Microplastic Survey And Health Risk Assessment Of Wetlands In The Yellow River Delta

Microplastic,the new type of environmental pollutants,is widely distributed around the world and has received great attentions.With the increasing annual output of plastics,a large number of large-sized plastics were found to be broken down into microplastics andaccumulated in the terrestrial environment.Furthermore,it migrates to the water body through erosion,surface runoff,etc.,and even migrates further into the marine environment.Although there have been a large number of studies on terrestrial microplastics and toxicity studies of microplastics,the current health risk assessment in this area is still relatively lacking.Therefore,referring the existing microplastic extraction methods,the distribution and forms of microplastics in the Yellow River Delta wetland were investigated by an improved micrplastic extraction method,and the toxic effects of typical microplastics in this area were studied.On the basis of investigation and toxicity data,a health risk assessment was conducted for the microplastics in the area.The main conclusions were as follows:（1）The survey in microplastic distribution showed that the total abundance of microplastics was 80-4640 items/kg（items/kg indicates the number of microplastics per kilogram of soil）in the Yellow River Delta wetland.The average abundance was1142.53 items/kg,and the particle size ranged at 5.78μm-3 mm.There were four forms of microplastics:fibers,films,granules and fragments.At each sample site,the abundance of microplastics was high in the form of granular,and it was about 40.00%in total.The microplastic material was mostly polystyrene（PS）,which accounting for58.87%in the samples.（2）PS in different particle sizes could adhere to the zebrafish embryonic chorion.Nano PS particles were observed to accumulate in the gill at72 hpf,enter the blood circulation at 96 hpf,andgradually accumulate in the brain and liver of the larvae at120 hpf.PS in different particle sizes would have toxic effects on zebrafish and caused an inflammatory effect on target organ（liver）,which would change the metabolic pathways associated with the antioxidant defense system in zebrafish larvae and resist the oxidative stress caused by microplastics.Moreover,nano PS particles induced higher toxicity than micro PS particles.（3）The results of health risk assessment verified that the carcinogenic risk under the skin contact exposure route was 2.17E-06,which indicated potential cancer risk.The carcinogenic risk under the respiratory inhalation exposure route was 9.05E-08(it was less than 10^-6),which indicated no potential cancer risk under this exposure route.Therefore,microplastics have potential cancer risk to human health under skin contact exposure in the Yellow River Delta wetlands.Microplastics must be managed and controlled in this area.