Soil And Water Quality Analysis Of Fenhe River Wetland Parks After Restoration In Linfen City

The soil,sediments and water of Fenhe River Wetland Parks after restoration in Linfen city were analyzed to understand the soil environment and nutrient supply of vegetation growing on the revetment wetlands of Fen River as well as the material composition and water quality of water sediments,and to evaluate the water condition and water purification efficiency in the wetlands.(1)The revetment green land soil was featured by pH of 7.0-8.4,bulk density of 1.04-1.44 g/cm~3,moisture content of 5.9%-17.5%,and conductivity of 0.167-0.747 m S/cm.The soil was clay loam and loam clay,and the contents of organic matter,total N,total P,alkaline N,available P and available K were 8.7-39.8,0.354-1.046,0.389-1.444 g/kg,12.9-50.3,2.6-31.2 and 86.4-329.2 mg/kg,respectively.Correlation analysis revealed a strong correlation between soil indexes and physical properties.According to the Nutrient Grading Standard from China’s Second National Soil Survey,the organic matter,total P and available P were all at Level 4,the total N was between Level 3 and 6,the alkaline N was between Level 5 and 6,and the available K was between Level 2 and 3.Compared with Level2 and 3 of the soil quality standard,the contents of available Ca,Mg,Fe,Mn,Cr,Zn,Cu,Ni,Cd and Pb were all below the standard.However,the Cd content was 0.104-0.581 mg/kg,which exceeded the soil background levels in both Shanxi Province and China.As for the pollution degrees of soil available metals,Cd pollution was light to moderate.The potential ecological risk analysis showed that Cd pollution was moderate to serious and made 98.99%contribution to the potential ecological risk.In general,it was at a low ecological risk level.The soil physiochemical properties affected the contents of available metals to different extents and were strongly correlated with the Cu,Ca,Pb and Cd contents.Principal component analysis suggested that the sources of Cd involved both human activities and agricultural activities,but all other elements were affected by the soil parent material.(2)The sediments were characterized by pH of 7.3-8.2 and conductivity of 0.505-0.960 m S/cm,and the texture was silty clay loam.The contents of organic matter,total N,total P,alkaline N,available P and available K in the sediments were 37.9,1.050,0.701 g/kg,64.0,13.4 and 175.3 mg/kg,respectively.Correlation analysis uncovered a strong correlation between nutrient indices and texture of sediments,and the organic matter,total N,alkali N and available K were homologous.The sediments were found with moderate organic pollution and severe comprehensive pollution,which reflected whether there was water eutrophication.Among the available Ca,Mg,Fe,Mn,Cr,Zn,Cu,Ni,Cd and Pb in the sediments,the Cd content was 0.15-0.21 mg/kg and caused light to moderate pollution,but no pollution was induced by other elements.As for the potential ecological risks,risk of Cd pollution was moderate and made 98.39%contribution to the potential ecological risk.In general,it was at low ecological risk.According to principal component analysis,Zn,Cu,Ni,Pb and Cd showed high loads in principal component 1 and thus made more contribution to the sediment pollution.(3)Since the contents of organic matter,N,P and heavy metals in the sediments were all higher than those in the surrounding soil,we conducted a water quality survey from April to December,2019.In terms of time distributions,the contents of COD,ammonia N,chlorophyll a,total N,total P,turbidity and TDS maximized to 109.5 mg/L in June,1.176mg/L in July,47.61μg/L in May,29.98 mg/L in November,0.380 mg/L in August,64.02 NUT in August,and 644 mg/L in August respectively.Thus,the levels of all indicators were high in summer.Furthermore,in terms of spatial distributions,the contents of various indicators were basically the lowest in artificial lakes,which were under relatively good water condition.The contents of COD,ammonia N,total N,total P and turbidity maximized near the outlet of the sewage plant,which was obviously point source pollution.In the east water areas,the chlorophyll a content was the highest,which was because of the abundance of aquatic plants and the long retention time of water.Due to the effect of the sewage plant,the contents of different indicators were all slightly higher at the river outlet than at the river inlet.Both the correlation analysis and principal component analysis indicated that COD,ammonia N,total P,total N and turbidity were positively and very significantly correlated,and all belonged to the first principal component,making great contribution to the water pollution.Furthermore,the TN/TP ratio of each sampling point was basically far beyond the limit value of 22.6,indicating the water bodies in the study area were P-limited and contained more N and less P.In single-factor analysis,compared with class V in surface water standard,the qualified rates of COD and total N were only 25%and 3%,respectively,and the qualified rates of ammonia N and total P were 99%and 92%respectively.In Nemerow evaluation,the pollution degree of artificial lakes was clean to light,but the pollution degrees of the river inlet,river outlet,east water areas,west river channel,and the outlet of the sewage plant were heavy to severe.In addition,the Nemerow water pollution index in the east water areas was smaller than in the west river channel,which was attributed to the widened water areas and the water purification function after the reconstruction.According to the evaluation of comprehensive nutritional status,the eutrophication level of artificial lakes was light to moderate,and the eutrophication levels of the river inlet,outlet,east water areas,west river channel,and the outlet of the sewage plant were moderate to severe.