Large Decrease in Acute Aquatic Toxicity of Linear Alkylbenzene Sulfonate in Hard Water and Seawater by Adding Adsorbent

Abstract

LAS (Linear Alkylbenzene Sulphonate) shows relatively high aquatic toxicity in hard freshwater or seawater. In this paper, we studied the effect of adsorbent on the aquatic toxicity of LAS in hard freshwater and seawater. Daphnia magna and Artemia salina were used for acute aquatic toxicity test in freshwater and seawater, respectively. Kaolin was used as a model adsorbent and toxic surface tension (g tox ) was used as an indicator of toxic condition. Results showed that the values of g tox of LAS to D. magna and A. salina were about 45-55 mN/m and 35-40 mN/m, respectively. Surface tension of LAS solution decreased and its aquatic toxicity increased with increasing the water hardness or the salinity. By adding adsorbent into the solutions, the surface activity and the aquatic toxicity were decreased greatly, and the effect of water hardness or salinity on surface tension and aquatic toxicity were removed. That is to say, the surface tension curve of soft freshwater corresponds with that of hard freshwater containing adsorbent and the surface tension curve at low salinity corresponds with that obtained for high salinity solutions containing the adsorbent. Therefore, our experimental data leads to the conclusion that the relatively high aquatic toxicity of LAS in concentrated solution of inorganic salts disappears in the presence of adsorbents. This is an important viewpoint in conducting environmental risk assessment of surfactants. (lethal concentration 50%); the concentration of a chemical in air or water that kills 50% of the test animals in a given time. **EC 50 (effective concentration 50%, harf maximal effective concentration); the concentration of a chemical where 50% of its maximal effect on the test animals is observed. In a toxicity test with D. magna, the effect means the inhibition of swimming ability.

Decreases in Surface Activities and Aquatic Toxicities of Linear Alkylbenzene Sulfonate and Alcohol Ethoxylates during Biodegradation

“…The result of 20 mg/L LAS showed the similar behavior to that of 10 mg/L LAS except that each change occurred about 24 to 48 h later than that of 10 mg/L ( ). In our previous studies 3,4) , g tox of LAS on Daphnia magna was about 50 mN/m. Death ratio of 50 % is expected for both 10 mg/L LAS ( ) and 20 mg/L LAS ( ) when surface tension is 50 ~ 60 mN/m, which corresponds to g tox of LAS under biodegradation.…”

“…Following three experiments were conducted for each surfactant: surface tension measurement to study the interfacial activity, HPLC analysis to analyze structural change during biodegradation, and acute aquatic toxicity test using Daphnia magna to study the toxicity. In this study, we used only Daphnia magna for toxicity test, because previous studies 3,4) , in which Oryzias latipes, Daphnia magna, Podocopida, and Artemia salina were used for acute toxicity test, showed that all of the organisms have toxic surface tension (g tox ).…”

“…In previous researches, we reported the effects of water properties, such as water hardness and existence of adsorbent, on surfactants' acute aquatic toxicity by using surface tension as an indicator of surfactant's interfacial activities 3,4) . Aquatic toxicity of LAS increased when the water hardness increased or amount of existing adsorbent increased, but the surface tension at a point where toxicity emerges (g tox ) showed a constant value if the kind of surfactant and experimental organism were fixed.…”

“…To use larval organisms born within the last 24 h for the toxicity test, only adult organisms were transferred to breeding vessels 24 h prior to the test. Specific feeding method of Daphnia magna is described in our previous paper 3,4) . Test solution for toxicity test was taken out from the solution under biodegradation.…”

Pollutant Diseases, Remediation and Recycling

“…Surfactants caused pooled in toxicity affecting the ecosystem and its inhabitants, the toxicity increasing down the trophic levels. The extent of surfactant toxicity is concentration dependant and it varies with season (Marcomini et al 2000 ), prevalence of anaerobic environment (Mungray and Kumar 2009 ), predominance of urban and industrial sewage outlets (Lara-Martin et al 2008 ), distance of sampling points from port of discharge (Gonzalez-Mazo et al 2002 ), occurrence of offshore oil spill or gas exploration, diurnal discharge of sewage (Kantin et al 1981 ), salinity (Lewis 1992 ), hardness of water (Oya et al 2008 ) and presence of adsorbents (Casellato and Negrisolo 1989 ;Marin et al 1994 ). The extend and mode of toxicity is also infl uenced by the chemistry of the pollutant surfactant, its alkyl chain length (Lewis 1991 ) and ethylene oxide (EO) molar ratio (Hall et al 1989 ).…”