پديد آورندگان :
سلطاني، زهرا دانشگاه آزاد اسلامي اراك - دانشكده علوم پايه , خاني، علي دانشگاه آزاد اسلامي ميانه، ايران - گروه شيمي و مهندسي شيمي , مهانپور، كاظم دانشگاه آزاد اسلامي اراك - دانشكده علوم پايه , مرجاني، اعظم دانشگاه آزاد اسلامي اراك - دانشكده علوم پايه
كليدواژه :
عدسك آبي , تبخيرسطحي , پوشش , آب سد
چكيده فارسي :
ميزان زياد تبخير از سطح آب، باعث كاهش قابل توجه استفاده بهينه از مخازن آب مي‌شود. يكي از بزرگ‌ترين مشكلات آب سدها در ايران، از دست رفتن مقدار زيادي از آب از طريق تبخير سطحي، به‌علت بالا بودن سرعت تبخير است. در اين پژوهش، كارايي گياه عدسك آبي به‌عنوان يك پوشش دوستدار محيط‌زيست روي آب در كاهش تبخير سطحي آب مورد بررسي قرار گرفت. براي اين منظور، يك سيستم پايلوت طراحي شد كه شامل دو حوضچه شيشه‌اي (آكواريوم) بود. يك حوضچه (حوضچه گياهي) به‌عنوان آكواريوم كشت گياه و ايجاد پوشش گياهي از آب سد بدون هيچ‌گونه افزودني از مواد مغذي گياهي پر شد و يك حوضچه ديگر (حوضچه غير گياهي) از آب سد بدون گياه پر شد. ديواره آكواريوم‌ها با ورق آلومينيومي پوشانده شد تا نور فقط از بالاي آكواريوم به آن تابيده شود. دو لامپ فلورسنت به‌عنوان منبع نور در بالاي هر حوضچه قرار گرفت. دماي اتاق در 25 درجه سلسيوس ثابت و مدت زمان نوردهي در طول يك شبانه‌روز، روي 14 ساعت تنظيم شد و به‌مدت يك ماه، هر 24 ساعت ميزان تبخير آب با استفاده از مقدار تغيير ارتفاع آب در حوضچه‌ها اندازه‌گيري شد و اثر پوشش گياهي، هوادهي و مقايسه پوشش زنده و غيرزنده عدسك آبي بررسي شد. نتايج نشان داد كه ميزان تبخير در حوضچه گياهي كمتر از حوضچه غير گياهي است. ميزان تبخير در حوضچه گياهي و غير گياهي به‌ترتيب برابر با 23/75 و 32/60 درصد بود. همچنين اثر هوادهي بر كاهش تبخير بررسي شد. هوادهي، رشد عدسك آبي را افزايش و ميزان تبخير را كاهش داد. همچنين نتايج نشان داد كه عدسك آبي غير زنده مي‌تواند به‌عنوان پوشش روي آب براي كاهش تبخير استفاده شود. مقايسه نتايج به‌دست آمده در محيط آزمايشگاه و هواي آزاد نشان داد كه ميزان تبخير در هر دو آكواريوم گياهي و غير گياهي در هواي آزاد نسبت به محيط آزمايشگاه بيشتر است.
چكيده لاتين :
The extremely high rate of evaporation from water surfaces greatly reduces optimal utilization of water reservoirs. One of the biggest problems of water in dams in Iran is the huge amount of
water loss through evaporation due to high evaporation rate. In this study, the efficiency of
duckweed (Lemna gibba L.) as an environmentally friendly cover on water in reducing water
evaporation has been investigated. For this purpose, a pilot system was designed that consisted
of two glassy ponds. One pond as duckweed culture medium filled with raw water of the dam
without the addition of any duckweed nutrients (plant pond), and another pond filled with raw
water of the dam without duckweed (unplanted pond). Duckweed (Lemna gibba L.) was
purchased from a typical aquarium market, and it was then cultured and used for batch
experiments. The raw water of Aydoghmush dam (Miyaneh, Iran) was used for culture medium.
The walls of the ponds were covered to prevent light from entering except at the top and the tow
fluorescent lamps (36 W, Pars Co.) as artificial light at the top of each pond were also located
(simulating natural climatic conditions). Temperature was maintained at 25 °C, and 14 hours of
photoperiod was applied to duckweed. Both ponds were also equipped with an aeration system
installed at the bottom of the pond. One of the aquariums as a growth medium and plant
covering (planted aquarium) and the other without duckweed as unplanted aquarium were
selected (both aquariums were filled with the raw water of the dam without the addition of any duckweed nutrients). For one month, every 24 hours, the amount of water evaporation was
measured using the amount of change of water height in the ponds. The effect of plant covering,
aeration and comparison of fresh and non-living duckweed covering on reducing surface water
evaporation were studied. The effect of plant covering on reducing surface water evaporation in
open air (outside) was also investigated. The results showed that the rate of evaporation in the
plant pond is lower than unplanted pond. The content of evaporation in the plant and unplanted
ponds is 23.75 and 32.60%, respectively. So, plant growth and creating coverage on the water’s
surface can be effective in reducing the surface evaporation of water storages such as dams. The
effect of aeration on reduction of evaporation was also investigated. The results indicated that
aeration enhanced growth rate of the plant and consequently, reduced the water evaporation.
This can be due to the following main reasons: 1) increasing the growth rate of the plant and the
formation of more plant covering on the surface of the water; 2) the formation of turbulent flow
in the surface layer of water and the replacement of water molecules with those molecules that
have the potential to escape from the surface of the water. The results also showed that nonliving
duckweed can be used as a cover on water to reduce water evaporation, and in the open
air, by creating plant covering on the surface of the water, 23.53% of the surface water
evaporation can be prevented. By comparing the results obtained in the laboratory and in the
open air, it is evident that the evaporation rate in both plant and unplanted aquariums is higher
than in the laboratory environment, which can be due to exposure to sunlight and wind.
