| Selenium is known to be an essential micronutrient for living organisms. The lack of selenium will cause a wide range of diseases. Hanyin County locates in the core area of Ankang Selenium Valley——the most widely distributed natural selenium-enriched region of china. Within the widely distributed, high selenium content soil and good biodiversity, Hanyin County is the ideal place for the production of high-quality natural selenium-enriched agricultural products.The conditions for hydride generation atomic fluorescence spectrometry (AFS) to detect trace selenium were optimized in this study. And HG-AFS was used to detect selenium content of a serious of crops and corresponding soil samples in Se-enriched region of Hanyin. By comparing the bio-absorption coefficient of the element selenium of different crops, screening a relatively strong ability of enrichment selenium crops.In order to study selenium distribution and existing forms in different selenium-enriched crops, inorganic selenium and protein selenium, polysaccharide selenium, nucleic acid selenium and other organic selenium were extracted and detected from the screened crops. The main research results were as follows:(1) The conditions for AFS to detect trace selenium were optimized. The optimum measurement conditions were as follows:the concentration of hydrochloric acid carrier was15%(v/v), the concentration of KBH4was20g/L, negative high voltage was270V, lamp current was80mA, carrier gas flow rate was300mL/min, shielding gas flow rate was800mL/min, the injection volume was0.50ml, the reading time was10s, the delay time was0.50s, the measuring method was standard curve and the reading mode was the peak area. The performance of detection method was evaluated. The method precision was0.71%, detection limit was0.080μg/L and the recovery rate was97.32%-103.46%. The detection method was reliable. (2) HG-AFS was used to detect selenium content of a serious of crops and corresponding soil samples in Se-enriched region of Hanyin. The results showed that selenium content of the soil samples in Se-enriched region of Hanyin were in the range of524.17～14324.75μg/kg, which were all Se-rich levels and even were high selenium levels in some areas.The soil selenium content were different in different parts, the order of soil selenium content was:the third group of Muyuhe village, Pingliang town>the seven group of Yihe village, Pingliang town> the second group of Caijiahe village, Pingliang town> the six group of Pingan village, Chengguan town> the five group of Muyuhe village, Pingliang town> the seven group of Pingan village, Chengguan town> the seven group of Caijiahe village, Pingliang town. The selenium content of crop samples were in the range of6.62～902.04μg/kg. Most were enough selenium or Se-rich level, only a handful of crops were less selenium or selenium deficiency level. The selenium content of different crops was different in the same area. The selenium content of the same crops was different in different areas. The selenium content of hydroponic crops was generally higher than dryland crops. The order of crops selenium content was: soybean> rice> rapeseed> pumpkin> garlic> sweet potato> potato> konjac> corn.(3) How much of selenium crops absorbed from the soil, is usually expresent by biological absorption coefficients (Ax). It reflects the capacity of enrichment selenium of different crops, which is the main parameter for screening and evaluating the capacity of enrichment selenium of crops.The results showed that different crops had different Ax of selenium. The same crop in different soil growth environment had different Ax of selenium. The order of the capacity of enrichment selenium of different crops was:soybean> rice> rapeseed> pumpkin> garlic> konjac> potato> sweet potato> maize. Soybean, rice and rapeseed were the three crops screened out that had stronger capacity of enrichment selenium.(4) Spring tea and autumn tea samples were collected from the tea gardens in Hanyin. And the selenium content of samples was detected. The results showed that the selenium content of spring tea was higher than autumn tea. And the capacity of enrichment selenium of tea was higher than other crops. Different organs of tea trees had different capacity of enrichment selenium. And the order was as follows:burr point>the first leaves>old leaves>the second leaves>stems. Burr point with apical dominance had the highest selenium content.(5) The selenium distribution and existing forms in selenium-enriched rice were studyed. The results showed that the selenium content of selenium-enriched milled rice mainly existed in the polished rice of which selenium content accounted for80.331%of the total ones of milled rice. Protein selenium of which selenium content accounted for64.59%of the total ones was the primary form presented in selenium-enriched rice. The second one was the inorganic free existence selenium, accounting for9.27%of the total sample selenium. And there were some selenium combinded with the polysaccharides and nucleic acid. The extraction rate of rice protein was75.90%. Alkali-soluble protein occupied the highest proportion, accounting for4.15%of the total sample, and albumin occupied the lowest proportion, accounting for0.47%of the total sample. The selenium content of Alkali-soluble protein was the most, accounting for32.91%of the total sample selenium. The selenium content of salt-soluble protein was the least, accounting for9.21%of the total sample selenium.(6) The selenium distribution and existing forms in selenium-enriched soybean were studyed. The results showed that protein selenium of which selenium content accounted for44.06%of the total ones was the primary form presented in selenium-enriched soybean. The second one was the polysaccharide selenium, accounting for23.58%of the total sample selenium. And there were some inorganic free existence selenium and selenium combinded with nucleic acid. The extraction rate of soybean protein was43.37%. Alkali-soluble protein occupied the highest proportion, accounting for9.66%of the total sample, and prolamin occupied the lowest proportion, accounting for1.87%of the total sample. The selenium content of Alkali-soluble protein was the most, accounting for21.85%of the total sample selenium. The selenium content of prolamin was the least, accounting for3.20%of the total sample selenium.(7) The selenium distribution and existing forms in selenium-enriched rapeseed were studied. The results showed that the selenium content of selenium-enriched rapeseed mainly existed in the rapeseed dregs of which selenium content accounted for97.63%of the total ones of rapeseed. Protein selenium of which selenium content accounted for45.92%of the total ones was the primary form presented in selenium-enriched rapeseed. The second one was the nucleic acid selenium, accounting for20.49%of the total sample selenium. And there were selenium combinded with polysaccharide and some inorganic free existence selenium. The extraction rate of soybean protein was48.97%. Alkali-soluble protein occupied the highest proportion, accounting for10.97%of the total sample, and salt-soluble protein occupied the lowest proportion, accounting for2.09%of the total sample. The selenium content of Alkali-soluble protein was the most, accounting for22.75%of the total sample selenium. The selenium content of salt-soluble protein was the least, accounting for6.91%of the total sample selenium. |
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