Chemical and biological assessment for Egyptian surface freshwater environment with reference to human activities.

The Egyptian freshwater was assessed in the River Nile, branches, main canals and certain drainages in eight Governorates, over eight successive seasons starting from spring 2008. Chemical assessment was made through ten parameters and the biological one was made through macro-invertebrates information. Results showed that means of Cd, Pb, Cu, Hg, Mn, Fe, Ni, Na, K & Ca varied in watercourses seasonally within somewhat narrow ranges, which may exceed the level of concern but with some elevations in branches, Rayahs and canals during certain seasons. Sites showed chemical levels over the permissible one or those gain total points < or = 6.3 according to the biological assessment indicate that very poor habitat or those of Hilsenhoff Biotic Index (HBI) equal to 7-10 indicate that organic pollution were observed in all the studied watercourses reflecting hazard non point source pollution. Damietta branch in the region of Damietta city characterized with elevations in the concentration of most chemicals examined. The percentages of sites that showed chemical level over the permissible one were 70.56% for K, 54.08% for Cu, 50.08% for Na, 22.08% for Cd, 11.36% for Fe, 5.6% for Pb, 1.92% for Ni, 1.12% for Mn, 0.16% for Ca and at last 0.0736% for Hg. The biological assessment was more able to define more polluted sites than did the chemical one. Human activity data revealed that each of the drains, Giza and Qalyubia canals showed the highest item conduction (animal or plant waste, macroscopic pollution and presence of bridges or barriers) and this was co parallel with their highest pollution recordation.

Semi field trials to control Biomphalaria alexandrina by different modes of exposure to certain plant and chemical molluscicides.

Semi-field trials were carried out in Snail Research Station under simulated natural conditions to evaluate different modes of exposure to Anagallis arvensis and Calendula micrantha as plant molluscicides and bayluscide and copper sulphate as chemical molluscicides. Firstly, B. alexandrina were exposed to the tested molluscicides alone and in addition to two densities of aquatic plants. No apparent effect of aquatic plants on the activity of both plant and chemical molluscicides, this may be due that the two densities of the aquatic plants used were insufficient to interfere with the molluscicides action. Secondly, snails were pre-exposed to three sub-lethal concentrations of the plant molluscicides for 24h then to three concentrations of the chemical molluscicides and vice versa. The results indicate that the pre-exposure increases the snail mortality significantly in all treatments of bayluscide and A. arvensis (except in the highest concentration when the snails firstly exposed to bayluscide then to A. arvensis, where the two compared treatment showed 100%) and in all treatments of bayluscide and C. micrantha. Also, in one treatment of copper sulphate and A. arvensis (in the highest concentration when the snails firstly exposed to A. arvensis then to copper sulphate) and in three treatments of copper sulphate and C. micrantha, (in least and moderate concentrations when snails firstly exposed to C. micrantha then to copper sulphate and in the highest concentration when snails firstly exposed to copper sulphate then to C. micrantha). Thirdly, snails were exposed to mixtures of six different ratios of bayluscide and each of A. arvensis and C. micrantha. The results indicated that the snail mortality increased significantly only in the first treatment of bayluscide and A. arvensis mixtures and in treatment number 6 of bayluscide and C. micrantha.

The molluscicidal efficacy of three products against Biomphalaria alexandrina and Lymnaea natalensis.

Toxicity of three local formulated products, Sol E.C (mineral oil), Sisi-6 (surfactant) and Castor bean oil E.C (plant oil) were tested against Biomphalaria alexandrina and Lymnaea natalensis, in two water sources. Results indicated that in dechlorinated water after 24 hr exposure, castor bean oil was the most toxic product against the snails, followed by Sisi-6 and sol (E.C) with LC90 of 250 ppm and 8 ppm against B. alexandrina and L. natalensis, respectively. When Nile water was used after 6 hr. exposure, a high concentration of castor bean oil (4 LC90) did not achieve 100% mortality of the snails. A 100% mortality was achieved by 2 LC90 of Sisi-6 with Nile water. On the other hand, caster bean oil was more fatal to eggs of the snails (LC90=660 ppm) than the other two products. In general, L. natalensis was more susceptible to the experimental products than B. alexandrina.