Phosphorus Export from an Agricultural Watershed: Linking Source and Transport Mechanisms

Abstract

Many source and transport factors control P loss from agricultural landscapes; however, little information is available on how these factors are linked at a watershed scale. Thus, we investigated mechanisms controlling P release from soil and stream sediments in relation to storm and baseflow P concentrations at four flumes and in the channel of an agricultural watershed. Baseflow dissolved reactive phosphorus (DRP) concentrations were greater at the watershed outflow (Flume 1; 0.042 mg L(-1)) than uppermost flume (Flume 4; 0.028 mg L(-1)). Conversely, DRP concentrations were greater at Flume 4 (0.304 mg L(-1)) than Flume 1 (0.128 mg L(-1)) during stormflow. Similar trends in total phosphorus (TP) concentration were also observed. During stormflow, stream P concentrations are controlled by overland flow-generated erosion from areas of the watershed coincident with high soil P. In-channel decreases in P concentration during stormflow were attributed to sediment deposition, resorption of P, and dilution. The increase in baseflow P concentrations downstream was controlled by channel sediments. Phosphorus sorption maximum of Flume 4 sediment (532 mg kg(-1)) was greater than at the outlet Flume 1 (227 mg kg(-1)). Indeed, the decrease in P desorption between Flumes 1 and 4 sediment (0.046 to 0.025 mg L(-1)) was similar to the difference in baseflow DRP between Flumes 1 and 4 (0.042 to 0.028 mg L(-1)). This study shows that erosion, soil P concentration, and channel sediment P sorption properties influence streamflow DRP and TP. A better understanding of the spatial and temporal distribution of these processes and their connectivity over the landscape will aid targeting remedial practices.

Size distribution and diffuse pollution impacts of PAHs in street dust in urban streams in the Yangtze River Delta

“…Distances between the streets and the receiving waters are short and there are no buffer strips. This results in contamination easily transfered into the receiving water bodies (McDowell et al, 2001;Heathwaite et al, 2005;Lu et al, 2007).…”

Atributos químicos de Latossolo após sucessivas aplicações de composto orgânico de dejeto líquido de suínos

“…A aplicação de resíduos orgânicos também pode promover, principalmente nas camadas mais superficiais do solo, o incremento dos teores de nutrientes como P, K, Ca e Mg (McDowell et al, 2001;Gatiboni et al, 2008;Ceretta et al, 2010a;Guardini et al, 2012;Lourenzi et al, 2013). Com isso, há melhoria no ambiente químico do solo para o crescimento de raízes, por causa do aumento da saturação por bases e da redução da saturação por Al (Lourenzi et al, 2011;Brunetto et al, 2012).…”

Nutrients in soil layers under no-tillage after successive pig slurry applications

“…(Ceretta et al, 2010), which is used as organic nutrient source in areas with annual crops and/or pastures. However, the amounts of manure applied are generally high and frequent and promote an accumulation of certain nutrients over the years, surpassing the soil adsorption capacity and crop requirements (McDowell et al, 2001;Berwanger et al, 2008;Scherer et al, 2010). Furthermore, the increased nutrient concentration in the soil may enhance element transfer by runoff and percolation, such as nitrogen (N) and phosphorus (P), contaminating surface water and groundwater supplies (Daudén et al, 2004;Bergström & Kirchmann, 2006;Ceretta et al, 2010).…”

“…However, the addition of high amounts of P in the manure causes a reduction in the adsorption capacity of soil adsorption sites (Siddique & Robinson, 2003;Adeli et al, 2008). As a result, phosphate ions are adsorbed with lower binding energy, increasing their concentration in soil solution (McDowell et al, 2001) and their transfer by runoff (Smith et al, 2001b;Daverede et al, 2004;Ceretta et al, 2010) and percolation Vadas, 2006) possibly causing eutrophication of water sources.…”