| Selenium is one of the essential trace elements in the human body.It has been demonstrated that selenium deficiency is associated with certain diseases in humans,such as Keshan disease and Kashin-Beck disease.China is a large country that suffers from selenium deficiency.Selenium is absent in 72%of the regions,and about 2/3 of the population suffers from inadequate selenium intake.Therefore,reasonable selenium supplementation is of great significance in protecting human health.Humans’access to selenium is mainly through the food chain,and eating agricultural products produced on natural selenium-rich soil is considered the safest way to obtain selenium.Therefore,the investigation and utilization of selenium-enriched soil resources can provide natural resources for biological selenium supplementation,and can also create conditions for the local development and utilization of selenium-rich resources.Therefore,this work has attached great importance to all levels of governments and researchers.The previous work showed that there is a large area of selenium-rich soil in the Qinxi area and there are natural conditions for the development of selenium-enriched agricultural products.Therefore,the research topics of selenium content and bioavailability in selenium-enriched soil in the Qinxi area are proposed,and the selenium content and distribution characteristics in the selenium-enriched soil in the study area,as well as the fertility characteristics and environmental quality in the selenium-enriched soil;Selenium content in cultivated crops on selenium-enriched soil was analyzed to determine the effectiveness of selenium in the selenium-enriched soil to provide theoretical basis for the rational utilization of local selenium-enriched soil and the development of local selenium-enriched agricultural products.The results of the study are as follows:1.The selenium content in selenium-enriched soil in the Qinxi study area was between0.297 mg/kg and 7.311 mg/kg,with an average value of 0.859 mg/kg,which was higher than the 2.7 times that of Anhui soil background value of 0.234 mg/kg.Selenium content in selenium-enriched soil shows a spatial feature that decreases from the hills to the alluvial plains in the middle river.The effective selenium content in soils in the study area ranged from 0.009 mg/kg to 1.241 mg/kg,with an average value of 0.084 mg/kg,and a variation coefficient of 130.76%.The selenium content in the selenium-enriched soil had a wide range of change.The availability of selenium is between 1.00%and 16.97%,with an average effective level of 9.92%.2.Selenium content in selenium-enriched soil in Qinxi Research Area varies with depth.Selenium content is 0.42mg/kg~1.345mg/kg in 0cm-20cm plough layer,and 0.25mg/kg~0.85mg/kg in 40cm~80cm depth.,80cm~120cm depth is in the range of 0.10mg/kg~0.84mg/kg.The selenium content in the soil decreased with the increase of soil depth,indicating that selenium has the characteristics of plough layer enrichment in the soil profile.3.The selenium content ranges of the four selenium-enriched soils in the Qinxi Research Area range from 0.297mg/kg to 7.311mg/kg for bamboo forest land,0.38mg/kg to 1.281mg/kg for paddy field and for tea plantation.0.49mg/kg~0.577mg/kg,vegetable garden 0.304mg/kg~1.320mg/kg.Average value:0.993 mg/kg for bamboo forest,0.692mg/kg for vegetable garden,0.525 mg/kg for paddy field,and 0.537 mg/kg for tea plantation.The coefficient of variation was 111.26%for bamboo forest,63.15%for vegetable garden,51.45%for paddy field and 5.44%for tea plantation.It can be seen that the average value of selenium content in the soil of bamboo forest land is the largest among the four utilization methods,and the smallest is the paddy field.Selenium has the largest change in soil amplitude in the bamboo forest,and the tea plantation has the smallest change.4.The results of soil nutrient determination in Se-rich creek soil area indicated that the highest soil organic matter in the selenium-enriched soil was 64.67 km~2,accounting for43.07%of the study area;the second soil was up to 55.67 km~2 total nitrogen.,accounting for 37.08%of the area of the study area;the three types of soil area is more than the available phosphorus is 54.62km~2,accounting for 36.37%of the study area.Total potassium and available potassium were concentrated on the four types and five types of soil,occupying 89.80 km~2 and 45.21 km~2 respectively,indicating that the nutrient fertility levels in the soil in the study area are quite different,and the potassium level is low.Index and method analysis showed that the fertility index values of the four utilization modes were between 70~80,the comprehensive fertility level was 2,and the fertility level was higher.The total soil selenium content was positively correlated with soil pH,organic matter,total nitrogen,alkali-hydrolyzable nitrogen,and available phosphorus.The amount of soil available selenium was positively correlated with organic matter,total nitrogen,alkali-hydrolyzed nitrogen,available phosphorus,and available potassium.5.The evaluation of environmental quality of soil with selenium-enriched soil in the Qinxi Research Area shows that As,Cd,Cu,and Zn are distributed in soils of all three levels.Among them,As,Cd,Cu,and Zn are all first-class soils and the area is greater than that of the second-class soils.The area is larger than the area of the three types of soil,while the Cd is the area of the second type of soil where the area distribution is greater than the first type of soil is greater than the area of the third type of soil;the Pb and Hg are mainly distributed in a type of soil and a second type of soil,and all of them are a type The soil area is larger than the second soil type.The single factor evaluation method and Nemerow comprehensive factor evaluation method showed that:the comprehensive pollution index of the soil in the study area was Fn=0.651,and the soil quality grade was grade 1,which was less than the safety limit of pollution degree of 0.700,indicating that the selenium-enriched soil in Qinxi area The soil in the area is at a clean level.The total amount of selenium in soil was positively correlated with the contents of Cd,Cu,and Hg,and the content of available selenium in soil was positively correlated with that of Cd,Cu,and Hg.6.The effective soil selenium in Selenium-enriched soil in Qinxi Research Area was between 24.54%and 93.15%,and the average effective degree was 74.82%.The effective level of available selenium in tea garden soil was the highest,and the effective level of available selenium in vegetable garden soil was the lowest.The bioavailability of total selenium for plants is between 1.78%and 8.37%,of which the bioavailability of tea is the highest and the bioavailability of vegetables is the lowest. |
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