Pre‐ and post‐impoundment nitrogen in the lower Missouri River

Abstract

Abstract:Large water-sample sets collected from 1899 through 1902, 1907, and in the early 1950s allow comparisons of pre-impoundment and post-impoundment (1969 through 2008) nitrogen concentrations in the lower Missouri River. Although urban wastes were not large enough to detectably increase annual loads of total nitrogen at the beginning of the 20 th century, carcass waste, stock-yard manure, and untreated human wastes measurably increased ammonia and organic-nitrogen concentrations during low flows. Average total-nitrogen concentrations in both periods were about 2.5 mg/l, but much of the particulate-organic nitrogen, which was the dominant form of nitrogen around 1900, has been replaced by nitrate. This change in speciation was caused by the nearly 80% decrease in suspendedsediment concentrations that occurred after impoundment, modern agriculture, drainage of riparian wetlands, and sewage treatment. Nevertheless, bioavailable nitrogen has not been low enough to limit primary production in the Missouri River since the beginning of the 20 th century. Nitrate concentrations have increased more rapidly from 2000 through 2008 (5 to 12% per year), thus increasing bioavailable nitrogen delivered to the Mississippi River and affecting Gulf Coast hypoxia. The increase in nitrate concentrations with distance downstream is much greater during the post-impoundment period. If strategies to decrease total-nitrogen loads focus on particulate N, substantial decreases will be difficult because particulate nitrogen is now only 23% of total nitrogen in the Missouri River. A strategy aimed at decreasing particulates also could further exacerbate land loss along the Gulf of Mexico, which has been sediment starved since Missouri River impoundment. In contrast, strategies or benchmarks aimed at decreasing nitrate loads could substantially decrease nitrogen loadings because nitrates now constitute over half of the Missouri's nitrogen input to the Mississippi. Ongoing restoration and creation of wetlands along the Missouri River could be part of such a nitrate-reduction strategy. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.Supporting information may be found in the online version of this article.

Effects of Water Depth and Phosphorus Availability on Nitrogen Removal in Agricultural Wetlands

“…For example, from 1996 to 2008, over 2400 wetlands were created in Sweden with support from different national programs, with the aim of remediating runoff from agriculture and decreasing N transport to the eutrophicated Baltic Sea [5]. In the US, the ongoing restoration and creation of wetlands along the Missouri River is part of a strategy to decrease N loads to the Mississippi River and eventually, to the Gulf of Mexico [6]. In Ireland, the Integrated Constructed Wetland concept has been used to address the pressure from different EU directives to improve water quality at the landscape scale since 2007 [7].…”

Pre- and Post-Construction Assessment of Nutrient Concentrations at Shallow Water Habitat Restoration Sites on the Lower Missouri River

“…This could be a function of location because Hermann is located downstream of two major tributaries (Gasconade and Moreau rivers) that drain watersheds with relatively little agricultural activity and another major tributary (Osage River) with multiple reservoirs resulting in a potential dilution effect. Blevins et al [24] suggested that total organic nitrogen and TN loadings between St. Joseph, MO and Hermann, MO experienced a dilution effect. Despite few significant differences in TN and NO 3 -NO 2 concentrations, visual comparisons of box plots showed that median elutriate concentrations at Benedictine, Bakers and Jameson were often located near the upper range of concentrations sampled at our monitoring stations, which suggests that an increase in TN and NO 3 -NO 2 concentrations in the Missouri River during chute construction may occur; however, the range of elutriate concentrations for these proposed construction sites still overlapped considerably with the range of monitoring station concentrations, especially for TN.…”

Water Point and Non-Point Nitrogen Pollution Due to Land-Use Change and Nitrate Deposition in China from 2000 to 2020

“…The urban areas and municipal waste can also provide a significant source of nitrate to the water system. For example, the growth rate of nitrate concentration in the Mississippi River was between 5% and 13% due to urbanization between 2000 and 2008 [10]. Approximately 64% of the nitrate in the water systems of Slovenia came from domestic wastewater and the agricultural sector [11].…”