Study On Toxic Effect Of Water Accommodated Fraction Of Oil And Dispersed Oil To Apostichopus Japonicas Juveniles

Dispersant was used for spilled oil processing, which promoted oil dissolved andharmed in the the bottom of the sea. But the influence of water accommodated fraction(WAF) and chemical enhanced water accommodated fraction (CEWAF) of oil onApostichopus japonicas juveniles was unknown. In order to evaluate the harmness ofWAF and CEWAF of oil on Apostichopus japonicas juveniles, study of toxic effects wasconducted from molecular level to explore the toxicity mechanism via laboratorysimulation method. The main conclusions of the study are as follows:1. Because that oil dispersant in225nm has an absorbance,concentration-absorbance curve of standard oil, crude oil, crude oil+dispersant, No.0diesel+dispersant was compared, and the corresponding oil as the respective TPHstandard curve was made, so that determination of total petroleum hydrocarbonsconcentration (TPH) of the WAF and CEWAF is more accurate. A preliminary analysisof the component distributions of the crude oil WAF and CEWAF was conducted withGC-MS. It was found that proportion of PAHs in the crude oil WAF is higher, thedistribution of components in the crude oil CEWAF was similar to that in crude oil itself,for the dispersants increased the ratio of alkanes in water. The TPH change with timewas compared between the WAF and CEWAF of crude oil by ultravioletspectrophotometry. The result showed that: initial TPH of crude oil WAF prepared atroom temperature is generally not more than20mg/L, and the TPH in aqueous phasegenerally decreased linearly in72h, because of the evaporation of volatile componentsand the rise of dispersed oil droplets to the surface. While at the initial12h, the declineof TPH was bigger, about1.40mg/L; then TPH reduced at the rate of no more than1mg/L per12h. Because of emulsification in the crude oil CEWAF, the order ofmagnitude of TPH was103mg/L, which changed little in the initial12h, but decreasedfor50%in24h. After36h, the crude oil CEWAF was layered with oil film on thesurface and the white floccus on the bottom. But the TPH is still at20%~30%ratio ofthe original, no obvious reduction.2. Skin smear tests of crude oil, No.0diesel oil and dispersant. The result showedthat: No.0diesel oil and dispersant on the skin made juveniles a short time ofcontraction, but failed to cause skin ulceration or abnormal activities significantly.Dispersant stimulation causes the strongest contraction of body in a short time, perhaps caused by the surfactant from dispersant. Impact of No.0diesel oil lasted for thelongest time of three, probably because the water-soluble low-molecular-weightcomponent permeated the skin, which cost the longest time to recover.3.96h acute toxicity test was conducted on Apostichopus japonicas juveniles withdispersant, the WAF and CEWAF of crude oil and No.0diesel oil. The result showedthat:(1) The toxicity of dispersant alone to juvenile is very low. At the beginning of thetest, body longitudinal shrinked for a short time from the group of the lowestconcentration of3000mg/L; and at the end of the experiment, some juveniles expeledtheir sticky cuvierian tubules in the group of1500mg/L and above, which phenomenonwas more serious than that in the test of the CEWAF of crude oil. Juveniles at the age of3and4months, were all survived in the groups below2121and4243mg/L in96hrespectively; and more than half were survived in the groups below6000and12000mg/L in96h respectively.(2) Juveniles can live a normal life in8.2mg/L of the crude oil WAF. While in theacute toxicity test of the crude oil CEWAF, some juveniles had foot or body shrinked in24h. From high to low concentration a row of the phenomenon would occurred thatsticky cuvierian tubules expelled, adhesion ability decline, tube foot retracted or someeven skin blister, fester or death along with the time. The half lethal concentration LC50(95%confidence limit) of the crude oil CEWAF were246.09mg/L (range211.16~286.81mg/L) and399.15mg/L (range374.71-425.19mg/L) on juveniles at the age of3and4months in96h.(3) The toxicity of the No.0diesel CEWAF to juvenile was significantly higherthan that of the crude oil CEWAF. For the adhesion ability of juveniles declined within5h, high mortality rate reached100%in the125.89mg/L group within72h, themortality of juveniles in the31.62mg/L group is less than50%. While juveniles allsurvived in the19.95mg/L group in96h, but also expelled their sticky cuvieriantubules.4. In order to explore toxic mechanism of water accomodated fractions of oil. Itwas analyzed that activity changes of catalase (CAT) and superoxide dismutase (SOD)in body wall at the sublethal concentrations of dispersant, the WAF and CEWAF ofcrude oil. It was found that physiological activity was not significantly affected by thecrude oil WAF. While the stress of the crude oil CEWAF to juvenile mainly displays insticky cuvierian tubules expelled, adhesion ability decline, unshaped feces, and moredeath rate in the recovery period, which showed toxic effect delayed. With stimulationof dispersant, there was a positive linear correlation between the number of juvenilesthat expelled cuvierian tubles and the logarithm of concentration. By one-way analysis of variance (ANOVA), the concentration of the WAF and CEWAF of crude oil didn’taffect enzyme activity of SOD and CAT significantly. Compared enzyme activity ofSOD and CAT of juveniles exposed to dispersant, the WAF and CEWAF of crude oil, itwas found that the effects was complex, and the enzyme activity value didn’t appearesimple correlation with the concentration and time. But the enzyme activity values of9-months-age juveniles exposed to the WAF of crude oil were generally lower thanthose exposed to the CEWAF, while the values of6-months-age juveniles exposed todispersant were lowest.This experiment added acute toxicology test data of oil spill pollution onApostichopus japonicas, and provided a certain reference value to assess environmentalsafety of dispersants in oil spill treating. The test was performed by antioxidant enzymeactivity of SOD and CAT as the response factor, toxic effects of dispersant, the WAFand CEWAF of crude oil on Apostichopus japonicas was studied on tissue levels, whichprovided reference for the further study of oil pollution effect on Apostichopusjaponicas.