ORIGINAL ARTICLE Nitrogen flow assessment in rapidly urbanizing Hai Duong province, downstream of Cau River Basin, Vietnam Thao Thi Ta 1 • Duc Anh Trinh 2 • Nga Thu Do 3,4 Received: 19 September 2016 / Accepted: 12 April 2017 Ó Springer Japan 2017 Abstract Hai Duong is a rapidly urbanizing province with a condensed network of rivers, located downstream of the Cau River Basin, one of the three most polluted river systems in Vietnam. Intensive agriculture and industrial development in the province has caused profound impact on the river water. This research aims to develop a material flow analysis (MFA) model, which can simulate and visualize nitrogen flows in Hai Duong province and its districts, to access the impact of agricultural activities and industrial parks on the surrounding environments. MFA was applied for Hai Duong province and its districts to estimate nitrogen flows in the whole province. The nitrogen loads to surface water, air, and soil/groundwater annually were 50,531 ± 10,801, 12,981 ± 1541, and 6055 ± 3121 tons, respectively. The quality of the developed model was assessed through a modified uncertainty anal- ysis procedure. Also, MFA results of nitrogen loads to the water environment were consistent with the analytical results. Nitrogen was largely derived from agricultural activities and domestic and industrial wastewater. Envi- ronmental flows in the next 10 years and reasonable solutions for improving environmental quality in the pro- vince are proposed. Keywords Nitrogen Á Material flow analysis (MFA) Á Cau River Basin Á Vietnam Introduction Material flow analysis (MFA) is a multi-process model based on the Law of Mass Conservation, and is able to trace the sources of pollution. In recent years, MFA has been modified and proven to be a powerful tool for rec- ognizing environmental problems, especially, assessing the environmental impact of human activities on nutrient flows, not only at the river basin scale [3, 15–17, 19], but also at the community scale [6] or even hamlet scale [14]. Pham et al. [14] has applied MFA in a hamlet to more precisely describe local nutrient management manners through conducting intensive questionnaire surveys, for reducing uncertainty of model structure and collected data. The objective of this study is to understand the historical changes in excreta management from 1980 to 2010 and the impact of fishponds on the nutrient cycle and water pol- lution by a material flow model of nitrogen (N) and phosphorus (P). However, data scarcity and uncertainty are common in many areas, especially, with larger boundary and in developing countries, so that MFA model has to be critically enhanced. Dynamic transport and transformation of nitrogen in paddy soil have been accounted for in the model in [4], additionally, a modified uncertainty analysis has been proposed in [5] for ensuring quality of MFA model. By assessing connections among processes in the entire system through the plausibility test, the uncertainty of data inputs and estimated outputs are evaluated. This & Nga Thu Do dothu_nga2005@yahoo.com 1 VNU University of Science, Vietnam National University (VNU), No. 19, Le Thanh Tong, Hanoi, Vietnam 2 Institute of Chemistry, Vietnam Academy of Science and Technology (VAST), No. 8, Hoang Quoc Viet, Hanoi, Vietnam 3 Electric Power University, No. 235, Hoang Quoc Viet, Hanoi, Vietnam 4 International Research Centre for River Basin Environment (ICRE), University of Yamanashi, 4-3-11 Takeda, Kofu, Yamanashi 400-8510, Japan 123 J Mater Cycles Waste Manag DOI 10.1007/s10163-017-0616-2