A Permanent Multilevel Monitoring and Sampling System in the Coastal Groundwater Mixing Zones

Luo, Xin; Kwok, King Lun; Liu, Yi; Jiao, Jiu Jimmy

doi:10.1111/gwat.12510

Cited by 20 publications

(9 citation statements)

References 50 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The surficial sediments have a hydraulic conductivity of 4.49 m/day and a porosity of 0.3 (Y. Liu, Jiao, & Liang, ). A permanent multilevel sampling system (Luo et al, ) containing 11 sampling sites (L1 to L5 above and S1 to S6 below the mean tidal mark) and 43 sampling tubes in total was installed in the intertidal aquifer (Figure c). The sampling system forms a sampling transect perpendicular to the coastline (Figure c).…”

Section: Methodsmentioning

confidence: 99%

Seasonality of Nutrient Flux and Biogeochemistry in an Intertidal Aquifer

2018

Self Cite

View full text Add to dashboard Cite

Biogeochemical reactions in coastal aquifers highly affect the nutrient flux associated with submarine groundwater discharge (SGD) to the ocean, which subsequently influences the oceanic environment and ecology. This study investigates a seasonal variation of SGD-derived nutrient flux to the ocean and nutrient biogeochemistry in an intertidal aquifer of Tolo Harbor, Hong Kong. The results show that the inventory of NO x À and PO 4 3À in the intertidal aquifer has a clear seasonality with a large inventory in summer, a small inventory in spring, and a median inventory in autumn and winter, respectively. Differently, the inventory of NH 4 + is large in winter and summer and small in spring and autumn, which results from the coupled effects of seasonal change of both production and removal of NH 4 + in the aquifer. The SGD-derived nutrient (NH 4 + , NO x À , and PO 4 3À ) flux is the highest in summer (271.71, 24.86, and 116.66 mmol·day À1 ·(m coastline) À1 ) and is the lowest in spring (114.83, 1.70, and 20.26 mmol·day À1 ·(m coastline) À1 ). The majority of SGD-derived nutrient flux is supported by the local remineralization of organic matter along with seawater infiltration. In autumn, the recharge of seawater induced by tidal pumping significantly shifts the biogeochemical balance of nutrients and is the major source of groundwater nutrients in the intertidal aquifer. Among the various nutrient fluxes (SGD, river discharge, atmospheric deposition, and benthic sediment diffusion) to Tolo Harbor, SGD-derived PO 4 3À flux is the second major source of seawater PO 4 3À in addition to benthic sediment diffusion. The PO 4 3À loading via SGD is of significance to the primary production in the phosphorus-limited environment in Tolo Harbor. After considering the natural attenuation of nutrients in a sandy/silty beach aquifer, this study suggests the overestimation of SGD-derived nutrient loading estimated previously that simply use average nutrient concentration of fresh SGD endmember and saline SGD endmember as the nutrient concentration of total SGD endmember.Plain Language Summary The biogeochemical reactions in the intertidal aquifer are the crucial influencing factors affecting the groundwater nutrients that are essential for oceanic environment and ecology. Seasonal hydrologic variations are of significance to the biogeochemical reactions in the aquifer and nutrient speciation and concentrations in coastal groundwater. The results of this study indicate that both nutrient inventories in the aquifer and nutrient fluxes to the sea are higher in summer and autumn than winter and spring. By comparing the nutrient flux carried by the submarine groundwater discharge with other pathways, nutrient flux carried by coastal groundwater is a major source of phosphorus in the sea and supports the primary production in the harbor, which can be demonstrated by the positive trend between the nutrient flux and chlorophyll-a concentration in seawater. However, the red tide occurrence in the harbor does not have a similar seasonal tr...

show abstract

Section: Methodsmentioning

confidence: 99%

Seasonality of Nutrient Flux and Biogeochemistry in an Intertidal Aquifer

2018

Self Cite

View full text Add to dashboard Cite

show abstract

“…A permanent multilevel sampling system (Luo et al, ) was installed in the intertidal zone of a sandy aquifer at Plover Cove. The system contains 11 sampling sites (named L1–L5 and S1–S6) with 2–5 sampling tubes in each site (Figure c).…”

Section: Methodsmentioning

confidence: 99%

Using Tidal Fluctuation‐Induced Dynamics of Radium Isotopes (²²⁴Ra, ²²³Ra, and ²²⁸Ra) to Trace the Hydrodynamics and Geochemical Reactions in a Coastal Groundwater Mixing Zone

Liu

Jiao

Liang

et al. 2018

Water Resources Research

Self Cite

View full text Add to dashboard Cite

The reactive transport of radium isotopes (224Ra, 223Ra, and 228Ra) in coastal groundwater mixing zones (CGMZs) is sensitive to shifts of redox conditions and geochemical reactions induced by tidal fluctuation. This study presents a spatial distribution and temporal variation of radium isotopes in the CGMZ for the first time. Results show that the activity of radium isotopes in the upper saline plume (USP) is comparatively low due to a short residence time and mixing loss induced by the infiltration of low radium seawater whereas the activity of radium isotopes in the salt wedge (SW) is comparatively high due to a long residence time in the aquifer. The spatial distribution of radium isotopes is determined by the partitioning of radium isotopes, groundwater residence time, and relative ingrowth rates of radium isotopes. In addition, the variation of radium isotopes in the USP lags slightly (∼0 h) whereas the fluctuation of radium isotopes in the SW lags significantly (∼12 h) behind sea level oscillation. Tidal fluctuation affects the partitioning of radium isotopes through controlling seawater infiltration and subsequently influences the dynamics of radium isotopes in the USP. Concurrently, seawater infiltration significantly affects geochemical processes such as the production of nutrients and total alkalinity. Therefore, radium dynamics in the USP have implications for these geochemical processes. The variation of radium isotopes in the USP also has potential implications for transformation of trace metals such as iron and manganese because of the close affinity of radium isotopes to manganese and iron oxides.

show abstract

“…A permanent multilevel sampling system (Luo et al, ) was installed in a transection perpendicular to the shoreline at Ting Kok (Liu, Jiao, Liang, et al, ). The system contains 11 sampling sites (namely L1 to L5, and S1 to S6) at different locations along a shore‐perpendicular sampling transection, and each sampling site has 2–5 sampling tubes with different depths (Figure ).…”

Section: Methodsmentioning

confidence: 99%

Tidal Pumping‐Induced Nutrients Dynamics and Biogeochemical Implications in an Intertidal Aquifer

et al. 2017

Self Cite

View full text Add to dashboard Cite

Tidal pumping is a major driving force affecting water exchange between land and sea, biogeochemical reactions in the intertidal aquifer, and nutrient loading to the sea. At a sandy beach of Tolo Harbour, Hong Kong, the nutrient (NH4+, NO2−, NO3−, and PO43−) dynamic in coastal groundwater mixing zone (CGMZ) is found to be fluctuated with tidal oscillation. Nutrient dynamic is mainly controlled by tidal pumping‐induced organic matter that serves as a reagent of remineralization in the aquifer. NH4+, NO2−, and PO43− are positively correlated with salinity. Both NH4+ and PO43− have negative correlations with oxidation/reduction potential. NH4+ is the major dissolved inorganic nitrogen species in CGMZ. The adsorption of PO43− onto iron oxides occurs at the deep transition zone with a salinity of 5–10 practical salinity unit (psu), and intensive N‐loss occurs in near‐surface area with a salinity of 10–25 psu. The biogeochemical reactions, producing PO43− and consuming NH4+, are synergistic effect of remineralization‐nitrification‐denitrification. In CGMZ, the annual NH4+ loss is estimated to be ~ 4.32 × 105 mol, while the minimum annual PO43− production is estimated to be ~ 2.55 × 104 mol. Applying these rates to the entire Tolo Harbour, the annual NH4+ input to the harbor through the remineralization of organic matters is estimated to be ~ 1.02 × 107 mol. The annual NH4+ loss via nitrification is 1.32 × 107 mol, and the annual PO43− production is ~ 7.76 × 105 mol.

show abstract

A Permanent Multilevel Monitoring and Sampling System in the Coastal Groundwater Mixing Zones

Cited by 20 publications

References 50 publications

Seasonality of Nutrient Flux and Biogeochemistry in an Intertidal Aquifer

Seasonality of Nutrient Flux and Biogeochemistry in an Intertidal Aquifer

Using Tidal Fluctuation‐Induced Dynamics of Radium Isotopes (²²⁴Ra, ²²³Ra, and ²²⁸Ra) to Trace the Hydrodynamics and Geochemical Reactions in a Coastal Groundwater Mixing Zone

Tidal Pumping‐Induced Nutrients Dynamics and Biogeochemical Implications in an Intertidal Aquifer

Contact Info

Product

Resources

About

A Permanent Multilevel Monitoring and Sampling System in the Coastal Groundwater Mixing Zones

Cited by 20 publications

References 50 publications

Seasonality of Nutrient Flux and Biogeochemistry in an Intertidal Aquifer

Seasonality of Nutrient Flux and Biogeochemistry in an Intertidal Aquifer

Using Tidal Fluctuation‐Induced Dynamics of Radium Isotopes (224Ra, 223Ra, and 228Ra) to Trace the Hydrodynamics and Geochemical Reactions in a Coastal Groundwater Mixing Zone

Tidal Pumping‐Induced Nutrients Dynamics and Biogeochemical Implications in an Intertidal Aquifer

Contact Info

Product

Resources

About

Using Tidal Fluctuation‐Induced Dynamics of Radium Isotopes (²²⁴Ra, ²²³Ra, and ²²⁸Ra) to Trace the Hydrodynamics and Geochemical Reactions in a Coastal Groundwater Mixing Zone