Investigation of Lake Sapanca water pollution, Adapazari, Turkey

Abstract

Lake Sapanca has been the only source of drinking and recreational water for the city of Adapazari, Turkey. This paper reports a study of the variation of nutrient loading and trophic state of the lake, and also water quality parameters of Lake Sapanca compared to those of the neighbouring Lake Iznik. Through one year, samples were taken every three months from 15 different points on the streams feeding and draining off the lake. Nitrate, NO₂‐N, NH₃‐N, TKN, PO₄‐P concentrations on the 12 streams fe and three draining off points were determined. Then, loading, discharge, and accumulation amounts of nitrogen and phosphorus causing eutrophication were calculated and the trophic state of the lake was determined. A simple model was used to analyse the response of Lake Sapanca when the phosphorus loading rate was changed. Through this model, the variation of different parameters (t, M, K, Q, V and A) with respect to phosphorus concentration (C) was studied to identify effects and results. The consequences of an eutrophic state and measures to protect the lake are also discussed.

Keywords:

• Drinking water
• Eutrophication
• Lake Sapanca
• Trophic state
• Water pollution

Notes

1. As a reminder, nitrogen and phosphorus are the most important nutrients limiting algal growth in natural water bodies [13]. Generally the limiting element for algal growth is phosphorus [1,14,15].

2. Limnologists and ecologists categorise lakes according to their biological productivity [10,15,17,18]. Oligotrophic lakes are nutrient poor. A slight increase in fertility results in a mesotrophic lake with some aquatic plant growth, greenish water and moderate production of game fish. Eutrophic lakes are nutrient rich. Plant growth, in the forms of microscopic algae and rooted aquatic weeds, produces a water quality undesirable for body‐contact recreation. This situation also effect fish habitat. Eutrophication is the process whereby lakes become enriched with nutrients that make the water undesirable for human use, both for water supplies and recreation. The process of eutrophication is directly related to the aquatic food. Algae use carbon dioxide, inorganic nitrogen, and orthophosphate and trace nutrients for growth and reproduction. Thus, the water becomes turbid and under extreme conditions takes on the appearance of pea soup. Decaying algae also settle to the bottom, reducing dissolved oxygen. The source of extra nutrients may be both point and non‐point pollution sources. The key to control rate of the lake eutrophication lies in limiting plant nutrients. In the majority of lakes investigated, either phosphorus or nitrogen was the limiting factor. Although this idea is not universally accepted, most authorities believe that as a lake becomes more eutrophic, phosphorus becomes the growth‐limiting element [15,19]. Lakes with annual mean total nitrogen and phosphorus concentrations greater than 0.8 mg/l and 0.1 mg/l, respectively, exhibit algal blooms and nuisance weed growths during most of the growing season [19].