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Zhang W, Li H, Cao H. Strong variability in nitrogen (N) removal rates in typical agricultural pond from hilly catchment: Evidence from diel and monthly dissolved N 2 measurement. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2022; 314:120196. [PMID: 36126768 DOI: 10.1016/j.envpol.2022.120196] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2022] [Revised: 08/23/2022] [Accepted: 09/13/2022] [Indexed: 06/15/2023]
Abstract
Ponds, depressional submerged landscapes that can store and process nitrogen (N)-enriched runoff from surrounding uplands, are recognized as biogeochemical hotspots for N removal. Despite their strong potential for N removal, information is limited concerning the specifics of their changing nature. Here, we investigated the dynamics of N removal rate in a typical agricultural pond from a hilly catchment, by unraveling the monthly and diel patterns of N2 concentrations and fluxes. Our observations showed that the N pollution in the pond was severe. Its averaged total N level reached 3.6 mg L-1, of which ∼72% consisted of NO3-N. Meanwhile, the water samples were supersaturated with N2, demonstrating N removal occurring in the pond. Further estimates of net N2 fluxes indicated that N removal rates exhibited obvious day-and-night and monthly differences. On the diel scale, N removal rates exhibited a distinct diurnal cycle, with nocturnal rates around 20% higher than during the day. Such a diel pattern can be mainly explained by the fluctuation in DO levels, showing that at nighttime when photosynthesis is absent, low DO environments are conducive to N removal. On a monthly scale, the monthly rates ranged from 0.02 to 0.49 mmol N2 m-2 h-1 (mean: 0.23 mmol N2 m-2 h-1), with generally higher removal rates in the warmer and concurrently rainy months (June-September). N levels in the pond were the corresponding primary explanatory variables. Assembled data from both monthly and hourly scales provided a more complete picture of the changing nature of N removal in ponds. Future work should carefully consider the effects of altered environmental conditions triggered by hydrological events to better reveal the control mechanisms behind the time-immediate N removal from lowland ponds.
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Affiliation(s)
- Wangshou Zhang
- Key Laboratory of Watershed Geographic Sciences, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, 210008, China.
| | - Hengpeng Li
- Key Laboratory of Watershed Geographic Sciences, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, 210008, China.
| | - Heng Cao
- Key Laboratory of Watershed Geographic Sciences, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, 210008, China
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Spellman P, Gulley J, Pain A, Flint M, Kim S, Rath S. Statistical evidence of recharge and supply controlling nitrate variability at springs discharging from the upper Floridan Aquifer. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 838:156041. [PMID: 35597350 DOI: 10.1016/j.scitotenv.2022.156041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2021] [Revised: 05/14/2022] [Accepted: 05/14/2022] [Indexed: 06/15/2023]
Abstract
Over the last several decades, rising nitrate concentrations in springs discharging from north Florida's karstic Upper Floridan Aquifer have coincided with proliferation of algae in Florida spring runs and subsequent ecosystem degradation. As agriculture and development are primary contributors to groundwater nitrate and are predicted to continue expanding, understanding unique contributions and transmission pathways of nitrate pollution is vital to restoring impaired spring ecosystems. In this study, we use statistics and signal processing to analyze continuous nitrate timeseries data collected over five years at four north Florida springs. We quantified a significant, low-frequency annual signal in nitrate concentrations superimposed on increasing nitrate trends. We show nitrate concentrations at springs increase during the rainy season, potentially in response to recharge and seasonal fertilizer application. Thus, we suggest seasonal fluctuations observed in nitrate concentrations are caused by increased recharge of nutrient-rich soil waters through fractures that deliver water on relatively short timescales to conduits during the rainy season. We further speculate the steady, monotonically increasing concentration is maintained by accumulation of Nitrogen as slow flow through matrix porosity through the remainder of the year. Seasonal nitrate concentrations resulting from flow through karst aquifers may thus be poorly simulated using equivalent porous media models that are increasingly being used for nutrient management, because they do not capture heterogenous flow and transport dynamics.
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Affiliation(s)
- Patricia Spellman
- University of South Florida, School of Geosciences, Tampa, FL 33620, United States of America.
| | - Jason Gulley
- University of South Florida, School of Geosciences, Tampa, FL 33620, United States of America
| | - Andrea Pain
- University of Maryland, Center for Environmental Science, Cambridge, MD 21613, United States of America
| | - Madison Flint
- University of Florida, Geological Sciences, Gainesville, FL 32611, United States of America
| | - Sunhye Kim
- University of South Florida, School of Geosciences, Tampa, FL 33620, United States of America
| | - Sagarika Rath
- University of Florida, Geological Sciences, Gainesville, FL 32611, United States of America
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Hua M, Li W, Ni B, Ma Q, Green A, Shen X, Claudepierre SG, Bortnik J, Gu X, Fu S, Xiang Z, Reeves GD. Very-Low-Frequency transmitters bifurcate energetic electron belt in near-earth space. Nat Commun 2020; 11:4847. [PMID: 32973130 PMCID: PMC7518438 DOI: 10.1038/s41467-020-18545-y] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Accepted: 08/31/2020] [Indexed: 11/17/2022] Open
Abstract
Very-Low-Frequency (VLF) transmitters operate worldwide mostly at frequencies of 10-30 kilohertz for submarine communications. While it has been of intense scientific interest and practical importance to understand whether VLF transmitters can affect the natural environment of charged energetic particles, for decades there remained little direct observational evidence that revealed the effects of these VLF transmitters in geospace. Here we report a radially bifurcated electron belt formation at energies of tens of kiloelectron volts (keV) at altitudes of ~0.8-1.5 Earth radii on timescales over 10 days. Using Fokker-Planck diffusion simulations, we provide quantitative evidence that VLF transmitter emissions that leak from the Earth-ionosphere waveguide are primarily responsible for bifurcating the energetic electron belt, which typically exhibits a single-peak radial structure in near-Earth space. Since energetic electrons pose a potential danger to satellite operations, our findings demonstrate the feasibility of mitigation of natural particle radiation environment.
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Affiliation(s)
- Man Hua
- Department of Space Physics, School of Electronic Information, Wuhan University, Wuhan, Hubei, China
- Center for Space Physics, Boston University, Boston, MA, USA
| | - Wen Li
- Center for Space Physics, Boston University, Boston, MA, USA.
| | - Binbin Ni
- Department of Space Physics, School of Electronic Information, Wuhan University, Wuhan, Hubei, China.
- CAS Center for Excellence in Comparative Planetology, Anhui, Hefei, China.
| | - Qianli Ma
- Center for Space Physics, Boston University, Boston, MA, USA
- Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, CA, USA
| | - Alex Green
- Center for Space Physics, Boston University, Boston, MA, USA
| | - Xiaochen Shen
- Center for Space Physics, Boston University, Boston, MA, USA
| | - Seth G Claudepierre
- Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, CA, USA
- Space Sciences Department, The Aerospace Corporation, EI Segundo, CA, USA
| | - Jacob Bortnik
- Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, CA, USA
| | - Xudong Gu
- Department of Space Physics, School of Electronic Information, Wuhan University, Wuhan, Hubei, China
| | - Song Fu
- Department of Space Physics, School of Electronic Information, Wuhan University, Wuhan, Hubei, China
| | - Zheng Xiang
- Department of Space Physics, School of Electronic Information, Wuhan University, Wuhan, Hubei, China
| | - Geoffrey D Reeves
- Space Science and Applications Group, Los Alamos National Laboratory, Los Alamos, NM, USA
- Space Sciences Division, New Mexico Consortium, Los Alamos, NM, USA
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Jacobs SR, Weeser B, Rufino MC, Breuer L. Diurnal Patterns in Solute Concentrations Measured with In Situ UV-Vis Sensors: Natural Fluctuations or Artefacts? SENSORS 2020; 20:s20030859. [PMID: 32041157 PMCID: PMC7039225 DOI: 10.3390/s20030859] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/29/2019] [Revised: 01/28/2020] [Accepted: 02/03/2020] [Indexed: 11/16/2022]
Abstract
In situ spectrophotometers measuring in the UV-visible spectrum are increasingly used to collect high-resolution data on stream water quality. This provides the opportunity to investigate short-term solute dynamics, including diurnal cycling. This study reports unusual changes in diurnal patterns observed when such sensors were deployed in four tropical headwater streams in Kenya. The analysis of a 5-year dataset revealed sensor-specific diurnal patterns in nitrate and dissolved organic carbon concentrations and different patterns measured by different sensors when installed at the same site. To verify these patterns, a second mobile sensor was installed at three sites for more than 3 weeks. Agreement between the measurements performed by these sensors was higher for dissolved organic carbon (r > 0.98) than for nitrate (r = 0.43–0.81) at all sites. Higher concentrations and larger amplitudes generally led to higher agreement between patterns measured by the two sensors. However, changing the position or level of shading of the mobile sensor resulted in inconsistent changes in the patterns. The results of this study show that diurnal patterns measured with UV-Vis spectrophotometers should be interpreted with caution. Further work is required to understand how these measurements are influenced by environmental conditions and sensor-specific properties.
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Affiliation(s)
- Suzanne R. Jacobs
- Center for international Development and Environmental Research (ZEU), Justus Liebig University, Senckenbergstr. 3, 35390 Giessen, Germany; (B.W.); (L.B.)
- Institute for Landscape Ecology and Resources Management (ILR), Justus Liebig University, Heinrich-Buff-Ring 26, 35392 Giessen, Germany
- Correspondence:
| | - Björn Weeser
- Center for international Development and Environmental Research (ZEU), Justus Liebig University, Senckenbergstr. 3, 35390 Giessen, Germany; (B.W.); (L.B.)
- Institute for Landscape Ecology and Resources Management (ILR), Justus Liebig University, Heinrich-Buff-Ring 26, 35392 Giessen, Germany
| | - Mariana C. Rufino
- Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ, UK;
- Centre for International Forestry Research (CIFOR), c/o World Agroforestry Centre, United Nations Avenue, Gigiri, 00100 Nairobi, Kenya
| | - Lutz Breuer
- Center for international Development and Environmental Research (ZEU), Justus Liebig University, Senckenbergstr. 3, 35390 Giessen, Germany; (B.W.); (L.B.)
- Institute for Landscape Ecology and Resources Management (ILR), Justus Liebig University, Heinrich-Buff-Ring 26, 35392 Giessen, Germany
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Rode M, Halbedel Née Angelstein S, Anis MR, Borchardt D, Weitere M. Continuous In-Stream Assimilatory Nitrate Uptake from High-Frequency Sensor Measurements. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2016; 50:5685-5694. [PMID: 27174385 DOI: 10.1021/acs.est.6b00943] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Recently developed in situ NO3– sensors provide new opportunities to measure changes in stream concentration at high temporal frequencies that historically have not been feasible. In this study, we used multiparameter sensor measurements to relate assimilatory NO3– uptake to metabolic rates and calculate continuous uptake rates for two stream reaches and a whole stream network. Two years of continuous 15 min data from a forest and agricultural reach of the Selke river (456 km2) revealed a strong correlation between assimilatory NO3– uptake and growth primary production (GPP) for the forest (r2 = 0.72) and agricultural (r2 = 0.56) stream reach. The slopes of these regressions were in agreement with predicted assimilatory N-uptake based on additional metabolic data. Mean yearly assimilatory NO3– uptake rates (Ua) were 7.4 times higher in the agricultural stream reach (mean 78.3 mg N m–2 d–1, max 270 mg N m–2 d–1) than in the forest stream reach (mean 10.7 mg N m–2 d–1, max 97.5 mg N m–2 d–1). Nitrate uptake velocities (Vf,a) tended to decrease with increasing nitrate concentrations for periods with high light availability. Percentage daily assimilatory NO3– uptake peaked at 47.4% of the daily NO3– loading input to the stream network across the entire watershed, whereas the percentage yearly assimilatory NO3– uptake was 9.0% of nitrogen loading to the stream network. This is a maximum because uptake can be revered by mineralization processes. The percentage yearly assimilatory NO3– uptake was lower in the forest-dominated upstream subwatershed (4.8%) than in the lower agriculture dominated subwatershed (13.4%).
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Scale-dependent linkages between nitrate isotopes and denitrification in surface soils: implications for isotope measurements and models. Oecologia 2016; 181:1221-31. [DOI: 10.1007/s00442-016-3626-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2015] [Accepted: 04/01/2016] [Indexed: 10/21/2022]
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Fork ML, Heffernan JB. Direct and Indirect Effects of Dissolved Organic Matter Source and Concentration on Denitrification in Northern Florida Rivers. Ecosystems 2013. [DOI: 10.1007/s10021-013-9705-9] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Cohen MJ, Kurz MJ, Heffernan JB, Martin JB, Douglass RL, Foster CR, Thomas RG. Diel phosphorus variation and the stoichiometry of ecosystem metabolism in a large spring-fed river. ECOL MONOGR 2013. [DOI: 10.1890/12-1497.1] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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