Study On The Oxidative Potential And Cytotoxicity Of PM_2.5 In Nanjing Area

Ambient fine particulate matter can cause oxidative stress by inducing excess reactive oxygen species in organisms,which can then lead to a variety of diseases.The ability of particulate matter to induce organisms to produce reactive oxygen species is called the oxidative potential(OP).Therefore,the assessment of OP of PM_2.5 is an important criterion to measure its health risks.In order to study the PM_2.5 health risk of Nanjing(a typical city in the Yangtze River Delta),the cellular and non-cellular methods were used to analyze the OP levels of PM_2.5,and the contribution of chemical components was preliminarily discussed.This study collected PM_2.5 samples in Nanjing area,China for four seasons in 2016.Toxicological experiments were performed on GC-2 spd to analyze the effects of PM_2.5 on cellular activity and oxidative damage.The oxidation potential(OP)of water-soluble PM_2.5fractions was measured by dithiothreitol(DTT)method.Metals,carbon fraction such as organic carbon(OC),elemental carbon(EC)and water-soluble organic carbon(WSOC)in PM_2.5 were also measured.The water-soluble chromophores in PM_2.5 were classified into humic-like and protein-like components(C1,C2,C3)by excitation emission matrix analysis.C1 represents microbial humic-like substances,C2 represents terrestrial humic-like substances,and C3represents fulvic acid-like and protein-like tryptophan.The absorbance coefficient at 365nm(Abs₃₆₅)characterizes the large molecular weight of aromatic substances.The correlation between these components with the OP of PM_2.5 were investigated.The annual mean mass concentration of PM_2.5 was 73?g/m³,with the significant seasonal variations:spring?winter?summer?autumn.The annual mean mass normalized DTT activity(DTT_m)was 0.02 nmol min^-1?g^-1 and the seasonal variation was not obvious.The annual mean volume normalized DTT activity(DTT_v)showed a relatively high value of 1.16nmol/min/m³ and ranked as winter?spring?autumn?summer.The relationship between each component of PM_2.5 with OP was determined by Pearson correlation coefficient and multiple linear regression.The results showed that the positive contribution of C2,representing terrestrial-like humic substances,and the negative contribution of Cr explained 70%of the OP in spring;Abs₃₆₅ and Cu were the largest contributors to the OP of particulate matter in summer;Abs₃₆₅,Mn,V and C3 contributed 91%of OP in autumn;Cu,Mn and C3 were the dominant contributors to OP in winter.The results suggest that oxidation potential of PM_2.5 is determined by fractions rather than mass concentration.Our results discussed the health risk of PM_2.5 due to reactive oxygen species,and provided a theoretical basis for subsequent policy development to reduce the health risk of PM_2.5 exposure by controlling emissions.