Evaluating stream water quality through land use analysis in two grassland catchments: impact of wetlands on stream nitrogen concentration.

We evaluated the impacts of natural wetlands and various land uses on stream nitrogen concentration in two grassland-dominated catchments in eastern Hokkaido, Japan. Analyzing land use types in drainage basins, measuring denitrification potential of its soil, and water sampling in all seasons of 2003 were performed. Results showed a highly significant positive correlation between the concentration of stream NO3-N and the proportion of upland area in drainage basins in both catchments. The regression slope, which we assumed to reflect the impact on water quality, was 24% lower for the Akkeshi catchment (0.012 +/- 0.001) than for the Shibetsu catchment (0.016 +/- 0.001). In the Akkeshi catchment, there was a significant negative correlation between the proportion of wetlands in the drainage basins and stream NO3-N concentration. Stream dissolved organic nitrogen (DON) and carbon (DOC) concentrations were significantly higher in the Akkeshi catchment. Upland and urban land uses were strongly linked to increases in in-stream N concentrations in both catchments, whereas wetlands and forests tended to mitigate water quality degradation. The denitrification potential of the soils was highest in wetlands, medium in riparian forests, and lowest in grasslands; and was significant in wetlands and riparian forests in the Akkeshi catchment. The solubility of soil organic carbon (SOC) and soil moisture tended to determine the denitrification potential. These results indicate that the water environment within the catchments, which influences denitrification potential and soil organic matter content, could have caused the difference in stream water quality between the two catchments.

[1]  S. Carpenter,et al.  NONPOINT POLLUTION OF SURFACE WATERS WITH PHOSPHORUS AND NITROGEN , 1998 .

[2]  William J. Mitsch,et al.  Wetlands and Lakes as Nitrogen Traps: Kessler, E. and M. Jansson, eds. 1994. Special Issue of Ambio 23:319–386. Royal Swedish Academy of Sciences, Stockholm. , 1995 .

[3]  R. Lowrance.  Groundwater nitrate and denitrification in a coastal plain riparian forest , 1992 .

[4]  S. Seitzinger,et al.  Bioavailability of DON from natural and anthropogenic sources to estuarine plankton , 2002 .

[5]  A. Page.  Methods of soil analysis. Part 2. Chemical and microbiological properties. , 1982 .

[6]  William H. McDowell,et al.  Biogeochemical Hot Spots and Hot Moments at the Interface of Terrestrial and Aquatic Ecosystems , 2003, Ecosystems.

[7]  P. Chapman,et al.  The nitrogen composition of streams in upland Scotland: some regional and seasonal differences. , 2001, The Science of the total environment.

[8]  Elizabeth W. Boyer,et al.  Anthropogenic nitrogen sources and relationships to riverine nitrogen export in the northeastern U.S.A. , 2002 .

[9]  Futoshi Nakamura.  河川・湿地における自然復元の考え方と調査・計画論 : 釧路湿原および標津川における湿地, 氾濫原, 蛇行流路の復元を事例として , 2003 .

[10]  D. Correll,et al.  Nutrient dynamics in an agricultural watershed: Observations on the role of a riparian forest , 1984 .

[11]  M. S. Cresser,et al.  The influence of catchment characteristics on the seasonality of carbon and nitrogen species concentrations in upland rivers of Northern Scotland , 2004 .

[12]  Ryusuke Hatano,et al.  Evaluating impact of land use and N budgets on stream water quality in Hokkaido, Japan , 2002, Nutrient Cycling in Agroecosystems.

[13]  C. L. Beek,et al.  Denitrification rates in relation to groundwater level in a peat soil under grassland , 2004, Biology and Fertility of Soils.

[14]  D. Jones,et al.  Dissolved organic nitrogen regulation in freshwaters. , 2004, Journal of environmental quality.

[15]  L. Sliva,et al.  Buffer zone versus whole catchment approaches to studying land use impact on river water quality. , 2001, Water research.

[16]  Denitrification potential in a grassland subsoil: effect of carbon substrates , 2004 .

[17]  P. Groffman,et al.  Denitrification enzyme activity of fringe salt marshes in New England (USA). , 2004, Journal of environmental quality.

[18]  M. Meybeck.  Carbon, nitrogen, and phosphorus transport by world rivers , 1982 .

[19]  Dennis P. Swaney,et al.  Regional nitrogen budgets and riverine N & P fluxes for the drainages to the North Atlantic Ocean: Natural and human influences , 1996 .

[20]  C.J.F. ter Braak,et al.  CANOCO Reference Manual and User's Guide to Canoco for Windows: Software for Canonical Community Ordination (Version 4) , 1998 .

[21]  Alan R. Hill,et al.  Nitrate Removal in Stream Riparian Zones , 1996 .

[22]  R. Hatano,et al.  Evaluating river water quality through land use analysis and N budget approaches in livestock farming areas. , 2004, The Science of the total environment.

[23]  L. Hedin,et al.  Nitrogen loss from unpolluted South American forests mainly via dissolved organic compounds , 2002, Nature.

[24]  M. Acreman,et al.  Wetland nutrient removal: a review of the evidence , 2004 .

[25]  R. Hatano,et al.  Evaluation of the impact of paddy fields on stream water nitrogen concentration in Central Hokkaido , 2004 .

[26]  D. Dowrick,et al.  Water table elevation controls on soil nitrogen cycling in riparian wetlands along a European climatic gradient , 2004 .

[27]  A. Hill,et al.  Denitrification and Organic Carbon Availability in Riparian Wetland Soils and Subsurface Sediments , 2004 .

[28]  M. Billett,et al.  A review of the export of carbon in river water: fluxes and processes. , 1994, Environmental pollution.

[29]  W. McDowell,et al.  Role of wetlands and developed land use on dissolved organic nitrogen concentrations and DON/TDN in northeastern U.S. rivers and streams , 2004 .

[30]  M. Hayes,et al.  Dissolved organic carbon losses from grazed grasslands under different management regimes. , 2001, Water research.