Studies On Characteristics Of Elements Enrichment And Transfer In The Rock-soil-herb System Of Ligusticum Chuanxiong

Ligusticum chuanxiong is one of the famous Sichuan geo-herbalism. The planting industry is one of the major economic projects of modern agricultural development to Pengzhou government and also one of the important sources to local farmers. With the deepening of standards in L.Chuanxiong quality, the heavy metal content in the soil and the pollution status of geochemical elements are the main factors affecting the planting industry development in producing area. Therefore, ascertain characteristics of elements enrichment and transfer in the rock-soil-herb system of Ligusticum chuanxiong have important significance to expand the producing area and improve the quality of herbs.In this paper, main conclusions were obtained as follow:(1) Test results show that in research area, the contents of major element N, P in farming soil are more abundant as 1657mg/kg and 1414.75mg/kg;K, Mg,Fe are partly missing just 0.772-0.833 times of the local background. In beneficial element, Mn content is generally low as 498mg/kg while content of Se, Mo are richer than the background level as 0.34mg/kg and 1.5 mg/kg.In heavy metals, content of As in plow layer is 8.29mg/kg and lower to the country background and higher than the local one’s. Cd, Zn, Cr, Pb content are normal to background values but Hg is much higher than the background as 0.27 mg/kg and the times to the background as 4.154、6.750 and 5.400. In line with the quality of agricultural food producing environmental assessment requirements, the quality evaluation of farming soil was analyzed by single factor index,comprehensive index, index of Mull(Igeo) and enrichment factor method, results show that there are different degrees of Cd, Pb, Zn pollution in planting soil layer.(2)In the whole soil profile, major elements N, P, S, beneficial elements Mo, B, Se, and the content of heavy metals were shown to increase with soil depth decreased, indicating its content mainly from the soil parent material. K, Ca, Mg, Si content increases with increasing depth of the soil profile, Mg showed an increasing trend after first reducing the soil profile, may be associated with rock types. Among 7 points, major elements, useful elements and heavy metals concentrations were higher in samples Ⅶ, there was no significant different among types of soil samples and indicate the environment has a greater impact on soil geochemical element contents between samples.In plant- soil- rock systems,the migration capability of element As, Hg, Zn, Pb is weak while Cd, Cr, Cu content is greater than soil and its pedogenic rock and indicate there are some artificial point source. The rhizome and aboveground of L. chuanxiong had a stronger enrichment of Cr as average indexes 1.399 and 1.160.Compared with soil,the two parts had a different enrichment tendency of heavy metals as rhizomes enriched more As, Cr, Hg while aboveground more Cd, Cu, Pb, Zn.The enrichment of elements in the overground part show the same order as the underground part as Mn> B> Mo> Se in L. chuanxiong.(3) Results show that irrigation water quality in study area is up to the mustard of irrigation water Ⅴ class standards and in line with the requirements of environmental quality of surface water with pollution-free of Cd, Cr, Pb, Se, As, Hg, and Zn, element content of Cd, Hg, Se were more than the local soil background values in atmospheric dust fall and the presence of Cd, Se were light- moderate pollution while Hg in strong contamination by Cumulative index method( Igeo index).(4) Content of heavy mental Pb exceeded the GAP standards in total 7 samples in rhizome and content of Cd, Cu, Hg, Zn were exceeded in aboveground.Evaluation by THQ method, the results show that the rhizome and overground parts had no obvious effect on human health in Cd, Pb for the THQ values are less than 1,but there are 42.86% and 57.14% samples in total herbs and have much more risk in Cr to human health. Compared with the rhizome,the arcial part has a higher risk index to human health. Compared with the standard of L. chuanxiong Product of Geographical Indication in Dujiangyan, content of heavy elements in herbs of Pengzhou only qualified in As, Hg,and Cd, Cu, Hg, Pb are far more differences,this maybe the main quality characteristics in different producing area.(5)To trace the source of heavy metals in the growth environment and in the herbs by correlation analysis and factor analysis, the results showed that element of Cd, Zn, Pb in surface soil mainly from soil parent material and As was affected by human farming activities mostly, while industrial activities affected the content of Cr significantly in study area.Research on atmospheric dust indicated that heavy metals in soil and in the parent material were the main source of Hg,also with the local coal, road traffic-related, element Cd, Se possibly comes from the local industry coal. Over all, the heavy metal content in rhizome and shoot of L. chuanxiong varied significantly between different sampling points mostly affected by their environment.(6) By comparing between four methods as vegetable-herb,paddy-herb(no tillage), paddy-herb(tillage) and drying-herb, result showed that the plant height and the ratio of WR/ WT were higher in method vegetable-herb with 52.940 cm and 38.04%;The fresh weight of single plant and fresh weight of single acrial part were much higher in method drying-herb than other three ones with 152.820 g and 101.720 g.there are no significant difference in fresh weight of single rhizome and output per hectare among four ways. Content of As are under the level of GAP Standard and food standard in China, but content of Cd, Pb were much more higher in vegetable–herb rotation system than the other ones and exceeded the food standards and GAP standards at the same time. Analysis shows the heavy metals may come from a large number of previous crop production as fertilization or spraying insecticide or both.The acrial part of L. chuanxiong enrich more Cd, Pb than the underground part and had a greater risk to human health than the latter.(7) In this study, the surroundings had very important impacts on content of heavy mental in soil, air falls and the plant parts focus on road traffic and population density. Soil-forming process, soil types and watering condition affect the distribution and enrichment of heavy metal lightly and only exist in parts of samples. In conclusion, the contribution of human activities had greater effect on L. chuanxiong rhizome and acrial part than the agro-geological background factors.In conclusion, the contribution of human activities had greater effect on L. chuanxiong rhizome and acrial part than the agro-geological background factors.