Ecological assessment of pollution load from drains on the environment of Burullus Lake, Egypt
摘要
Industrial, agricultural and domestic wastes derived from drains increase the load of pollution on the environment of Burullus Lake. Pollutants can cause adverse effect on ecosystem components (water, sediment and plants). The distribution of metals and salinity gradients are significantly affected by the lake’s hydrological connection to the Mediterranean Sea via El-Boughaz Inlet. The present study aims to assess the load of pollutants derived from drains water and sediments around Burullus Lake. For water samples: Pb ranged from 128.9 µg/l to 401.4 µg/l, Fe ranged from 45.1 µg/l to 27660.6 µg/l, Ni ranged from 32.4 µg/l to 117.5 µg/l, Cd ranged from 1.5 µg/l to 6.2 µg/l, Cr ranged from 1403 µg/l to 18,880 µg/l and Zn ranged from 1237 µg/l to 23,262 µg/l. For sediment samples: Pb ranged from 9.25 µg/g to 56.25 µg/g, Fe ranged from 8511.04 µg/g to 9364.55 µg/g, Ni ranged from 20.63 µg/g to 271.13 µg/g, Cd ranged from 0.049 µg/g to 0.95 µg/g, Cr ranged from 1.68 µg/g to 18.53 µg/g and Zn ranged from 6.44 µg/g to 195.80 µg/g. Samples were taken from the northern, eastern, western and southern inlets around Burullus Lake. Water and sediment samples were collected for physical and chemical analysis. Water parameters such as depth, transparency, dissolved oxygen (DO), pH, salinity, nutrients (NH4, NO2, NO3 PO4 and SiO4), chemical oxygen demand (COD), total nitrogen (TN), total phosphorus (TP), chlorophyll-a and organic matter were measured in situ at ten stations. Pb, Fe, Ni, Cd, Cr, and Zn were among the heavy metals measured in water and sediment by using atomic absorption spectrometry. Using the heavy metal pollution index (HPI), the ecological risk of these heavy metals in water was investigated. In sediment, some indices were applied as enrichment factor (EF), contamination factor (Cf), degree of contamination (DC), geoaccumulation index (Igeo), pollution load index (PLI), ecological risk (Er), sediment pollution index (SPI), toxic unit (TU) and toxic risk index (TRI). The load of heavy metals pollution ranged from 0.27 to 0.1.0 The EF indicated that Pb, Ni, Cd and Cr from moderate enrichment to significant enrichment, meanwhile the most abundant element was Cd with significant enrichment. Igeo ranged from unpolluted to moderate polluted (0 < Igeo ≤ 1) and Cf indicated moderate pollution levels (1 ≤ Cf ≤ 3). The DC ranged from 4.13 to 10.37, so the DC < 12 indicated low degree of contamination in the sediment. Pollution Load Index was included in the nonpolluted category (PLI ≤ 1). Er values of all metals were < 40 so they were of low ecological risk, except Cd. The Er ranged from moderate to considerable pollution. SPI of all sites was < 2 so it considered natural in the studied sediment. TU of all sites varied from low to moderate risk. TRI varied from no risk to considerable risk. Burullus Lake received large amounts of industrial wastes in the northern part than other parts. Accordingly ecosystem components of Burullus Lake impacted by these drains has a moderate quality for ecological risk assessment. The ecological risk indices produced from the study of the analyzed elements suggest a pattern of growing potential ecological dangers, pointing to a significant level of pollution inside drains of Burullus Lake. More research is required to determine the connection between pollution levels and the biota’s physiological reaction.