| The plastic pieces less than 5 mm were defined as microplastic（MPs）.The length between 5-20 mm is mesoplastic（EPs）.In resent years,MPs（EPs）pollution is being increasingly recognized as a global concern in all environments.MPs（EPs）not only polluted the local soil,but also polluted the air locally and downwind as they are picked up by dust and blown by wind.In this study,the contents of MPs（EPs）in surface soil,wind-blown sand and dust of farmland covered with（without）film mulch in Bashang area of Hebei Province,field investigation and laboratory experiment were combined.In this paper,the density flotation method was used to extract MPs（EPs）from the samples.The MPs（EPs）observation andμ-Fourier-transform infrared spectroscopy were carried out.The distribution characteristics and influencing factors of MPs（EPs）in surface soil,wind-blown sand and dust were studied.The main conclusions are as follows:（1）For the farmlands with（without）film mulch,the results reveal that fibers,fragments,and films constitute the major types of MPs（EPs）in farmland soil and wind-blown sand and dust,fiber had the largest proportion（about 70%）and followed by fragment and the proportion of film is the smallest.The MPs（EPs）abundances of1-3 mm,<1 mm,3-5 mm and 5-20 mm items kg-1 successively decrease.The main colors of MPs（EPs）were blue,black and transparent.（2）In the farmland with plastic film,the abundance of MPs is831.25±247.76-1295.65±390.78 items kg-1,the abundance of EPs is62.50±51.75-210.87±140.58 items kg-1.In the farmland without plastic film,the abundance of MPs is 518.75±203.43-828.26±364.89 items kg-1,the abundance of EPs is 50.00±37.80-139.13±131.39 items kg-1.It is found that the abundance of MPs（EPs）in farmland with plastic film is higher than that in farmland without plastic film.（3）For the farmlands with（without）film mulch,the detail MPs（EPs）particles size distribution fit the logistic model.The inflection point is approximately equal to2000μm.It increased sharply before 2000μm and gradually slowed down after 2000μm.（4）For the farmlands with（without）film mulch,the enrichment of MPs（EPs）in wind-blown sand and dust showed different degrees.The MPs（EPs）enrichment ratio of wind-blown sand is between 0.22（0.11）and 2.77（5.66）,and that of dust is between 1.01（2.06）and 52.21（76.05）.The enrichment of MPs（EPs）in wind-blown dust is one to two orders of magnitude higher than that in wind-blown sand.（5）Wind speed affects the enrichment of MPs（EPs）in wind-blown sand and dust.Enrichment ratios of plastic debris are proportional to wind speed.The greater the wind speed,the more MPs（EPs）are enriched in wind-blown sand and dust.The type of MPs（EPs）is independent of the enrichment of MPs（EPs）in wind-blown sand and dust.MPs are more likely to accumulate in wind-blown sand and dust than EPs.（6）The monthly forward trajectory frequencies of MPs（EPs）-contaminated air masses at Kangbao County were calculated using HYSPLIT.During March and May,the geographical distribution extended to about 2000 km from the county.The regions of greatest（>90%）frequency passed through the Beijing-Tianjin megacity belt from March to June. |
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