Distribution Of Biogenic Elements, Pollution Assessment And Stoichiometry Analysis Of Soil From The Liaohe Estuarine Wetland

In order to understand the distribution of biogenic elements, the potentialecological hazards and stoichiometry characteristics, surface soil samples andsediment cores were collected from Liaohe estuarine wetland in May and August2009. Biogenic elements were analyzed and their Potential ecological risks wereevaluated. Biogenic elements included total organic carbon, total nitrogen and totalphosphorus. There are scientific and practical values to do research on the Liaoheestuarine wetland.Concentrations of total organic carbon were in the range of0.19%～1.36%、0.17%～1.44%in surface soil from Liaohe estuarine wetland in the spring andsummer and autumn, the average mass fraction of total organic carbon were0.70%and0.68%, coefficient of variation were0.49and0.51. The concentrations of totalorganic carbon were relatively low compared to other regions. In generalconcentrations of total organic carbon did not change with the seasons, total organiccarbon content in the surface soil is spring>summer, the content showing the trend ofhigh in the middle and low in north and south sides. Vertical distribution of totalorganic carbon increased from bottom to surface, the partial layer of total organiccarbon content fluctuations may due to differences of terrigenous total organic carboninput year from year. From the TOC/TN ratios of surface sediments, the average ofwhich were4.98and5.23, it is suggested that the sources of total organic carbon maybe river aquatic life from Liaohe and marine aquatic organisms, and dominated byinternal sources of total organic carbon.Concentrations of total nitrogen were in the range of0.07%～0.29%,0.06%～0.19%in surface soil from Liaohe estuarine wetland in the spring and summer and autumn, the average mass fraction of total nitrogen were0.13%and0.12%respectively, coefficient of variation were0.35and0.30. The content of total nitrogenshowing the trend of high in the middle and low in north and south sides. Theconcentrations of total nitrogen were relatively low compared to other regions.Affected by the depositional environment, sediment early diagenesis and humanactivities, the vertical distribution of total nitrogen characteristics of degraded areasare different, vertical distribution of total nitrogen increased from bottom to surface.Concentrations of total phosphorus were in the range of0.41～0.66‰,0.57～0.97‰in surface soil from Liaohe estuarine wetland in the spring and summer, theaverage mass fraction of total phosphorus were0.72‰and0.51‰respectively,coefficient of variation were0.16and0.14. The concentrations of total phosphoruswere relatively low compared to the Lakes sediment content, but higher than sedimentor soil of seaside region harbor. Generally speaking vertical distribution of totalphosphorus increased from bottom to surface.Ecological risk analysis evaluation of surface soil from Liaohe estuarinewetland in spring and summer suggested that the organic carbon、 total nitrogen andtotal phosphorus pollution meet the standard of ClassⅡ.Organic pollution evaluation of surface soil from Liaohe estuarine wetlandresults show that: Overall, the organic index mean of the surface soil from Liaoheestuarine wetland in spring and summer, were respectively0.11,0.10, in a clean state,the mean value of w (ON) were0.13%,0.12%in spring and autumn respectively, inless clear state. For the regional, the degree of pollution of the tidal flats area wassignificantly lower than the reed area, which may be related to the role of tidaldilution of pollutants. The area organic most polluted was in the well area and nearby,which also shows the impact of oil extraction on the environment. The extent ofpollution of the spring and summer were basically the same.The main reason for the difference of TOC up to five times is the differentvegetation of the chek alkali canopy wetlands and reed wetland. As chek alkalicanopy growth at the beach shoals area, affected by the tidal fluctuations and theshorter alternating wet and dry cycle effect, it had better wetland denitrification. Emissions of the irrigation water, industrial and domestic wastewater, and otheranthropogenic disturbance factors narrowed both wetland differences in total nitrogento a certain extent. Vegetation types have little effect on total phosphorus, the totalphosphorus content is mainly affected by soil type and regional climatic conditions.Since the carbon and nitrogen are the structural elements of organisms, in vivocontent is almost constant and has a homology, their sources are organic compounds.Therefore, the significant positive correlation between them.Comprehensive analysis TOC and TN content of two types of wetlands, at afixed sampling time, concentrations of TOC and total nitrogen showed "fluctuation"features, but the contrast concentrations of TOC and total nitrogen between summerand spring, TOC content of soil showed growth, and since Liaohe estuarine wetlandsoils showed alkaline, the volatilization of part the ammonia caused some loss of thenitrogen in such conditions, in August due to high temperatures, volatilization evenstronger, so total nitrogen showed unchanging or even reduce, lead the results doesnot meet the "fluctuation" features. Comparison of the two Wetland degradationshowed that subject to human disturbance and vegetation degradation, reed showed astronger capacity to maintain the balance of carbon, nitrogen and phosphorus.