Using ¹⁵N, ¹⁷O, and ¹⁸O To Determine Nitrate Sources in the Yellow River, China

Abstract

Many previous studies have used δ(15)N and δ(18)O of nitrate (δ(15)NNO3 and δ(18)ONO3) to determine the nitrate sources in rivers but were subject to substantial uncertainties and limitations, especially associated with evaluating the atmospheric contribution. The Δ(17)O of nitrate (Δ(17)ONO3) has been suggested as an unambiguous tracer of atmospheric NO3(-) and may serve as an additional nitrate source constraint. In the present study, triple nitrate isotopes (δ(15)NNO3, Δ(17)ONO3, and δ(18)ONO3) were used for the first time to assess the sources and sinks of nitrate in the Yellow River (YR) basin, which is the second longest river in China. Results showed that the Δ(17)ONO3 of the water from the YR ranged from 0‰ to 1.6‰ during two normal-water seasons. This suggested that unprocessed atmospheric nitrate accounted for 0-7% of the total nitrate in the YR. The corrected δ(15)NNO3 and δ(18)ONO3 values with atmospheric imprints being removed indicated that the main terrestrial sources of nitrate were sewage/manure effluents in the upstream of the YR and manure/sewage effluents and ammonium/urea-containing fertilizer in the middle and lower reaches which made comparable contributions to the nitrate. In addition, there was a significant positive relationship between δ(15)NNO3 and δ(18)ONO3 values of river water (p < 0.01) which may signal the presence of denitrification. This study indicates that the triple nitrate isotope method is useful for assessing the nitrate sources in rivers, especially for the measurements of atmospheric nitrate contribution.

Quantifying the effects of clear-cutting and strip-cutting on nitrate dynamics in a forested watershed using triple oxygen isotopes as tracers

“…While the annual average M atm / M total ratio was less than 16 % in 2003 (Table 1), it increased to 41 % in 2004 in response to strip-cutting, then slightly decreased to 31 % in 2005. The M atm / M total ratios after strip-cutting were much higher than those determined for normal natural discharges, such as 3.1-7.7 % in southern California (Michalski et al, 2004), 7.4 ± 2.6 % on Rishiri Island , and 0-7 % in the Yellow River (Liu et al, 2013), as well as that dissolved in soil solution of temperate forest in northern Michigan (9 % on average) (Costa et al, 2011) and that dissolved in an oligotrophic lake water column in Japan (9.7 ± 0.8 %) . As a result, we can easily differentiate the ratios observed after strip-cutting from other normal M atm / M total ratios in stream water using the 17 O values of nitrate, indicating that they can serve as a useful and powerful tracer for quantification of artificial alternations in forested watersheds.…”

“…3). The 17 O value of +14.3 ‰ corresponds to the highest 17 O value ever reported for dissolved nitrate in natural stream water (Michalski et al, 2004;Tsunogai et al, 2010;Dejwakh et al, 2012;Liu et al, 2013), as well as that in soil solution (Michalski et al, 2004;Costa et al, 2011). (Fig.…”

Using Dual Isotopes and a Bayesian Isotope Mixing Model to Evaluate Nitrate Sources of Surface Water in a Drinking Water Source Watershed, East China

“…It should be noted that organic nitrogen productions from manure and sewage were much higher in MSW and ZSW as a result of intensive agriculture and livestock feeding activities. Other potential source isotopic values (M & S, NS, NF and NFA) were based on the relevant literature [8,[31][32][33][34][35][36][37][38][39][40], as shown by boxes in Figure 5. It is clear to see nitrate concentrations being affected by the five sources.…”

“…The source values of δ 15 N-NO 3 − and δ 18 O-NO 3 − for NP were measured from the precipitation samples in the watershed (as shown in Table 3 [8,[31][32][33][34][35][36][37][38][39][40]. It was assumed that the fractionation factors equal zero, as denitrification did not occur in surface water in the study area.…”

Variation in nitrate isotopic signatures in sewage for source apportionment with urbanization: a case study in Beijing, China

“…The updated δ 15 N-NO 3 − (4.0-19.0 ‰) and δ 18 O-NO 3 − (3.5-16.8 ‰) value ranges indicated for sewage were concluded by Xue et al (2009). They were recently referred by most field studies worldwide related to NO 3 − source identification (Nestler et al 2011), including the field studies in America (Kaushal et al 2011), Belgium (Xue et al 2012;Xue et al 2013), and China (Cao et al 2012;Chen et al 2012;Liu et al 2013;Yue et al 2013;Ren et al 2014). However, the data of NO 3 − isotope could vary considerably depending on the local sewage treatment process, especially with regard to the degree of nitrification and denitrification (Anisfeld et al 2007).…”