| In order to clarify the temporal and spatial variability of soil nutrients and heavy metals in prefecture-level farmland scales,this paper took soil samples of rice-wheat rotation in Xinghua.Taixing.Jingjiang.Jiangyan,Hailing and Gaogang as the research object,based on classical statistics,combined with geostatistics and GIS spatial interpolation method,using GPS positioning sampling of the cultivated layer soil(0-20cm)in the study area.We determined the organic matter(OM),Total Nitrogen(TN),Alkali-hydrolyzable Nitrogen(AHN),Available Phosphorous(AP),Available Potassium(AK),and total arsenic,total cadmium,total chromium,total copper,total lead,total zinc content and other indicators in 2017 and 2018.We also carried out the research on the spatial and temporal variability of soil nutrient content and heavy metal at farmland scale.We also carried out soil nutrient grade and soil heavy metal quality safety evaluation.The main results were as follows:1.In 2017,the average contents of OM,TN,AHN,AP and AK were 28.1 g/kg?1.32 g/kg?115.7 mg/kg?15.1 mg/kg?112.5 mg/kg.in 2018.the average contents of OM,TN,AHN,AP and AK were 44.5 g/kg?1.43g/kg?122.2 mg/kg?38.9mg/kg?125.7 mg/kg respectively.OM,TN.AP and AK were significantly different in the two years,and AHN was not significant.From the spatial distribution map,in 2017 and 2018,the content of OM and AK was low in the southern region and high in the northern region,while the TN,AHN and AP were higher in the south than in the north.2.From the evaluation of nutrient grades,the OM and AP contents had fluctuations between years,while the content of TN.AHN and AK did not differ much between the two years.The content of TN was rich in both two years.The two-year content level of the content of AHN was average.AP was average in 2017 and was been rich in 2018.The grade of the content of AK was both rich in two years which was with little difference between two years.3.In 2017,the average contents of total arsenic,total cadmium,total chromium,total copper,total lead,total zinc were 6.83 mg/kg?0.45 mg/kg?54.8mg/kg?11.3 mg/kg?12.5 mg/kg?63.3 mg/kg.The average contents were 7.56 mg/kg?0.46 mg/kg?54.4 mg/kg?19.5 mg/kg?14.8 mg/kg?71.6 mg/kg in 2018.Total copper,total lead and total zinc were at extremely significant level during years.The total cadmium and total chromium were at not significantly different level during years.In 2017 and 2018,the ratio of[C0/(C0+C)]of six heavy metals was as follows:total arsenic>total zinc>total lead>total chromium>total cadmium>total copper and total arsenic>total zinc>total Chromium>total Copper>total lead>total cadmium.total cadmium in2018,total copper in 2017 and total lead in 2018 have strong spatial autocorrelation.Total arsenic,total cadmium,total chromium,total copper,total lead,total Zinc in 2017 and total chromium,total copper and total zinc in 2018 had a moderate spatial correlation.The spatial correlation of total arsenic in 2018 is weak.The distribution patterns of total arsenic,total chromium,total lead and total zinc were similar between two years,both of which were higher in the southern and northern areas and lower in the central regions.In 2017,the total cadmium value was higher in the central region,but the northern region was higher in 2018.The distribution of total copper in the two years is not much different,but its higher value is mainly concentrated in the south and north.Total arsenic,total chromium,total copper,total lead and total zinc were all clean in two years,while in 2017,there were cadmium pollution in Gaogang District and the western of Taixing City and the northern Xinghua City in 2018.4.According to the correlation analysis between soil nutrients and heavy metals,the overall correlation between nutrients and heavy metals in 2018 is stronger than that in 2017.Total arsenic,total copper,total zinc and OM,TN,AHN,AP,AK are in 2018.There was a significant positive correlation between the total chromium,total lead and OM,TN,AHN,and AK in 2018 which was significantly positively correlated with AP.The correlation between total cadmium and nutrients was weak,and it was negatively correlated with AHN and AP.Based on the single factor index method,except for the the content of cadmium in Gaogang was probably been Severely pollution of in 2017 and the total cadmium in Xinghua was been lightly polluted in 2018,the content of total arsenic,total chromium,total copper,total lead and total zinc were not exceeded the standard.According to the Nemero comprehensive index method,there is probably a certain risk of heavy metal pollution in a few areas of Taizhou under the conditions of this experiment... |
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