This pioneered study is aimed to determine the levels and distributions of organotin compounds (OTCs) in sediment samples collected from five Egyptian lakes located in the southern-eastern Mediterranean Sea. The paper has given an account of and the reasons for the widespread distribution of Tributyltin (TBT) in northern lakes. The percentage of TBT ranged from 4% - 100% OTC revealing recent inputs of TBT. The highest average of TBT (2.84 μg/g Sn dry wt) was measured in lake Edku. Dibutyltin (DBT) was observed at most sampled sites. Relatively higher abundance of DBT was observed in sediments of EL-Burullus (0.69 μg/g Sn dry wt). One of most significant findings to emerge from this study is the absence of any strong and significant correlation between TBT and DBT in sediments from five northern lakes. The absence of such correlation might give a clear evidence that both compounds did not come from the same source. The observed OTC levels indicate some highly localized areas of contamination which are severe enough to cause harmful effects on marine flora and fauna. Except for El-Burllus, Triphenyltin (TPhT) was not measured in sediments of most stations. TPhT was the predominant species in El-Burullus, which indicate a source of pollution mostly originated from industrial and agricultural waste water discharge, organic wastes, commercial fertilizers, chemical wastes and pesticides. The percentages of OTC to total tin ranged from 1% to 35%. El-Brullus, Edku and El-Bardaweel exhibited the highest percentages. As a result of lack of enforcement on the control of OTC, the study has thrown up many questions need further detailed environmental assessment of OTC.
Tin compounds are sparingly soluble in water and are likely to partition to soils and sediments. Most commercially used OTCs are relatively immobile in environment media due to their low vapor pressures, low water solubility and high affinity for soil and organic sediments [
In spite of legislative regulations for OTC, it is likely that OTC will continue to be produced and used as effective biocides, especially in developing countries. They continue to be used also in material and wood preservatives as effective biocides [
DBT has mainly been related to the degradation of TBT via microbial activity and/or photochemical reactions. In recent years evidence for a direct entrance of DBT into the environment was found due to municipal wastewaters, sewage sludge and land fill leachates. For example, the major application of DBT is as additives to plastics particularly to polyvinyl chloride (PVC) to prevent degradation due to changes in temperature or lighting. PVC is used in water pipes rigid sheeting (e.g. for roofing) and bottles [
TPhT compounds have been used extensively as algaecide and molluscicides in antifouling products since 1960s [
Despite the presence of few studies that have been conducted to investigate the levels and distribution of OTC in the south eastern Mediterranean Sea [
The Egyptian Mediterranean coast exhibits five lakes (
The aim of this study is to determine the levels and distributions of organotin compounds (OTCs) in sediment samples collected from these Egyptian lakes located in the southern-eastern Mediterranean Sea.
Fifty four water and sediment samples were collected during summer 2009 (
Transparency was measured using 25 cm diameter enameled Secchi disk. Total suspended matter was
obtained from one liter water sample then filtered through washed, dried and weighed 0.45 mm membrane filters. The filters with its contents were kept for drying in the oven at 105˚C until constant weight. The difference in the dry weight of filters before and after filtration was expressed in mg/l suspended matter [
Depths, water temperature, transparency, electrical conductivity, salinity, pH, DO, BOD, and OOM for each lake are listed in Tables 2(a)-(e). Depths varied between 0.25 m measured at station 4 of lake El-Burullus and 4.5 m measured at station 9 of lake Edku, revealing the shallowness of the area. Water temperature varied in a narrow range depending on the mean of daily number of sunshine hours and the time of sampling. The minimum value of 27.0˚C was observed at station 1 of Lake El-Bardaweel, while the maximum value 31.2˚C was measured at station 9 of Lake El-Manzalah. The water transparency is generally low due to the shallowness of these lakes and the continuous disturbance of the mud bottom by wind actions [
Element | LOD | Certified value | Found | SD | Recovery% | 95% confidence interval |
---|---|---|---|---|---|---|
Sn | 0.3 ppb | 52.5 ppm | 50.1 ppm | 3.700 | 95.4 | 46.9 - 54.3 |
Mean concentration of certified value associated with the mean concentration (found) at 95% confidence interval of Sn in sediments (n = 6). SD: Standarddeviation; LOD: Limit of detection.
Physicochemical characteristics of water | Organotin compounds in sediments | ||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Stations | Depth (m) cm | Trans (cm) cm | Temp (˚C) ˚C | EC µS/cm µS/cm | Sal‰ | pH | DO mg/l | BOD mg/l | OOM mgO2/l | T-Sn µg/g | DBT µg/g | TBT µg/g | TPhT µg/g | ∑OT | TBT/DBT | ∑OT/ T-Sn% | Igeo |
1 | 1.0 | 25 | 29.3 | 11.32 | 6.5 | 8.28 | 4.0 | 15.6 | 23.6 | 19.98 | Nd | 1.04 | Nd | 1.04 | - | 5 | 2.5 |
2 | 1.5 | 25 | 28.9 | 12.92 | 7.5 | 8.38 | 5.6 | 16.9 | 28.8 | 21.96 | 0.44 | 0.84 | 0.34 | 1.62 | 1.91 | 7 | 2.7 |
3 | 2.0 | 35 | 29.6 | 2.38 | 1.1 | 7.26 | 0.0 | 41.5 | 63.6 | 19.71 | Nd | 0.14 | Nd | 0.14 | - | 1 | 2.5 |
4 | 1.8 | 42 | 27.8 | 5.18 | 2.8 | 7.86 | 2.4 | 31.2 | 55.4 | 15.57 | 0.21 | 0.88 | Nd | 1.09 | 4.19 | 7 | 2.2 |
5 | 2.1 | 15 | 28.0 | 3.29 | 1.6 | 7.86 | 2.6 | 16.5 | 42.2 | 16.65 | Nd | 2.14 | Nd | 2.14 | - | 13 | 2.3 |
6 | 3.4 | 35 | 28.1 | 8.69 | 4.9 | 8.64 | 10.0 | 16.5 | 22.1 | 26.55 | 1.74 | 1.72 | 0.22 | 3.68 | 0.99 | 14 | 2.9 |
7 | 1.5 | 60 | 27.8 | 5.65 | 3.1 | 7.66 | 2.6 | 15.7 | 24.3 | 22.05 | Nd | 0.87 | Nd | 0.87 | - | 4 | 2.7 |
8 | 0.7 | 40 | 29.1 | 4.68 | 2.5 | 7.92 | 3.5 | 12.6 | 26.4 | 19.26 | 0.05 | 0.29 | Nd | 0.34 | 5.80 | 2 | 2.5 |
9 | 1.5 | 100 | 27.8 | 8.02 | 4.5 | 7.95 | 6.4 | 18.6 | 28.3 | 15.48 | 2.11 | 2.29 | 0.63 | 5.03 | 1.09 | 32 | 2.2 |
10 | 0.8 | 20 | 30.2 | 8.70 | 4.9 | 8.37 | 13.0 | 16.8 | 28.9 | 22.51 | 1.78 | 1.25 | 0.39 | 3.42 | 0.70 | 15 | 2.7 |
Max. | 3.4 | 100 | 30.2 | 12.9 | 7.5 | 8.64 | 13.0 | 41.5 | 63.6 | 26.55 | 2.11 | 2.29 | 0.63 | 5.03 | 5.80 | 32 | 2.9 |
Min. | 0.7 | 15 | 27.8 | 2.38 | 1.1 | 7.26 | 0.0 | 12.6 | 22.1 | 15.48 | Nd | 0.14 | Nd | 0.14 | 0.70 | 1 | 2.2 |
Average | 1.6 | 40.0 | 28.7 | 7.8 | 3.9 | 8.02 | 5.01 | 20.2 | 34.4 | 19.97 | 1.06 | 1.15 | 0.40 | 2.61 | 1.08 | 13 | 2.5 |
SD | 0.8 | 24.8 | 0.9 | 3.4 | 2.4 | 0.4 | 3.9 | 9.0 | 14.5 | 3.5 | 0.92 | 0.7 | 0.2 | 1.6 | 2.1 | 9.2 | 0.2 |
Stations | Depth (m) cm | Tras (cm) cm | Temp (˚C) ˚C | EC µS/cm | Sal‰ | pH | DO mg/l | BOD mg/l | OOM mgO2/l mg/l | T-Sn µg/g | DBT µg/g | TBT µg/g | TPhT µg/g | ∑OT | TBT/DBT | ∑OT/ T-Sn% | Igeo |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | 1.5 | 30 | 27.2 | 3.58 | 1.8 | 8.57 | 8.0 | 6.2 | 13.9 | 16.7 | 2.04 | 2.63 | 0.81 | 5.48 | 1.29 | 33 | 2.3 |
2 | 0.9 | 30 | 27.7 | 2.41 | 1.1 | 8.56 | 7.6 | 7.2 | 10.2 | 22.68 | 1.31 | 2.41 | Nd | 3.72 | 1.84 | 16 | 2.7 |
3 | 1.0 | 32 | 28.7 | 2.33 | 1.1 | 8.75 | 8.2 | 7.6 | 10.3 | 24.41 | 1.3 | 4.88 | Nd | 6.18 | 3.75 | 25 | 2.8 |
4 | 2.0 | 40 | 28.1 | 2.52 | 1.2 | 8.71 | 8.5 | 6.4 | 9.6 | 18.36 | 2.02 | 4.03 | Nd | 6.05 | 2.00 | 33 | 2.4 |
5 | 2.1 | 50 | 28.1 | 2.28 | 1.0 | 8.32 | 8.5 | 6.2 | 10.6 | 17.46 | 0.91 | 1.34 | 0.68 | 2.93 | 1.47 | 17 | 2.3 |
6 | 1.8 | 45 | 27.9 | 1.53 | 0.6 | 7.68 | 2.7 | 8.5 | 16.8 | 12.06 | 0.66 | 3.4 | Nd | 4.06 | 5.15 | 34 | 1.8 |
7 | 1.8 | 45 | 28.5 | 1.61 | 0.6 | 8.32 | 9.3 | 6.4 | 14.6 | 23.94 | 2.81 | 3.98 | Nd | 6.79 | 1.42 | 28 | 2.8 |
8 | 0.7 | 35 | 28.0 | 2.03 | 0.9 | 8.44 | 7.0 | 6.4 | 10.6 | 17.28 | 0.64 | 1.27 | 0.77 | 2.68 | 1.98 | 16 | 2.3 |
9 | 4.5 | 30 | 29.4 | 2.01 | 0.9 | 8.87 | 18.2 | 17.2 | 22.1 | 18.99 | 0.67 | 1.65 | 0.74 | 3.06 | 2.46 | 16 | 2.5 |
Max. | 0.7 | 50 | 29.4 | 3.58 | 1.8 | 8.87 | 18.2 | 17.2 | 22.1 | 24.41 | 2.81 | 4.88 | 0.81 | 6.79 | 5.15 | 34 | 2.8 |
Min. | 4.5 | 30 | 27.2 | 1.53 | 0.6 | 7.68 | 2.7 | 6.2 | 9.6 | 12.06 | 0.64 | 1.27 | Nd | 2.93 | 1.29 | 16 | 1.8 |
Average | 2.0 | 38.0 | 28.2 | 2.26 | 1.0 | 8.47 | 8.67 | 8.0 | 13.2 | 19.09 | 1.37 | 2.84 | 0.33 | 4.54 | 2.07 | 24 | 2.4 |
SD | 1.1 | 7.8 | 0.6 | 0.60 | 0.4 | 0.4 | 4.0 | 3.5 | 4.2 | 4.0 | 0.8 | 1.3 | 0.1 | 1.6 | 1.3 | 8.1 | 0.3 |
Stations | Depth (m) cm | Trans (cm) cm | Temp (˚C) ˚C | EC µS/cm µS/cm | Sal‰ | pH | DO mg/l | BOD mg/l | OOM mgO2/l mg/l | T-Sn µg/g | DBT µg/g | TBT µg/g | TPhT µg/g | ∑OT | TBT/ DBT | ∑OT/T-Sn% | Igeo |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | 0.50 | 30 | 29.7 | 4.68 | 2.5 | 8.26 | 7.2 | 5.6 | 25.5 | 22.05 | 1.46 | 1.26 | Nd | 2.72 | 0.86 | 12 | 2.7 |
2 | 3.0 | 40 | 30.5 | 8.36 | 4.7 | 8.35 | 7.6 | 5.4 | 23.4 | 14.4 | 2.21 | 0.21 | 2.07 | 4.49 | 0.10 | 31 | 2.1 |
3 | 1.3 | 35 | 29.3 | 5.28 | 2.8 | 8.94 | 8.9 | 7.6 | 20.6 | 21.96 | 2.29 | 0.16 | 2.11 | 4.56 | 0.07 | 21 | 2.7 |
4 | 2.5 | 20 | 30.3 | 4.60 | 2.4 | 8.77 | 6.6 | 5.0 | 23.5 | 31.59 | 1.64 | 0.48 | 1.29 | 3.41 | 0.29 | 11 | 3.2 |
5 | 1.5 | 30 | 28.9 | 3.80 | 1.9 | 8.75 | 7.2 | 6.0 | 20.6 | 22.32 | 0.35 | 0.73 | 1.51 | 2.59 | 2.09 | 12 | 2.7 |
6 | 1.2 | 18 | 29.0 | 3.30 | 1.6 | 8.44 | 6.6 | 5.6 | 17.6 | 32.22 | 1.49 | 1 | 1.23 | 3.72 | 0.67 | 12 | 3.2 |
7 | 1.2 | 30 | 29.9 | 3.57 | 1.8 | 8.30 | 7.6 | 5.6 | 21.8 | 22.5 | 2.85 | 1.35 | 3.33 | 7.53 | 0.47 | 33 | 2.7 |
8 | 1.0 | 30 | 29.0 | 2.78 | 1.3 | 8.74 | 7.2 | 6.5 | 22.5 | 25.83 | 2.34 | 0.32 | 3.83 | 6.49 | 0.14 | 25 | 2.9 |
9 | 1.2 | 35 | 29.3 | 2.02 | 0.9 | 8.70 | 7.2 | 6.5 | 22.5 | 23.49 | 3.32 | 0.39 | 3.96 | 7.67 | 0.12 | 33 | 2.8 |
10 | 1.3 | 50 | 29.1 | 1.25 | 0.4 | 8.65 | 7.4 | 4.8 | 22.8 | 21.87 | 2.15 | 0.76 | 1.07 | 3.98 | 0.35 | 18 | 2.7 |
11 | 1.4 | 60 | 29.3 | 1.07 | 0.3 | 8.54 | 7.5 | 4.5 | 19.6 | 20.16 | 0.11 | 0.23 | 1.62 | 1.96 | 2.09 | 10 | 2.5 |
12 | 1.10 | 70 | 30.0 | 1.15 | 0.4 | 8.92 | 8.2 | 6.1 | 17.5 | 25.38 | 0.78 | 1.34 | 0.93 | 3.05 | 1.72 | 12 | 2.9 |
Max. | 3.0 | 70 | 30.5 | 8.36 | 4.7 | 8.94 | 8.9 | 7.6 | 23.5 | 32.22 | 3.32 | 1.35 | 3.96 | 7.67 | 2.09 | 33 | 2.9 |
Min. | 0.25 | 18 | 28.9 | 1.07 | 0.3 | 8.26 | 6.6 | 4.5 | 17.5 | 14.40 | 0.11 | 0.16 | Nd | 1.96 | 0.07 | 11 | 2.1 |
Average | 1.3 | 37.3 | 29.5 | 3.49 | 1.8 | 8.61 | 7.43 | 5.77 | 21.49 | 23.65 | 1.75 | 0.69 | 2.09 | 4.53 | 0.39 | 19 | 2.76 |
SD | 0.7 | 15..52 | 0.5 | 2.1 | 1.3 | 0.2 | 0.6 | 0.85 | 2.4 | 4.8 | 1.0 | 0.5 | 1.1 | 1.9 | 0.8 | 9.13 | 0.3 |
Stations | Depth (m) cm | Trans (cm) cm | Temp (˚C) ˚C | EC µS/cm µS/cm | Sal‰ | pH | DO mg/l | BOD mg/l | OOM mgO2/l mg/l | T-Sn µg/g | DBT µg/g | TBT µg/g | TPhT µg/g | ∑OT | TBT/DBT | ∑OT/ T-Sn% | Igeo |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | 0.4 | 12 | 28.4 | 5.3 | 2.9 | 7.8 | ND | 24.6 | 34.3 | 18.72 | 1.67 | 1.47 | 1.46 | 4.6 | 0.88 | 25 | 2.4 |
2 | 1.0 | 33 | 28.7 | 13.5 | 7.9 | 8.5 | 6.4 | 3.2 | 14 | 19.15 | 1.36 | 1.25 | Nd | 2.61 | 0.92 | 14 | 2.5 |
3 | 1.1 | 32 | 28.0 | 5.1 | 2.7 | 7.9 | 6.8 | 12.8 | 19.3 | 18.72 | 1.48 | 1.75 | 0.83 | 4.06 | 1.18 | 22 | 2.4 |
4 | 0.9 | 50 | 30.2 | 17.5 | 10.4 | 8.6 | 7.2 | 6.4 | 22.9 | 24.21 | 1.5 | 3.27 | 1.24 | 6.01 | 2.18 | 25 | 2.8 |
5 | 0.9 | 44 | 28.3 | 4.1 | 2.1 | 7.9 | 8.6 | 5.2 | 19.8 | 17.91 | 0.52 | 1.45 | Nd | 1.97 | 2.79 | 11 | 2.4 |
6 | 1.3 | 75 | 30.6 | 3.5 | 1.8 | 8.6 | 7.2 | 4.6 | 21.3 | 19.08 | 0.6 | 0.98 | Nd | 1.58 | 1.63 | 8 | 2.5 |
7 | 1.2 | 50 | 29.7 | 32.2 | 20.2 | 8.6 | 8.6 | 3.6 | 19.8 | 23.67 | 0.77 | 3.93 | Nd | 4.7 | 5.10 | 20 | 2.8 |
8 | 1.2 | 70 | 31.1 | 6.9 | 3.8 | 8.7 | 7.4 | 4.2 | 16.4 | 26.64 | 1.31 | 4.61 | Nd | 5.92 | 3.52 | 22 | 2.9 |
9 | 1.2 | 52 | 31.2 | 4.0 | 2.1 | 9.2 | 6.2 | 5.2 | 16.6 | 22.59 | 1.23 | 3.7 | 1.68 | 6.61 | 3.01 | 29 | 2.7 |
10 | 1.5 | 50 | 31.1 | 17.0 | 10.2 | 8.3 | 8.2 | 4.1 | 17.2 | 19.89 | 0.66 | 3.37 | Nd | 4.03 | 5.11 | 20 | 2.5 |
11 | 0.5 | 25 | 28.0 | 6.8 | 3.7 | 8.2 | 3.2 | 14.8 | 28.3 | 22.68 | 0.63 | 3.83 | Nd | 4.46 | 6.08 | 20 | 2.7 |
Max. | 0.4 | 75 | 31.2 | 32.2 | 10.4 | 9.2 | 8.6 | 24.6 | 34.3 | 26.64 | 1.67 | 4.61 | 1.68 | 7.96 | 6.08 | 25 | 2.9 |
Min. | 1.5 | 12 | 28.0 | 3.5 | 1.8 | 7.8 | 3.2 | 3.2 | 14 | 17.91 | 0.52 | 0.98 | Nd | 1.58 | 0.88 | 11 | 2.4 |
Average | 1.1 | 44.8 | 29.6 | 10.5 | 6.2 | 8.39 | 6.98 | 8.06 | 20.9 | 21.21 | 1.07 | 2.69 | 1.30 | 5.06 | 2.51 | 24 | 2.6 |
SD | 0.3 | 18.58 | 1.32 | 8.9 | 5.7 | 0.42 | 1.6 | 6.7 | 5.9 | 2.9 | 0.4 | 1.3 | 0.4 | 1.6 | 1.8 | 6.3 | 0.2 |
Stations | Depth (m) cm | Trans (cm) cm | Temp (˚C) ˚C | EC µS/cm µS/cm | Sal‰ | pH | DO mg/l | BOD mg/l | OOM mgO2/l mg/l | T-Sn µg/g | DBT µg/g | TBT µg/g | TPhT µg/g | ∑OT | TBT/DBT | ∑OT/T-Sn% | Igeo |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | 1.3 | 125 | 27.0 | 81.40 | 57.7 | 8.42 | 8.8 | 3.6 | 4.7 | 16.62 | 0.28 | 3.22 | 0.89 | 4.39 | 11.50 | 26 | 2.3 |
2 | 0.6 | 125 | 27.2 | 73.40 | 51.0 | 8.56 | 8.8 | 3.2 | 3.7 | 16.81 | 0.38 | 3.72 | 0.08 | 4.18 | 9.79 | 25 | 2.3 |
3 | 0.9 | 70 | 28.1 | 81.20 | 57.4 | 8.66 | 9.1 | 3.8 | 4.8 | 15.47 | 0.69 | 2.99 | 0.62 | 4.3 | 4.3 3 | 28 | 2.2 |
4 | 4.2 | 150 | 28.8 | 67.30 | 46.2 | 8.40 | 9.3 | 3.9 | 3.6 | 13.48 | 0.39 | 3.26 | 0.93 | 4.58 | 8.36 | 34 | 2.0 |
5 | 1.9 | 60 | 28.6 | 76.00 | 53.2 | 8.50 | 8.5 | 3.3 | 3.2 | 11.97 | 0.47 | 2.97 | Nd | 3.44 | 6.32 | 29 | 1.8 |
6 | 1.9 | 60 | 29.5 | 69.80 | 48.2 | 8.50 | 8.3 | 3.5 | 3.6 | 7.47 | 0.49 | 1.44 | 0.7 | 2.63 | 2.94 | 35 | 1.1 |
7 | 0.9 | 60 | 29.3 | 70.40 | 48.7 | 8.46 | 9.1 | 3.2 | 3.3 | 7.38 | 0.48 | 0.55 | Nd | 1.03 | 1.15 | 14 | 1.1 |
8 | 1.5 | 70 | 27.1 | 77.40 | 54.3 | 8.11 | 7.7 | 2.8 | 2.8 | 13.19 | 0.09 | 1.1 | Nd | 1.19 | 12.22 | 9 | 1.9 |
9 | 0.5 | 120 | 27.7 | 65.00 | 44.5 | 8.24 | 8.5 | 2.9 | 3.0 | 10.06 | 0.64 | 1.12 | 0.48 | 2.24 | 1.75 | 22 | 1.5 |
10 | 3.2 | 200 | 27.1 | 58.70 | 39.5 | 8.33 | 8.5 | 3.1 | 2.9 | 9.99 | 0.56 | 1.21 | 0.16 | 1.93 | 2.16 | 19 | 1.5 |
11 | 1.9 | 200 | 27.2 | 74.20 | 53.2 | 8.33 | 7.5 | 3.3 | 4.0 | 10.16 | 0.71 | 1.11 | 0.61 | 2.43 | 1.56 | 24 | 1.6 |
12 | 1.4 | 100 | 28.3 | 93.10 | 67.7 | 8.62 | 8.3 | 3.5 | 4.2 | 10.34 | 0.55 | 0.68 | 0.63 | 1.86 | 1.24 | 18 | 1.6 |
Max. | 4.2 | 200 | 29.5 | 39.10 | 67.7 | 8.66 | 9.3 | 3.1 | 4.7 | 16.81 | 0.71 | 3.72 | 0.93 | 5.36 | 12.22 | 35 | 2.3 |
Min. | 0.5 | 60 | 27.0 | 58.70 | 39.5 | 8.11 | 7.5 | 2.8 | 2.8 | 7.38 | 0.09 | 0.55 | Nd | 1.19 | 1.15 | 9 | 1.1 |
Average | 1.8 | 111.7 | 28.0 | 74.0 | 51.8 | 8.43 | 8.5 | 3.7 | 3.7 | 11.91 | 0.48 | 1.95 | 0.57 | 3.00 | 4.06 | 25 | 1.74 |
SD | 108.4 | 51.5 | 0.9 | 8.9 | 7.3 | 0.2 | 0.5 | 0.3 | 0.7 | 3.3 | 0.2 | 1.2 | 0.3 | 1.3 | 4.4 | 7.7 | 0.4 |
prevailed in the area of station 12 is a result of the isolation of this area in addition to the high rate of evaporation. The minimum value (0.3‰) was measured at station 11. The water salinity at different areas revealed that the salinity decreased in the order: Bardaweel > El-Manzalah > Mariout > El-Brullus > Edku depending on the amount of drainage waters. Conductivity showed a similar trend as salinity during the study period. The maximum EC value (93.10 mS/cm) was observed at station 12 of Lake El-Bardaweel, while the lowest one (1.07 mS/cm) was measured at station 11 of Lake El-Brullus. The water of the Nile delta Lakes lies in alkaline side (Tables 2(a)-(e)). pH values ranged between 7.26 - 8.92. Station 3 of Lake Maruit sustained the lowest pH value, while station 3 of Lake El-Brullus maintained the maximum value. The average values of pH at different areas decreased in the order: El-Brullus > Edku > El-Bardaweel > El-Manzalah > Mariout. The obtained results of dissolved oxygen showed a complete depletion at station 3 of Lake Maruit, while the maximum of 18.2 mg/l was observed at station 9 of Lake Edku. The average values of DO at different areas decreased in the order: Edku > El-Bardaweel> El-Brullus > El-Manzalah> Mariout. The obtained values of biological oxygen demand (BOD) were varied in a wide range. The minimum value (2.8 mg/l) was measured at station 8 of lake El-Bar- daweel, while the maximum of 41.5 mg/l was measured at station 3 of lake Maruit. The average values of BOD at different areas revealed that the BOD decreased in the order: Mariout > El-Manzalah > Edku > El-Brullus > El-Bardaweel. The observed oxidizable organic matter varied also in a wide range between different Lakes (Tables 2(a)-(e)). The maximum value (63.6 mgO2/l) was measured at station 3 of Lake Mariout and the minimum (2.8 mgO2/l) was observed at station 8 of Lake El-Bardaweel. The average values of OOM at different areas decreased in the order: Mariout > El-Burullus > El-Manzalah > Edku > El-Bardaweel revealing high load of anthropogenic pollutants, i.e. agricultural, sewage and industrial in the lake Mariout [
The concentrations of total Sn (T-Sn) in sediments are shown in Tables 2(a)-(e). The results show that concentrations of T-Sn are scattered in the ranges of 15.48 - 26.55 µg/g dry wt, 12.06 - 24.41 µg/g dry wt, 14.4 - 32.22 µg/g dry wt, 17.91 - 26.64 µg/g dry wt and 7.38 - 16.81 µg/g dry wt for lakes Mariout, Edku, El-Brullus, El- Manzallah and El-Bardaweel, respectively. The highest average value of T-Sn was measured in sediments of Lake El-Brullus due shipping activities, sewage and industrial wastes from different drains. A negative correlation (r = −0.67 at p > 0.001) was found between T-Sn and salinity (
Tributyl tin (TBT) concentrations in sediments (Tables 2(a)-(e)) varied widely depending on the location and ranged from 0.14 to 2.29 μg/g Sn dry wt , from 1.27 to 4.88 μg/g Sn dry wt, from 0.16 to 1.35 μg/g Sn dry wt, from 0.98 to 4.61 μg/g Sn dry wt; and from 0.55 to 3.72 μg/g Sn dry wt for lakes Mariout; Edku; El-Brullus; El-Manzallah and El-Bardaweel, respectively. It is clear that TBT is the predominant species of OTC in all lakes except lake El-Brullus (Tables 2(a)-(e)) with percentage to total OTC ranged from 32% to 100%. The present study cleared out that concentrations of TBT in investigated sediments are higher than that of its degradation where the ratio of TBT/DBT > 1 in most samples. This indicates that TBT is still being introduced into the aquatic environment, most probably due to the use of antifouling paints.
The highest average values of TBT are measured in Lake Edku and El-Manzallah. The highest TBT concentrations measured in Lake Edku are probably due to the presence of thick layer of green phytoplankton and herbicides covering the surface of most investigated areas. The presence of such thick layer inhibits transmittance of UV and consequently decreasing photo-degradation process for TBT compounds compared to other lakes. Intensive fishing activities in the lake are leading to historical deposition of TBT compounds. Moreover, the spreading of large number of islands through the lake that helps in increasing human activities as a main anthropogenic source of TBT compounds. The three large drains El-Barseik, Edku and El-Boseily, in addition to a number of sub-drains connected with main drains are acting as additional sources of pollution with TBT compounds (Tables 2(a)-(e)). On the other hand, higher concentrations of TBT in sediments of lake El-Manzallah are resulted from large number of boats and intensive fishing activities, the water transparency is generally low at lake El-Manzallah (0.45 m) due to the continuous disturbance of the mud bottom by wind action (Tables 2(a)-(e)) revealing relatively low photo-degradation of TBT by sunlight. Impacts of different drains, i.e. Hadous, Ramsisand and Bahr El-Baqar that discharge large quantities of industrial, agricultural and domestic wastes are also considered.
The Australian sediment quality guidelines for TBT are 5 ng/g and 70 ng/g for low and high trigger values [
Area | DBT | TBT | TPhT | References |
---|---|---|---|---|
Egyptian Northern Lakes Sanricu Coast, Japan North East Coast, Spain Barcelona Harbor, Spain Aegean Sea, Turkey River Thames, UK North West Coast, Spain Cadiz Coast, Spain German North Sea and Baltic Sea Marinas Scheldt Estuary, The Netherlands Spanish Northeastern Coast Mediterranean Sea, Egypt Suez Gulf, Egypt | 0.05 - 3.32 l - 3.4 0.047 - 3.519 - - 0.012 - 0.219 0.0005 - 0.357 - - - - Nd - 2.16 0.07 - 2.27 | 0.16 - 4.61 0.002 - 14 0.051 - 7.673 0.098 - 4.702 Nd - 3.008 - - - - - - Nd - 8.55 0.35 - 0.77 | - - - - - - 0.015 - 0.940 0.015 - 3.540 0.007 - 0.012 12.27 - - | Present study [ |
DBT concentrations in sediments of the northern lakes varied widely and ranged from 0.05 to 2.11 μg/g Sn dry wt, from 0.64 to 2.81 μg/g Sn dry wt, from 0.11 to 3.32 μg/g Sn dry wt, from 0.52 to 1.67 μg/g Sn dry wt and from 0.09 to 0.71 μg/g Sn dry wt for lakes Mariout, Edku, El-Brullus, El-Manzallah, and El-Bardaweel, respectively. Presence of DBT at most sampled sites of lakes indicates that there is an important photochemical and biological degradation process on these sediments, together with its mobilization. This idea is confirmed by a relative higher abundance of DBT in sediments of lake El-Brullus (Tables 2(a)-(e)). TBT/DBT ratios are found >1 confirms also an active degradation process. However, this ratio may also indicate that either TBT inputs to Lake El-Brullus are older or that new inputs are absent or negligible than TBT degradation rate [
Comparing concentrations of DBT to those reported in literature (
TPhT in sediments of the northern lakes were not observed in most sediments and its concentrations ranged from Nd to 0.63 μg/g Sn dry wt, Nd to 0.81 μg/gSn dry wt, Nd to 3.96 μg/g Sn dry wt, Nd to 1.68 μg/g Sn dry wt, and Nd―0.93 μg/g Sn dry wt for lakes Mariout, Edku, El-Brullus, El-Manzallah and El-Bardaweel; respectively. Variations occurring among lakes depending on changes in chemical and physical characteristics of each lake, various sources of pollutants, degradation process and drains run-off. It is clear from Tables 2(a)-(e) that TphT is the predominant species in lake El-Brullus. It exhibited concentrations of TPhT range from Nd to 3.96 μg/g Sn dry wt. This could be attributed to the presence of several numbers of drains, channels and sub-drains, i.e. drain west El-Burullus, El-Hoksa, Terra and Brimbal canal discharging a huge amounts of agriculture wastes containing TPhT which is used as fungicide in agriculture purposes into the lake. TPhT concentrations are decreasing in the following order: El-Burullus > (2.59 μg/g Sn) > El-Manzallah (1.30 μg/g Sn) > Edku (0.75 μg/g Sn) > El-Bardaweel (0.57 μg/g Sn) > Mariout (0.40 µg μg/g Sn). Although a significant positive correlation (r = 0.67, p = 0.001) was found between DBT and TPhT, a weak negative correlation (r = −0.37, p = 0.001) was found between TBT and TPhT in sediments from northern lakes revealing different sources of pollution (
Parameters | Depth | Trans | Temp | EC | Salinity | pH | DO | OOM | BOD | DBT | TBT | TPhT |
---|---|---|---|---|---|---|---|---|---|---|---|---|
T-Sn | −0.31 | −0.55 | 0.43 | −0.66 | −0.67 | 0.29 | −0.05 | 0.37 | 0.12 | 0.45 | 0.07 | 0.38 |
DBT | −0.15 | −0.37 | 0.22 | −0.48 | −0.48 | 0.19 | 0.09 | 0.26 | 0.06 | −0.03 | 0.67 | |
TBT | −0.05 | 0.10 | −0.05 | 0.10 | 0.09 | 0.17 | 0.13 | −0.29 | −0.21 | −0.37 | ||
TPhT | 0.15 | 0.38 | 0.44 | −0.41 | −0.41 | 0.22 | −0.24 | 0.37 | −0.12 |
Comparing concentrations of TphT to that reported in the Literature (
The results in Tables 2(a)-(e) show that the highest average concentrations of total OTC were found in sediments of lake El-Manzallah (5.06), lake Edku (4.54), Lake El-Brullus (4.53) compared to Lake El-Bardaweel (3.0) and Lake Mariout (2.61) depending on the pollution sources. A percentage of total OTC to total tin concentration were ranged from 13% to 25% in sediments of the northern lakes. Lake Edku (24%), lake El-Brullus (19%), lake El-Manzallah (24%) and Lake El-Bardaweel (25%) were remarkably higher than Lake Mariout (13%) as shown in Tables 2(a)-(e). Significant levels of OTC were found in sediments of these lakes.
Results of the present investigation show that the degree of pollution in the northern lakes is influenced by industrial and sewage discharges. Concentrations found of TBT, DBT and TPhT in the sediments are a consequence of the historical use of OTC, mainly related to fishing activities in the lakes. Regular monitoring of OTC pollution to assess hazardous effects for the aquatic life is recommended.
OTCs in the five northern lakes revealed some highly localized areas of contamination that were severe enough to cause harmful effects on marine flora and fauna. Levels of contamination are depending mainly on the shipping activity, changes in chemical and physical characteristics of each lake, various sources of pollutants, degradation process and drains run-off. No correlation between TBT and DBT in sediments demonstrated that both compounds did not come from the same source (i.e. antifouling paints), indicating their different deposition, and confirming the slow rate of degradation in sediments. The results concluded that sediments of the Egyptian northern lakes were highly to grossly contaminate by TBT. Among the five northern lakes, Lake El-Brullus shows the maximum concentration of ∑OT. The high input of OTC particularly in sediments, overrides any removal by degradation pathway. Up to the present, no studies on biological effects have been done in this area. The present research concluded that TBT levels suggested that stringent legislative measures were needed to curb the usage of these contaminants in marine paints. Otherwise, OTC would have detrimental effect on our marine resources and ecosystem, which probably could not reverse.