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Environ Earth Sci (2014) 71:40214028 DOI 10.1007/s12665-013-2785-1
ORIGINAL ARTICLE
Characteristics of dissolved organic nitrogen (DON) in the surface water of Beijing Olympic Forest Park
Shouliang Huo Honglei Yu Beidou Xi
Fengyu Zan Chaowei Zhu Jingtian Zhang
Received: 2 May 2013 / Accepted: 29 August 2013 / Published online: 11 September 2013 Springer-Verlag Berlin Heidelberg 2013
Abstract The characteristics of dissolved organic nitrogen (DON) in surface water from Beijing Olympic Forest Park (BOFP) were investigated in this study. Nanoltration (NF) pretreatment procedure using two NF membranes (NF90 and NF270) was applied to increase the accuracy and precision of DON measurements in surface water samples with high dissolved inorganic nitrogen/total dissolved nitrogen (DIN/TDN) ratios. Compared to NF90, NF270 showed better performance in lowering the DIN/ TDN ratio and retaining DOC in both the synthetic water and raw water samples. DON concentrations ranged from0.01 to 0.83 mg N L-1 in water samples collected over four different months and showed a seasonal variation. The DON increased in summer due to the higher activity of decomposers on recent litterfall or because of a higher production of biomass in the surface water body. The molecular weight (MW) fractions of\3 kDa accounted for more than 50 % of the total DOC concentration and the fractions of \3 kDa contributed to more than 48 % of the total DON concentration. It could be concluded that most of the DON present in surface water of BOFP was composed of small molecules, which were mainly composed of
monomers such as amino acids and urea, readily available for the uptake by phytoplankton and heterotrophic bacteria.
Keywords Dissolved organic nitrogen (DON)
Nanoltration Molecular weight distribution
Surface water
Introduction
Dissolved organic nitrogen (DON) was historically believed to be composed mainly of refractory compounds resistant to biological degradation and generally unavailable as sources of N nutrition for phytoplankton or bacteria (Berman and Bronk 2003). Some studies reported that concentrations of DON exceed those of the total dissolved inorganic nitrogen (DIN) and a large fraction (1272 %) of DON was bioavailable for phytoplankton and bacteria (Bronk et al. 1994, 2007).
Despite the growing interest in DON cycling in natural ecosystems, the analytical methods still face serious limitations. The high standard deviation and negative concentration were observed in traditional measurements of...