A　sampling　campaign　of　PM2.5　in　Beijing　from　2002　to　2004　and　from　2011　to　2013　was　performed　to　investigate　the　changes　of　typical　characteristics　of　PM2.5　at　the　representative　city　over　Northern　China　in　the　past　decade.　A　spring　PM(2.)5　monitoring　network　was　operated　to　study　the　long-range　transport　of　PM2.5　in　five　cities　along　the　pathway　of　dust　storm　across　Northern　and　Eastern　China　in　spring　2004.　PM2.5　concentrations　gradually　decreased,　but　PM2.5　pollution　still　retained　a　high　level　and　has　been　changed　from　dust　type　to　haze-fog　pollution　at　Beijing　in　the　past　decade.　The　seasonal　variation　of　PM2.5　was　spring　＞　winter　＞　autumn　＞　summer　during　2002-2004,　but　winter　＞　autumn　＞　summer　＞　spring　in　2011-2013.　The　mass　concentration　of　mineral　aerosol　was　in　the　order　of　spring　＞　winter　＞　summer　＞　autumn,　and　reached　the　highest　level　in　dust　storm　episodes　during　the　past　decade.　Secondary　inorganic　aerosol　(SIA)　followed　the　order　of　summer　＞　autumn　＞　winter　＞　spring　during　2002-2004,　however　winter　＞　autumn　＞　summer　＞　spring　during　2011-2013,　and　reached　the　highest　level　in　haze　events.　The　concentrations　of　SO42-　NO3-　and　NH4+　of　SIA　displayed　the　order　of　SO42-　＞　NO3-　＞　NH4+　in　haze　days.　SO42-　concentrations　in　different　seasons　during　2011-2013　were　almost　lower　than　those　in　corresponding　period　in　2002-2004　respectively.　But　NO3-　and　NH4+　concentrations　in　autumn　and　winter　of　2011-2013　were　higher　than　those　in　2002-2004.　The　OA　and　SOA　concentrations　followed　the　order　of　winter　＞　autumn　＞　summer　and　spring,　and　SOA　was　one　of　the　significant　components　in　OA.　The　secondary　chemical　transformation　was　the　most　significant　source　for　PM2.5　during　2011-2013,　compared　with　that　in　2002　-2004.　Atmospheric　pollution　has　exhibited　severe　complicated　pollution.　Dust　storm　carried　not　only　large　amounts　of　mineral　dust,　but　also　some　secondary　inorganic　aerosol　(SIA)　and　organic　aerosol　(OA),　which　would　have　significant　impact　on　the　wide　downwind　areas.　The　mass　fraction　of　mineral　aerosol　decreased　from　the　dust　source　to　the　downwind　coastal　sites,　while　those　of　secondary　and　carbonaceous　components　increased.　(C)　2015　Elsevier　Ltd.　All　rights　reserved.