Coastal　reclamation　for　cropland　has　led　to　the　accumulation　of　heavy　metals　in　soils,　bringing　about　pervasive　and　severe　risks　for　environment　and　human　health.　However,　less　is　known　about　the　influence　of　long-term　reclamation　on　heavy　metals　risk,　mobility　and　bioavailability　in　cropland　soil.　In　this　study,　we　determined　six　heavy　metals　(Cd,　Cr,　Ni,　Cu,　Zn　and　Pb)　and　their　fractionations　in　soils　from　five　croplands　across　a　100-year　reclamation　chronosequence　in　the　Pearl　River　estuary.　Results　showed　that　across　five　reclaimed　soils,　Cd　posed　seriously　ecological　risk　and　bioavailability　according　to　assessments　based　on　both　total　contents　(single-metal　pollution　index:　Cd　＞　Cu　＞　Zn　＞　Ni　＞　Cr　＞　Pb)　and　fractionations　(risk　assessment　code:　Cd　＞　Zn　＞　Cu　＞　Ni　＞　Pb　＞　Cr).　Cr,　Ni,　Cu,　Zn　and　Pb　posed　slightly　to　moderately　ecological　risks,　and　were　mainly　bound　to　residual　(73.70%)　and　reducible　(15.86%)　fractions　with　lower　mobility　and　bioavailability.　With　the　highest　risks　level,　mobility,　toxicity　and　bioavailability　(5.67%　exchangeable　and　11.75%　carbonate　fractions　bound),　Cd　was　identified　as　the　main　pollution　factor　in　study　area.　Principal　component　analysis　and　Pearson＇s　correlation　analysis　revealed　that　anthropogenic　reclamation　activities　(including　phosphate　fertilizers,　pesticides　and　sewage　irrigation)　were　the　major　sources　of　these　heavy　metals.　Long-term　reclamation　activities　induced　the　increases　of　soil　organic　matter,　clay　contents,　total　concentrations　and　non-residual　fractions　of　heavy　metals　by　46.14%,　538.98%,　42.87%　and　219.78%,　respectively,　demonstrating　significant　promotions　in　level　and　mobility　of　heavy　metals　due　to　longer-term　agricultural　activities,　higher　soil　clay　and　organic　matter　content.　©　2021　Elsevier　B.V.