Application Research Of Statistical Analysis Methods For Heavy Metal Pollution In Rice

Rice plays an important role in food.More than half of the world's people and more than 60% of the population in our country take the rice as the main food.However,the food security in our country is increasingly threatened by metal pollution in recent years.With the improvement of people's awareness of food safety and more attention paid to the food quality from our country,more and more domestic and foreign scholars carry out researches on the heavy metal pollution and its governance.While some studies only based on small-scale planting experiments and couldn't reflect the situation of heavy metal pollution to rice in larger scale.And some researchers in the national monitoring department only use some simple statistics and no in-depth analysis on the monitoring data.This paper makes comprehensive analysis about the heavy metal pollution situation in rice of Hunan Province by the classical statistical methods and spatial statistical methods.Firstly,descriptive statistical analysis and comparison about the content,detection rate and over-standard rate of heavy metal in rice of every city in Hunan province are conducted.And the results on map to explore the whole situation of metal pollution in rice in Hunan province and its spatial distribution pattern are given.Then the spatial distribution pattern of heavy metal pollution in rice field is explored by spatial autocorrelation.Finally,research on the influence of heavy metal on rice yield by geographical weight regression is carried out.The main conclusions are as follows:The Cd polluted zones of rice is mainly concentrated in the north of Hunan Province.The total Hg polluted area of rice is mainly concentrated in the north of Hunan.The As polluted region of rice is mainly concentrated in the southeastern of Hunan.Their geographical locations are adjacent,which may explain the similarity of pollution situations.The results show that there is a positive correlation of Cd polluted situation of rice between different cities in Hunan province,so as the total As.While the total Hg polluted situation of rice is negatively correlated.On the whole,the Cd pollution and total As polluted situations show the "low-high" cluster trend in geography,that is,the polluted rice by Cd and total As in Shaoyang is less serious than that in the surrounding area.The relationship between the Cd pollution and the yield per unit area of rice in different regions of Hunan province shows that the lower concentration of Cd takes a positive effect on rice's growth,but when it exceeds a certain concentration,the growth rate is inhibited.And the relationship between the Cd pollution level and output can be approximated by a quadratic function.Due to the existence of spatial heterogeneity,the relationship between the Cd pollution level and the yield per unit area is not the same in different cities in Hunan,and the Cd content corresponding to the largest yield per unit area of rice gradually increased from north to south and from west to east.