Characterizing the capacity of hyporheic sediments to attenuate groundwater nitrate loads by adsorption

Abstract

Nitrate has been recognized as a global threat to environmental health. In this regard, the hyporheic zone (saturated media beneath and adjacent to the stream bed) plays a crucial role in attenuating groundwater nitrate, prior to discharge into surface water. While different nitrate removal pathways have been investigated over recent decades, the adsorption capacity of hyporheic sediments under natural conditions has not yet been identified. In this study, the natural attenuation capacity of the hyporheic-sediments of the Ghezel-Ozan River, located in the north-west of Iran, was determined. The sampled sediments (from 1 m below the stream bed) were characterized via XRD, FT-IR, BET, SEM, BJH, and Zeta potential. Nitrate adsorption was evaluated using a batch experiment with hyporheic pore-water from each study site. The study was performed in the hyporheic sediments of two morphologically different zones, including Z located in the parafluvial zone having the clay sediment texture (57.8% clay) with smectite/Illite mixed layer clay type and Z located in the river confluence area containing silty clay sediment texture (47.6% clay) with smectite/kaolinite mixed layer clay type. Data obtained from the batch experiment were subjected to pseudo-first order, pseudo-second order, intra-particle diffusion, and Elovich mass transfer kinetic models to characterize the nitrate adsorption mechanism. Furthermore, to replicate nitrate removal efficiencies of the hyporheic sediments under natural conditions, the sampled hyporheic pore-waters were applied as initial solutions to run the batch experiment. The results of the artificial nitrate solution correlated well with pseudo-second order (R>95%; in both Z and Z) and maximum removal efficiencies of 85.3% and 71.2% (adsorbent dosage 90 g/L, pH = 5.5, initial adsorbate concentration of 90 mg/L) were achieved in Z and Z, respectively. The results of the nitrate adsorption analysis revealed that the nitrate removal efficiencies varied from 17.24 ± 1.86% in Z during the wet season to 28.13 ± 0.89% in Z during the dry season. The results obtained by this study yielded strong evidence of the potential of hyporheic sediments to remove nitrate from an aqueous environment with great efficiency.

Nutrient Dynamics at the Sediment-Water Interface: Influence of Wastewater Effluents

“…NO 3 − and NH 4 + concentrations decreased at D3.0 compared with D1.0. As nutrients were transported from the midriver reach, and the conversion to N 2 gas (i.e., nitrifier denitrification) or other forms of nitrogen (e.g., associated with biological storage) was likely achieved (Fear 2003;Mulholland et al 2008;Meghdadi 2018). D3.0 concentrations of NO 3 − were higher than the upstream reach, which was consistent with the findings of Perryman et al (2011) who pointed out that NO 3 − increased downstream with increasing river discharge due to short water residence time.…”

“…For NO 3 − and NH 4 + , fluxes are primarily controlled by concentration changes and nitrogen form transformation within the N-cycle (Chen et al 2012). These processes includes denitrification, nitrification, dissimilatory nitrate reduction to ammonium (DNRA), mineralization, and biological nitrogen fixation, which are mainly performed by microorganisms such as nitrifying bacteria, denitrifying bacteria, and mineralized bacteria associated with the decomposition of organic matter (Fear 2003;Mulholland et al 2008;Meghdadi 2018). Thus, the fluxes of NO 3 − and NH 4 + are mainly determined by the microbial activity involved in the N-cycle process (Simon et al 2010;Lavelle et al 2019).…”

Síntesis De Zβ A Partir de Cenizas Volantes, Utilizadas En Liberación Controlada De Nitratos

“…El proceso de adsorción se desarrolla mediante desplazamiento del ion cloruro por el ion nitrato y justificado por la regla de afinidad de agua equivalente, donde el grupo amonio con tendencia a un ion del tipo caotrópico sigue una mayor afinidad del orden NO 3 -> Br -> Cl -. [51] Los materiales de esta investigación presentaron CICE superior a materiales reportados en la literatura como los que se muestran en la Tabla 3, como la mordenita, ferrierita y clinoptilolita [27] esta última superada únicamente por la ZSM-5, mientras que la adsorción de nitratos fue superior en la Zβ-APTES frente a materiales naturales como la caolinita, esmectita e illita [52] aunque no supera materiales como clinoptilolita-HDTMA y esmectita [27] o biocarbón-montmorillonita [53] sí presenta un mejor resultado en la relación CICE/ mmol de NO 3 adsorbidos, lo que indica un máximo aprovechamiento de grupos hidroxilo del material para la funcionalización.…”

Combination of Pd–Cu Catalysis and Electrolytic H2 Evolution for Selective Nitrate Reduction Using Protonated Polypyrrole as a Cathode

“…Because of their high toxicity and low carbon/nitrogen ratio, biological denitrification can hardly be applied in nitrate removal from these industrial wastewaters. , Therefore, it has gained more and more attention to effectively remove nitrate in industrial wastewater in recent years. A lot of new techniques such as physicochemical adsorption, ion exchange, photocatalysis, , and electrochemical reduction have been developed to separate or remove nitrate, among which bimetallic catalytic reduction has attracted a lot of attention because it is environmentally acceptable and highly reducible under mild conditions. − Besides these, the most important is nitrate which can be efficiently reduced to harmless nitrogen directly instead of nitrite or ammonia by using hydrogen as the reductant. In most cases, nitrite and ammonia are more harmful than nitrate no matter for the environment or human health …”