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Nitrogen Dynamics In A Catchment, The Porsuk, Central Anatolia

Congress: 2015
Author(s): Burcu Ozkaraova Gungor, Ozgur Cakmak
Ondokuz Mayis University1, Ministry of Environment and Urban Planning2

Keyword(s): Sub-theme 2: Surface water and groundwater,
AbstractIntroduction For the status evaluation of water bodies on an integrated scale, the determination of source contribution plays a crucial role. In complex systems where rural point and nonpoint sources of nutrients can be found, the influence of point sources on the nutrient concentration may be masked by the input from diffuse sources. However, as best management practices are being developed and implemented to abate nonpoint source pollution, point sources such as WWTP effluents may become even more of a dominant contributor to nutrient inputs into aquatic systems. Bearing such considerations in mind, studies show that both point and diffuse source problems need to be tackled, especially if the objectives of `good ecological status` and `good chemical status` of the EU Water Framework Directive (WFD) are to be met.

The assessment of spatial and temporal variation in nutrient dynamics within river basin districts is also obligatory for an achievement of the WFD objectives. Some parts of the WFD have also been transposed by Turkey, as a candidate country. Water quality monitoring has been carried out in Turkey since 1979. Most studies cover individual regions and do not extend to the entire catchment, as it is for the Porsuk Stream. The Porsuk Stream catchment comprises two major basins. The stream rises from sources within the Kütahya Province, carries the water to the Porsuk Dam, which is located north of the Kütahya Plain, and continues flowing through the Eskiþehir Province until it discharges into the Sakarya River. Its approximate travel distance is about 460 km with a total drainage area of 11,325 km2. The Porsuk Dam, which is located between the Kütahya and Eskiþehir basins, is the primary drinking water source for the city Eskiþehir, but it is also used for industrial and agricultural purposes. This study aims to characterise the spatial variations in ammonium, nitrite and nitrate nitrogen concentrations with respect to point and nonpoint sources.

Sources of Pollution and Location of Monitoring Stations The study area represents a variety of human activities, namely urbanisation, industry and agriculture. The Porsuk Stream receives a contaminant load from some 600,000 inhabitants. within the Kütahya Province and another load from some 706,000 inhabitants within the Eskiþehir Province. Septic tanks are used for the wastewater collection in smaller settlements. The monitoring stations were chosen with respect to the presence of municipal (WWTP) and industrial point sources within the Kütahya and Eskiþehir provinces. The first six stations are located along the Upper Porsuk Stream, which is upstream of the Porsuk Dam located in the Kütahya Province. The following eight stations are located downstream of the dam, along the stream flowing through the city of Eskiþehir (Fig. 1). The monitoring data was obtained from the General Directorate of State Hydraulic Works (DSI) Region III, which has taken water samples from the stations located along the entire Porsuk Stream with a frequency ranging from once a month to once every three months.

Results and Discussion Mean nitrate concentrations were generally higher in the upstream stations (1.1 mg/L) (Fig. 2c). Downstream of the KWWTP (SW-3), a general decrease in the nitrate concentration (<0.7 mg NO3-N/L) was observed, which might be attributed to the low nitrate content of insufficiently treated sewage effluent. An increase in the nitrate concentration was detected at SW-5, which was due to the wastewater discharge from the nitrogen fertilizer factory (NFF). The nitrate concentration in the stream water decreased as it flowed towards the Porsuk Dam. Downstream of the Porsuk Dam, at SW-7 and SW-8, an increase in the mean nitrate concentration up to 1.1 and 1.8 mg NO3-N/L was recorded, respectively. This rise in nitrate was related to the higher dissolved oxygen status of the stream water that lead to oxidation (SW-7) and the discharge of the Eþenkara stream and treated effluents from other industries present in the neighbourhood (SW-8). After the ESBF, which is not causing to an increase, a decreasing trend was observed for nitrate. The low nitrate concentration of the EWWTP effluent caused a decrease in detected nitrate, which continued until SW-14 for all years. The monitoring station SW-14 is located in a rural area. Agricultural activities and septic tanks are the main contaminant sources, which might have caused a nitrate increase via baseflow and/or surface runoff. The convergence of the Pürtek Stream also seems to influence the water quality of the Porsuk Stream.

The mean ammonium concentrations from monitoring stations SW-1 and SW-2 were below 0.2 mg NH4-N/L, but increased remarkably to approximately 5.1 mg NH4-N/L after the KWWTP discharge (SW-3) (Fig. 2e). A decrease in the ammonium concentration at SW-4 was observed. However, the effluent discharge from the NFF again caused an increase in the concentration at SW-5. The NFF, discharging about 6500 m3/d untreated wastewater (Governorship of Kütahya 2005). The observed increasing trend continued for SW-6, due to the discharge of the Güvez Stream carrying domestic and industrial effluents from other point sources, such as the Seyitömer Power Plant (Governorship of Eskiþehir 2006). Generally, a spatial improvement in water quality was not observed until the Porsuk Dam. Downstream of the Porsuk Dam, the ammonium concentration represented back ground (<0.7 mg NH4-N/L). However, at station SW-9, the discharge from the ESBF caused an increase in the mean ammonium concentrations. The concentration of ammonium longitudinally decreased downstream of the input until the EWWTP. At station SW-11, the ammonium concentration increased to values above 10 mg NH4-N/L. The EWWTP receives sewage of approximately 400.000 people, which is approximately two times higher than that of the KWWTP. Downstream of the EWWTP, a decreasing spatial trend was observed.

Conclusions (1) The contamination of the stream water was significantly higher downstream of the city of Kütahya and Eskiþehir. (2) Along the stream, increases in concentrations were linked to the municipal WWTP and the nitrogen fertilizer factory of Kütahya, in addition to the sugar beet factory and municipal WWTP of Eskiþehir. (3) The contribution of tributaries was recognisable, but a differentiation between the nonpoint sources and smaller intermediate point sources located along the tributaries was difficult. However, the presence of ammonium as the major nitrogen compound showed that the influence of point sources was more pronounced and was mostly masking the input of diffused sources. (4) Despite the fact that the ammonium and nitrate concentrations were much lower than the 1980s observations, both point and diffuse source problems need to be resolved in order to achieve the objectives of `good ecological status` and `good chemical status` of the EU Water Framework Directive (WFD).

Acknowledgements We would like to thank the General Directorate of State Hydraulic Works (DSI) Region III for supplying the water quality data.

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