الفهرس 
AcknowledgementOnly 14 pages are availabe for public view
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Abstract
This study was carried out to investigate the effect of some hydrobiological factors and certain\common wate~ pollutants on the acute toxicity of copper sulfate and ~yluscide against Biomphalaria alexandrina and Bulinus truncatus snails. pH, temperature, salinity, fauna and flora were chosen representing the hydrobiological factors, while ammonia and pollution by sewage representing water pollutants. The experiments performed included: 1- Determination of the effect of pH, temperature, salinity, ammonia and pollution by sewage on the survival of !!. alexandrine. and B.truncatus after various periods of exposure. from the above experiments, the normal tole ranee range for both snail species \~s determined, this range was used for the following toxicity bioassays. 2- Determination of the Lc50 values for the chosen mollusc1cides after various periods of exposure (24 - 96 bra) a.gainst the e.dul t snails in dechlorinated tap water (control) . 3- Studying the influence of’ eaoh individual factor on the previously determined L050 values of’ the tested molluscioid.es. .. 4- Studying the influence of some organisms in the fauna . ~ J (Daphnia ]2ulex, Physa acuta and Tilapia. ]2011 tica) and flora. (Spirogyr~, ~V!nna gj.bba and Ceratophylll.lnl demersum) on the previously determined molluscicides toxic i ty. Under the influence of a certe.in factor, when the L050 value for the molluscicide is higher than the control value (in dechlorinated tap water), this indicates protec tion or decreased toxicity. On the other hand, values < below that of the control means potentiation or increased toxici ty. The results obtained in the present study showed: 1- The LC50 values of copper sulfate and Bayluscide for B.truncatus were lower than that for B.aleY~ndrina . This means that there is a good correlation between the toxic:t.ty of the compound and the snail species. 2- Bayluscide was found to be more potent toxicant tlmn copper sulfate against the two snail species as the mode of action of Bayluscide is different from that of copper sulfate. 3- It \’las also found that, there is a rapid decrease in the amount of each compound required to kill 50 of both snail species with increasing time of exposure from 24 - 96 hom.s. 4- The two sna:i.l species could live in pH ranging from 4 to 10 up to seven gays, but they were killed in pH less than 4 and more than 10. It was also found that, snails have the ability to change the harmfUl pH of acidity (pH 5) or high alkalinity (pH 10) to become after 6 days between 8.3 - 8.7 which is considered the preferable pH for snails. It is suggested that snails may alter the unfavourable pH by removing or adding some substances from their excretory system. 5- For short exposure time (24 hrs) copper sulfa te was ineffective at high alkaline pH (9-10), but it was more toxic in acid solutions. On the other hand, Bayluscide which was more toxic in dechlorinated tap water (pH 882). was ineffective in media with high acidity or high alkalinity. 6- The effect of pH on the toxicity of both compounds was less when the expostn”e times were lengthened (more than 24 brs up to 96 hrs). This may be due to that the a.bility of snails to change the pH is obvious during the long period (96 brs). On the ot he r hand t when the initial pH (acid or alkaline) was fixed through 96 hrs the effect of pH on the toxicity of each mollu scicide was like the case with exposure for ahort period (24 bra). 7- Both snail species were able to survive as long as 96 hra with temperatm”e range of 10 - 33°0. The therIr.al death point v~s found t~ be between 35°0 and 40°0. 8- For s~ort exposure times (24 brs), snails could withstand higher concentrations of copper sulfate at lower temperature (10°C) than at higher temperature (33°C). , 9- The effect of temperature on the toxicity of copper sulfate was less with increasing exposure times (96h.rs). 10- On the other hand, temperature had no effect on the toxicity of Bayluscide. 11- Both snail species could survive in water containing 250 p.p.m chlorides for six days but 50 of B.~runcatus and ~.alexandrina died when exposed for 10 days to a 3500 p.p.m and 4500 p.p.m chlorides respectively. 12- Salinity from 50 - 250 p.p.m. had no effect on the toxicity of both molluscicideso 13- Copper Bulfate was more potent toxicant than Baylu scide against the tested fauna (Daphnia pulex, Physa acu ta and Tila pia no 1 it ice. . 14- There was no difference in the toxic:i- ty of copper Bulfate and Bayluscide against ~4~lexandrina and B.~runcatus in the presence or absence of these fauna except a slight decrease in the toxicity of Baylusoide against both srbil species when Tilapia nolitica ~~s present. 15- The toxicity of both compounds was decreased signi ficantly in the presenoe of SpiroRyra and Ceratoph~ llum demersum, but ”,vas not affected in the presence of a g:f.bba. 16- Both snail species were able to survive for seven days in water containing 15 p.p.m ammonia, but snails were killed when exposed to concentrations more than l5p.p.m ammonia . 17- The toxicity of copper sulfate B.nd Bayluscide was decreased with inoreasing ammonia concentration from 0 - 15 p.p.~ especially when exposure times were relatively short (24 hra). However ammonia. had no effect on the acute toxicity of each molluacicide when exposure times were lengthened (96 brs). 18- Both snail species were able to survive for 4 days in solutions containing 50 pollution by sewage and for one day in solutions containing 100 pollution by sewage. 19- The toxicity of copper suI fate and Bayluscide was highly affected in water polluted by sewage