N, P, Si budgets for the Red River Delta (northern Vietnam): how the delta affects river nutrient delivery to the sea

Abstract

The Red River Delta (RRD) (Vietnam), a region experiencing rapid population growth, industrialization, and economic development, concentrates 54% of the population of the whole Red River watershed in less than 10% of the basin area. Our study aimed at understanding and quantifying the processes by which the delta affects the nutrient fluxes coming from the upstream watershed before they reach the sea. A comprehensive budget of nitrogen (N), phosphorus (P), and silica (Si) fluxes associated with natural and anthropogenic processes in the terrestrial and hydrological system of the delta was established for five sub-basins of the delta for the period 2000-2006, based on official statistical data, available measurements, and our own sampling campaigns and enquiries. The results show that anthropogenic inputs of N and P brought into the delta area are higher than the amounts delivered by the river from the upstream watershed. However, the amounts of these two elements ultimately delivered to the coastal zone from the delta are lower than the amounts carried by the upstream river, showing extremely efficient retention of both the soils and the delta's drainage network. For Si (taking into account both dissolved and amorphous solid forms), the retention is much lower. High retention of N and P and low retention of Si in the delta area have up to now protected the coastal zone from severe eutrophication problems.Electronic supplementary material The online version of this article

Exploring global nitrogen and phosphorus flows in urban wastes during the twentieth century

“…These industries were often situated at the (downstream) borders of urban areas [ Plaats , ]. Due to scarcity of data, we estimated gross industrial nutrient flows as a fraction of gross human urban nutrient flows [ Billen et al ., ; Billen et al ., ; Liu , ; Luu et al ., ; Quynh et al ., ]. Since the 1950s, detergent‐producing or detergent‐consuming industries add to P discharges.…”

“…For both N and P, industrial waste nutrient emissions were assumed to equal 2 times the urban domestic emissions in 1900, 0.5 in 1960, and 0.15 times domestic emissions in 2000 using linear interpolation for the years in between. This trend is based on historical and recent industrial nutrient loadings to the environment [ Bixio et al ., ; Liu , ; Luu et al ., ; Quynh et al ., ] (SI 9). For the early twentieth century, literature describing the situation in the Netherlands and the Seine, Scheldt, and Zenne river basins in Western Europe was used [ Billen et al ., ; Billen et al ., ; Billen et al ., ; Garnier et al ., ], while for the late twentieth century, studies of the Red River Delta (Northern Vietnam) [ Luu et al ., ], the Red River Basin (China and Vietnam) [ Quynh et al ., ], the Nete river (Belgium), the Seine and Zenne river basins (Belgium and France) [ Billen et al ., ], and Africa [ Nyenje et al ., ] provided (semi)quantitative estimates of industrial nutrient loadings.…”

The nitrogen cascade from agricultural soils to the sea: modelling nitrogen transfers at regional watershed and global scales

“…In the five abovementioned example watersheds, the relative importance of these two NANI pathways (delivery to the sea versus emission-retention) varies a great deal: in the Ebro River basin, the largest share of introduced reactive nitrogen is retained or dissipated upstream in the watershed, with very low transfer to the river outlet; hence, there are limited problems of coastal eutrophication [8]. The same is true for the Hong basin, but most of the retention occurs downstream in the delta area [22]. By contrast, in the Seine, Scheldt and Mississippi river basins, a much higher fraction of NANI is delivered to the sea, causing severe marine eutrophication in the receiving coastal waters [23,24].…”

Large-Scale Assessment of Coastal Aquaculture Ponds with Sentinel-1 Time Series Data

“…We only used Sentinel-1A data because The Red River Delta (RRD) is Vietnam's second largest delta and includes eight provinces, the capital city of Hanoi and the main port of Hai Phong. The region experienced rapid urbanization and industrialization and became the most important economic zone in Vietnam [47,48]. Rising sea level, increasing salt water intrusion, and decrease in rainfall upstream are major factors for salinization in the coastal area of the delta.…”