| Xinjizhou Wetland Park is the first continental beach-type national wetland park in China,and is an important water source for the Nanjing area.Investigating the soil quality is of great significance to the protection and utilization of Xinjizhou National Wetland Park,which can also protect fishery resources and purify water sources in the Yangtze River.Therefore,a total of 128 surface soil samples(0～30 cm)were collected in September 2020 and May 2021 in this study.The soil nutrient content and heavy metal content were analyzed,and the distribution characteristics of soil nutrients and heavy metals were discussed.The principal component analysis and correlation analysis were used to explore the influencing factors of soil heavy metals and nutrients.Finally,the single factor pollution index method,Nemerow comprehensive index method and potential ecological risk index method were used to evaluate the environmental quality of wetland soil,and the principal component analysis and membership function were used to evaluate the soil fertility level of the wetland.The main research results are as follows:(1)During the two years,wetland soil p H ranged from 7.90 to 8.60.In 2020,the average contents of available Boron(available B),available Iron(available Fe),available Manganese(available Mn),available Nitrogen(AN),available Phosphorus(AP)and available Potassium(AK)in wetland soil were 0.59,46.63,54.29,71.00,27.13 and 107.89mg/kg.In 2021,the average contents of available B,available Fe,available Mn,AN,AP and AK in wetland soil were 0.61,74.53,34.44,65.38,28.61 and 120.96 mg/kg.In 2020,the average contents of Organic Matter(OM),total Nitrogen(TN),total Phosphorus(TP)and total Potassium(TK)in wetland soil were 17.05,0.81,1.65 and 17.56 g/kg.In 2021,the average contents of OM,TN,TP and TK in wetland soil were 118.61,0.89,1.82 and 19.74 g/kg.During the two years,the contents of total phosphorus and total potassium in wetland soil increased significantly(P < 0.05).From the perspective of spatial distribution,soil nutrients were mainly concentrated in the south of the wetland.The contents of soil OM,AN,AP,AP,TN,TP and TK in Xinzhou Island were higher than those in other islands,and the contents of phosphorus and potassium in wetland soil were rich.During the two years,the contents of AP,AK,TN,TP and TK in the soil of each island increased.Principal component analysis and correlation analysis showed that the main factors affecting soil nutrients in wetlands were parent materials,agricultural activities of residents many years ago,topography and vegetation in the islands.(2)In 2020,the average contents of Cu,Pb,Zn and Cd in wetland soil were 43.87,12.82,101.43 and 0.35 mg/kg.In 2021,the average contents of Cu,Pb,Zn and Cd in wetland soil were 37.37,26.42,146.20 and 0.49 mg/kg.During the two years,Pb,Zn and Cd in wetland soil increased significantly.From the perspective of spatial distribution,in 2020,the high values of Cu,Pb,Zn and Cd in wetland soil were distributed in the low-lying areas along the Yangtze River.In 2021,the high value areas of Cu,Pb,Zn and Cd in wetland soil were mainly distributed in Xinjizhou Island.The results of principal component analysis and correlation analysis showed that Cu,Pb,Zn and Cd in wetland soil in 2020 were affected by soil parent materials and previous agricultural activities.In 2021,heavy metals in wetland soil were not only affected by soil parent materials and agricultural production activities of former residents,but also by the construction industry.(3)In 2020,the average comprehensive index of wetland soil fertility was 0.39,and the comprehensive index of each island ranked as Xinshengzhou > Regenerationzhou =Zimuzhou > Xinjizhou.In 2021,the comprehensive fertility index of wetland soil was 0.57,and the comprehensive fertility index of each island ranked as Xinshengzhou > Zimuzhou >Zihuizhou > Xinjizhou > Regenerationzhou.During the two years,the comprehensive soil fertility of each island increased,and the areas with high comprehensive fertility index were Xinshengzhou,Zimuzhou and Zihuizhou.The soil background value of Nanjing was taken as the evaluation standard.In 2020,the single-factor pollution levels of Cu,Zn and Cd in wetland soil were potential pollution;the Nemerow comprehensive pollution index in wetland soil was 1.59,and the comprehensive pollution degree was mild pollution.The potential ecological risk index is 66.54,and the risk level is low ecological risk.In 2021,the single factor pollution level of Cu,Pb and Zn in wetland soil was potential pollution,and the single factor pollution level of Cd was mild pollution.Nemerow comprehensive pollution index was 2.18,and the comprehensive pollution degree was moderate;the potential ecological risk index is 90.78,and the risk level is low.Compared with 2020,the comprehensive pollution degree of wetland soil in 2021 was upgraded to moderate pollution,and the potential ecological risk index increased. |
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