Interaction Of Lead And Arsenic In Soil And Its Effect On Vegetable Growth

With the rapid development of social economy,more and more attention has been given to the dangers of heavy metals.Heavy metals pollution poses a great potential threat to soil ecosystem because of their characteristics of concealment,accumulation and irreversibility.Heavy metals may cause the growth of agricultural crops obstructed,decline in quality,and will have an impact on the human health.it is of great significance for the prevention and control of combined contamination of soil heavy metal and human health by exploring the mechanism of Pb-As interaction affecting the mobility and bioavailability of Pb and As.In this paper,lead?Pb?and arsenic?As?heavy metals were used as study objects and pot experiment was conducted to study the migration and transformation behavior of lead and arsenic in soil-plant system under single and combined pollution conditions.Results were as following:The seedling stage soil of don't grow Brassica campestris L.and grow Brassica campestris L.,Pb inhibits the release of As in pore water,When adding lower amount of compound heavy metals,As promotes the release of Pb in pore water,When adding higher amount of compound heavy metals,As inhibits the release of Pb in pore water.The mature stage soil of don't grow Brassica campestris L.,the concentration of As in pore water increased first and then inhibited with the increase of exogenous Pb concentration.As promoted the release of Pb in pore water.The interaction between Pb and As in the soil of Brassica campestris L.and Capsicum annuum L.has a synergistic effect on the mobility of Pb/As.Root is the main part of the accumulation of Pb and As in Brassica campestris L.and Capsicum annuum L..Brassica campestris L.showed higher enrichment ability of Pb than As and Capsicum annuum L.showed higher enrichment ability of As than Pb.The interactive effects of Pb and As enhanced As accumulation in Brassica campestris L..Single and complex Pb and As pollution significantly reduce the transport of Pb to Pb,but have no significant effect on the transport of As(except for 30 mg?kg^-1As treatment).Pb-As interaction affected the accumulation of Pb and As in different parts of Capsicum annuum L.,and had no significant effect on the transport of Pb(except for 30 mg?kg^-1As treatment).under Brassica campestris L.different growth cycles,different treatments and different types of plant conditions,there is no significant difference in the morphology and abundance of arsenic in pore water,mainly in the form of H₂AsO₄^-,while the main Pb species and their abundances in pore water has changed.The species of Pb in the pore water of non-planted Brassica campestris L.seedlings exists in the form of FA-Pb,PbSO₄,PbNO₂⁺,PbNO₃⁺,Pb?NO₄?₂^2-,Pb?NO₃?₂,Pb?NO₂?₂and PbH₂PO₄⁺;The species of Pb in the pore water of planted Brassica campestris L.seedlings exists in the form of Pb²⁺,PbSO₄,PbNO₂⁺,Pb?SO₄?₂^2-,PbCl⁺,Pb?NO₃?₂ and PbH₂PO₄⁺;The species of Pb in the pore water of non-planted Brassica campestris L.mature exists in the form of PbSO₄,PbNO₂⁺,PbNO₃⁺,Pb?SO₄?₂^2-,Pb?NO₃?₂,Pb?NO₂?₂ and PbH₂PO₄⁺;The species of Pb in the pore water of planted Brassica campestris L.mature exists in the form of PbCl₂,PbCl₃^-,PbSO₄,PbCl₄^2-,PbNO₃⁺,Pb?SO₄?₂^2-,Pb?NO₃?₂ and PbH₂PO₄⁺;The species of Pb in the pore water of planted Capsicum annuum L.mature exists in the form of Pb²⁺,PbSO₄,PbNO₂⁺,PbCl⁺and PbNO₃⁺.The available Pb content in soil extracted by EDTA was significantly correlated with the total Pb content in soil.The content of available As in the soil extracted by NH₄H₂PO₄ was significantly correlated with the total amount of As in soil.There was no significant correlation between Pb content in pore water and the available Pb content in soil extracted by EDTA and HNO₃ in Brassica campestris L.soil,while there was a significant correlation between the Pb content in pore water and the available Pb content in soil extracted by EDTA and HNO₃ in Capsicum annuum L.soil.The content of soil available As extracted by NH₄H₂PO₄ was positively correlated with As content in pore water.There was a significant correlation between the Pb content in Brassica campestris L.and Capsicum annuum L.and the available Pb content extracted by EDTA.The content of available As in the soil extracted by NH₄H₂PO₄ was significantly correlated with the content of As in Brassica campestris L.,but not correlated with the content of As in Capsicum annuum L..It is more accurate to evaluate the bioavailability of available As and Pb in soil extracted by NH₄H₂PO₄ and EDTA,respectively.