu ◽  
Cong Nguyen Van ◽  
Tarao Mitsunori
Keyword(s):  
Organic Matter ◽  
Rice Husk ◽  
Mekong Delta ◽  
Application Rate ◽  
N2o Emissions ◽  
Application Rates ◽  
Reduce Emissions ◽  
Local Water ◽  
Ch4 And N2o ◽  
Rice Husk Biochar

Background: Biochar is a promising material in mitigating greenhouse gases (GHGs) emissions from paddy fields due to its remarkable structural properties. Rice husk biochar (RhB) and melaleuca biochar (MB) are amendment materials that could be used to potentially reduce emissions in the Vietnamese Mekong Delta (VMD). However, their effects on CH4 and N2O emissions and soil under local water management and conventional rice cultivation have not been thoroughly investigated. Methods: We conducted a field experiment using biochar additions to the topsoil layer (0-20 cm). Five treatments comprising 0 t ha-1 (CT0); 5 t ha-1 (RhB5) and 10 t ha-1 (RhB10), and 5 t ha-1 (MB5) and 10 t ha-1 (MB10) were designed plot-by-plot (20 m2) in triplicates. Results: The results showed that biochar application from 5 to 10 t ha-1 significantly decreased cumulative CH4 (24.2 – 28.0%, RhB; 22.0 – 14.1%, MB) and N2O (25.6 – 41.0%, RhB; 38.4 – 56.4%, MB) fluxes without a reduction in grain yield. Increasing the biochar application rate further did not decrease significantly total CH4 and N2O fluxes but was seen to significantly reduce the global warming potential (GWP) and yield-scale GWP in the RhB treatments. Biochar application improved soil Eh but had no effects on soil pH. Whereas CH4 flux correlated negatively with soil Eh (P < 0.001; r2 = 0.552, RhB; P < 0.001; r2 = 0.502, MB). The soil physicochemical properties of bulk density, porosity, organic matter, and anaerobically mineralized N were significantly improved in biochar-amended treatments, while available P also slightly increased. Conclusions: Biochar supplementation significantly reduced CH4 and N2O fluxes and improved soil mineralization and physiochemical properties toward beneficial for rice plant. The results suggest that the optimal combination of biochar-application rates and effective water-irrigation techniques for soil types in the MD should be further studied in future works.

scholarly journals Organic matter influences transformation products of ferrihydrite exposed to sulfide

2020 ◽  
Vol 7 (11) ◽  
pp. 3405-3418
Author(s):  
Laurel K. ThomasArrigo ◽  
Sylvain Bouchet ◽  
Ralf Kaegi ◽  
Ruben Kretzschmar
Keyword(s):  
Organic Matter ◽  
Transformation Products ◽  
Mineral Transformation ◽  
Iron Mineral ◽  
Transformation Pathways

In the presence of sulfide, organic matter influences iron mineral transformation pathways and kinetics.

scholarly journals Numerical Modeling of Arsenic Mobility during Reductive Iron-Mineral Transformations

2016 ◽  
Vol 50 (5) ◽  
pp. 2459-2467 ◽  
Author(s):  
Joey Rawson ◽  
Henning Prommer ◽  
Adam Siade ◽  
Jackson Carr ◽  
Michael Berg ◽  
...  
Keyword(s):  
Numerical Modeling ◽  
Iron Mineral ◽  
Arsenic Mobility ◽  
Mineral Transformations

scholarly journals Seasonal influences on groundwater arsenic concentrations in the irrigated region of the Cambodian Mekong Delta

2020 ◽  
Vol 728 ◽  
pp. 138598 ◽  
Author(s):  
S. Tweed ◽  
S. Massuel ◽  
J.L. Seidel ◽  
K. Chhuon ◽  
S. Lun ◽  
...  
Keyword(s):  
Mekong Delta ◽  
Groundwater Arsenic ◽  
Seasonal Influences

scholarly journals Rice plants reduce methane emissions in high-emitting paddies

F1000Research ◽  
2019 ◽  
Vol 7 ◽  
pp. 1349 ◽  
Author(s):  
Masato Oda ◽  
Nguyen Huu Chiem
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Methane Emission ◽  
Rice Variety ◽  
Mekong Delta ◽  
Rice Paddy ◽  
Methane Emissions ◽  
Paddy Fields ◽  
Rice Plants ◽  
Oxygen Pathways

Background: Rice is understood to enhance methane emissions from paddy fields in IPCC guidelines. However, rice actually has two opposite functions related to methane: i) emission enhancement, such as by providing emission pathways (aerenchyma) and methanogenetic substrates; and ii) emission suppression by providing oxygen pathways, which suppress methanogenesis or enhance methane oxidation. The overall role of rice is thus determined by the balance between its enhancing and suppressing functions. Although previous studies have suggested that rice enhances total methane emissions, we aimed to demonstrate in high-emitting paddy fields that the overall methane emission is decreased by rice plants. Methods: We compared methane emissions with and without rice plants in triple cropping rice paddy fields in the Mekong Delta, Vietnam. The gas samples are collected using chamber method and ware analyzed by gas chromatography. Results: We found that rice, in fact, suppressed overall methane emissions in high-emitting paddies. The emission reductions increased with the growth of rice to the maximum tillering stage, then decreased after the heading stage, and finally recovered.  Discussion:  Our result indicates that the overall methane emission is larger than that of rice planted area. In addition, although many studies in standard-emitting paddies have found that the contribution of soil organic matter to methanogenesis is small, prior studies in high-emitting paddies suggest that methanogenesis depended mainly on soil organic matter accumulated from past crops. The higher the methane emission level, the lower the contribution of the rice-derived substrate; conversely, the higher the contribution of the rice providing oxygen. Finally, rice plants reduce methane emissions in high-emitting paddies. Conclusion: The present study demonstrates that during the growing season, rice is suppressing methane emissions in high-emitting paddies. This means the significance of using the rice variety which has high suppressing performance in high-emitting paddies.

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