Sources of nitrate in rivers draining sixteen watersheds in the northeastern US: Isotopic constraints
Sources of nitrate in rivers draining sixteen watersheds in the northeastern US: Isotopic constraints
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DOI：
10.1023/a:1015744002496
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发表时间：
2002-04-01
期刊：
影响因子：
4
通讯作者：
Paustian, K
中科院分区：
文献类型：
--
作者：
Mayer, B;Boyer, EW;Paustian, K
在对美国东北部16个流域的比较研究中，评价了利用硝酸盐（NO3-）的氮氧同位素比值来阐明河流硝酸盐来源和转化的可行性。1999年1月至12月期间，在流域出口处对河水进行了重复采样，以测定其浓度、δ（15）N值、δ（15）N（NO3-）和δ（18）O（NO3-）值结合土地利用和氮通量信息，主要提供了河流NO3-的来源信息。在主要森林流域，河流硝酸盐的平均浓度低于0.4 mg NO3- -N L-1，δ（15）N（硝酸盐）值低于+5ppm，δ（18）O（硝酸盐）值在+12和+19ppm之间。这表明，河流硝酸盐几乎完全来自土壤硝化过程，在某些集水区，可能有少量的硝酸盐来自大气沉积。在有大量农业和城市土地使用的流域。河流中硝酸盐浓度高达2.6mgNO3--N-L-1，δ（15）N（硝酸盐）值在+5 ~+8ppm之间，δ（18）O（硝酸盐）值一般低于+15ppm。硝酸盐浓度之间的相关性，三角洲（15）N（硝酸盐）值，和N通量表明，硝酸盐在废水中构成了一个主要的，和硝酸盐在粪肥中的一个次要的额外来源河流硝酸盐。大气硝酸盐沉积或含硝酸盐的肥料是不是一个显着的河流硝酸盐在流域的农业和城市土地利用的重要来源。虽然补充研究表明，在流中的反硝化作用是显着的，在16个流域的出口处采样的河流硝酸盐的同位素组成没有提供证据的反硝化作用的形式升高三角洲（15）N（硝酸盐）和三角洲（18）O（硝酸盐）值。在流内反硝化过程中氮和氧的同位素富集因子相对较低，并且来自上述来源的硝酸盐的连续混合物被认为是造成这一发现的原因
The feasibility of using nitrogen and oxygen isotope ratios of nitrate (NO3-) for elucidating sources and transformations of riverine nitrate was evaluated in a comparative study of 16 watersheds in the northeastern U.S.A. Stream water was sampled repeatedly at the outlets of the watersheds between January and December 1999 for determining concentrations, delta(15)N values, and delta(18)O values of riverine nitrate.In conjunction with information about land use and nitrogen fluxes, delta(15)N(nitrate) and delta(18)O(nitrate) values provided mainly information about sources of riverine nitrate. In predominantly forested watersheds, riverine nitrate had mean concentrations of less than 0.4 mg NO3- -N L-1, delta(15)N(nitrate) values of less than +5parts per thousand, and delta(18)O(nitrate) values between +12 and +19parts per thousand. This indicates that riverine nitrate was almost exclusively derived from soil nitrification processes with potentially minor nitrate contributions from atmospheric deposition in some catchments. In watersheds with significant agricultural and urban land use. concentrations of riverine nitrate were as high as 2.6 mg NO3--N L-1 with delta(15)N(nitrate) values between +5 and +8parts per thousand 3 and delta(18)O(nitrate) values generally below +15parts per thousand. Correlations between nitrate concentrations, delta(15)N(nitrate) values, and N fluxes suggest that nitrate in waste water constituted a major, and nitrate in manure a minor additional source of riverine nitrate. Atmospheric nitrate deposition or nitrate-containing fertilizers were not a significant source of riverine nitrate in watersheds with significant agricultural and urban land use. Although complementary studies indicate that in-stream denitrification was significant in all rivers, the isotopic composition of riverine nitrate sampled at the Outlet of the 16 watersheds did not provide evidence for denitrification in the form of elevated delta(15)N(nitrate) and delta(18)O(nitrate) values. Relatively low isotopic enrichment factors for nitrogen and oxygen during in-stream denitrification and continuous admixture of nitrate from the above-described sources are thought to be responsible for this finding