Study On Soil Cadium Pollution In The Urban-Rural-Integration-Area

As connecting link urban and rural areas,the Urban-Rural-Integration-Area fringe of the main food supply of urban area,waste is also accepted by the city's main venue,a strong sense of human activities affect the ecological environment in the region.From the 90's since the 20th century, industrialization and urbanization caused by increasing concentration of heavy metals in soils are of concern to scientists.Cadmium is a dangerous element of the environmental contaminants;crops will not only lead to a decline in production and quality,but also for animals and humans have a strong poisoning effect.Therefore,the study of urban-rural ecotone characteristics of soil cadmium pollution,evaluation of their potential hazards is essential.In this paper,the typical Urban-Rural-Integration-Area---Xiema town of Chongqing as an example,and its cadmium were studied.Through analysis of 21 soil samples and 6 vegetables (lettuce) samples,study on cadmium pollution in soil in the study area;study of cadmium contamination in soil;soil cadmium occurrence and distribution patterns of the relationship to soil properties;bioavailability of soil cadmium;static soil cadmium adsorption,desorption and adsorption study of influencing factors;And study soil cadmium pollution early warning based on the DGH in the study area.The results are as follows:1.The analysis of the study area to test a total of 21 soil samples,15 soil samples were polluted by cadmium,the total number of soil samples accounted for 71.4%.Light pollution one of 12 copies, 3 moderately polluted copies,respectively,the total number of soil samples to 57.1%,14.3%, cadmium level integrated pollution light pollution.Calculation of the study area of the potential ecological risk of cadmium of the average coefficient of 93.32,reaching the level of intensity of potential ecological risk,the study area caused soil pollution should be sufficient attention..2.The study area in the form of soil cadmium content in order of the average:RES＞OM＞EXC＞CAR＞OX＞WS.Effective state ion exchange with the state into a highly significant correlation coefficient of 0.911 shows that ion exchange with a higher Cd bioavailability.Study on occurrence of cadmium in soil species distribution and soil physical and chemical properties of the correlation is not great.3.The study area vegetables(lettuce) in the cadmium content exceeding serious.Cadmium in soil of the study area has been safe production of vegetables,the more seriously affected. Application of neutral 1mol·L^-1 of NH₄Ac cadmium in purple soil extraction to measure bioavailability of cadmium in soil is feasible.And cadmium in the form of cadmium ion-exchange NH₄Ac-Cd up with very significant positive correlation and therefore a higher bioavailability. Analysis of cadmium in vegetables and soil in the form of the relationship between cadmium,come to vegetables(lettuce) and cadmium content in soil cadmium ion-exchange was a significant positive correlation,which again shows the cadmium ion-exchange high biological effectiveness. Recommended to take effective measures to strengthen urban-rural ecotone management,in order to reduce the cadmium in soil ecological harm.4.The study area of purple soil on the cadmium adsorption isotherm Freundlich equation can be used,Temkin equations to describe,from the overall perspective,Freundlich equation better fit. With the number of desorption of cadmium adsorption increased,but accounted for adsorption and desorption of cadmium in cadmium ratio changed little,with the adsorption capacity is not increased. The impact of soil organic matter in soil of cadmium are holding an important factor in solid.Cd²⁺ concentration of solution increased,the soil temperature will be the adsorption of cadmium increased.5.The Cd element in the soil of study area does not have DGH characteristics,so the Cd element in the soil of study area is not likely to break into DGH.