| Wanyuan is a typical mountain farming city in China. Agricultural acreage is relatively narrow and small, which somehow leads to a weak agricultural foundation and small income by farming. Therefore, adjusting and optimizing agricultural structure and developing high-quality farming with local features is the basic way of improving rural income. Wanyuan, locating in the Daba mountains, is next to the famous Se-enriched area Ziyang county in Shanxi province. They have similar geography, calimate conditions and geological background, which possibaly results in natural Se-enriched resource in Wanyuan.Microelement selenium is closely bound up with human health. It has abilities of oxidation resistance, humunity improvement and cancer prevention. Furthermore, it can relieve the harm of poisonous element to body through the antagonism with Pb, Cd,Hg etc. With these biological functions observed, the concept of supplying selenium through food has been paid more attention. Se-enriched food, especially the natural and green Se-enriched food has become more welcome to people.So far scholars have already proved the high content of Se in soil and the existence of Se-enriched soil and Se-enriched tea-leaf. Baiyang Se-enriched tea-leaf has become the typical representative of Se-enriched agricultural products in Wanyuan. However, the detailed information of Se geochemical characteristics, soil environmental quality, content of Se in crops and the safety of crops in typical area that local demands and government supports is rare.Based on the sub-project of Sichuan geological prospecting fund “the agro-geology research and appraisal of Wanyuan high-quality featured agricultural area”, taking ten typical agricultural areas as research object, ascertaining the geochemical characteristics of elements like Se and Cd in rocks, soil, crops,irrigation water,near-surface atmospheric dust and pollution sources. Based on the research mentioned above, establishing a geochemistry assessment model of Wanyuan typical agricultural area land quality and grading the land quality in ten areas, which provides theoretical basises and reasonable suggestion for developing high-quality featured agriculture and preventing land source.The result is following:(1)The Se content in ten areas is various, the basic trend is reducing gradually from north-east to south-west. Se content of soil in every single typical agriculture area is affected by stratum, pedogenic rock and organic content obviously. Mineral affects the content partially, taking barium ores and coal mine as examples, Se content of soil they exist is higher apparently. The Se bioavailability in soil has a negative correlation with Se total content. The Se bioavailability of soil in Dazhu Town and Miaozi country, with high Se content, is the lowest among ten areas.(2)The land quality in typical areas is mainly influnenced by Cd content, situation of standard-exceeding in other heavy metals is few Eventhough the heavy metal content in Dazhu and Miaozi is more higher that of other areas, the bioavailability is relatively lower. There exists polluted soil in Parts of areas, such as Dazhu, Miaozi and Changshi. The content of heavy metals in typical areas is mainly affected by natural background, mineral products is the main cause of soil pollution.(3)There are Se-enriched crops in Wanyuan, the Se-enriched rate is 31.20%. Se content in different kinds of crops in different areas is not the same however. Crops like kiwi fruit in Siluo, tea-leaf in Baiyang, pepper in Yongning and Changshi, potato and corn in Dazhu, kidney bean in Shiren, rice in Yongning have a higher Se-enriched rate. Some crops are not safe. Except for crops in Jiuyuan are all safe, crops in other areas are harmful partly,especially rice,pepper and Eucommia ulmoides.(4)Both the quality of irrigation water and near-surface atmospheric dust are relatively clean, only the near-surface atmospheric dust in coal mining areas is harmfull because of the Cd exceeding the limits.(5)Combining the land quality, crops safty, near-surface atmospheric dust and irrigation water, then establishing a geochemical evaluation model for land quality in typical areas and grading the land quality in ten areas. The land quality in Tiekuang, Baiyang, Jiuyuan and Yongning that based more on the second grade is the best in ten areas and that in Shiren, Zhaotang and Changshi is on the second place.Land qualit y in Miaozi and Dazhu is the worst because of their polluted soil. |
PDF Full Text Request