[Distribution and Sources of Microplastics in Farmland Soil Along the Fenhe River].

This study investigated the distribution and sources of microplastics smaller than 1 mm in farmland soil along the Fenhe River. Microplastics in soil samples were separated and extracted using the traditional density centrifugation method. The quantity and type of microplastics were examined with a stereomicroscope. The micro-morphology of plastic particles were observed with a scanning electron microscope-energy dispersive spectrometer. The chemical composition was determined using Fourier transform infrared spectroscopy. The results indicate that the average abundance of microplastics in farmland soil along the Fenhe River is 290.5 n ·kg-1. These microplastics occur as fibers, films, fragments, and foams. Fiber microplastics are the most abundant, accounting for 52.67% of the total, and are mostly composed of polyethylene. Films and fragments mainly consist of polypropylene whereas the foams consist of polystyrene. Soil samples from different parts of the Fenhe River can be ranked according to the microplastics content in the following order:downstream>midstream>upstream. The abundance of microplastics in soil from the downstream region of the Fenhe River was 500.0 n ·kg-1, twice that of from the upstream and midstream regions. The results of the random forest model indicate that the sources of microplastics in farmland soil along the Fenhe River are closely related to the amount of agricultural films, population, gross domestic product, and industrial production. Among these factors, the amount of agricultural films is a key factor that influences the occurrence of microplastics in farmland soil along the Fenhe River.

[Using fenestration and decompression technique to treat enormous odontogenic keratocyst].

3 cases of enormous odontogenic keratocyst were treated with the technique of fenestration and decompression other than removal of jaws. After a follow-up period of two years, radiographic assessment showed that the image of keratocyst disappeared basically, neogenetic bone had been found and the defect of jaws had been restored. The teeth had no dysfunction, the lower lip had no numbness and the keratocyst epithelium was modulated histologically to mucosa after decompression. Fenestration and decompression are satisfied conservative approaches to treat enormous keratocyst which usually is treated by removal of jaws and extraction of teeth.