Chinese coastal seas are facing heavy atmospheric nitrogen deposition

Abstract

As the amount of reactive nitrogen (N) generated and emitted increases the amount of N deposition and its contribution to eutrophication or harmful algal blooms in the coastal zones are becoming issues of environmental concern. To quantify N deposition in coastal seas of China we selected six typical coastal sites from North to South in 2011. Concentrations of NH _3 , HNO _3 , NO _2 , particulate NH _4 ^+ (pNH _4 ^+ ) and pNO _3 ^− ranged from 1.97– 4.88, 0.46 –1.22, 3.03 –7.09, 2.24 – 4.90 and 1.13–2.63 μ g N m ^−3 at Dalian (DL), Changdao (CD), Linshandao (LS), Fenghua (FH), Fuzhou (FZ), and Zhanjiang (ZJ) sites, respectively. Volume-weighted NO _3 ^− –N and NH _4 ^+ –N concentrations in precipitation varied from 0.46 to 1.67 and 0.47 to 1.31 mg N L ^−1 at the six sites. Dry, wet and total deposition rates of N were 7.8–23.1, 14.2–25.2 and 22.0 – 44.6 kg N ha ^−1 yr ^−1 across the six coastal sites. Average N dry deposition accounted for 45.4% of the total deposition and NH _3 and pNH _4 ^+ contributed to 76.6% of the dry deposition. If we extrapolate our total N deposition of 33.9 kg N ha ^−1 yr ^−1 to the whole Chinese coastal sea area (0.40 million km ^2 ), total N deposition amounts to 1.36 Tg N yr ^−1 , a large external N input to surrounding marine ecosystems.