Behavioral Characteristics Of Nitrogen And Phosphorus In Wetlands And Research On Phytoremediation

In this study,the water and surface sediments were collected from the Nanhai wetland and along the Yellow River in Baotou,Inner Mongolia.The contents of nitrogen and phosphorus and their fractions were determined,the pollution of total nitrogen and total phosphorus in water were evaluated,and APCS-MLR was used for quantitative source apportionment.At the same time,a study on the phytoremediation of Nanhai Lake was carried out by selecting Scirpus Tabernaemontani,Typha orientalis,Juncus effuses,Iris pseudacorus L.and Lythrum salicaria.The results showed that based on WTP,86%of the sampling sites in Nanhai wetland exceeded the class V water standard,and in addition to the P2 and P4 point for rich eutrophic type,the other sites were in the heavy eutrophic type.Based on WTN,64%of the sampling sites in Nanhai wetland exceeded the class V water standard.Based on WTN,the concentration of WTP in the Yellow River and Nanhai wetland was in the heavy eutrophication type.In wetland plant area,5 sampling sites were in heavy eutrophication type,while the rest were in eutrophication type.The average concentration of NO3--N was in the order of Yellow River>the area around Nanhai Lake>central area of Nanhai Lake>wetland plant area.Among the four fractions of phosphorus,the concentration of PIP was Yellow River>the area around Nanhai Lake>central area of Nanhai Lake>wetland plant area,the concentration of POP was central area of Nanhai Lake>the area around Nanhai Lake>Yellow River>wetland plant area,the concentration of DIP was central area of Nanhai Lake>the area around Nanhai Lake>wetland plant area>Yellow River,and the concentration of DOP was wetland plant area>the area around Nanhai Lake>central area of Nanhai Lake>Yellow River.The STN content of 5%of the sampling points in the study area was in severe pollution,119%of the sampling points were in moderate pollution,the remaining 77%of the sampling points were in mild pollution,66%of the sampling points were in severe pollution,and 34%of the sampling points were in moderate pollution.There were 16 sampling points along the Yellow River were considered at the security level.Most of the sampling sites in Nanhai wetland were in the content range that could cause the lowest level of ecotoxic effects.The content of EN-NO3--N in the surface sediments of the study area was ordered as wetland plant area>the area around Nanhai Lake>Yellow River,which is consistent with the distribution of EN-NH4+-N.The average content of HN was wetland plant area>the area around Nanhai Lake>Yellow River.The order of Ex-P content was the area around Nanhai Lake>wetland plant area>Yellow River,the order of BD-P content was wetland plant area>the area around Nanhai Lake>Yellow River,and the order of NaOH-P content was Yellow River>wetland plant area>the area around Nanhai Lake.Compared with the surface sediments in Yellow River,P area and the area around Nanhai Lake had higher release risk and bioavailable phosphorus?Through correlation analysis,principal component analysis and multiple linear regression receptor model of absolute principal component score(APCS-MLR),the sources of nitrogen and phosphorus in Nanhai wetland were analyzed.The results showed that the Yellow River water diversion,pesticide and fertilizer,industrial wastewater and domestic sewage,and degradation of animal and plant residues were the main pollution sources of wetland in Nanhai wetland,with contributions of 31.05%,25.42%,25.36%and 18.17%,respectively.The WTP removal rates of Scirpus Tabernaemontani,Typha orientalis,Juncus effuses and Iris pseudacorus L.and blank treatment groups were 64.29%,55.17%,56.16%,57.18%and 29.46%,respectively.Allium fistulosum had the best plant growth and the highest phosphorus removal rate.The WTN removal rates of Scirpus Tabernaemontani,Typha orientalis,Juncus effuses,Iris pseudacorus L.and Lythrum salicaria and blank treatment groups were 58.25%,59.75%,22.92%,70.46%,47.90%and 30.10%,respectively.In the late stage of phytoremediation,algae appeared in the water of blank treatment group.Combined with plant growth and nitrogen and phosphorus removal rate,Scirpus Tabernaemontani,was the best remediation plant.The removal rate of DIP was 88.89%,and the removal effect was significant.The final removal rate of NH4+-N and NO3--N in Scirpus Tabernaemontani treatment group was 70.98%and 81.45%respectively.After phytoremediation,TP and TN were accumulated in stem,leaf and root.