Supplemental Figure
Supplemental Figure 1 The study area and water quality monitoring sites
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Supplemental Figure 2 Box-and-Whisker plots of δ15N values of NO3- from
various sources and sinks.
Note: 1) Reference: Bateman and Kloppmann, 2007; Besard et al., 2003; Cao et
al., 1991; Choi et al., 2002, 2003, 2007; Curt et al., 2004; Deutsch et al., 2006; Durka
et al., 1994; Elliott et al., 2007; Finlay et al., 2007; Fogg et al.,1998; Hales et al., 2007;
Heaton et al., 1986; Iqbal et al., 1997; Karr et al., 2001; Kendall, 1998; Lee et al.,
2008; Li et al., 2007; Mariotti et al., 1988; Mayer et al., 2001; Mcclelland and Valiela,
1998; Piatek et al., 2005; Pardo et al., 2004; Roadcap et al., 2001; Rock and Mayer,
2002; Spoelstra et al., 2007; Townsend et al., 2007; Wassenaar, 1995; Widory et al.,
2004; Zhang et al., 2008; Li and Liu, 2006; Xing et al., 2001.
2) Number of samples: NO3- in precipitation: n=61; Manure=58; Sewage:n=24;
Soil N: n=23; NO3- fertilizer: n=18; NH4+ in fertilizer: n=117; NH4+ in precipitation:
n=31.
100
18
δ O(‰)SMOW
80
60
40
20
0
Nitrate precipitation
Nitrate fertilizer
Nitrification
Supplemental Figure 3 Box-and-Whisker plots of δ18O values of NO3- from
various sources and sinks.
Note: 1) Reference: Amberger and Schmidt, 1987; Aravena and Evans, 1993;
Cao et al., 1991; Deutsch et al., 2006; Durka et al., 1994; Finlay et al., 2007; Fukada
et al., 2004; Hales et al., 2007; Kendall, 1998, 2007; Lee et al., 2008; Mayer et al.,
2001; Piatek et al., 2005; Pardo et al., 2004; Rock and Mayer, 2002; Spoelstra et al.,
2007; Wassenaar, 1995; Williard et al., 2001; Li and Liu, 2006.
2) Number of samples: NO3- in precipitation: n=40; NO3- fertilizer: n=15;
Nitrification: n=36.
Reference:
[1] Cao, Y.C., Sun, G.Q., Xing, G.X., Xu, H., 1991. Natural abundance of
15N
in main N-containing chemical
fertilizers of China. Pedosphere, 1, 377–382.
[2] Li, X., Masuda, H., Koba, K., Zeng, H., 2007. Nitrogen isotope study on nitrate-contaminated groundwater in
the Sichuan Basin, China. Water, Air, and Soil Pollution, 178(1-4), 145-156.
[3] Zhang, Y., Liu, X. J., Fangmeier, A., Goulding, K. T. W., Zhang, F. S., 2008. Nitrogen inputs and isotopes in
precipitation in the North China Plain. Atmospheric Environment, 42(7), 1436-1448.
[4] Townsend-Small, A., McCarthy, M.J., Brandes, J.A., Yang, L., Zhang, L., Gardner, W.S., 2007. Stable isotopic
composition of nitrate in Lake Taihu, China, and major inflow rivers. Hydrobiologia, 581(1), 135-140.
[5] Elliott, E.M., Kendall, C., Wankel, S.D., Burns, D.A., Boyer, E.W., Harlin, K., 2007. Nitrogen isotopes as
indicators of NOx source contributions to atmospheric nitrate deposition across the Midwestern and
Northeastern United States. Environ Sci Technol, 41:7661–7667.
[6] Heaton, T.H.E., 1986. Isotopic studies of nitrogen pollution in the hydrosphere and atmosphere: a review.
Chem. Geol. (Isot. Geosci. Sect.), 59, 87–102.
[7] Fogg, G.E., Rolston, D.E., Decker, D.L., Louie, D.T., Grismer, M.E., 1998. Spatial variation in nitrogen isotope
values beneath nitrate contamination sources. Groundwater, 36(3), 418-426.
[8] Iqbal M Z, Krothe N C, Spalding R F. 1997. Nitrogen isotope indicators of seasonal source variability to
ground water. Environ. Geol, 32, 210–218.
[9] Choi, W.J., Han, G.H., Lee, S.M., Lee, G.T., Yoon, K.S., Choi, S.M., Ro, H.M., 2007. Impact of land-use types
on nitrate concentration and δ15N in unconfined groundwater in rural areas of Korea. Agriculture,
Ecosystems & Environment, 120(2), 259-268.
15N
[10] Choi, W.J., Lee, S.M., Ro, H.M., Kim, K.C., Yoo, S.H., 2002. Natural
abundances of maize and soil
amended with urea and composted pig manure. Plant Soil, 245, 223–232.
[11] Choi, W.J., Ro, H.M., Lee, S.M., 2003. Natural
15N
abundances of inorganic nitrogen in soil treated with
fertilizer and compost under changing soil moisture regimes. Soil Biol. Biochem, 35,1289–1298.
[12] Curt, M.D., Aguado, P., Sanchez, G., Bigeriego, M., Fernandez, J., 2004. Nitrogen isotope ratios of synthetic
and organic sources of nitrate water contamination in Spain. Water, Air, and Soil Pollution, 151(1-4),
135-142.
[13] Widory, D., Kloppmann, W., Chery, L., Bonnin, J., Rochdi, H., Guinamant, J.L., 2004. Nitrate in groundwater:
an isotopic multi-tracer approach. Journal of Contaminant Hydrology, 72(1), 165-188.
[14] Bateman, A.S., Kelly, S.D., 2007. Fertilizer nitrogen isotope signatures. Isot. Environ. Health Stud, 43,
237–247.
[15] Xing, G.X., Cao, Y.C., Shi, S.L., Sun, G.Q.,
Du, L.J.,
Zhu, J.G., 2001. Nitrate pollution sources and
denitrification of water environment in Tai Lake region. Science in China (Series B), 31(2): 130-137. (in
Chinese)
[16] Roadcap, G.S., Hackley, K.C., Hwang, H.H., Johnson, T.M., 2001, April. Application of nitrogen and oxygen
isotopes to identify sources of nitrate. In Illinois Groundwater Consortium Conference, Carbondale, IL.
[17] Karr, J.D., Showers, W.J., Gilliam, J.W., Andres, A.S., 2001. Tracing nitrate transport and environmental
impact from intensive swine farming using delta nitrogen-15. Journal of Environmental Quality, 30(4),
1163-1175.
[18] Mariotti, A., Landreau, A., Simon, B., 1988. 15N isotope biogeochemistry and natural denitrification process in
ground water: application to the chalk aquifer in northern France. Geochim. Cosmochim. Acta, 52,
1869–1878.
[19] McClelland, J.W., Valiela, I., 1998. Linking nitrogen in estuarine producers to land-derived sources[J]. Limnol.
Oceanogr, 43, 577–585.
[20] Bedard-Haughn, A., Van Groenigen, J.W., Van Kessel, C., 2003. Tracing
15N
through landscapes: potential
uses and precautions. Jourbal of Hydrology, 2003, 272:175–190.
[21] Li, S.L., Liu, C.Q., 2006. The character and application of
18O-NO 3
in the groundwater of Guiyang[J].
Carsologica Sinica, 25(2): 108-111. (in Chinese)
[22] Wassenaar, L.I., 1995. Evaluation of the origin and fate of nitrate in the Abbotsford Aquifer using the isotopes
of 15N and 18O in NO3-. Appl. Geochem, 10, 391–405.
[23] Rock, L., Mayer, B., 2002. Isotopic assessment of sources and processes affecting sulfate and nitrate in
surface water and ground water of Luxembourg. Isot. Environ. Health Stud, 38, 191–206.
[24] Mayer, B., Bollwerk, S.M., Mansfeldt, T., Hütter, B., Veizer, J., 2001. The oxygen isotope composition of
nitrate generated by nitrification in acid forest floors. Geochimica et Cosmochimica Acta, 65(16),
2743-2756.
[25] Deutsch, B., Mewes, M., Liskow, I., Voss, M., 2006. Quantification of diffuse nitrate inputs into a small river
system using stable isotopes of oxygen and nitrogen in nitrate. Org. Geochem, 37,1333–1342.
[26] Spoelstra, J., Schiff, S.L., Hazlett, P.W., Jeffries, D.S., Semkin, R.G., 2007. The isotopic composition of nitrate
produced from nitrification in a hardwood forest floor. Geochimica et cosmochimica acta, 71(15),
3757-3771.
[27] Kendall, C., 1998. Tracing sources and cycling of nitrate in catchments. In: Kendall, C., McDonnell, J.J.
(Eds.), Isotope Tracers in Catchment Hydrology. Elsevier, Amsterdam, 519–576.
[28] Durka, W., Schulze, E.D., Gebauer, G., Voerkeliust, S., 1994. Effects of forest decline on uptake and leaching
of deposited nitrate determined from 15N and 18O measurements. Nature, 372(6508), 765-767.
[29] Piatek, K.B., Mitchell, M.J., Silva, S.R., Kendall, C., 2005. Sources of nitrate in snowmelt discharge:
evidence from water chemistry and stable isotopes of nitrate. Water, Air, and Soil Pollution, 165(1-4), 13-35.
[30] Hales, H.C., Ross, D.S., Lini, A., 2007. Isotopic signature of nitrate in two contrasting watersheds of Brush
Brook, Vermont, USA. Biogeochemistry, 84, 51–66.
[31] Lee, K.S., Bong, Y.S., Lee, D., Kim, Y., Kim, K., 2008. Tracing the sources of nitrate in the Han River
watershed in Korea, using δ15N-NO3- and δ18O- NO3- values. Sci Total Environ, 395(2-3), 117-124.
[32] Pardo, L.H., Kendall, C., Pett-Ridge, J., Chang, C. C., 2004. Evaluating the source of streamwater nitrate
using δ15N and δ18O in nitrate in two watersheds in New Hampshire, USA. Hydrological Processes, 18(14),
2699-2712.
[33] Finlay, J.C., Sterner, R.W., Kumar, S., 2007. Isotopic evidence for in-lake production of accumulating nitrate
in Lake Superior. Ecol. Appl, 17, 2323–2332.
[34] Aravena, R., Evans, M.L., Cherry, J.A., 1993. Stable Isotopes of Oxygen and Nitrogen in Source
Identification of Nitrate from Septic Systems. Ground Water, 1993, 31: 180-186.
[35] Williard, K.W., DeWalle, D.R., Edwards, P.J., Sharpe, W. E., 2001.
18O
isotopic separation of stream nitrate
sources in mid-Appalachian forested watersheds. Journal of Hydrology, 252(1), 174-188.
[36] Kendall, C., Elliott, E.M., Wankel, S.D., 2007. Tracing anthropogenic inputs of nitrogen to ecosystems. In:
Michener R, Lajtha K, editors. Stable isotopes in ecology and environmental science. 2nd ed. Blackwell
publishing; 375–449.
[37] Amberger, A., Schmidt, H.L., 1987. Natural isotope contents of nitrate as indicators for its origin. Geochim.
Cosmochim. Acta, 51, 2699–2705.
[38] Fukada, T., Hiscock, K.M., Dennis, P.F., 2004. A dual isotope approach to the nitrogen hydrochemistry of an
urban aquifer. Appl. Geochem, 19, 709–719.