Abstract
During the last decades, population growth and the associated intensification of anthropogenic activities (agriculture, industrialization and urbanization) has increased nutrient inputs to Pampean lotic bodies. However few studies have evaluated the influence of these changes on water quality. The objectives of this study were to determine nitrogen (N) and phosphorus (P) fractions, trophic status and nutrient limitation of a typical Pampean stream, and to compare nutrient contents and speciation with different land uses (urban/industrial versus agricultural). Stream water samples were obtained monthly between 2010 and 2012 from six locations along the Pergamino stream. The stream was highly productive (eutrophic/hypertrophic) and nutrient concentrations were greater than the environmental quality standards from different parts of the world as a result of point and diffuse source inputs in addition to the naturally high baseline nutrient concentrations. In the case of N, organic and particulate fractions predominated in sites surrounded by agriculture, while inorganic forms predominated in sites dominated by urban/industrial effluent discharges. Nutrients spatial variation along the Pergamino stream presented the lowest concentrations in the headwaters, the highest concentrations when crossing the city of Pergamino and intermediate values towards the mouth. In this basin, despite being located in the most important agricultural region of Argentina, urban and industrial point source discharges resulted in greater impairment of water quality than diffuse sources linked to agriculture. Between the city of Pergamino and the stream mouth, total N and P concentrations decreased by 50% as a result of dilution due to increased flow and other natural self-cleansing mechanisms. It is imperative to design a monitoring programme and to adopt management strategies designed to reduce nutrient input to avoid saturating the stream’s capacity to retain and process nutrient inputs.
Highlights
Nutrient concentrations exert a strong control on the biological productivity of fresh waters and both of these variables are used to define their trophic state through indexes
Examining nutrient spatial variation along the Pergamino stream, we found that sites with urban/industrial effluent discharges (site C) had the highest concentrations of total nitrogen (TN), total phosphorus (TP) and Soluble reactive phosphorus (SRP), sites A and B had the lowest concentrations and sites D, E and F had intermediate values (Figure 3 and Supplementary Table)
When we analysed the relative contribution of each fraction, we found a higher proportion of Particulate nitrogen (PN) and Dissolved organic nitrogen (DON) in sites A and B compared with the urban site C
Summary
Small-scale, low-order streams connect the terrestrial environment with large rivers. The production system of the Pampas is different too: agricultural intensification began in the 1980s, twenty years later than in industrialized countries (Viglizzo et al 2011) and average fertilizer rates range between one third and one fifth of those of the United States and United Kingdom (Banco Mundial database); farmers rarely apply fresh manure, and a large proportion of beef production is still forage-based (only one out of four animals slaughtered in the country goes through a confinement system (Moscuza 2010; Robert et al 2009) These differences suggest that nutrient loads and stream water quality are different from those described in the Northern Hemisphere. The objectives of this study were to determine water concentrations of different N and P fractions, trophic state and nutrient limitation for algal growth in a typical Pampean stream, and to compare them with different land uses (urban/industrial versus agricultural) along the watercourse. Like other Pampean streams, it is effluent, and groundwater discharge constitutes its base flow (Galindo et al 2007)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
