Applying Isotope Techniques and Modeling to Identify the Nitrogen Source in Göksu Delta
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Department of Environmental Engineering, Faculty of Engineering, Mersin University
Olcay Gülçiçek   

mersin university, Department of Environmental Engineering, Faculty of Engineering, Mersin University, 33340 MERSİN, Turkey
Submission date: 2018-04-30
Final revision date: 2018-08-08
Acceptance date: 2018-08-16
Online publication date: 2019-04-29
Publication date: 2019-05-28
Pol. J. Environ. Stud. 2019;28(5):3179–3195
Göksu Delta is an important wetland area in Turkey and has been declared a first-degree site and has been included in the Ramsar list. Agricultural activities continue for 12 months of the year due to the favorable climate in the delta and these activities are the most important income source for the people living in the region. Investigations to date have identified the presence of nitrogen pollutants in delta groundwater. However, studies have yet to be conducted on the source of nitrogen contaminants. This study has identified source(s) of nitrogen through the combined use of isotope methods and groundwater modeling.15N and 18O stable isotope analysis were done for identifying the source(s) of nitrogen pollution. We used a three-dimensional Visual MODFLOW model to simulate the alluvial aquifer around the delta. After establishing the groundwater fate and transport model (MT3DMS), we investigated the source of nitrate pollution by particle tracking analyses (MODPATH). The results of δ15N showed that nitrogen in delta groundwater was greatly affected by agricultural activities, but was mainly sourced from domestic wastewater. Similar to isotopic results with the particle tracking model, 5 years ago it was determined that nitrate ions came from domestic wastewater of Silifke city and surrounding settlements that lack wastewater treatment facilities.