TY - JOUR
T1 - Small-Scale Geochemical Heterogeneities and Seasonal Variation of Iron and Sulfide in Salt Marshes Revealed by Two-Dimensional Sensors
AU - Zhu, Qingzhi
AU - Cochran, J. Kirk
AU - Heilbrun, Christina
AU - Yin, Hang
AU - Feng, Huan
AU - Tamborski, Joseph J.
AU - Fitzgerald, Patrick
AU - Cong, Wen
N1 - Funding Information:
We would like to thank the Science and Resilience Institute at Jamaica Bay for supporting field work, Robert C. Aller for discussion of results, Yu Qian for assistance in the field. Patricia Rafferty (National Parks Service) Don Riepe, and Elizabeth Manclark (American Littoral Society) provided much appreciated logistical support. Funding. This work was supported by finding from the National Park Service (Task Agreement P14AC01395, Cooperative Agreement P14AC00888). The sensors were partially support by NSF OCE 1737749 and NSF OCE 1332418.
Publisher Copyright:
© Copyright © 2021 Zhu, Cochran, Heilbrun, Yin, Feng, Tamborski, Fitzgerald and Cong.
PY - 2021/4/29
Y1 - 2021/4/29
N2 - Loss of tidal wetlands is a world-wide phenomenon. Many factors may contribute to such loss, but among them are geochemical stressors such as exposure of the marsh plants to elevated levels on hydrogen sulfide in the pore water of the marsh peat. Here we report the results of a study of the geochemistry of iron and sulfide at different seasons in unrestored (JoCo) and partially restored (Big Egg) salt marshes in Jamaica Bay, a highly urbanized estuary in New York City where the loss of salt marsh area has accelerated in recent years. The spatial and temporal 2-dimensional distribution patterns of dissolved Fe2+ and H2S in salt marshes were in situ mapped with high resolution planar sensors for the first time. The vertical profiles of Fe2+ and hydrogen sulfide, as well as related solutes and redox potentials in marsh were also evaluated by sampling the pore water at discrete depths. Sediment cores were collected at various seasons and the solid phase Fe, S, N, C, and chromium reducible sulfide in marsh peat at discrete depths were further investigated in order to study Fe and S cycles, and their relationship to the organic matter cycling at different seasons. Our results revealed that the redox sensitive elements Fe2+ and S2– showed significantly heterogeneous and complex three dimensional distribution patterns in salt marsh, over mm to cm scales, directly associated with the plant roots due to the oxygen leakage from roots and redox diagenetic reactions. We hypothesize that the oxic layers with low/undetected H2S and Fe2+ formed around roots help marsh plants to survive in the high levels of H2S by reducing sulfide absorption. The overall concentrations of Fe2+ and H2S and distribution patterns also seasonally varied with temperature change. H2S level in JoCo sampling site could change from <0.02 mM in spring to >5 mM in fall season, reflecting significantly seasonal variation in the rates of bacterial oxidation of organic matter at this marsh site. Solid phase Fe and S showed that very high fractions of the diagenetically reactive iron at JoCo and Big Egg were associated with pyrite that can persist for long periods in anoxic sediments. This implies that there is insufficient diagenetically reactive iron to buffer the pore water hydrogen sulfide through formation of iron sulfides at JoCo and Big Egg.
AB - Loss of tidal wetlands is a world-wide phenomenon. Many factors may contribute to such loss, but among them are geochemical stressors such as exposure of the marsh plants to elevated levels on hydrogen sulfide in the pore water of the marsh peat. Here we report the results of a study of the geochemistry of iron and sulfide at different seasons in unrestored (JoCo) and partially restored (Big Egg) salt marshes in Jamaica Bay, a highly urbanized estuary in New York City where the loss of salt marsh area has accelerated in recent years. The spatial and temporal 2-dimensional distribution patterns of dissolved Fe2+ and H2S in salt marshes were in situ mapped with high resolution planar sensors for the first time. The vertical profiles of Fe2+ and hydrogen sulfide, as well as related solutes and redox potentials in marsh were also evaluated by sampling the pore water at discrete depths. Sediment cores were collected at various seasons and the solid phase Fe, S, N, C, and chromium reducible sulfide in marsh peat at discrete depths were further investigated in order to study Fe and S cycles, and their relationship to the organic matter cycling at different seasons. Our results revealed that the redox sensitive elements Fe2+ and S2– showed significantly heterogeneous and complex three dimensional distribution patterns in salt marsh, over mm to cm scales, directly associated with the plant roots due to the oxygen leakage from roots and redox diagenetic reactions. We hypothesize that the oxic layers with low/undetected H2S and Fe2+ formed around roots help marsh plants to survive in the high levels of H2S by reducing sulfide absorption. The overall concentrations of Fe2+ and H2S and distribution patterns also seasonally varied with temperature change. H2S level in JoCo sampling site could change from <0.02 mM in spring to >5 mM in fall season, reflecting significantly seasonal variation in the rates of bacterial oxidation of organic matter at this marsh site. Solid phase Fe and S showed that very high fractions of the diagenetically reactive iron at JoCo and Big Egg were associated with pyrite that can persist for long periods in anoxic sediments. This implies that there is insufficient diagenetically reactive iron to buffer the pore water hydrogen sulfide through formation of iron sulfides at JoCo and Big Egg.
KW - 2-D distributions
KW - Fe and HS
KW - Jamaica Bay
KW - planar optical sensors
KW - salt marsh geochemistry
UR - http://www.scopus.com/inward/record.url?scp=85105956286&partnerID=8YFLogxK
U2 - 10.3389/feart.2021.653698
DO - 10.3389/feart.2021.653698
M3 - Article
AN - SCOPUS:85105956286
VL - 9
JO - Frontiers in Earth Science
JF - Frontiers in Earth Science
SN - 2296-6463
M1 - 653698
ER -