Distribution Characteristics And Pollution Risk Assessment Of Typical Trace Contaminants In Huixian Wetland

Wetlands,as the “kidney of the earth”,are currently facing the threat of environmental pollutants.River wetlands are the most affected wetland ecosystems by pollutants.Guilin Huixian Wetland is the largest karst landform original wetland in the Lijiang River Basin.Its ecological status is important and special,while the long-standing human activities in the wetland increase its possibility of being contaminated by heavy metals and antibacterials.This paper mainly analyzes the typical trace contaminants such as heavy metals and antibiotics in the surface water,sediments and plants of the ancient Guiliu Canal section of Huixian Wetland during summer and autumn,in order to obtain the temporal and spatial distribution of these two types of unconventional pollutants.Information such as characteristics and pollution levels.Among them,the heavy metals include As,Hg,Cr,Ni,Cu,Zn and Pb.Antibacterials include ofloxacin(OFL),ciprofloxacin(CIP),tetracycline(TC),sulfadiazine(SDZ),sulfamethoxazole(SMX),sulfamerazine(SMR),sulfamethazine(SMZ)and trimethoprim(TMP).1.Temporal and spatial distribution characteristics and pollution evaluation of heavy metals.(1)The determination and analysis of heavy metals in surface water indicate that the average contents of Cr,Cu and Zn are higher,while the average contents of Ni,Pb,As and Hg are lower.The average contents of As,Hg,Cr,Cu,Zn and Pb in summer are higher than those in autumn,while Ni is opposite.Correlation analysis show that the distribution characteristics of heavy metals in surface water are related to physical and chemical indicators,and there are correlations among different heavy metals and show seasonal differences,and similar conclusions are found in sediments.Based on the limits of As,Hg,Cu,Zn and Pb in Class III surface water,it is found that the water quality in both seasons are Class IV surface water.Surface water is heavily polluted in summer and lightly polluted in autumn,the pollution degree rating is mainly affected by the Hg content characteristics.Compared with the drinking water quality limits,it is found that the Pb and Ni content of some samples are high,and 7 of the 12 points are not suitable for drinking water.Compared with the irrigation water quality limits of farmland,it is found that surface water at various points can be used as irrigation water for farmland.(2)The determination and analysis of heavy metals in sediments indicate that the average contents of Cr and Zn are higher,followed by Ni,Pb,Cu and As,while the average content ofHg is lower.The average contents of Hg,Cr,Ni and Zn are higher in summer than those in autumn,while As,Cu and Pb are opposite.Based on the pollution risk screening values of the agricultural land,it is found that the sediments are lightly polluted in summer and autumn.The detection values of As,Hg,Cr,Cu and Zn at some sample points in both seasons exceeded the risk screening values,but they are lower than the risk management values.Ten of the 12 samples have high contents of heavy metals.Based on the background value of heavy metal contents in the soil of Guilin City,it is found that the pollution level is clean to partial moderate pollution in summer and clean to moderate pollution in autumn.It is mainly moderate ecological risk in summer,and it is half of the slight ecological risk and half of the moderate ecological risk in autumn.In the two seasons,except for the strong ecological risk of Hg,the other heavy metals all have slight ecological risks.Points 2,3,4 and 5 are highly polluted,and this section is greatly affected by human activities such as industrial and agricultural production and living.(3)The determination and analysis of heavy metals in various parts of plants indicate that the average contents of Zn is higher,followed by Pb and Ni,while the average contents of Cr and Cu are lower.The average contents of Cr and Zn in stems and leaves,and the average contents of Cu in roots and stems are higher in summer than those in autumn,and the rest are lower in summer than in autumn.In summer,the order of Cr and Zn average contents are root>stem>leaf,and Cu,Ni and Pb are root>leaf>stem.In autumn,the order of Cr,Cu,Zn and Pb are root>leaf>stem,while Ni is stem>root>leaf.The enrichment coefficient method is used to calculate the enrichment relationship between heavy metals in plants and heavy metals in surface water or sediments.It indicates that the BCFs are higher in autumn than in summer,and the enrichment ability of Ni,Cu,Zn and Pb are higher than that of Cr.Points 1,5,6,7,9,10,11 and 12 have the potential to enrich heavy metals.Correlation analysis show that there are strong correlations between various heavy metals in plants and heavy metals in surface water and sediments,and show seasonal differences.2.Temporal and spatial distribution characteristics and pollution evaluation of antibacterials.(1)The determination and analysis of antibacterials in surface water indicate that the average content of TC is higher,followed by CIP and OFL,while the average contents of SDZ,SMZ,SMX,SMR,TMP are relatively lower.The average contents of OFL,CIP,TC,SMZ,TMP are lower in summer than in autumn,while SDZ is opposite.The highest average contents of antibiotics in summer and autumn are quinolones and tetracyclines,respectively.And the lowest in the two seasons are antibacterial synergists.The risk quotient method is used to evaluate the ecological risk of all the antibacterials,it is found that OFL and CIP arehigh-risk grades in summer and autumn.TC and SMX are low-risk grades in summer and medium-risk grades in autumn.SDZ,SMZ and TMP are low-risk grades in summer and autumn.Correlation analysis show that there are correlations between antibacterials in surface water and show seasonal differences,and similar conclusions are found in sediments.(2)The determination and analysis of antibacterials in sediments indicate that the average contents of TC is higher,followed by OFL and CIP,while the average contents of SDZ,SMX,SMR,SMZ,TMP are relatively lower.The average contents of CIP,SMX,SMZ are higher in summer than those in autumn,while OFL,TC,SDZ are opposite,and the average contents of SMR,TMP are equal in summer and autumn.The highest average contents of antibiotics in summer and autumn are quinolones and tetracyclines,respectively.And the lowest in the two seasons are antibacterial synergists.(3)The determination and analysis of antibacterials in various parts of plants indicate that the average contents of OFL,TC and TMP are higher in plants,followed by CIP,SDZ and SMR,while the average contents of SMX and SMZ are relatively lower.Except for the average contents of SMX,SMR,SMZ,TMP in the roots,the average contents of SMR,SMZ in the stems,and the average contents of OFL,TC,SMR in the leaves during summer are lower than those during autumn,the rest are higher during summer than during autumn.When it is higher than autumn.In summer,OFL,CIP,TMP are mainly concentrated in the roots,SMR,SMZ are mainly concentrated in the stems,and TC,SDZ,SMX are mainly concentrated in the leaves.In autumn,OFL,CIP,SMZ,SMX,TMP are mainly concentrated in the roots,TC,SMR are mainly concentrated in the stem,and SDZ is mainly concentrated in the leaves.The average contents of antibacterial synergists in roots and stems are the highest in summer,the tetracyclines is the lowest,while in leaves are opposite.In autumn,the average contents of antibacterial synergists,tetracyclines,sulfonamides are the highest in the roots,stems,leaves,respectively.The average contents of tetracyclines are the lowest in roots and leaves.,and antibacterial synergists is the lowest in stems.Correlation analysis show that there are correlations between various antibacterials in plants and antibacterials in surface water and sediment,and show seasonal differences.In general,there are different degrees of pollution of heavy metals in surface water and sediments,and there is a phenomenon of enrichment of heavy metals in plants.At the same time,antibiotics in surface water,sediments and plants have been detected.Although the concentrations are low,they have constituted ecological risks and need to be taken seriously.