Photolysis Of Lamivudine And Triclosan In Aqueous Solution And Toxic Assessment Of Their Photolytical Products To Hydrobiose

Photolysis is one of the most important ways of pharmaceuticals and personalcare products (PPCPs) elimination in natural environment. Photolysis can alsoinfluence the ecotoxicological effects of these PPCPs. The knowledge of thephotolysis kinetics and mechanism is essential to predict the behaviors of thesepollutants in natural water. Furthermore, assessment of their potential risks andtoxicity effects to aquatic ecosystem of these PPCPs and theirs photolysis products isa increasing concerned problem. In most conventional studies, photolysis kinetics isusually carried out by single-varialble-at-a-time (SVAT, the the most common practiceholding all other variables constant) method, but this method is time-consuming andunable to identify the interactions between different variables, as well as theinefficiency to predict the true photolysis reaction constant. The central compositedesign (CCD) is one of the methods based on response surface methodology (RSM).CCD used in this study can overcome these shortcomings mentioned above.Furthermore, three typical hydrobios at various trophic levels including Daphniamagna, S. capricornutum, Photobacterium Phosphoreum, instead of only luminescentbacteria, was employed to investigate the toxicity of two PPCPs and their photolysisproducts.The aim of the present study was to investigate the effects of selected varialbleon the photolysis kinetics of Lamivudine (LAM) and Triclosan (TCS). Threehydrobios was chosen to evalulate the acute and chronic reproduction toxicity ofLAM and TCS and their photolysis products.(1) In the study of LAM Photolysis. ThepH (3~11) and ionic strength (0.05M~1M) show little effect. Increasing LAMconcentration (10μM~100μM) and humic acid (HA) concentration (3mg/L~15mg/L)led to the decrease of the photolysis efficieney and photolysis rate constant. On thecontrary, Increasing Cl concentration (0.0625M~0.625M) and NO3concentration(5μM~50μM) led to the encourage of the photolysis efficieney and photolysis rateconstant. Four experimental variables, initial LAM concentration, HA cencertration,Cl concentration and NO3concentration were selected in the multivariableexperimental design. The optimized conditions were as following: initial LAMconcentration at30μM, HA concentration at0, Cl concentration at0.5M and NO3concentration at40μM. The distribution experiments of reactions specious (suchas·OH,1O2, H2O2/O2) during the photocysis process were investigated systemically, and the results indicated that the·OH at30%,1O2at21%and H2O2/O2at18%are themain reaction species, the other reaction species play minor role in the photocatalyticprocess.(2) LAM shows no acute toxicity to Daphnia magna, S. capricornutum andPhotobacterium Phosphoreum. The EC50to Photobacterium Phosphoreum (15min)and Daphnia magna (48h) are more than1000mg/L. For the reproduction experimentof Daphnia magna exposed to LAM solution (from10μM to0.4mM), no Daphniamagna dead in the experiment, sensitive parameters are first brooding time and firstspawn time, and other pointers show little response. The test of toxicity of photocysisproducts show that enhanced toxicity on Daphnia magna as well as PhotobacteriumPhosphoreum was found.(3) On basis of the study we have known, four experimentalvariables including initial TCS concentration, HA cencertration, initial pH and lightintensity were selected in the multivariable experimental design. The optimizedconditions were as following: initial LAM concentration at10μM, HA cencertration at0, initial pH at11and light intensity at0.44mW cm-2.(4) The acute toxicity of TCSto Daphnia magna, S. capricornutum and Photobacterium Phosphoreum were0.055mg/L,0.092mg/L and0.32mg/L. The reproduction experiment of Daphniamagna exposed to TCS solution from0.0001mg/L to0.128mg/L severally, severalDaphnia magna dead in the high concentration experiment (0.128mg/L), sensitivepointers is first brooding time, first spawn time, total brooding number and intrinsicgrowth rate, and other pointers show little response. The results show enhancedtoxicity on Daphnia magna as well as Photobacterium Phosphoreum and S.capricornutum.