Environmental Geochemical Characteristics Of Natural Nuclides In Different Tailings And Waste Residues

Guizhou is a major province of mineral resources in our country.The natur al radionuclides such as ²³⁸U,²³²Th,²²⁶Ra and ⁴⁰K contained in industrial wast e residues and tailings generated during mining and smelting processes,waste r esidues and tailings stockpiles enter the environment through different ways un der long-term geochemical action.The impact cannot be ignored.This paper se lects the tailings and waste slag samples from typical tailings ponds and indust rial waste slag yards in Guizhou Province,and analyzes the natural nuclides ²³⁸U,²²⁶Ra,²³²Th,and ⁴⁰K in the samples.Characteristics of nuclide content;usi ng static soaking experimental methods to explore the law of natural nuclide m igration from tailings and waste residues to the water environment and its influ encing factors;using a variety of radioactive risks assessment methods to cond uct analysis on tailings ponds and waste slag dumps Radiological risk assessme nt.The main findings are as follows:(1)The distribution of natural nuclide content in different tailings and wa ste residues is quite different.The natural nuclide content of antimony tailings sand is lower,lower than the average value of soil in Guizhou Province,while the natural nuclide content of red mud samples is higher,²³⁸U,²²⁶Ra,²³²Th T he maximum content of and 40K is as high as 219.45Bq/Kg,299.92Bq/Kg,363.94Bq/Kg,531.25Bq/Kg,and only ²³⁸U and ²²⁶Ra of phosphogypsum have bee n detected.The content is 5.01Bq/Kg and 55.38Bq/Kg.The ⁴⁰K content of man ganese tailings and electrolytic manganese slag is relatively high.The ⁴⁰K cont ent of manganese tailings is between 685.83Bq/Kg?911.61Bq/Kg,the average v alue is nearly twice that of red mud;the ⁴⁰K content of electrolytic manganese slag is higher than 500Bq/Kg.(2)In the two antimony tailings study sections at different depths,the con tents of four natural nuclides,²³⁸U,²²⁶Ra,²³²Th and ⁴⁰K,increase with the incr ease in depth,showing enrichment characteristics with obvious enrichment horiz ons;each nuclide is in the section The degree of enrichment in BM is slightly different.Among them,the ²³²Th enrichment is the most obvious,followed by²³⁸U enrichment,²²⁶Ra is slightly enriched,and ⁴⁰K is hardly enriched due to its higher activity.(3)Static immersion experiments show that the release ability of natural n uclides ²³⁸U,²²⁶Ra,²³²Th and ⁴⁰K is different.²³⁸U and ²²⁶Ra are more easily released into water under acidic conditions,while ²³²Th is less released.The fo ur natural nuclides have a lower release rate in the extract.The order of conte nt is ⁴⁰K>²²⁶Ra>²³⁸U>²³²Th;by calculating the relative leaching rate,it is found that 40K is easily released into the water body under alkaline conditions,and the release law of natural nuclides in different tailings waste residues is also d ifferent;80 and 120 mesh two kinds of particles The net bubble test results of the diameter electrolytic manganese slag sample show that ²³⁸U,²²⁶Ra and ²³²Th are more easily released in the sample with a small particle size,while ⁴⁰K is the opposite.(4)The internal exposure index,external exposure index,equivalent radiu m concentration,and air dose absorption rate were used to evaluate the radioac tivity levels of tailings and phosgene.The results showed that the exposure ind ex of antimony tailings and phosphogypsum was relatively small,while the int ernal exposure index of red mud samples was The external exposure index is r elatively high,exceeding the relevant standards for building materials;the equi valent radium concentration evaluation results show that the radioactivity levels of the tailings pond and the slag yard are in the order of red mud yard>man ganese tailing yard>antimony tailing yard,red mud yard concentration The val ue is higher than the safety limit of 370Bq/Kg.The air absorbed dose rate eva luation method shows that the red mud storage yard has a higher radioactive ri sk.