Physicochemical Characteristics and Eutrophication Condition of Alexandria Beach Water Associated with Corniche Widening

Abstract

As a result of the constant increase of population and industrial expansion, the seawater in Alexandria, Egypt has become one of the most contaminated regions of the Mediterranean Sea. Thus, the recent implementation of safety measures and concrete bulkheads was set to protect the coastal line from sea level rise, resulting from climate change, causing poor water quality and an increased trend of eutrophication. Therefore, water quality evaluation and eutrophication status of Alexandria coastal water were addressed. The water samples were seasonally collected from July 2018 to April 2019 covering different coastal areas in Alexandria. The measured averages and ranges of these studied variables were as follows: temperature 23.6 0 C (19-33.5 0C), salinity 38.0 (33.9-40.1), pH (7.0-8.5), DO 8.4 mg/l (5.2-13.6 mg/l), OOM 4.6 mg O2/l (0.6-14.7mg O2/l), BOD 4.0 mg O2/l (0.5-9.1 mg O2/l), and chlorophyll-a 2.010 mg/m3(0-16.354 mg/m3). For eutrophication studies, the dissolved nutrient salts sustained high values, with an annual average of 16.43 μM for nitrate, 0.84 μM for nitrite, 11.19 μM for ammonia, 1.37 μM for phosphate and 7.56 μM for silicate. Sidi-Gaber was the most suffering station from bad water quality and eutrophication conditions according to TRIX and Eutrophication Index (EI) due to the disposal of land-based and resort effluents created by ongoing construction and beach activities. Different types of eutrophication conditions were observed among studied beaches throughout the year. The water quality index (WQI) revealed that Sidi-Gaber, Stanly and Miami stations were more contaminated than the other stations. Moreover, principal component analysis (PCA) depicts the existence of oxygen-consuming contaminants, which might be attributed due to impacts from rural domestic wastewater and municipal point source of the discharge. Pre-treatment of the landbased effluents before their disposal into the sea, the renewal of the isolated parts of the beach with seawater, or the full closure of all outlets at the seacoast are recommended.