稀土矿城市不同季节大气可吸入颗粒物中稀土含量特征及颗粒物细胞毒性

为探讨典型稀土矿城市不同季节大气可吸入颗粒物(inhalable particulate matter,PM10)中稀土元素污染特征及其细胞毒性响应,将前期采集于包头市的PM10颗粒物进行提取,检测PM10中的稀土元素(rare earth elements,REEs)含量,并将人肺上皮细胞(A549)暴露于不同浓度水平(25,50,100μg·m L-1)的PM10样品和标准颗粒物1649b(standard reference material,SRM1649b)暴露液,用WST-1法测定暴露24 h后的细胞活性,用2’7’二氯荧光素二醋酸盐(2’7’-dichlorofluorescein diacetate,DCFH-DA)荧光探针法和彗星实验分别测定暴露3 h后的细胞内活性氧(reactive oxygen species,ROS)产生水平和DNA双链损伤程度。结果表明,包头春、夏季大气PM10和SRM1649b均引起A549细胞活性下降,并诱导细胞内ROS生成量增加,造成显著的细胞内DNA损伤,含REEs的大气颗粒物毒性显著高于标准颗粒物。与春季相比,包头夏季PM10对细胞活性的抑制程度更高,造成更多的DNA双链损伤,从而表现出更强的细胞毒性和遗传毒性。包头PM10呈现明显的轻稀土元素(light rare earth elements,LREEs)富集,铈(Ce)、钷(Pm)、镧(La)和钕(Nd)含量占稀土总量的50%以上。LREEs均与细胞活性和细胞内ROS产生水平呈负相关性,包头春季和夏季PM10中稀土元素含量的差异是导致包头PM10细胞毒性效应不同于标准颗粒物且具有季节性差异的原因之一。

Seasonal Variation of Rare Earth Element Concentrations in PM10 and Their Cytotoxicity in A Typical Rare Earth Mining City

To investigate the toxicity and pollution characteristics of rare earth elements(REEs)in inhalable partic-ulate matter (PM10)of Baotou City,PM10samples were collected for exposure experiments.The concentrations of REEs in PM10were characterized and A549 cells were exposed to PM10collected in spring and summer, together with a standard reference material 1649b(SRM1649b)at the levels of 25,50 and 100 μg·mL-1.The WST-1 meth-od was used to measure the cell viability of A549 cells after 24 h exposure time.The 2'7'-dichlorofluorescein di-acetate(DCFH-DA) method and the comet assay were used to measure the intracellular reactive oxygen species (ROS)production and DNA damage of A549 cells,respectively, after 3 h exposure time. The results showed that all samples of PM10in both seasons and SRM1649b inhibited the cell viability,induced ROS production and caused significant DNA strand breaks of A549 cells.The toxicity of PM10containing REEs was significantly higher than that of the standard reference material.Compared to PM10in spring,the PM10in summer of Baotou City inhibited cell viability much more and caused more DNA strand breaks of A549 cells, indicating stronger cytotoxicity and genotoxicity.PM10of Baotou City tended to enrich light rare earth elements(LREEs)and the amount of Ce,Pm La and Nd accounted for more than 50% of total REEs in PM10.LREEs were negatively related to cell viability and ROS production.The difference of LREEs in PM10in different seasons in Baotou was one of the reasons for the seasonal variation of PM10cytotoxic effects.