Effects of land-use change on nutrient discharges from the Patuxent River watershed

Estuaries - Tập 26 Số 2 - Trang 244-266 - 2003
Weller, Donald E.1, Jordan, Thomas E.1, Correll, David L.1, Liu, Zhi-Jun1
1Smithsonian Environmental Research Center, Edgewater

Tóm tắt

We developed an empirical model integrating nonpoint source (NPS) runoff, point sources (PS), and reservoir management to predict watershed discharges of water, sediment, organic carbon, silicate, nitrogen, and phosphorus to the Patuxent River in Maryland. We estimated NPS discharges with linear models fit to measurements of weekly flow and 10 material concentrations from 22 study watersheds. The independent variables were the proportions of cropland and developed land, physiographic province (Coastal Plain or Piedmont), and time (week). All but one of the NPS models explained between 62% and 83% of the variability among concentration or flow measurements. Geographic factors (land cover and physiographic province) accounted for the explained variability in largely dissolved material concentrations (nitrate [NO3], silicate [Si], and total nitrogen [TN]), but the explained variability in flow and particulates (sediment and forms of phosphorus) was more strongly related to temporal variability or its interactions with land cover and province. Average concentrations of all materials increased with cropland proportion and also with developed land (except Si), but changes in cropland produced larger concentration shifts than equivalent changes in developed land proportion. Among land cover transitions, conversions between cropland and forest-grassland cause the greatest changes in material discharges, cropland and developed land conversions are intermediate, and developed land and forest-grassland conversions have the weakest effects. Changing land cover has stronger effects on NO3 and TN in the Piedmont than in the coastal Plain, but for all other materials, the effects of land-use change are greater in the Coastal Plain. We predicted the changes in nutrient load to the estuary under several alternate land cover configurations, including a state planning scenario that extrapolates current patterns of population growth and land development to the year 2020. In that scenario, declines in NPS discharges from reducing cropland are balanced by NPS discharge increases from developing an area almost six times larger than the lost cropland. When PS discharges are included, there are net increases in total water, total phosphorus, and TN discharges.

Tài liệu tham khảo

citation_journal_title=Nature; citation_title=Effect of stream channel size on the delivery of nitrogen to the Gulf of Mexico; citation_author=R. B. Alexander, R. A. Smith, G. E. Schwarz; citation_volume=403; citation_publication_date=2000; citation_pages=758-761; citation_doi=10.1038/35001562; citation_id=CR1 citation_title=Atmospheric nitrogen flux from the watersheds of major estuaries of the United States: An application of the SPARROW watershed model; citation_inbook_title=Nutrient Loading in Coastal Water Bodies: An Atmospheric Perspective, Volume 57; citation_publication_date=2001; citation_pages=119-170; citation_id=CR2; citation_author=R. B. Alexander; citation_author=R. A. Smith; citation_author=G. E. Schwarz; citation_author=S. D. Preston; citation_author=J. W. Brakebill; citation_author=R. Srinivasan; citation_author=P. A. Pacheco; citation_publisher=American Geophysical Union citation_journal_title=Water Resources Bulletin; citation_title=An examination of land use—Nutrient export relationships; citation_author=M. N. Beaulac, K. H. Reckhow; citation_volume=18; citation_publication_date=1982; citation_pages=1013-1022; citation_id=CR3 citation_title=Hydrological simulation program FOR-TRAN (HSPF): User's manual for release 11. EPA-600/R-97-080; citation_publication_date=1997; citation_id=CR4; citation_author=B. R. Bicknell; citation_author=J. C. Imhoff; citation_author=J. L. Kittle; citation_author=A. S. Donigan; citation_author=R. C. Johanson; citation_publisher=U.S. Environmental Protection Agency citation_journal_title=Estuaries; citation_title=Public policy and the changing landscape; citation_author=N. E. Bockstael, E. G. Irwin; citation_volume=26; citation_publication_date=2003; citation_pages=210-225; citation_doi=10.1007/BF02695963; citation_id=CR5 citation_journal_title=Journal of Environmental Quality; citation_title=Chesapeake Bay eutrophication: Scientific understanding, ecosystem restoration, and challenges for agriculture; citation_author=D. E. Boesch, R. B. Brinsfield, R. E. Magnien; citation_volume=30; citation_publication_date=2001; citation_pages=303-320; citation_id=CR6 citation_journal_title=Estuaries; citation_title=Inputs, transformations, and transport of nitrogen and phosphorus in Chesapeake Bay and selected tributaries; citation_author=W. R. Boynton, J. H. Garber, R. Summers, W. M. Kemp; citation_volume=18; citation_publication_date=1995; citation_pages=285-314; citation_doi=10.2307/1352640; citation_id=CR7 citation_journal_title=Esturies; citation_title=From ecology to economics: Tracing human influence in the Patuxent River estuary and its watershed; citation_author=D. Breitburg, D. L. Lipton, T. E. Jordan; citation_volume=26; citation_publication_date=2003; citation_pages=280-297; citation_doi=10.1007/BF02695967; citation_id=CR8 citation_title=Census of agriculture, 1987 on CD-ROM technical documentation; citation_publication_date=1990; citation_id=CR9; citation_publisher=U.S. Department of Comerce citation_journal_title=Ecological Applications; citation_title=Nonpoint pollution of surface waters with phosphorus and nitrogen; citation_author=S. Carpenter, N. F. Caraco, D. L. Correll, R. W. Howarth, A. N. Sharpley, V. H. Smith; citation_volume=8; citation_publication_date=1998; citation_pages=559-568; citation_doi=10.1890/1051-0761(1998)008[0559:NPOSWW]2.0.CO;2; citation_id=CR10 citation_title=Contribution of atmospheric deposition to the total nitrogen loads to thirty-four estuaries on the Atlantic and Gulf coasts of the United States; citation_inbook_title=Nutrient Loading in Coastal Water Bodies: An Atmospheric Perspective, Volume 57; citation_publication_date=2001; citation_pages=77-105; citation_id=CR11; citation_author=M. S. Castro; citation_author=C. T. Driscoll; citation_author=T. E. Jordan; citation_author=W. G. Reay; citation_author=W. R. Boynton; citation_author=S. P. Seitzinger; citation_author=R. V. Styles; citation_author=J. E. Cable; citation_publisher=American Geophysical Union citation_title=CoastWatch Change Analysis Project (C-CAP): Chesapeake Bay land cover classification data, 1984 and 1988–89; citation_publication_date=1992; citation_id=CR12; citation_publisher=National Oceanographic Data Center, National Oceanic and Atmospheric Administration, U.S. Department of Commerce citation_title=Nutrients in Chesapeake Bay; citation_inbook_title=Contaminant Problems and Management of Living Chesapeake Bay Resources; citation_publication_date=1987; citation_pages=298-320; citation_id=CR13; citation_author=D. L. Correll; citation_publisher=Pennsylvania Academy of Science citation_journal_title=Journal of the American Water Resources Association; citation_title=Effects of interannual variation in precipitation on stream discharge from Rhode River subwatersheds; citation_author=D. L. Correll, T. E. Jordan, D. E. Weller; citation_volume=35; citation_publication_date=1999; citation_pages=73-82; citation_doi=10.1111/j.1752-1688.1999.tb05453.x; citation_id=CR14 citation_journal_title=Water Air and Soil Pollution; citation_title=Effects of precipitation and air temperature on nitrogen discharges from Rhode River watersheds; citation_author=D. L. Correll, T. E. Jordan, D. E. Weller; citation_volume=115; citation_publication_date=1999; citation_pages=547-575; citation_doi=10.1023/A:1005194630598; citation_id=CR15 citation_journal_title=Journal of Environmental Quality; citation_title=Effects of precipitation and air temperature on phosphorus fluxes from Rhode River watersheds; citation_author=D. L. Correll, T. E. Jordan, D. E. Weller; citation_volume=28; citation_publication_date=1999; citation_pages=144-154; citation_id=CR16 citation_journal_title=Journal of Environmental Quality; citation_title=Precipitation effects on sediment and associated nutrient discharges from Rhode River watersheds; citation_author=D. L. Correll, T. E. Jordan, D. E. Weller; citation_volume=28; citation_publication_date=1999; citation_pages=1897-1907; citation_id=CR17 citation_journal_title=Water Resources Research; citation_title=Transport of nitrogen and phosphorus from Rhode River watersheds during storm events; citation_author=D. L. Correll, T. E. Jordan, D. E. Weller; citation_volume=35; citation_publication_date=1999; citation_pages=2513-2521; citation_doi=10.1029/1999WR900058; citation_id=CR18 citation_title=Nitrogen input-output budgets for forests in the Chesapeake Bay watershed; citation_inbook_title=Atmospheric Deposition of Contaminants to the Great Lakes and Coastal Waters; citation_publication_date=1997; citation_pages=431-442; citation_id=CR19; citation_author=D. L. Correll; citation_author=D. E. Weller; citation_publisher=SETAC Press, Inc. citation_journal_title=Ecological Monographs; citation_title=Integrated ecologic economic modeling of the Patuxent River watershed, Maryland; citation_author=R. Costanza, A. Voinov, R. Boumans, T. Maxwell, F. Villa, L. Wainger, H. Voinov; citation_volume=73; citation_publication_date=2002; citation_pages=203-231; citation_id=CR20 citation_journal_title=Estuaries; citation_title=A watershed perspective on nutrient enrichment, science, and policy in the Patuxent River, Maryland: 1960–2000; citation_author=C. F. D'Elia, W. R. Boynton, J. G. Sanders; citation_volume=26; citation_publication_date=2003; citation_pages=171-185; citation_doi=10.1007/BF02695960; citation_id=CR21 citation_title=STORET reach retrieval documentation; citation_publication_date=1985; citation_id=CR22; citation_author=T. DeWald; citation_author=R. Horn; citation_author=R. Greenspun; citation_author=P. Taylor; citation_author=L. Manning; citation_author=A. Montalbano; citation_publisher=U.S. Environmental Protection Agency citation_title=Chesapeake Bay watershed pilot project EPA/620/R94/020; citation_publication_date=1994; citation_id=CR23; citation_publisher=U.S. EPA-EMAP citation_journal_title=Journal of Environmental Quality; citation_title=Estimating nutrient exports to estuaries; citation_author=C. R. Frink; citation_volume=20; citation_publication_date=1991; citation_pages=717-724; citation_id=CR24 citation_journal_title=Estuaries; citation_title=Estimation of net physical transport and hydraulic residence times for a Coastal Plain estuary using box models; citation_author=J. D. Hagy, W. R. Boynton, L. P. Sanford; citation_volume=23; citation_publication_date=2000; citation_pages=328-340; citation_doi=10.2307/1353325; citation_id=CR25 citation_title=Modern Factor Analysis; citation_publication_date=1976; citation_id=CR26; citation_author=H. H. Harman; citation_publisher=University of Chicago Press citation_journal_title=Landscape Ecology; citation_title=Predicting nutrient and sediment loadings to streams from landscape metrics: A multiple watershed study from the United States Mid-Atlantic region; citation_author=K. B. Jones, A. C. Neale, M. S. Nash, R. D. Remortel, J. D. Wickham, K. H. Riiters, R. V. O'Neill; citation_volume=16; citation_publication_date=2001; citation_pages=301-312; citation_doi=10.1023/A:1011175013278; citation_id=CR27 citation_journal_title=Marine Ecology Progress Series; citation_title=Long-term trends in estuarine nutrients and chlorophyll, and short-term effects of variation in watershed discharge; citation_author=T. E. Jordan, D. L. Correll, J. Miklas, D. E. Weller; citation_volume=75; citation_publication_date=1991; citation_pages=121-132; citation_id=CR28 citation_journal_title=Limnology and Oceanography; citation_title=Nutrient dynamics at the interface of a watershed and estuary; citation_author=T. E. Jordan, D. L. Correll, J. Miklas, D. E. Weller; citation_volume=36; citation_publication_date=1991; citation_pages=251-267; citation_doi=10.4319/lo.1991.36.2.0251; citation_id=CR29 citation_journal_title=Journal of Environmental Quality; citation_title=Nutrient interception by a riparian forest receiving inputs from adjacent cropland; citation_author=T. E. Jordan, D. L. Correll, D. E. Weller; citation_volume=22; citation_publication_date=1993; citation_pages=467-473; citation_id=CR30 citation_journal_title=Journal of Environmental Quality; citation_title=Effects of agriculture on discharges of nutrients from coastal plain watersheds of Chesapeake Bay; citation_author=T. J. Jordan, D. L. Correll, D. E. Weller; citation_volume=26; citation_publication_date=1997; citation_pages=836-848; citation_id=CR31 citation_journal_title=Journal of the American Water Resources Association; citation_title=Nonpoint source discharges of nutrients from Piedmont watersheds of Chesapeake Bay; citation_author=T. J. Jordan, D. L. Correll, D. E. Weller; citation_volume=33; citation_publication_date=1997; citation_pages=631-645; citation_doi=10.1111/j.1752-1688.1997.tb03538.x; citation_id=CR32 citation_journal_title=Water Resources Research; citation_title=Relating nutrient discharges from watersheds to land use and stream-flow variability; citation_author=T. J. Jordan, D. L. Correll, D. E. Weller; citation_volume=33; citation_publication_date=1997; citation_pages=2579-2590; citation_doi=10.1029/97WR02005; citation_id=CR33 citation_title=Mattawoman creek watershed nutrient and sediment dynamics: Final contract report to Charles County, Maryland; citation_publication_date=2000; citation_id=CR34; citation_author=T. E. Jordan; citation_author=D. L. Correll; citation_author=D. E. Weller; citation_publisher=Smithsonian Environmental Research Center citation_journal_title=Estuaries; citation_title=Flux of particulate matter in the tidal marshes and subtidal shallows of the Rhode River estuary; citation_author=T. E. Jordan, J. W. Pierce, D. L. Correll; citation_volume=9; citation_publication_date=1986; citation_pages=310-319; citation_doi=10.2307/1351410; citation_id=CR35 citation_journal_title=Bioscience; citation_title=Human contributions to terrestrial nitrogen flux; citation_author=T. E. Jordan, D. E. Weller; citation_volume=46; citation_publication_date=1996; citation_pages=655-664; citation_doi=10.2307/1312895; citation_id=CR36 citation_journal_title=Estuaries; citation_title=Sources of nutrient inputs to the Patuxent River estuary; citation_author=T. E. Jordan, D. E. Weller, D. L. Correll; citation_volume=26; citation_publication_date=2003; citation_pages=226-243; citation_doi=10.1007/BF02695964; citation_id=CR37 citation_title=Agricultural chemical use and ground water quality: Where are the potential problem areas?; citation_publication_date=1992; citation_id=CR38; citation_author=R. L. Kellogg; citation_author=M. S. Maizel; citation_author=D. W. Gross; citation_publisher=U.S. Department of Agriculture citation_title=Synthesis of nutrient and sediment data for watersheds within the Chesapeake Bay drainage basin; citation_publication_date=1995; citation_id=CR39; citation_author=M. J. Langland; citation_author=P. L. Lietman; citation_author=S. Hoffman; citation_publisher=U.S. Geological Survey citation_title=Cross-media models of the Chesapeake Bay watershed and airshed; citation_publication_date=1999; citation_id=CR40; citation_author=L. C. Linker; citation_author=G. W. Shenk; citation_author=R. L. Dennis; citation_author=J. S. Sweeney; citation_publisher=Chesapeake Bay Program Office citation_journal_title=Journal of the American Water Resources Association; citation_title=Effects of land cover and geology on stream chemistry in watersheds of Chesapeake Bay; citation_author=Z.-J. Liu, D. E. Weller, D. L. Correll, T. E. Jordan; citation_volume=36; citation_publication_date=2000; citation_pages=1349-1366; citation_doi=10.1111/j.1752-1688.2000.tb05731.x; citation_id=CR41 citation_title=Nutrient and sediment concentrations, trends, and loads from five subwatersheds in the Patuxent River basin, Maryland, 1986–1996; citation_publication_date=1999; citation_id=CR42; citation_author=J. S. Lizgarra; citation_publisher=U.S. Geological Survey citation_title=A water quality model for the Patuxent estuary; citation_publication_date=1992; citation_id=CR43; citation_author=W. Lung; citation_publisher=School of Engineering and Applied Science, University of Virginia citation_journal_title=Estuaries; citation_title=A water quality model for the Patuxent estuary: Current conditions and predictions under changing land-use scenarios; citation_author=W. S. Lung, S. Bai; citation_volume=26; citation_publication_date=2003; citation_pages=267-280; citation_doi=10.1007/BF02695966; citation_id=CR44 citation_title=Land use/land cover information for Maryland; citation_publication_date=1991; citation_id=CR45; citation_publisher=Maryland Office of Planning citation_title=Nonpoint source assessment and accounting system: Final report for the FFY '91 Section 319 grant; citation_publication_date=1993; citation_id=CR46; citation_publisher=Maryland Office of Planning citation_title=Development and application of the nonpoint source assessment and accounting system: Final report for the FFY '92 Section 319 grant; citation_publication_date=1995; citation_id=CR47; citation_publisher=Maryland Office of Planning citation_title=Methods used to estimate 1997–2020 land use change; citation_publication_date=2000; citation_id=CR48; citation_publisher=Maryland Office of Planning citation_title=Scale effects in landscape studies; citation_inbook_title=Landscape Heterogeneity and Disturbance, Volume 64; citation_publication_date=1987; citation_pages=15-36; citation_id=CR49; citation_author=V. Meentemeyer; citation_author=E. O. Box; citation_publisher=Springer-Verlag citation_title=Soil survey geographic (SSURGO) database: Data use information; citation_publication_date=1995; citation_id=CR50; citation_publisher=U.S. Department of Agriculture citation_journal_title=Ophelia; citation_title=Coastal marine eutrophication: A definition, social causes, and future consequences; citation_author=S. W. Nixon; citation_volume=41; citation_publication_date=1995; citation_pages=199-219; citation_id=CR51 citation_journal_title=Journal of Environmental Quality; citation_title=Statewide GIS/Census data assessment of nitrogen loadings from septic systems in Pennsylvania; citation_author=E. Nizeyimana, G. W. Petersen, M. C. Anderson, B. M. Evans, J. M. Hamlett, G. M. Baumer; citation_volume=25; citation_publication_date=1996; citation_pages=346-354; citation_id=CR52 citation_journal_title=Science; citation_title=Chesapeake Bay anoxia: Origin, development, and significance; citation_author=C. B. Officer, R. B. Biggs, J. L. Taft, L. E. Cronin, M. A. Tyler, W. R. Boynton; citation_volume=223; citation_publication_date=1984; citation_pages=22-27; citation_doi=10.1126/science.223.4631.22; citation_id=CR53 citation_journal_title=Science; citation_title=Chesapeake Bay: An unprecedented decline in submerged aquatic vegetation; citation_author=R. J. Orth, K. A. Moore; citation_volume=222; citation_publication_date=1983; citation_pages=51-54; citation_doi=10.1126/science.222.4619.51; citation_id=CR54 citation_journal_title=Science; citation_title=Control of nitrogen export from watersheds by headwater streams; citation_author=B. J. Peterson, W. M. Wollheim, P. J. Mulholland, J. R. Webster, J. L. Meyer, J. L. Tank, E. Marti, W. B. Bowden, H. M. Valett, A. E. Hershey, W. M. McDowell, W. K. Dodds, S. K. Hamilton, S. Gregory, D. D. Morall; citation_volume=292; citation_publication_date=2000; citation_pages=86-90; citation_doi=10.1126/science.1056874; citation_id=CR55 citation_title=Application of spatially referenced regression modeling for evaluation of the total nitrogen loading in the Chesapeake Bay watershed; citation_publication_date=1999; citation_id=CR56; citation_author=S. D. Preston; citation_author=J. W. Brakebill; citation_publisher=U.S. Geological Survey citation_journal_title=Journal of Environmental Quality; citation_title=Hypoxia in the Gulf of Mexico; citation_author=N. N. Rabalais, R. E. Turner, W. J. Wiseman; citation_volume=30; citation_publication_date=2001; citation_pages=320-329; citation_doi=10.2134/jeq2001.302320x; citation_id=CR57 citation_title=SAS/STAT User's Guide, Version 8; citation_publication_date=1999; citation_id=CR58; citation_publisher=SAS Institute, Inc. citation_journal_title=Biogeochemistry; citation_title=Nitrogen retention in rivers: Model development and application to watersheds in the Eastern U.S.A.; citation_author=S. P. Seitzinger, R. V. Styles, E. W. Boyer, R. B. Alexander, G. Billen, R. W. Howarth, B. Mayer, N. Breeman; citation_volume=57/58; citation_publication_date=2002; citation_pages=199-237; citation_doi=10.1023/A:1015745629794; citation_id=CR59 citation_journal_title=Water Resources Research; citation_title=Regional interpretation of water-quality monitoring data; citation_author=R. A. Smith, G. E. Schwarz, R. B. Alexander; citation_volume=33; citation_publication_date=1997; citation_pages=2781-2798; citation_doi=10.1029/97WR02171; citation_id=CR60 citation_title=Factors affecting nutrient trends in major rivers of the Chesapeake Bay watershed; citation_publication_date=2000; citation_id=CR61; citation_author=L. A. Sprague; citation_author=M. J. Langland; citation_author=S. E. Yochum; citation_author=R. E. Edwards; citation_author=J. D. Blomquist; citation_author=S. W. Philips; citation_author=G. W. Shenk; citation_author=S. D. Preston; citation_publisher=U.S. Geological Survey citation_title=Hydrologic unit model for United States (HU-MUS); citation_inbook_title=Proceedings of Advances in Hydro-science and Engineering, Volume 30; citation_publication_date=1993; citation_pages=454-462; citation_id=CR62; citation_author=R. Srinivasan; citation_author=J. G. Arnold; citation_author=R. S. Muttiah; citation_author=C. Walker; citation_author=P. T. Dyke; citation_publisher=University of Mississippi citation_title=Smart growth options for Maryland's tributary strategies; citation_publication_date=1998; citation_id=CR63; citation_author=J. Tassone; citation_author=D. M. Weller; citation_author=R. E. Hall; citation_author=N. M. Edwards; citation_publisher=Maryland Office of Planning citation_journal_title=Annual Review of Ecology and Systematics; citation_title=Landscape ecology: The effect of pattern on process; citation_author=M. G. Turner; citation_volume=20; citation_publication_date=1989; citation_pages=171-197; citation_doi=10.1146/annurev.es.20.110189.001131; citation_id=CR64 citation_journal_title=Bioscience; citation_title=Changes in Mississippi River water quality this century—Implications for coastal food webs; citation_author=R. E. Turner, N. N. Rabalais; citation_volume=41; citation_publication_date=1991; citation_pages=140-147; citation_doi=10.2307/1311453; citation_id=CR65 citation_title=Land use change in the Chesapeake Bay drainage basin; citation_publication_date=1999; citation_id=CR66; citation_publisher=U.S. Geological Survey citation_title=National land cover characterization project; citation_publication_date=2001; citation_id=CR67; citation_publisher=U.S. Geological Survey citation_journal_title=Photogrammetric Engineering and Remote Sensing; citation_title=Regional characterization of land cover using multiple sources of data; citation_author=J. E. Vogelmann, T. Sohl, S. M. Howard; citation_volume=64; citation_publication_date=1998; citation_pages=45-67; citation_id=CR68 citation_journal_title=Environmental Monitoring and Assessment; citation_title=Regional land cover characterization using Landsat Thematic Mapper data and ancillary data sources; citation_author=J. E. Vogelmann, T. Sohl, S. M. Howard, D. M. Shaw; citation_volume=51; citation_publication_date=1998; citation_pages=415-428; citation_doi=10.1023/A:1005996900217; citation_id=CR69 citation_journal_title=Ecological Modelling; citation_title=Surface water flow in landscape models: 2. Patuxent watershed case study; citation_author=A. A. Voinov, H. Voinov, R. Costanza; citation_volume=119; citation_publication_date=1999; citation_pages=211-230; citation_doi=10.1016/S0304-3800(99)00056-3; citation_id=CR70 citation_journal_title=Bulletin of the Ecological Society America; citation_title=Scale-dependent success in quantifying cropland from satellite-based land cover data; citation_author=D. E. Weller, D. L. Correll, T. E. Jordan, J. M. Coffee; citation_volume=77; citation_publication_date=1996; citation_pages=474-474; citation_id=CR71 citation_title=Maryland's changing land use: Past, present, and future; citation_publication_date=2001; citation_id=CR72; citation_author=D. M. Weller; citation_author=N. Edwards; citation_publisher=Maryland Department of Planning citation_journal_title=Journal of the American Water Resources Association; citation_title=Land use and stream water nitrate-N dynamics in an urban-rural fringe watershed; citation_author=B. G. Wernick, K. E. Cook, H. Schreier; citation_volume=34; citation_publication_date=1998; citation_pages=639-650; citation_doi=10.1111/j.1752-1688.1998.tb00961.x; citation_id=CR73