| Spartina alterniflora was introduced into China in 1979 as an ecological engineering species because of its good characteristics of reducing coastal tides erosion,trapping sediments and protecting coastal levees.However,S.alterniflora has become a threat to coastal ecosystems in eastern China,which spreads rapidly in coastal areas with its strong adaptability and reproductive capacity.Studies showed that uptake and accumulation of metals in S.alterniflora salt marshes.In the last few years,it has become one of the hotspots of coastal ecosystem researches.Fe,Cu,and Zn are three kinds of transition metal elements in soil,and they are also necessary micronutrients for plant growth.When the content of metal elements in soil of coastal wetland increases,the risk of heavy metal pollution increases,resulting in soil environmental pollution and threatening the ecosystem balance of coastal wetland.We collected soil samples and plant samples,in order to further explore the impact of the invasion of S.alterniflora on the distribution of Fe,Cu,and Zn in soil in estuary wetland of Jiaozhou Bay,the ecological risk of heavy metal pollution,and the uptake and accumulation characteristics of Fe,Cu,and Zn by different organs of S.alterniflora.Soil samples were collected in March,May,July,September and November 2017 at the S.alterniflora wetland and the mudflat of Jiaozhou Bay,and plant samples were collected simultaneously.The contents of Fe,Cu and Zn in soil samples and plant samples were determined by Inductively Coupled Plasma Optical Emission Spectrometer(ICPOES).The contents of organic matter,soluble salt,pH,water content,bulk density and soil particle size were determined and analyzed.The main results are as follows:(1)The contents of Fe,Cu,and Zn in soil of S.alterniflora wetland were higher than those in the mudflat,and the differences of Fe and Cu contents in the two sampling areas were significant(p<0.05).The invasion of S.alterniflora significantly increased Fe contents in soil.There were significant differences in Fe contents of 0-50 cm soil layers between the two sampling areas(p<0.05).In May and July,Fe contents in S.alterniflora wetland increased firstly and then decreased with soil depth.Cu contents of 20-40 cm soil layers in the two sampling areas were significantly different(p<0.05).The contents of Fe,Cu,and Zn of S.alterniflora wetland increased first and then decreased with sampling months,the maximum values were September,July and September,respectively.(2)Compared with the mudflat,the increases of Fe contents in March,May,July,September and November in soil of S.alterniflora wetland were 25.36%,29.50%,17.52%,30.28% and 14.48%,the increases of Cu contents were 6.66%,21.42%,47.23%,56.46% and 13.77%,and the increases of Zn contents were 33.61%,10.96%,-23.32%,15.81% and 20.05%,respectively.The increasing trend of Cu contents in soil of S.alterniflora wetland was up firstly and then down,while the increasing trend of Zn contents was opposite to that of Cu.The geo-accumulation index and potential ecological risk index of Cu and Zn in soil of the mudflat were lower than those in S.alterniflora wetland,indicated that the invasion of S.alterniflora increased the risk of metals pollution in soil.But on the whole,the risk of heavy metals pollution in estuary wetland of Jiaozhou Bay was low.(3)The contents of metal elements in roots,stems and leaves of S.alterniflora were Fe > Zn > Cu.The uptake and accumulation of metal elements in roots,stems and leaves of S.alterniflora changed with the growth of the plant.The contents of Fe,Cu,and Zn in roots were generally higher than those in stems and leaves.The biomass of roots and leaves was significantly different during the plant growth.In all sampling months,stem biomass was higher than that of root and leaf biomass,Zn and Cu contents in stems were higher,which made the accumulation of Zn and Cu in stems higher than those in roots and leaves.(4)The correlation analysis suggested that Fe contents in soil of S.alterniflora wetland and the mudflat were significantly positively correlated with organic matter content and soluble salt content(P<0.01).Fe contents in the mudflat were positively correlated with Cu contents(P<0.05),positively correlated with water content(P<0.01),negatively correlated with bulk density(P<0.01).There was a significant negative correlation between Zn contents in the two sampling areas and pH value(P<0.01),and a significant positive correlation between Zn contents in the mudflat and soil organic matter(P<0.05).Cu contents in the two sampling areas were significantly positively correlated with Zn contents in soil(P<0.01).Cu contents in the mudflat were significantly positively correlated with organic matter(P<0.01).The results indicated that Fe contents in soil were greatly affected by organic matter content and soluble salt,Zn contents were greatly affected by pH,and Cu contents and Zn contents in soil were closely related. |
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