Persistent organochlorines can accumulate in food chains. This bioaccumulation has been well documented with the pesticide dichlorodiphenyltrichloroethane (DDT) 123. Organochlorine pesticides are washed into the aquatic ecosystem by water runoff and soil erosion. Pesticides can also drift during application and contaminate aquatic systems samples 45. Wild birds and mammals are damaged by pesticides and these animals are bio indicator species 678. Organophosphate pesticides have been the insecticides most commonly used by professional pest control bodies 9. Chlorpyrifos (O,O - diethyl O -(3,5,6-trichloro-2-pyridinyl) phosphorothioate; CAS No. 2921-88-2; CPY). CPY is a widely used organophosphorus insecticide that is available in a granular formulation for treatment in soil 10. Pesticides are used to control wide range of pests including Mosquitoes. Mosquito borne diseases infect over 7000000 people every year globally, being prevalent in more than 100 countries across the world 11121314. WHO has declared mosquitoes as “public enemy number one”. Worldwide, malaria causes one to two million deaths annually. Lymphatic filariasis has been reported to affect at million people in 73 countries including Africa and Pacific Islands 15. Mosquitoes serve as vectors of life threatening diseases such as malaria 16125. The current study aimed to monitor water pollutants (persistent organic, minerals and pesticides) and to assess the potential adverse effect of polluted water on the bio indicator insects; mosquitoes. The aim of the current study was to Screen the pollutants, water quality parameters and mineral content in irrigation water from El Mahmodia stream, El-Beheira Governorate. Determine the adverse effects of some the detected-pesticides (Chlorpyrifos) on the larvae of second instar Culex mosquito larvae as a bio-indicator. Water requirements of different sectors increase rapidly with time due to rapid population increase, ambitious agricultural expansion 17. Quality of Nile water worsened dramatically in the past few years 1823. It is anticipated that the dilution capacity of the River Nile system will diminish as the program to expand irrigated agriculture moves forward and the growth in industrial capacity increases the volume of pollutants discharged into the Nile 19125. The major pollution sources of Nile and main canals are effluents from agricultural drains and treated or partially treated industrial and municipal wastewaters 201314.

There are 76 drains discharging drainage water into Nile system with annual volume of about the half of the total drainage water 21. Impact of this drainage water on Nile quality has been reported by several authors 18. Statistics indicate that over one billion of the world population lack access to safe water, and nearly two billion lack safe sanitation worldwide 2278. A growing number of water related diseases such as diarrhea and lymphatic filariasis are responsible for the major health problems in the majority of rural and urban residents 231314. The quantities and quality of wastewater from agricultural lands are highly variable. The most important pollutants found in runoff from agricultural areas are sediments, animal wastes, plant nutrients in addition to domestic wastes 23. Water pollution sources, has become of public interest. Natural events and anthropogenic influences can affect the aquatic environment in many ways 125. Discharge of partially treated, industrial and domestic wastewater, leaching of pesticides and residues of fertilizers are the factors that affect the quality of water 19.Water pollution occurs when a body of water is adversely affected due to it is unfitting for its intended use 24378.The aquatic environment is subjected to various types of pollutants which enter water bodies 252. Among the various pollutants, heavy metals are the most toxic, persistent and abundant pollutants that can accumulate in aquatic habitats 261314.

Trace metals such as Zn, Cu and Fe play biochemical role in the life processes of all aquatic plants and animals. In the Egyptian irrigation system, the main source of Cu and Pb are industrial wastes, while that of Cd is the phosphatic fertilizers 2723. The most anthropogenic sources of metals are industrial sources as paints and petroleum contamination 28125. The agricultural drainage water contains pesticides 231314. The physicochemical characteristics of the Nile water include temperature, turbidity, water electrical conductivity (EC), total suspended solids (TSS) and total dissolved solids (TDS), pH value, dissolved oxygen (DO), nutrients, biological oxygen demand (BOD), chemical oxygen demand (COD), total organic carbon (TOC), major anions and cations and heavy metals 278. There are more than half a million tons of unused in several developing and transitional countries 29. Obsolete pesticides have accumulated in almost every developing country or economy in transition over the past several decades 30. The FAO is recording the inventories of Latin America 3123. It is difficult to estimate the exact quantities of obsolete pesticides because many of the products are very old and documentation is often lacking 3278.

Chlorinated pesticides (OCPs) and polychlorinated biphenyls (PCBs) were routinely used in large quantities for agricultural and industrial purposes 3323. Insecticides overuse led to several ecological drawbacks over the past years 34. Mosquitoes of family Culicidae, are vectors for a number of mosquito borne infectious diseases 35 that are maintained in nature through the biological transmission by blood feeding mosquitoes to susceptible vertebrate hosts causing malaria and filariasis 36. Mosquitoes are a major public health threat as they play a vital role in transmitting serious human diseases to million people annually 37. Culex pipiens is a worldwide mosquito transmitting many dangerous diseases as filarial worms and avian malaria 38. With the emergence of C pipiens resistance to many insecticides, control is becoming more difficult 39. The control of mosquito is becoming challenging because climate change and global trade favor the spread of invasive mosquito species 40, and strongly increase the associated risk of vector borne diseases 41. Most strategies for mosquito control are based on the use of insecticides 42 and developing resistance 43. Treated populations can recover after application of the insecticide. Vector control is by far the most successful method for reducing incidences of mosquito borne diseases 6. The discovery of the subsequent development of organochlorines, organophosphates and pyrethroids suppressed natural product research, as the problem for insect control were thought be solved 4423^{7 8}.

Water samples were taken from El Mahmodia stream 31̊ 06̍ 16̎ N 30̊ 18̍ 52̎ E. Water samples (2.5 L) were collected in clean glass bottles at water surface and 50 cm below water surface. Water samples were collected during the period of September 2016 to August 2017 (samples were taken seasonally); 45. The four sites were chosen to represent different regions along El Mahmodia stream. Water samples were taken (about 20 cm) below the water surface to avoid floating matter. Determination of Zn, Cu, Fe, Mn, PO₄, NO₃, NH₄, HCO₃, K, Na, Ca, Cl, Pb and Cd in the streams water were carried out according to (APHA, 1995). Field instruments (pH and conductivity) were measured in situ 46. Water temperatures were measured in situ using a calibrated thermometer 46. Turbidity test determined by Turbidity meter type WTW TurpSS0 calibrated using 0, 10 and 1000 Unit (NTU) 46. Electric conductivity (EC); samples were measured at 25°C as a standard temperature using ATC bench electric conductivity meters, Jenway, model 4310 46. Total dissolved solids (TDS); samples were measured at 25°C as a standard temperature using ATC bench electric conductivity meters, Jenway, model 4310 46. Turbidity was measured using the Turbid meter WTW Turb model 550 46. The Dissolved oxygen (DO) was measured using WTW Model 315i electronics was used to determine the dissolved oxygen value 46. Biological oxygen demand (BOD) was determined using WTW-TS-type 606/4-i BOD 46. After digestion, COD is determined by using spectrophotometer PF-11 Viso Colour Model Nanocolour Macherey-Nagel (MN) 46. Ammonia (NH₃) measured using Kjeldahl closed system model Gerhardt Vabodest 10S according to 47. Nitrate (NO₃) was determined in water samples by using Kjeldhal closed system model Gerhardt Vabodest 10S according to 47. Chloride was determined by methods of 47. Carbonates and bicarbonates were determined by using the methods of 47. Calcium and magnesium were determined according to 46. Phosphate was determined according to 47 by using spectrophotometer Model 6405. Sodium was determined using Sherwood Flame Photometer Model 410 46. Potassium was determined using Sherwood Flame Photometer Model 410 46.

Heavy metal ions were measured by using the Atomic Absorption spectrophotometer Model THERMO SCIENTIFIC ICE 3000 series AAS with hollow cathode lamp for each element being measured (Cu, Pb, Zn, Cd and Fe) according to 48. Microbiological examination (MPN) was carried out according to 47, using Mac Conky broth w/Natural Red (HIMEDIA M007) medium.

GC-MS analysis of water: Extraction of water samples using Empore disc technology according to EPA 3535 49 with little modification was used to extract pesticide residues from water 49. Instrumentation analysis of pollutant residues in water Extracts of water (2 µl) were analyzed utilizing a GC-MS. The GC-MS was controlled by a computer system which has EI-MS libraries (Willey spectral library of more than 140000 compounds). The carrier gas was at a constant flow rate of 1.1 ml/min. The target compounds were identified by their full scan mass spectra and retention time using the total ion current as a monitor to give a Total Ion Chromatogram (TIC).

Physicochemical determination of water samples were collected in August 2017 from four locations repeats along El Mahmodia stream, Water samples were taken (about 20 cm) below the water surface to avoid floating matter. The Electrical Conductivity (Ec) was determined with a mean of 0.50 mg/l and ± 0.01 for SD (Table 1). From Figure 1, it is detected that the Electrical Conductivity has a significance differences (p <0.05). It was also noted that the mean of the pH was 7.68 mg/l, ±0.05 for SD (Table 3). The Total Dissolved Solids (TDS) recorded with a mean of 249 mg/l, SD was ±14.16. Turbidity Also recorded with the mean of 9.17 mg/l, SD of ±2.66 (Table 1 (.The Total Suspended Solids (TSS) recorded with a mean of 50 mg/l, SD was ±3.36, it is detected that the Total suspended solids has a significance differences (p <0.05).

The total solids (TS) were determined with the mean of 293.3mg/l, ±27.83 for SD. The Dissolved Oxygen (DO) detected with 4.35 mg/l for its mean, SD value was ±0.1 (Table 1 (.The mean the Biological Oxygen Demand (BOD) was 23.75 mg/l, ±2.5 for SD, the BOD has a significance differences (p <0.05(. It is detected also the Chemical Oxygen Demand (COD) with a mean of 24.75 mg/l SD value was ±3.86. The Microbiological examination (MPN) determined with 12075 mg/l for its mean ±3379.7 for SD (Table 1), it is detected with 49.91 mg/l for its mean, SD value was 0 (Table 2) (Figure 2)

The potassium (K) determined with 7.99 mg/l for mean value. The calcium (Ca) means detected with 31.8 mg/l, SD value was±4.54. 16.38 mg/l is the value of magnesium (Mg) mean which recorded, SD value was ±5.30 (Table 2). The chloride (Cl) mean was 56.40 mg/l, with SD ±3.28. The detectable mean of bicarbonate alkalinity (HCO₃) was 253.3 mg/l, with SD ±11.71 HCO₃, as shown that the HCO₃ has a significance differences (p <0.05(. Ammonia (NH₄) detected with a mean of 1.42 mg/l, SD value was ±0.93. NO₃ (Nitrate) mean value was 5.89 mg/l, with SD ±0.93. Phosphorus (PO₄) detected with 0.01 mg/l for its mean, SD value was ±0.004. Iron (Fe) detected with a mean value 0.65 mg/l, with SD ±0.24 (Table 2) Copper (Cu) detected with a mean of 10.91 mg/l, SD value was ±2.59. Manganese (Mn) detected with a mean value 0.09 mg/l, SD value was ±0.01. 0.002 mg/l was the mean value of cadmium (Cd), with SD ±0.001(Table 2).

Various physicochemical parameters like temperature, pH, DO, turbidity, BOD, nitrate, phosphate, TDS, and fecal coliform were determined by following the standard methods 46. As water temperature increases, the rate of chemical reactions increases. The temperature affects the rate of growth and life cycles of most aquatic organisms. It is known to influence the pH, alkalinity, and DO concentration in the water. Water temperatures along El Mahmodia stream did not show any significant difference (at p<0.05).The temperature of El Mahmodia stream is higher than the limited values 31°C as mentioned by Ali et al.55. The turbidity is derived from silt, clay, and sand particles, while organic turbidity is composed of planktonic organisms and detritus. In the present study, turbidity value was reported as 9.17 NTU. The increasing of turbidity values is referred to increasing of suspended materials will reduce light penetration and restrict plant growth and hence food resources and habitat for organisms. Results of t-test showed that there was a significant difference (p<0.05) between the different sites. The results of turbidity values exceeded the permissible limits of law and the guidelines of WHO 53, (5 NTU) for drinking water. The stream water is valid for drinking after treatment and for irrigation. Electrical Conductivity (EC); the electric conductivity of the El Mahmodia stream water was determined as 0.50 m S/cm. The EC increases in El Mahmodia stream due to increasing of the dissolved ions resulted from the human activities especially agriculture. The measured EC values were within the permissible limits of the water used for irrigation of agricultural crop lands (0.31–1.87 mS cm–1) 50.

The suspended particles are the main source of turbidity in water. In this study, the suspended solid concentration in waters a long El Mahmodia stream was reported as 51 mS/cm. In this study, the suspended solid concentrations in waters along El Mahmodia stream within the permissible limits of law 48/1982 (<100 mg/l). Total Dissolved Solids (TDS) concentration in water samples collected along El Mahmodia stream was 249 mg/l. The TDS show an increase in its values at all recommended sites. In irrigation water, the salinity hazard is related to the high values of TDS. The total dissolved salts along the El Mahmodia stream were less than 450 mg/l and there was no restriction on using it for some susceptible crops 56.Results of t-test showed that there was a significant difference (p<0.05) between different sites along El Mahmodia stream. Generally, all TDS values along the stream water were founded within the permissible limits of law 48/1982 (500 mg/l). The water stream receives fluxes of elements through natural processes by weathering of bed rocks. The basalts contain weak olivine and pyroxene minerals that are enriched in some elements such as Na, Li, Fe, Mn and Mg in addition to Si. These elements transport with water to increase the TDS of the streams, in contrast to the White Nile water that flows from the equatorial highlands enriched mainly in granites. The TDS of Lake Tana, source of the Blue Nile, varies from 50 to 138 mg/l with an average of 103 mg/l 57. The major ions represented by TDS have been also significantly increased by anthropogenic contaminations. The average salinity of the Nile River at Cairo ranges from 175 to 680 mg/l with an average of 261 mg/l 58. The pH is an important limiting chemical factor for aquatic life which may affect the aquatic organisms’ biochemical reactions. The severe changes of pH of the water may cause a harmful or even lethal effect on aquatic organisms and consequently affect the animal and human health. Water streams have pH ranging, between 6 and 9, and any changes in this range in pH can affect life forms in aquatic systems 59. In the present study the pH of the stream water was 7.68. The lowering of pH value of El Mahmodia stream that appear from drainage water may be attributed to greater input of organic matter where the high organic matter led to decrease in pH values 52. The increase of pH values at the streams water is a result of photosynthesis 23125. The unpolluted streams normally show a near neutral or slightly alkaline pH. The stream has pH values within the permissible limits of law 48/1982 (7.94–8.50) and are not harmful for aquatic life and irrigation, where the pH of most natural water ranges between 6 and 8.5 51. The range of normal pH for irrigation water is from 6.5 to 8.4 50. Dissolved oxygen is essential for aquatic life specially fish and other aquatic species require oxygen. Dissolved oxygen allows aerobic bacteria to degrade a wide variety of organic matter and oxidize inorganic salts. The concentration of DO along the stream was 4.35 (Table 1). The decrease of DO may be attributed to the consumption of DO by respiration of phytoplankton, aquatic plants, and fish, and decay of the aerobic bacteria 60. Dissolved oxygen value was greatly affected by pollution load where the lowest DO is recorded at all sites, and the excessive effluent discharge of pollution with high load of organic matter into the two stream leads to deoxygenating of water. Waste discharges that are characterized by high inorganic matter and nutrients can lead to decreases in DO concentrations as a result of the increased microbial activity (respiration) occurring during the degradation of the organic matter 612362 Radwan, 2014, 2016, 2018).The concentration of dissolved oxygen (DO) in stream water was below the permitted limit in Egypt >5 (Egyptian Law 48/1982).

Oxygen concentration in water is very important for fish. It is worth mentioning that unpolluted waters typically have BOD values of 2 mg/l or less, whereas those receiving wastewater may have values up to 10 mg/l or more, particularly near to the point of wastewater discharge 52. BOD in this study, recorded with increased Values 23.75 mg/l at El Mahmodia stream. There was an increase in BOD concentration at stream water (Table 1). The values of BOD exceeded the desirable limits of (Egyptian Law 48/1982) 63 which was<6-10 mg/l. The high BOD values indicate excessive export of biodegradable organic matter increasing the de-oxygenation of water to the level where fish and other aquatic life cannot survive 651251314. The COD is widely used as a measure of the susceptibility to oxidation of the organic and inorganic materials present in water bodies and in the effluents resulting from sewage and industrial plants 6651278. The COD in our study was 24.75 mg/l. The values of COD exceeded the desirable limits of 63 which was<10-15 mg/l. The COD high values indicate excessive export of biodegradable organic matter increasing the de-oxygenation of water to the level where fish and other aquatic life cannot survive 65. Fecal pollution is a major concern for many rivers where it can originate from human sources and nonhuman sources. Fecal coliform can be used as indicator for water pollution and hence for water quality measure 67. The fecal coliform was recorded with 12075mg/l. The high value of MPN, where the high levels of organic pollution exist, the values of MPN exceeded the desirable limits of (Egyptian Law 48/1982) which was 5000/100cm³. The increase of nutrients, ammonia and phosphates, is generally indicative of diffuse pollution (agriculture and septic tanks) and industrial wastewater treatment plants. Nutrients are considered as essential elements needed to the growth and reproduction of plants and animals. Nitrogen compounds occur as nitrate, nitrite, ammonia and organic nitrogen. Ammonia was measured in water samples collected from stream with 5.89 mg/l. Its concentrations were recorded above the detection limit of > 0.01 mg/l. Natural sources of nitrate in surface waters are the interaction with igneous rocks, land drainage, plant and animal debris 562362. Determination of nitrate and nitrite in rivers gives a general indication of the nutrient status and level of organic pollution. The decrease of nitrate along the stream water may be related to the presence of denitrifying bacteria or related to biological uptake. In the study area along the El Mahmodia stream, the nitrate concentrations were found to be within the permissible limits of law 48/1982 (not exceed 45 mg/l). As the World Health Organization 68 recommended maximum limit for drinking water is 10 mg/l NO₃-N, waters with higher nitrate concentrations represent a significant health risk. Comparing the results of nitrate of the stream water with FAO guidelines (5 mg/l N), it was found that there is a restriction on its use for sensitive crops.

The ammonia NH₃ concentration in stream water was 1.42mg/l, the concentrations exceed the desirable Limits <0.5 (Egyptian Law (48/1982). These high values may be attributed to the increased de nitrification in water, when the oxygen concentration is low. The total alkalinity (HCO₃ concentrations) in water samples was 253.3 mg/l. The concentrations of HCO₃ concentrations was high that can be attributed to the decomposition in the dead phytoplankton leading to the release of CO₂ dissolving to water in the form of HCO₃. The concentration of HCO₃ measured at El Mahmodia stream exceeds the permissible limits of Egyptian Law (48/1982) which was<200 mg/l. Phosphorus is an essential nutrient element for living organisms and exists in water bodies as both dissolved and particulate forms. Natural sources of phosphorus are mainly derived from weathering processes of phosphorus bearing rocks and the decomposition of organic matter 522362. Phosphorus concentration in stream water was 0.01 mg/l. The stream has Total Phosphorus values within the permissible limits of law 48/1982 (1 mg/l). The most common major cations in the study area are Ca²⁺, Na⁺, Mg²⁺, and K⁺. Calcium concentration along the study area of El Mahmodia stream was 31.8 mg/l. It is the major cation of the Nile water, which probably comes mainly from the rocks 69. The mean average of sodium concentration was 49.91 mg/l. The mean results of sodium concentration level is below the permissible limits of the WHO 51 which was 200 mg/l. magnesium concentration was 16.38 mg /l, it is below the permissible limits of the 53 which was 100 mg/l. The potassium cation occurs in high concentration (higher than 6 mg/l) it recorded at 7.99 mg/l at stream water. The K minerals are below the permissible limits of the BIS 53, which was 12 mg/l. The major anion in the Nile water is the chloride (Cl). The concentration of the anion in stream water was 56.40 mg/l, it is below the permissible limits of law 48 (less than 200 mg/l) and the guidelines of WHO 51.

The term “heavy metal” refers to any metal and metalloid element that has a relatively high density ranging from 3.5 to 7 g/cm3 and is toxic or poisonous at low concentrations 70131478. They include mercury (Hg), cadmium (Cd), arsenic (As), chromium (Cr), thallium (Tl), zinc (Zn), nickel (Ni), copper (Cu), and lead (Pb). It is often used as a group name for metals and metalloids that have been associated with contamination. Heavy metals are natural constituents of the earth’s crust 71. In Egypt and other developing countries, where environmental protection laws have not been enforced, industrial and domestic wastes are dumped randomly into water bodies 72125. Five heavy metal elements were measured in this study. The low concentration values of the heavy metals in the stream water are due to their deposition with sediments on the stream’s bottom 73. The cadmium concentration in the stream water was 0.002 mg/l and this concentration within the allowable limits according to WHO 51, which was (< 0.003mg/l). Lead concentration in the stream water along the study areas was neutral (Table 2). Iron (Fe) is the third most abundant metal in the earth’s crust after silicon and aluminum. In the study area, the mean concentration level of Fe was 0.65 mg/l. The concentrations of Fe are within the permissible limits of law 48/1982 (<1 mg/l) and the guideline of WHO 51, which is <1 mg/l. The major sources of manganese (Mn) are ferromanganese production and municipal wastewater. The major sources for manganese in air and water are iron and steel manufacturing and the burning of diesel fuel in the motor cars 231314. The truck mounted fogging machine which are used by farmers in El Mahmodia stream could be a reason for Mn level in El Mahmodia stream water. Along the study area at El Mahmodia stream, the manganese concentration was 0.09 mg/l. The results of manganese were agreed within the permissible limits of law 48/1982 (<0.5 mg/l) and the guideline of WHO 51 is (<0.5 mg/l). The primary sources are domestic wastewater and atmospheric deposition. The high levels of Cu in water can be attributed to industrial and agricultural discharge 56. Along the study area in El Mahmodia stream, the copper concentration was 10.91 mg/l. This may be attributed to the huge amounts of raw sewage, agricultural and industrial wastewater discharged into the stream 74. They are above the permissible limits of law 48/1982 (<1.0 mg/l), the values of the measured metal Cu were recorded at El Mahmodia stream. GC–MS analysis of El Mahmodia stream water showed the presence of various organic chemicals, insecticide at different Rts identified using NIST mass spectral library. The peaks were recorded at Rt 5.37, 5.65, 6.1, 6.3, 6.41, 6.57, 7.03, 7.13, 7.28 (Detected compounds repeated in the four seasons) which corresponded to the presence of Decamethyl cyclo pentasiloxane, 1-(2-Acetoxyethyl)-3,6-diazahomoadamantan-9-one oxime, Nonadecane, 2',6'-Dihydroxyacetophenone, bis(trimethylsilyl) ether,4H-1-Benzopyran-4-one,2-(3,4-dimethoxyphenyl)-3,7-dimethoxy-,11,16-Bis(acetyloxy)-3,20-dioxopregn-4-en-21-yl acetate, 9,12-Octadecadienoic acid (Z,Z)-, 2,3-bis^{(trimethylsilyl)oxy}propyl ester, m-Dioxane, 5-(hexadecyloxy)-2-pentadecyl-, trans-, Dodecamethylcyclohexasiloxane, 2-(9-Borabicyclo^3.3.1non-9-yloxy)-3-(2 phenyl non-9-yloxy)ethyl]sulfanyl)propyl ether, respectively based on the match with NIST library.

Most of the organic pollutants detected at the peaks in GC–MS data analysis were identified as endocrine disrupting phthalate esters, fatty acids, phenolic acids, carcinogens, and aquatic toxicants, plasticisers, which are classified as “priority pollutants” due to their severe toxicity in living being 752362. Phthalates such as Phthalic acid, butyl tetradecyl ester, Phthalic acid, octadecyl ester Phthalic acid, butyl 2-ethylbutyl ester, Phthalic acid, di (2-propylpentyl) discharged along with industrial wastewaters cause water pollution and disturb the ecology of the receiving water bodies by creating serious toxicity to aquatic organisms, such as fishes, as result of bioaccumulation and thus cause toxic effects 76. Phthalates also are reported to cause endocrine disruption in humans and animals upon long term exposure 75. Phthalic acid is used in industry has been reported to cause mutagenicity, developmental toxicity, and reproductive toxicity in animals 77.

Dihydroxybenzoic acid might be raised in El Mahmodia stream water as a key metabolite of biodegradation of polyaromatic hydrocarbons (PAHs) during wastewater treatment 78. 2,6-Dihydroxybenzoic has been reported as using in blending and formulating a variety of personal care products including shampoos, and deodorants and as a solvent in commercial dry cleaning products and industrial cleaning fluids 79. Aquatic toxicants reduce the algal growth in the aquatic ecosystem and thereby reduce photosynthesis and ultimately disturb the ecological functioning of receiving water bodies 801314. Fatty acids (n-Hexadecanoic acid, Hexnedioic acid, trans-9- octadecanoic acid) might have originated in during the industry Benzeneacetonitrile, α-4methylene]-4-nitro-, 1,2-Benzenedicarboxylic acid, butyl phenylmethyl ester, Benzeneacetonitrile, α-[4-(dimethylamino)-2, 5-dimethoxyphenyl]methylene]-4-nitro-, from other Benzyl compounds are considered to be moderately aquatic toxicant and poses moderate to low toxicity to aquatic animals, such as fishes, and also is listed as a Group 2A carcinogen [81, 18]. The major pollution sources of Nile and main canals are effluents from agricultural drains and treated or partially treated industrial and municipal waste waters [82, 7, 8]. The drainage water contains dissolved salts which washed from agricultural lands as well as residues of pesticides and fertilizers, at the end these pesticides collected in El Mahmodia stream water, causing severe damage to it. Impact of the drainage water on Nile quality has been reported by Abdel-Dayem etal. 18; Radwan et al.78. In El Mahmodia stream drainage water mixed with drinking water due to human activities along the stream, there is a large amount of organochlorine pesticides detected in the stream water samples such as Dieldrin 8384. There is no access waste water treatment in Abo Homes rural areas, 20% of Egyptian villages have inadequate potable water 85. In Egypt, water supply and sewage services are not implemented simultaneously. In the rural areas, where half of the population lives, 90% of the people have no access to waste water treatment facilities 86871314. The aquatic environment is subjected to various types of pollutants which enter water bodies 88125.

It is estimated that the total amount of reused treated wastewater in Egypt was about 1.4 billion m3 in 2000 89. Industrial waste water is considered the second of the main sources of Nile water pollution. There are about 129 factories discharging their waste water into the River Nile system. Effluent wastewater is often partially treated 90. Major pollutants in agricultural drains are salts, nutrients, pesticide residues, toxic organic and inorganic pollutants 91. The persistence of the organochlorine compounds and their metabolites, which are often more toxic than the original compound, is dependent on environmental conditions 9293. Toxic substances such as heavy metals and organic micro pollutants occur due to the mixing of domestic with industrial and commercial activities 91. Organochlorines (OCs) are a generic term for pesticides containing chlorine; however, the term is commonly used to refer to the older persistent materials, including aldrin, BHC, chlordane, DDT, dieldrin, heptachlor, lindane, or toxaphene. Most have now been deregistered or their use has been severely restricted.The present results of winter season showed that the significant effect of season on water samples in El Mahmodia stream comparing with summer season data of Azab et al. who reported that in summer season, organochlorines were significantly higher in water samples.

In the present study, bioassays were carried out to evaluate the insecticidal concentration of chlorpyrifos on the second instar Culex larvae. Surveys in Egypt date back to 1903. According to these surveys eighteen culicine and eleven anopheline species have been encountered in the different parts of Egypt. Culex pipiens, the main filariasis vector in Egypt. Published field and laboratory studies with mosquito control pesticides have concentrated on differential effects with mosquito larvae. The exposure time has an important effect on the values of LC₅₀ in this study. In most cases, the LC₅₀ values had synergistic interactions with time; thus, it increased after 48h of exposure when compared to 24 h of exposure (Table 3). Very high concentrations of the Chloropyrifos led to high mortality rates. The LC₅₀ of Chloropyrifos insecticide in the case of Culexpipnes was 24.52 ppm after 24h, and increased to 755.65 ppm after 48h. The lower value was 14.78 ppm after 24h which also increased to 258.10 ppm after 48 h., the higher value of LC₅₀ was 45.6576 ppm after 24h and the same value became 5485.96 ppm after 48h. The LC₂₅ of Chloropyrifos insecticide was detected as 2.51 ppm after the first 24h and measured at 72.37 ppm after the second 48h.

The mean level of physicochemical parameters and heavy metals as Turbidity, BOD, COD, NH₄, HCO₃, MPN, Cu and physicochemical parameters which determined showed an increase in its values compared to the standard safety criteria of the Egyptian Law (48/1982), the guideline of WHO 51 and FAO 50. In El Beheira Governorate, pesticides are used along a large scale. Organochlorine and organophosphate are persistent pesticides which leave residues in drinking water that remain for days to many years.

Organochlorine pesticides, prohibited since the early 1980s, are still detectable in the environment. Organophosphates are found in high rate in the stream, Chloropyrifos is an Organophosphate pesticides found at concentration of 0.09 m/l in the stream water. Effect of the exposure time of Chloropyrifos insecticide on the LC₅₀, LC₂₅ and LC₉₅ values had a synergistic interactions with time as it increased after 48h of exposure when compared to 24 h of exposure. The 0.09 ppm concentration of Chloropyrifos had no effect on the second instar Culex larvae, as there is no mortality. Also there is no effect on mosquito mortality after 72h and 96h of exposure to the detected concentration of Chloropyrifos insecticide.

There is an important need for Egyptian agriculture ministry to reduce the numbers and quantities of pesticides used in the agriculture sector. It is clear that the main challenge for the sustainability of water resources is the control of water pollution. The Ministry of the Environment in Egypt is observing the enforcement of the legislation regarding the treatment of industrial and domestic wastewater. It is also advocating organic farming and limiting the use of chemical fertilizers and pesticides to reduce water pollution. Improving the quality of drainage water especially in the main drains.