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Field, laboratory, and modeling study of reactive transport of groundwater arsenic in a coastal aquifer.

ABSTRACT: A field, laboratory, and modeling study of As in groundwater discharging to Waquoit Bay, MA, shed light on coupled control of chemistry and hydrology on reactive transport of As in a coastal aquifer. Dissolved Fe(III) and As(III) in a reducing groundwater plume bracketed by an upper and a lower redox interface are oxidized as water flows toward the bay. This results in precipitation of Fe(III) oxides, along with oxidation and adsorption of As to sediment at the redox interfaces where concentrations of sedimentary HCl-leachable Fe (80-90% Fe(III)) are 734 +/- 232 mg kg(-1) and sedimentary phosphate-extractable As (90-100% As(VI) are 316 +/- 111 microg kg(-1) and are linearly correlated. Batch adsorption of As(III) onto orange, brown, and gray sediments follows Langmuir isotherms and can be fitted by a surface complexation model (SCM) assuming a diffuse layer for ferrihydrite. The sorption capacity and distribution coefficient for As increase with decreasing sediment Fe(II)/Fe. To allow accumulation of the amount of sediment As, similar hydrogeochemical conditions would have been operating for thousands of years at Waquoit Bay. The SCM simulated the observed dissolved As concentration better than a parametric approach based on Kd. Site-specific isotherms should be established for Kd- or SCM-based models.

SUBMITTER: Jung HB

PROVIDER: S-EPMC2746402 | biostudies-literature | 2009 Jul

REPOSITORIES: biostudies-literature

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Field, laboratory, and modeling study of reactive transport of groundwater arsenic in a coastal aquifer.

Jung Hun Bok HB Charette Matthew A MA Zheng Yan Y

Environmental science & technology 20090701 14

A field, laboratory, and modeling study of As in groundwater discharging to Waquoit Bay, MA, shed light on coupled control of chemistry and hydrology on reactive transport of As in a coastal aquifer. Dissolved Fe(III) and As(III) in a reducing groundwater plume bracketed by an upper and a lower redox interface are oxidized as water flows toward the bay. This results in precipitation of Fe(III) oxides, along with oxidation and adsorption of As to sediment at the redox interfaces where concentrati ...[more]

PMID: 19708362

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Project description:The discovery of anaerobic ammonia oxidation (anammox) expanded our knowledge on the microbial nitrogen cycle. Previous studies report that anammox bacteria are distributed in a wide range of habitats and plays significant roles in the global nitrogen cycle. However, most studies focus only on individual ecosystems or datasets from public databases. To date, our understanding of how anammox bacteria respond to environmental properties and are distributed in different habitats on a global scale, remain unclear. To explore the global distribution of anammox bacteria, samples were collected from different habitats at different locations globally, including wetlands, drylands, groundwater aquifers and snow from 10 countries across six continents. We then used high-throughput amplicon sequencing targeting the functional gene hydrazine synthase (HZS) and generated community profiles. Results showed that Candidatus Brocadia is detected as the dominant genus on a global scale, accounting for 80.0% to 99.9% of the retrieved sequences in different habitats. The Jettenia-like sequences were the second most abundant group, accounting for no more than 19.9% of the retrieved sequences in all sites. The samples in drylands, wetlands and groundwater aquifers showed similar community composition and diversity, with the snow samples being the most different. Deterministic processes seem stronger in regulating the community composition of anammox bacteria, which is supported by the higher proportion explained by local-scale factors. Groundwater aquifers showed high gene abundance and the most complex co-occurrence network among the four habitat types, suggesting that it might be the preferred habitat of anammox bacteria. There is little competition between anammox bacterial species based on co-occurrence analysis. Hence, we could infer that environmental factors such as anaerobic and stable conditions, instead of substrate limitations, may be vital factors determining the anammox bacteria community. These results provide a better understanding of the global distribution of anammox bacteria and the ecological factors that affect their community structuring in diverse habitats.

Dataset Information

Field, laboratory, and modeling study of reactive transport of groundwater arsenic in a coastal aquifer.

Publications

Field, laboratory, and modeling study of reactive transport of groundwater arsenic in a coastal aquifer.

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