Abstract:Remediation of nitrate pollution of Earth’s rivers and aquifers is hampered by cumulative biogeochemical processes and nitrogen sources. Isotopes (δ15N, δ18O) help unravel spatiotemporal nitrogen(N)-cycling of aquatic nitrate (NO3−). We synthesized nitrate isotope data (n = ~5200) for global rivers and shallow aquifers for common patterns and processes. Rivers had lower median NO3− (0.3 ± 0.2 mg L−1, n = 2902) compared to aquifers (5.5 ± 5.1 mg L−1, n = 2291) and slightly lower δ15N values (+7.1 ± 3.8‰, n = 29… Show more
“…The occurrence and significant correlation of nitrate and its isotopes with CECs suggest that wastewater inputs derived via tributaries is an important admixture source in the Danube River (Table SI-3 , Fig. SI-3 ) confirming earlier studies in the DRB 9 , 10 and in other basins worldwide 21 , 31 – 33 . The positive correlation of nitrate isotopes with caffeine and DNP showed these CECs are relevant chemical tracers of the sewage inputs (Fig.…”
Section: Discussionsupporting
confidence: 81%
“…4 ). Figure 4 The δ 15 N-NO 3 vs δ 18 O-NO 3 framed within potential nitrate sources according to Matiatos et al 21 . …”
Section: Resultsmentioning
confidence: 99%
“…It is also likely that assimilation and nitrification occur in the water column of the Danube River, however no parallel enrichment in δ 15 N-NO 3 and δ 18 O-NO 3 was observed. This is expected to be a seasonal feature and would require higher time–frequency sampling at key points along the Danube River, and ideally covering the winter period with low biological activities 21 . Another possible N removal process is assimilation or uptake of inorganic nitrogen compounds into living organisms via biosynthesis, which has also been observed as a main removal process of nitrate in Central European rivers during summer months 15 .…”
Section: Discussionmentioning
confidence: 99%
“…Stable hydrogen ( δ 2 H) and oxygen isotope ( δ 18 O) ratios in precipitation and runoff are well-established conservative tracers of water origin, mixing, and dilution patterns in global rivers 13 . Nitrogen and oxygen isotope ratios of nitrate ( δ 18 O-NO 3 , δ 15 N-NO 3 ) help to delineate NO 3 − sources and biogeochemical cycling processes 14 – 21 , but challenges remain when NO 3 − sources have overlapping 15 N isotopic compositions (e.g., sewage and manure) 21 . Additional tracers, such as CECs (pharmaceuticals, detergents, artificial sweeteners, industrial compounds, etc.)…”
Dispersed and unknown pollution sources complicate water management in large transboundary watersheds. We applied stable isotopes of water and nitrate together with contaminants of emerging concern (CECs: carbamazepine, caffeine, sulfamethoxazole, perfluorooctanoic acid and 2,4-dinitrophenol) to evaluate mixing and inputs of water and contaminants from tributaries into the mainstem of the transboundary Danube River. Stable isotope (δ18O, δ2H) variations from low values (− 13.3 ‰, − 95.1 ‰) in the Upper Danube after the Inn River confluence to high values (− 9.9 ‰, − 69.7 ‰) at the Danube River mouth revealed snowmelt dominated tributary mixing (~ 70%) in the mainstem. Stable isotopes of nitrate (δ15N-NO3) in the Danube River varied from lower values (+ 6.7 ‰) in the Upper Danube to higher values after the mixing with Morava River (+ 10.5 ‰) and showed that cold snowmelt can reduce biological activity and controls nitrate biotransformation processes in the mainstem up to 1000 km downstream. Data on emerging contaminants affirmed the low biodegradation potential of organic compounds transferred into the mainstem by tributaries. We found pollutant source tracing in large rivers is complicated by mixing of multiple sources with overlapping isotopic signatures, but additional tracers such as CECs improve the interpretation of hydrological processes (e.g., water transit time) and support tracing of nitrate pollution sources, and biogeochemical processes. Our approach can be applied to other watersheds to improve the understanding of dilution and mixing processes. Moreover, it provides directions for improving national and transboundary water quality monitoring networks.
“…The occurrence and significant correlation of nitrate and its isotopes with CECs suggest that wastewater inputs derived via tributaries is an important admixture source in the Danube River (Table SI-3 , Fig. SI-3 ) confirming earlier studies in the DRB 9 , 10 and in other basins worldwide 21 , 31 – 33 . The positive correlation of nitrate isotopes with caffeine and DNP showed these CECs are relevant chemical tracers of the sewage inputs (Fig.…”
Section: Discussionsupporting
confidence: 81%
“…4 ). Figure 4 The δ 15 N-NO 3 vs δ 18 O-NO 3 framed within potential nitrate sources according to Matiatos et al 21 . …”
Section: Resultsmentioning
confidence: 99%
“…It is also likely that assimilation and nitrification occur in the water column of the Danube River, however no parallel enrichment in δ 15 N-NO 3 and δ 18 O-NO 3 was observed. This is expected to be a seasonal feature and would require higher time–frequency sampling at key points along the Danube River, and ideally covering the winter period with low biological activities 21 . Another possible N removal process is assimilation or uptake of inorganic nitrogen compounds into living organisms via biosynthesis, which has also been observed as a main removal process of nitrate in Central European rivers during summer months 15 .…”
Section: Discussionmentioning
confidence: 99%
“…Stable hydrogen ( δ 2 H) and oxygen isotope ( δ 18 O) ratios in precipitation and runoff are well-established conservative tracers of water origin, mixing, and dilution patterns in global rivers 13 . Nitrogen and oxygen isotope ratios of nitrate ( δ 18 O-NO 3 , δ 15 N-NO 3 ) help to delineate NO 3 − sources and biogeochemical cycling processes 14 – 21 , but challenges remain when NO 3 − sources have overlapping 15 N isotopic compositions (e.g., sewage and manure) 21 . Additional tracers, such as CECs (pharmaceuticals, detergents, artificial sweeteners, industrial compounds, etc.)…”
Dispersed and unknown pollution sources complicate water management in large transboundary watersheds. We applied stable isotopes of water and nitrate together with contaminants of emerging concern (CECs: carbamazepine, caffeine, sulfamethoxazole, perfluorooctanoic acid and 2,4-dinitrophenol) to evaluate mixing and inputs of water and contaminants from tributaries into the mainstem of the transboundary Danube River. Stable isotope (δ18O, δ2H) variations from low values (− 13.3 ‰, − 95.1 ‰) in the Upper Danube after the Inn River confluence to high values (− 9.9 ‰, − 69.7 ‰) at the Danube River mouth revealed snowmelt dominated tributary mixing (~ 70%) in the mainstem. Stable isotopes of nitrate (δ15N-NO3) in the Danube River varied from lower values (+ 6.7 ‰) in the Upper Danube to higher values after the mixing with Morava River (+ 10.5 ‰) and showed that cold snowmelt can reduce biological activity and controls nitrate biotransformation processes in the mainstem up to 1000 km downstream. Data on emerging contaminants affirmed the low biodegradation potential of organic compounds transferred into the mainstem by tributaries. We found pollutant source tracing in large rivers is complicated by mixing of multiple sources with overlapping isotopic signatures, but additional tracers such as CECs improve the interpretation of hydrological processes (e.g., water transit time) and support tracing of nitrate pollution sources, and biogeochemical processes. Our approach can be applied to other watersheds to improve the understanding of dilution and mixing processes. Moreover, it provides directions for improving national and transboundary water quality monitoring networks.
“…The resultant fluxes of reactive nitrogen can adversely affect freshwater ecosystems through eutrophication and acidification, as well as impact human health through nitrate contamination of groundwater used for drinking water supplies (eg. Vitousek, 199;Matiatos et al, 2021). However, the loss of reactive nitrogen to the vadose zone, where leaching from surface to groundwater and slow transit times leads to the longterm storage of nitrate is poorly quantified (Ascott et al, 2017).…”
Amorphous materials are distinguished by their exceptional attributes, notably their expansive surface area and the profusion of active sites they present. Consequently, the amorphization process stands as an efficacious strategy to augment the catalytic efficacy of electrocatalysts. This is achieved through the meticulous construction of the surface architecture and the precise modulation of the electronic configuration of these materials. Therefore, this review aims to offer a thorough examination of the latest progress in the application of amorphous materials for the enhancement of electrocatalytic processes, with a particular emphasis on the nitrate (NO3‐) reduction reaction (NITRR) and the carbon dioxide reduction reaction (CO2RR). Initially, we delve into the structural benefits inherent to amorphous materials, outlining the diverse synthesis techniques and characterization methodologies utilized in their development. Following this, we illustrate the utilization of various amorphous materials in NITRR and CO2RR, accentuating how the amorphous framework influences electrocatalytic activities. Concludingly, we encapsulate the merits and the obstacles encountered in the application of amorphous electrocatalysts for NITRR and CO2RR, whilst also forecasting the future direction for the creation of innovative amorphous electrocatalysts.
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