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Guo Z, Su R, Zeng J, Wang S, Zhang D, Yu Z, Wu QL, Zhao D. NosZI microbial community determined the potential of denitrification and nitrous oxide emission in river sediments of Qinghai-Tibetan Plateau. ENVIRONMENTAL RESEARCH 2022; 214:114138. [PMID: 35988830 DOI: 10.1016/j.envres.2022.114138] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Revised: 08/10/2022] [Accepted: 08/15/2022] [Indexed: 06/15/2023]
Abstract
Denitrification in river sediments is the hotspot of nitrogen removal and nosZI gene is essential for reducing nitrous oxide (N2O) emissions. However, few studies tried to link nosZI communities with variations of denitrification rates in sediments along the high-elevation rivers. Here, we investigated the spatial variation of potential denitrification rates of sediments along a section (hereafter YJ) of the middle reaches of the Yarlung Zangbo River in the Qinghai-Tibetan Plateau. We also used the real-time quantitative PCR (qPCR) and high-throughput sequencing techniques to evaluate the abundance and composition of nosZI-containing microbial groups. The influences of physicochemical factors and denitrifier communities on potential denitrification rates were further revealed through structural equation modeling. The obtained results indicated that potential denitrification rates and N2O/(N2O + N2) ratio in the sediments along YJ section were greatly different. Moreover, the alpha diversity and composition of nosZI-containing microbial community in river sediments differed remarkably, mainly driven by the ammonia nitrogen (NH4+-N), organic matter (OM) and pH in sediments. The relative abundances of Zoogloeaceae, Oxalobacteraceae, Rhodospirillaceae and Bradyrhizobiaceae significantly differed among five groups (P < 0.05). Structural equation modeling further suggested that nitrogen nutrients directly influenced the potential denitrification rates, while total phosphorus (TP) showed indirect effects on potential denitrification rates through modulating denitrifier abundances and nosZI community. The abundance and composition of nosZI community were powerful predictors in regulating denitrification rates and N2O/(N2O + N2) ratio. Our findings highlight that the nosZI-containing microbial groups play a non-negligible role in nitrogen removal and N2O mitigation in high-elevation river sediments.
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Affiliation(s)
- Zixu Guo
- Joint International Research Laboratory of Global Change and Water Cycle, State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University, Nanjing, 210098, China
| | - Rui Su
- Joint International Research Laboratory of Global Change and Water Cycle, State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University, Nanjing, 210098, China; State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, 210008, China
| | - Jin Zeng
- State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, 210008, China
| | - Shuren Wang
- Joint International Research Laboratory of Global Change and Water Cycle, State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University, Nanjing, 210098, China; State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, 210008, China
| | - Danrong Zhang
- Joint International Research Laboratory of Global Change and Water Cycle, State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University, Nanjing, 210098, China
| | - Zhongbo Yu
- Joint International Research Laboratory of Global Change and Water Cycle, State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University, Nanjing, 210098, China
| | - Qinglong L Wu
- State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, 210008, China; Sino-Danish Centre for Education and Research, University of Chinese Academy of Sciences, Beijing, 100039, China
| | - Dayong Zhao
- Joint International Research Laboratory of Global Change and Water Cycle, State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University, Nanjing, 210098, China.
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Abstract
Riparian zones are dynamic ecosystems that form at the interface between the aquatic and terrestrial components of a landscape. They are shaped by complex interactions between the biophysical components of river systems, including hydrology, geomorphology, and vegetation. Remote sensing technology is a powerful tool useful for understanding riparian form, function, and change over time, as it allows for the continuous collection of geospatial data over large areas. This paper provides an overview of studies published from 1991 to 2021 that have used remote sensing techniques to map and understand the processes that shape riparian habitats and their ecological functions. In total, 257 articles were reviewed and organised into six main categories (physical channel properties; morphology and vegetation or field survey; canopy detection; application of vegetation and water indices; riparian vegetation; and fauna habitat assessment). The majority of studies used aerial RGB imagery for river reaches up to 100 km in length and Landsat satellite imagery for river reaches from 100 to 1000 km in length. During the recent decade, UAVs (unmanned aerial vehicles) have been widely used for low-cost monitoring and mapping of riverine and riparian environments. However, the transfer of RS data to managers and stakeholders for systematic monitoring as a source of decision making for and successful management of riparian zones remains one of the main challenges.
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Vizuete-Jaramillo E, Grahmann K, Mora Palomino L, Méndez-Barroso L, Robles-Morua A. Using ion-exchange resins to monitor nitrate fluxes in remote semiarid stream beds. ENVIRONMENTAL MONITORING AND ASSESSMENT 2022; 194:376. [PMID: 35437732 DOI: 10.1007/s10661-022-10041-8] [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: 04/20/2021] [Accepted: 04/05/2022] [Indexed: 06/14/2023]
Abstract
Monitoring in remote areas can represent a real challenge in environmental studies. Numerous techniques have been developed over the last decades to monitor nutrients and other elements in different systems. However, not all of them are suitable for field applications, particularly when the locations are difficult to access or its accessibility depends on seasonal climate conditions. This study was aimed to test the applicability and efficiency of resin samplers and resin bags to monitor nitrates fluxes (NO3-N) in two small semi-arid catchments in Northwestern Mexico. Resin samplers were installed in the hyporheic zone below the river bed in order to monitor the vertical fluxes of NO3-N and remained there for 5 months (during the summer rains). Resin bags were anchored in rock outcrops upstream of the resin samplers before the onset of the summer rainfall season and replaced every 2 weeks during 4 months to capture pulses of NO3-N in ephemeral streams. NO3-N pulses in the stream are a potential source of NO3-N that can infiltrate into the soil. Results of the resin samplers found a difference of up to 12 kg ha-1 season-1 between the two catchments. The resin bags showed a higher accumulation of NO3-N in the catchment with lower vegetation cover (160.3 mg L-1 season-1) compared to the one with higher vegetation (67.8 mg L-1 season-1). Measured nitrate fluxes at both sites responded to rainfall pulses recorded during the monitoring period. Resin samplers and resin bags can be used together, to assess nutrient fluxes on the surface and in the soil and can be tested in any type of ecosystem. In this particular case, these methods demonstrated an efficient way of determining spatio-temporal nitrate fluxes in semi-arid ecosystems in remote areas that are difficult to access, monitor, and collect data.
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Affiliation(s)
- Efrain Vizuete-Jaramillo
- Departamento de Ciencias del Agua Y del Medio Ambiente, Instituto Tecnológico de Sonora (ITSON), Cd. Obregón, México
| | - Kathrin Grahmann
- Working Group "Resource-Efficient Cropping Systems", Research Area 2 "Landuse and Goverance", Leibniz Centre for Agricultural Landscape Research (ZALF), Müncheberg, Germany
| | - Lucy Mora Palomino
- Departamento de Ciencias Ambientales Y del Suelo, Universidad Nacional Autónoma de México (UNAM), México, D.F., México
- Laboratorio Nacional de Geoquímica Y Mineralogía (LANGEM), México, D.F., México
| | - Luis Méndez-Barroso
- Departamento de Ciencias del Agua Y del Medio Ambiente, Instituto Tecnológico de Sonora (ITSON), Cd. Obregón, México
- Laboratorio Nacional de Resiliencia Costera (LANSREC), Sisal, Yucatán, México
| | - Agustín Robles-Morua
- Departamento de Ciencias del Agua Y del Medio Ambiente, Instituto Tecnológico de Sonora (ITSON), Cd. Obregón, México.
- Laboratorio Nacional de Geoquímica Y Mineralogía (LANGEM), México, D.F., México.
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Senal MI, Møller AB, Koganti T, Iversen BV. Delineation of Nitrate Reduction Hotspots in Artificially Drained Areas through Assessment of Small-Scale Spatial Variability of Electrical Conductivity Data. SENSORS 2022; 22:s22041508. [PMID: 35214406 PMCID: PMC8879662 DOI: 10.3390/s22041508] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Revised: 02/07/2022] [Accepted: 02/09/2022] [Indexed: 02/04/2023]
Abstract
Identification of nitrate reduction hotspots (NRH) can be instrumental in implementing targeted strategies for reducing nitrate loading from agriculture. In this study, we aimed to delineate possible NRH areas from soil depths of 80 to 180 cm in an artificially drained catchment by utilizing electrical conductivity (EC) values derived by the inversion of apparent electrical conductivity data measured by an electromagnetic induction instrument. The NRH areas were derived from the subzones generated from clustering the EC values via two methods, unsupervised ISODATA clustering and the Optimized Hot Spot Analysis, that highly complement each other. The clustering of EC values generated three classes, wherein the classes with high EC values correspond to NRH areas as indicated by their low redox potential values and nitrate (NO3−) concentrations. Nitrate concentrations in the NRH were equal to 13 to 17% of the concentrations in non-NRH areas and occupied 26% of the total area of the drainage catchments in the study. It is likely that, with the identification of NRH areas, the degree of nitrogen reduction in the vadose zone may be higher than initially estimated at the subcatchment scale.
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Affiliation(s)
- Maria Isabel Senal
- Department of Agroecology, Aarhus University, Blichers Allé 20, 8830 Tjele, Denmark; (A.B.M.); (T.K.)
- Correspondence: (M.I.S.); (B.V.I.)
| | - Anders Bjørn Møller
- Department of Agroecology, Aarhus University, Blichers Allé 20, 8830 Tjele, Denmark; (A.B.M.); (T.K.)
| | - Triven Koganti
- Department of Agroecology, Aarhus University, Blichers Allé 20, 8830 Tjele, Denmark; (A.B.M.); (T.K.)
| | - Bo V. Iversen
- Department of Agroecology, Aarhus University, Blichers Allé 20, 8830 Tjele, Denmark; (A.B.M.); (T.K.)
- Aarhus University Centre for Water Technology (WATEC), Department of Agroecology, Blichers Allé 20, 8830 Tjele, Denmark
- Correspondence: (M.I.S.); (B.V.I.)
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Suchy AK, Palta MM, Stromberg JC, Childers DL. High Potential Nitrate Removal by Urban Accidental Wetlands in a Desert City: Limitations and Spatiotemporal Patterns. Ecosystems 2019. [DOI: 10.1007/s10021-019-00465-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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6
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Seasonal Salinization Decreases Spatial Heterogeneity of Sulfate Reducing Activity. SOIL SYSTEMS 2019. [DOI: 10.3390/soilsystems3020025] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Evidence of sulfate input and reduction in coastal freshwater wetlands is often visible in the black iron monosulfide (FeS) complexes that form in iron rich reducing sediments. Using a modified Indicator of Reduction in Soils (IRIS) method, digital imaging, and geostatistics, we examine controls on the spatial properties of FeS in a coastal wetland fresh-to-brackish transition zone over a multi-month, drought-induced saltwater incursion event. PVC sheets (10 × 15 cm) were painted with an iron oxide paint and incubated vertically belowground and flush with the surface for 24 h along a salt-influenced to freshwater wetland transect in coastal North Carolina, USA. Along with collection of complementary water and soil chemistry data, the size and location of the FeS compounds on the plate were photographed and geostatistical techniques were employed to characterize FeS formation on the square cm scale. Herein, we describe how the saltwater incursion front is associated with increased sulfate loading and decreased aqueous Fe(II) content. This accompanies an increased number of individual FeS complexes that were more uniformly distributed as reflected in a lower Magnitude of Spatial Heterogeneity at all sites except furthest downstream. Future work should focus on streamlining the plate analysis procedure as well as developing a more robust statistical based approach to determine sulfide concentration.
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Webster AJ, Groffman PM, Cadenasso ML. Controls on denitrification potential in nitrate-rich waterways and riparian zones of an irrigated agricultural setting. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2018; 28:1055-1067. [PMID: 29465768 DOI: 10.1002/eap.1709] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Revised: 01/26/2018] [Accepted: 01/29/2018] [Indexed: 06/08/2023]
Abstract
Denitrification, the microbial conversion of NO3- to N gases, is an important process contributing to whether lotic and riparian ecosystems act as sinks for excess NO3- from agricultural activities. Though agricultural waterways and riparian zones have been a focus of denitrification research for decades, almost none of this research has occurred in the irrigated agricultural settings of arid and semiarid climates. In this study, we conducted a broad survey of denitrification potential in riparian soils and channel sediments from 79 waterway reaches in the irrigated agricultural landscape of California's Central Valley. With this approach, we sought to capture the wide range of variation that arose from diverse waterway management and fluctuating flow conditions, and use this variation to identify promising management interventions. We explored associations of denitrification potentials with surface water NO3- -N, organic matter, flow conditions, vegetation cover, near-channel riparian bank slope, and channel geomorphic features using generalized linear mixed models. We found strong associations of sediment denitrification potentials with reach flow conditions, which we hypothesize was the result of variation in microbial communities' tolerance to dry-wet cycles. Denitrification potentials in riparian soils, in contrast, did not appear affected by flow conditions, but instead were associated with organic matter, vegetation cover, and bank slope in the riparian zone. These results suggest a strong need for further work on how denitrification responds to varying flow conditions and dry-wet cycles in non-perennial lotic ecosystems. Our findings also demonstrate that denitrifier communities respond to key features of waterway management, which can therefore be leveraged to control denitrification through a variety of management actions.
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Affiliation(s)
- Alex J Webster
- Department of Plant Sciences, University of California Davis, Shields Avenue, Davis, California, 95616, USA
- Graduate Group in Ecology, University of California Davis, Shields Avenue, Davis, California, 95616, USA
| | - Peter M Groffman
- Cary Institute of Ecosystem Studies, Millbrook, New York, 12545, USA
- Advanced Research Center and Brooklyn College, City University of New York, New York, New York, 12210, USA
| | - Mary L Cadenasso
- Department of Plant Sciences, University of California Davis, Shields Avenue, Davis, California, 95616, USA
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Tu J, Tu W, Tedders SH. Spatial variations in the associations of term birth weight with ambient air pollution in Georgia, USA. ENVIRONMENT INTERNATIONAL 2016; 92-93:146-56. [PMID: 27104672 DOI: 10.1016/j.envint.2016.04.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2015] [Revised: 03/29/2016] [Accepted: 04/04/2016] [Indexed: 05/12/2023]
Abstract
Birth weight is an important indicator of overall infant health and a strong predictor of infant morbidity and mortality, and low birth weight (LBW) is a leading cause of infant mortality in the United States. Numerous studies have examined the associations of birth weight with ambient air pollution, but the results were inconsistent. In this study, a spatial statistical technique, geographically weighted regression (GWR) is applied to explore the spatial variations in the associations of birth weight with concentrations of ozone (O3) and fine particulate matter (PM2.5) in the State of Georgia, USA adjusted for gestational age, parity, and six other socioeconomic, behavioral, and land use factors. The results show considerable spatial variations in the associations of birth weight with both pollutants. Significant positive, non-significant, and significant negative relationships between birth weight and concentrations of each air pollutant are all found in different parts of the study area, and the different types of the relationships are affected by the socioeconomic and urban characteristics of the communities where the births are located. The significant negative relationships between birth weight and O3 indicate that O3 is a significant risk factor of LBW and these associations are primarily located in less-urbanized communities. On the other hand, PM2.5 is a significant risk factor of LBW in the more-urbanized communities with higher family income and education attainment. These findings suggest that environmental and health policies should be adjusted to address the different effects of air pollutants on birth outcomes across different types of communities to more effectively and efficiently improve birth outcomes.
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Affiliation(s)
- Jun Tu
- Department of Geography and Anthropology, Kennesaw State University, 1000 Chastain Road, Kennesaw, GA 30144-5591, USA.
| | - Wei Tu
- Department of Geology and Geography, Georgia Southern University, Statesboro, GA 30460-8149, USA
| | - Stuart H Tedders
- Jiann-Ping Hsu College of Public Health, Georgia Southern University, Statesboro, GA 30460-8015, USA
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Grazhdani D. Assessing the variables affecting on the rate of solid waste generation and recycling: An empirical analysis in Prespa Park. WASTE MANAGEMENT (NEW YORK, N.Y.) 2016; 48:3-13. [PMID: 26482808 DOI: 10.1016/j.wasman.2015.09.028] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Revised: 09/04/2015] [Accepted: 09/21/2015] [Indexed: 05/20/2023]
Abstract
Economic development, urbanization, and improved living standards increase the quantity and complexity of generated solid waste. Comprehensive study of the variables influencing household solid waste production and recycling rate is crucial and fundamental for exploring the generation mechanism and forecasting future dynamics of household solid waste. The present study is employed in the case study of Prespa Park. A model, based on the interrelationships of economic, demographic, housing structure and waste management policy variables influencing the rate of solid waste generation and recycling is developed and employed. The empirical analysis is based on the information derived from a field questionnaire survey conducted in Prespa Park villages for the year 2014. Another feature of this study is to test whether a household's waste generation can be decoupled from its population growth. Descriptive statistics, bivariate correlation analysis and F-tests are used to know the relationship between variables. One-way and two-way fixed effects models data analysis techniques are used to identify variables that determine the effectiveness of waste generation and recycling at household level in the study area. The results reveal that households with heterogeneous characteristics, such as education level, mean building age and income, present different challenges of waste reduction goals. Numerically, an increase of 1% in education level of population corresponds to a waste reduction of 3kg on the annual per capita basis. A village with older buildings, in the case of one year older of the median building age, corresponds to a waste generation increase of 12kg. Other economic and policy incentives such as the mean household income, pay-as-you-throw, percentage of population with access to curbside recycling, the number of drop-off recycling facilities available per 1000 persons and cumulative expenditures on recycling education per capita are also found to be effective measures in waste reduction. The mean expenditure for recycling education spent on a person for years 2010 and 2014 is 12 and 14 cents, respectively and it vary from 0 to €1. For years 2010 and 2014, the mean percentage of population with access to curbside recycling services is 38.6% and 40.3%, and the mean number of drop-off recycling centers per 1000 persons in the population is 0.29 and 0.32, respectively. Empirical evidence suggests that population growth did not necessarily result in increases in waste generation. The results provided are useful when planning, changing or implementing sustainable municipal solid waste management.
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Affiliation(s)
- Dorina Grazhdani
- Agricultural University of Tirana, Faculty of Economy & Agribusiness, Department of Agribusiness, Kamëz, Tirana, Albania.
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Collins S, Belnap J, Grimm N, Rudgers J, Dahm C, D'Odorico P, Litvak M, Natvig D, Peters D, Pockman W, Sinsabaugh R, Wolf B. A Multiscale, Hierarchical Model of Pulse Dynamics in Arid-Land Ecosystems. ANNUAL REVIEW OF ECOLOGY EVOLUTION AND SYSTEMATICS 2014. [DOI: 10.1146/annurev-ecolsys-120213-091650] [Citation(s) in RCA: 123] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- S.L. Collins
- Department of Biology, University of New Mexico, Albuquerque, New Mexico 87131;
| | - J. Belnap
- US Geological Survey, Southwest Biological Science Center, Moab, Utah 84532
| | - N.B. Grimm
- School of Life Sciences, Arizona State University, Tempe, Arizona 85287
| | - J.A. Rudgers
- Department of Biology, University of New Mexico, Albuquerque, New Mexico 87131;
| | - C.N. Dahm
- Department of Biology, University of New Mexico, Albuquerque, New Mexico 87131;
| | - P. D'Odorico
- Department of Environmental Sciences, University of Virginia, Charlottesville, Virginia 22904
| | - M. Litvak
- Department of Biology, University of New Mexico, Albuquerque, New Mexico 87131;
| | - D.O. Natvig
- Department of Biology, University of New Mexico, Albuquerque, New Mexico 87131;
| | - D.C. Peters
- USDA Jornada Experimental Range, New Mexico State University, Las Cruces, New Mexico 88012
| | - W.T. Pockman
- Department of Biology, University of New Mexico, Albuquerque, New Mexico 87131;
| | - R.L. Sinsabaugh
- Department of Biology, University of New Mexico, Albuquerque, New Mexico 87131;
| | - B.O. Wolf
- Department of Biology, University of New Mexico, Albuquerque, New Mexico 87131;
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Marton JM, Roy Chowdhury R, Craft CB. A comparison of the spatial variability of denitrification and related soil properties in restored and natural depression wetlands in Indiana, USA. INTERNATIONAL JOURNAL OF BIODIVERSITY SCIENCE, ECOSYSTEM SERVICES & MANAGEMENT 2014. [DOI: 10.1080/21513732.2014.950981] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
Affiliation(s)
- John M. Marton
- School of Public and Environmental Affairs, Indiana University, 702 North Walnut Grove Ave, Bloomington, IN 47405, USA
| | - Rinku Roy Chowdhury
- Department of Geography, Indiana University, 701 East Kirkwood Ave, Bloomington, IN 47405, USA
| | - Christopher B. Craft
- School of Public and Environmental Affairs, Indiana University, 702 North Walnut Grove Ave, Bloomington, IN 47405, USA
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Wang S, Cao Z, Li X, Liao Z, Hu B, Ni J, Ruan H. Spatial-seasonal variation of soil denitrification under three riparian vegetation types around the Dianchi Lake in Yunnan, China. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2013; 15:963-971. [PMID: 23525252 DOI: 10.1039/c3em30808a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Outbreaks of nuisance cyanobacterial bloom are predicted to occur frequently under the effect of severe eutrophication in the water body of Lake Dianchi since the 1990s. Riparian buffers are now well recognized for their roles in the removal of inorganic nitrogen mainly via denitrification. Little is known, however, about the mechanisms of nitrate removal in the riparian buffers of Lake Dianchi. We investigated the wet and dry seasonal dynamics of denitrification rate (DNR) in the soil profiles along the topographic gradient in three riparian buffers with different vegetation types (i.e. forest, open forest, and grass). A strong vertical pattern was observed in soil organic C and N concentrations (i.e. total N, DON, NO3-N, and NH4-N) along the soil layers. We also found significantly higher in situ denitrification activity in the upper horizon along each topohydrosequence while the activities of soil denitrification could be detected down to deeper soil horizons (0.1 to 0.8 mg N per kg dry soil per day), which may contribute significantly to the reduction of the ground water nitrate. Meanwhile, the DNR in the zones near the lake was significantly higher than that in zones near the border with the upland terrace, and also in the wet seasons than in dry seasons. Denitrification rates in the forest, open forest and grass sites were significantly different only in wet seasons. Especially, we found soil organic C had a strong correlation with denitrification in all sites, despite the large intersite variability of soil and vegetation. Our data suggested spatial heterogeneity of substrate availability along a hydrologic and topographic gradient can be the primary control on spatial-seasonal patterns of denitrification in riparian buffers.
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Affiliation(s)
- Shaojun Wang
- Department of Environmental Science and Engineering, Southwest Forestry University, Bailongshi, Kunming, China.
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13
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Tu J. Spatial variations in the relationships between land use and water quality across an urbanization gradient in the watersheds of Northern Georgia, USA. ENVIRONMENTAL MANAGEMENT 2013; 51:1-17. [PMID: 21858555 DOI: 10.1007/s00267-011-9738-9] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2010] [Accepted: 07/25/2011] [Indexed: 05/10/2023]
Abstract
A spatial statistical technique, Geographically Weighted Regression (GWR) is applied to study the spatial variations in the relationships between four land use indicators, including percentages of urban land, forest, agricultural land, and wetland, and eight water quality indicators including specific conductance (SC), dissolved oxygen, dissolved nutrients, and dissolved organic carbon, in the watersheds of northern Georgia, USA. The results show that GWR has better model performance than ordinary least squares regression (OLS) to analyze the relationships between land use and water quality. There are great spatial variations in the relationships affected by the urbanization level of watersheds. The relationships between urban land and SC are stronger in less-urbanized watersheds, while those between urban land and dissolved nutrients are stronger in highly-urbanized watersheds. Percentage of forest is an indicator of good water quality. Agricultural land is usually associated with good water quality in highly-urbanized watersheds, but might be related to water pollution in less-urbanized watersheds. This study confirms the results obtained from a similar study in eastern Massachusetts, and so suggest that GWR technique is a very useful tool in water environmental research and also has the potential to be applied to other fields of environmental studies and management in other regions.
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Affiliation(s)
- Jun Tu
- Department of Geography and Anthropology, Kennesaw State University, Kennesaw, GA 30144-5591, USA.
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14
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Alfarouk KO, Ibrahim ME, Gatenby RA, Brown JS. Riparian ecosystems in human cancers. Evol Appl 2012; 6:46-53. [PMID: 23396634 PMCID: PMC3567470 DOI: 10.1111/eva.12015] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2012] [Accepted: 08/29/2012] [Indexed: 02/06/2023] Open
Abstract
Intratumoral evolution produces extensive genetic heterogeneity in clinical cancers. This is generally attributed to an increased mutation rate that continually produces new genetically defined clonal lineages. Equally important are the interactions between the heritable traits of cancer cells and their microenvironment that produces natural selection favoring some clonal ‘species’ over others. That is, while mutations produce the heritable variation, environmental selection and cellular adaptation govern the strategies (and genotypes) that can proliferate within the tumor ecosystem. Here we ask: What are the dominant evolutionary forces in the cancer ecosystem? We propose that the tumor vascular network is a common and primary cause of intratumoral heterogeneity. Specifically, variations in blood flow result in variability in substrate, such as oxygen, and metabolites, such as acid, that serve as critical, but predictable, environmental selection forces. We examine the evolutionary and ecological consequences of variable blood flow by drawing an analogy to riparian habitats within desert landscapes. We propose that the phenotypic properties of cancer cells will exhibit predictable spatial variation within tumor phenotypes as a result of proximity to blood flow. Just as rivers in the desert create an abrupt shift from the lush, mesic riparian vegetation along the banks to sparser, xeric and dry-adapted plant species in the adjacent drylands, we expect blood vessels within tumors to promote similarly distinct communities of cancer cells that change abruptly with distance from the blood vessel. We propose vascular density and blood flow within a tumor as a primary evolutionary force governing variations in the phenotypic properties of cancer cells thus providing a unifying ecological framework for understanding intratumoral heterogeneity.
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Keser S, Duzgun S, Aksoy A. Application of spatial and non-spatial data analysis in determination of the factors that impact municipal solid waste generation rates in Turkey. WASTE MANAGEMENT (NEW YORK, N.Y.) 2012; 32:359-371. [PMID: 22104614 DOI: 10.1016/j.wasman.2011.10.017] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2011] [Revised: 10/11/2011] [Accepted: 10/11/2011] [Indexed: 05/31/2023]
Abstract
In studies focusing on the factors that impact solid waste generation habits and rates, the potential spatial dependency in solid waste generation data is not considered in relating the waste generation rates to its determinants. In this study, spatial dependency is taken into account in determination of the significant socio-economic and climatic factors that may be of importance for the municipal solid waste (MSW) generation rates in different provinces of Turkey. Simultaneous spatial autoregression (SAR) and geographically weighted regression (GWR) models are used for the spatial data analyses. Similar to ordinary least squares regression (OLSR), regression coefficients are global in SAR model. In other words, the effect of a given independent variable on a dependent variable is valid for the whole country. Unlike OLSR or SAR, GWR reveals the local impact of a given factor (or independent variable) on the waste generation rates of different provinces. Results show that provinces within closer neighborhoods have similar MSW generation rates. On the other hand, this spatial autocorrelation is not very high for the exploratory variables considered in the study. OLSR and SAR models have similar regression coefficients. GWR is useful to indicate the local determinants of MSW generation rates. GWR model can be utilized to plan waste management activities at local scale including waste minimization, collection, treatment, and disposal. At global scale, the MSW generation rates in Turkey are significantly related to unemployment rate and asphalt-paved roads ratio. Yet, significances of these variables may diminish at local scale for some provinces. At local scale, different factors may be important in affecting MSW generation rates.
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Affiliation(s)
- Saniye Keser
- Department of Environmental Engineering, Middle East Technical University, 06800 Ankara, Turkey
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Roach WJ, Grimm NB. Denitrification mitigates N flux through the stream-floodplain complex of a desert city. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2011; 21:2618-2636. [PMID: 22073648 DOI: 10.1890/10-1613.1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The Indian Bend Wash (IBW) flood-control project relies on a greenbelt to carry floods through Scottsdale, Arizona, USA. The greenbelt is characterized by a chain of shallow artificial lakes in a larger floodplain of irrigated turf, which has been protected from encroaching urban development. As such, this urban stream-floodplain complex can be divided into three subsystems: artificial lakes, channelized stream segments, and floodplain. We conducted experiments to evaluate which, if any, of these subsystems were important sites of denitrification, and to explore factors controlling denitrification rates. Denitrification enzyme activity (DEA) bioassays were conducted on sediments from eight lake and six stream segments as well as soil samples from eight floodplain transects. Mass-specific potential denitrification rates were significantly higher in lakes than in streams or floodplains. Nutrient limitation bioassays revealed that nitrate (NO3-) limited denitrification in lake sediments, a surprising finding given that NO3(-)-rich groundwater additions frequently raised lake NO3(-) concentration above 1 mg N/L. Experiments on intact lake cores suggested that denitrification was limited by the rate NO3(-) diffused into sediments, rather than its availability in overlying water. Floodplain denitrification was limited by water content, not NO3(-) or C, and irrigation of soils stimulated denitrification. We constructed a N budget for the IBW stream-floodplain complex based on our experimental results. We found that both lakes and floodplains removed large quantities of N, with denitrification removing 261 and 133 kg N ha(-1) yr(-1) from lake sediments and floodplain soils, respectively, indicating that lakes are hotspots for denitrification. Nevertheless, because floodplain area was >4.5 times that of lakes, floodplain soils removed nearly 2.5 times as much N as lake sediments. Given the desert's low annual precipitation, a finding that floodplain soils are active sites of denitrification might seem implausible; however, irrigation is common in urban landscapes, and it elevated annual denitrification in IBW. Based on our results, we conclude that construction of artificial lakes created hotspots while application of irrigation water created hot moments for denitrification in the stream-floodplain complex, demonstrating that management decisions can improve the ability of urban streams to provide critical ecosystem services like N retention.
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Affiliation(s)
- W John Roach
- School of Life Sciences, Arizona State University, P.O. Box 874501, Tempe, Arizona 85287, USA
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Denitrification Potential in Lake Sediment Increases Across a Gradient of Catchment Agriculture. Ecosystems 2011. [DOI: 10.1007/s10021-011-9413-2] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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