Transformation And Effect Mechanism Of Mn²⁺/Cr⁶⁺ In Water-Soil-Carbonate System

Aim at the hot issue of groundwater combined pollution, select subterranean river basin for mostly research objects, choice heavy metal combined pollution in water-soil-carbonate mediums for research direction. By Physics simulation experiment, the mechanism of groundwater single heavy metal poluution and combined pollution were studied by application of environmental sciences, environmental aquatic chemistry, soil chemistry, and SPSS statistical methods. Physical simulation experiment is divided into six parts:single manganese, Cr⁶⁺ pollute experiment; manganese/nitrate nitrogen, manganese/chloride ion combined pollution experiment; Cr⁶⁺/nitrate nitrogen, Cr⁶⁺/chloride ion combined pollution experiment; manganese/ Cr⁶⁺ combined pollution experiment; heavy metal transportation and transformation in soil and heavy metal adsoption test in surface of carbonate. By experiment, preliminary reveal the transference and translation rules of N/Cl/Mn/Cr combined contaminations in water-soil-rock system:1. In single and combined pollute conditions, adsorption amounts and transfer speed of Mn²⁺/Cr⁶⁺ are different in different combined pollution types; Mn²⁺/Cr⁶⁺ has obvious interaction, namely, presence of Mn²⁺, accelerate the adsorption ability of Cr⁶⁺ in soil-rock system, both behave additive effect.2. In single system, physical desorbed quantities of Mn and Cr⁶⁺ are more than the chemical desorbed quantities, corresponding proportion is about 10:1 and 25:4. It illustrate that Mn²⁺ and Cr⁶⁺ tranfer easily in single system, form heavy metal pollute easily.3. Mn²⁺ puts up different transference characteristics in different systems: in single system, single transfer distance of Mn²⁺ is about 30cm; for influence of Cl^-, single transfer distance of Mn²⁺ is over 40cm, and transfer faster; In Mn²⁺-NO₃^- system, at 28.5cm to 38.5cm from infall, content of Mn²⁺ changes slowly, it indicates that single transfer distance of Mn is about 40cm. Namely, in Mn²⁺-Cl^- system, Mn²⁺ has better migration. The presences of NO₃^- and Cl^- accelerate soil adsorbing of Mn²⁺, they behave marked synergetic.4. NO₃^- restrains the adsoption of Cr⁶⁺, it is obviouse antagonism. Cl^- accelerate the adsoption of Cr⁶⁺, Cr⁶⁺,Cl^- behaves synergetic.5. In different systems, Cr⁶⁺ behaves different transference characteristics: in single system, single transfer distance of Cr⁶⁺ is about 20cm; For the presence of Cl^-, single transfer distance of Cr⁶⁺ is about 10cm; For the presence of NO₃^-, Cr⁶⁺ transfer equally, so Cr⁶⁺ has better transfer property in Cr⁶⁺ - NO₃^-combined system.5. The result of SEM indicates that in Mn/Cl^-system, the adsorption of Mn²⁺ is 0.14 mg/cm², the adsorption ratio of Mn²⁺ in water-soil-rock system is clearly different, it is 3.8: 2.7: 1, that indicated adsorption of Mn²⁺ at the suface of marble is accelerated by Cl^-.