【摘要】 随着内蒙古就地煤电转化发展方式的推行,周边土壤中来自大气汞沉降逐步加剧。为了解牧草对汞的富集能力与耐性机理,选取内蒙古草场常见四种牧草:羊草、紫花苜蓿、披碱草和高羊茅进行研究。通过野外汞沉降模拟试验及汞胁迫盆栽种植试验,分别测定土壤、牧草中的总汞含量及牧草的生理生化值,分析被试牧草汞含量与土壤汞含量相关性。供试土壤为砂土,pH在7.43—8.53,当土壤中汞含量不高于1.0 mg?kg^-1时,四种牧草富集系数皆大于1。结果表明:不同牧草对汞富集能力不同并且会受土壤中汞含量影响,牧草对汞的富集系数随汞胁迫浓度增高而逐渐下降,汞胁迫下牧草细胞膜脂过氧化程度提高,牧草通过提高抗氧化酶酶活、脯氨酸含量调节细胞是其耐受汞的重要机理。更多还原

【Abstract】 Background, aim, and scope Some of large coal enterprises in Inner Mongolia have been striving to develop coal-fired power plants and promoting the integration of coal and electricity, which leads to the rapid increase of coal consumption in Inner Mongolia. During the coal combustion, the phenomenon of mercury emissions into the atmosphere appears, which results in serious impacts on environmental pollution. This paper aims to study the mercury enrichment capacity of various herbages and their tolerance to mercury through the experiment of mercury stress in herbages in Inner Mongolia. Materials and methods The experimental materials included Leymus chinensis, Medicago sativa, Elymus dahuricus, Festuca elata, the herbages and seeds were provided by the grassland station of the Chinese Academy of Sciences in Dongwuzhu, Inner Mongolia, the experimental soil was collected from grassland of Chinese Academy of Sciences in Dongwuzhu, Inner Mongolia.The method of microwave digestion was used to determine mercury content in plant and soil, malondialdehyde（MDA） was determined by colorimetric method, the soluble protein was determined by coomassie brilliant blue staining, the soluble sugar content was determined by anthrone method, respectively. Results In the case of low concentration of mercury, all the four kinds of herbages had certain adsorption capacity on mercury, but when the concentration of mercury in soils continued to increase, mercury enrichment effect of four kinds of herbages did not increase as expected like enrichment plants. When the mercury concentration in soil was not higher than that of the soil quality standard, the enrichment coefficient（EC） of the four herbages were all greater than 1,which reflected better ability to accumulate mercury. Average mercury adsorption efficiency of Leymus chinensis was 26.22%, followed by Elymus dahuricus, the adsorption efficiency was 24.61%, then is Festuca elata, the adsorption efficiency was 22.69%, the lowest was Medicago sativa, the adsorption efficiency was 15.57%. The correlation between heavy metals in plant and soil is related to the physiological characteristics of plant, indicating that the mercury content in herbage is related to the mercury content in soil. With the increase of mercury stress concentration, the content of malondialdehyde（MDA） in the four kinds of herbages decreased first and then rose.After reaching the lowest value, the MDA content of the four herbages increased with the increase of mercury stress concentration. Among them, Medicago sativa had the greatest change in MDA content under mercury stress, which was mostly affected by mercury. When the mercury stress concentration was 64.0 mg ? kg^-1, the proline content of the four kinds of herbages was the highest, respectively 7.48 times, 5.63 times, 3.42 times and4.02 times of the control group. Among the four kinds of herbages, Leymus chinensis was most powerful for the stress resistance of mercury. Discussion Enrichment coefficient is the ratio of the content of certain heavy metals in plants to that in soils, which is one of the important indexes to evaluate the enrichment ability of plants to heavy metals. The greater the enrichment coefficient, the stronger the accumulation ability. Four kinds of herbages have adsorption effect on mercury in soil at various levels of mercury stress. The mercury content in herbage is correlated with mercury content in soil. MDA and proline can reflect mercury physiological toxicity to plants.Conclusions The mercury accumulation in plants is significantly affected by different concentrations of mercury stress. Four kinds of herbages have certain adsorption and transfer ability to mercury in soil. When the mercury stress concentration is low(<16.0 mg ? kg^-1), Medicago sativa has the strongest adsorption capacity. After the increase of mercury stress concentration(>16.0 mg ? kg^-1), Elymus dahuricus has the strongest adsorption capacity. The mercury enrichment coefficient decreases with the increase of mercury stress concentration, among which the maximum enrichment coefficient of Leymus chinensis is the highest. Mercury stress has significant effect on the physiology of different herbages. When the mercury content in soil is too high, it will produce toxic effect on the growth of four kinds of herbages. Under a certain concentration of mercury stress, the herbages can balance cell osmotic pressure by raising proline content, promoting the antioxidant enzymes activity, slowing down the increase of reactive oxygen species and membrane lipid peroxidation caused by mercury stress, thus maintaining the normal growth environment of plants. Recommendations and perspectives Inner Mongolia is a coal-producing province, while promoting the economic development model of coal-electricity integration, longterm planning and protection of grassland ecology should be carried out. Faced with increasing coal-fired power generation, mercury released from coal-fired power plants will also increase. Proper measures should be taken to control mercury content in gas emissions from coal-fired power plants, so as to prevent the impact of long-term and low concentration mercury emissions from coal-fired power plants on grassland vegetation from the source.更多还原