Geochemical Features Of The Soil Elements And Its Ecological Efficiencies In The ShuangTaizi River Estuary

The Shuangtaizi estuary of Liaohe River is the important estuary in the northern China, which has formed the muddy coast estuary by the nature evolution for long time. The meandering river, the reed swamp, the muddy tidal flat and various biotic communities commonly consist of the characteristic delta wetland ecosystem. While the excessive human activities are aggravating, it lead to the deterioration of the ecological environment, the larger-area extinction of plant community of Suaeda heteroptera, the vanishing of the unique nature ecological landscape, which seriously affect on exploiting of the tourist resource in the area.This paper analyzes systemically supergene geochemical feature of soil elements and its plants ecological efficiency by sampling, researching plant community in the tidal flat, size analysis and content analysis of element of sample in the studying area. The main conclusions can be summed up as follows.The main grain size of sediment on the tidal flat is slit, with average content of 72.40%, and next size is respectively clay (21.82%) and sand (5.84%), so the type of sediment is muddy clay deposit. The skewness of all the size distribution curves is positive deviation but for two curves. The coefficient of kurtosis of the size distribution curve lies between 4~7, so the curves are very sharp, and unimodal distribution which indicates that the hydrodynamic force condition is approximately consistent in the tidal flat. The average grain size of tidal sediment in the east estuary lies between 12.63~31.16μm, with the average value of 17.18μm, which is thinner than the grain size of Sandaogou tidal sediment in the west estuary, because the average grain size of Sandaogou tidal sediment in the west estuary where the erosion efficiency has emerged, lies between 29.30~32.40μm, with the average value of 30.76μm. The grain size of tidal flat from littoral zone to estuary zone varies gradually from thick to thin, which is determinated by the hydrodynamic force and the estuarine terrain.Generalizing the research data of soil physical behavior in the tidal flat, we find some rules as follows. Firstly, around the Suaeda heteroptera plant flourishing the most soil color is for tawny, its texture for loam or clay soil, its tightness for a little tightness, and the soil contains lots of roots. Secondly, around its degeneration area the most soil color is for grayish brown, its texture for sandy loam and loam soil, its tightness also for a little tightness, and the roots have decreased obviously. Finally, around its extinction area the soil color is also for tawny, its texture most for sandy loam soil, its tightness for comparative tightness, and the roots have completely disappeared in the soil.Investigating their macroelement characteristics in the supergene geochemical environment, we find some conclusions as follows. Firstly the regulations of macroelements distribution closing to ocean is comparatively complicated, while in the direction far away form coast, the distributions of Al2O3, CaO, TFe2O3, MgO are similar, and the distribution of SiO2 is just different from the former, and the distribution of K2O, Na2O is consistent. Secondly, Al2O3, CaO, TFe2O3, MgO and SiO2 consists in the significant negative correlativity, while K2O and Al2O3, CaO, TFe2O3 consists in the significant positive correlativity, and Na2O is correlative only with K2O and MgO, not correlative with else elements.Investigating their microelement characteristics in the supergene geochemical environment, we find some conclusions as follows. Firstly, some microelements happen to accumulate, such as Cu, Pb, Zn, but V runs off. Secondly, the microelement distributions far away from the coast take on the banding distribution except Ti and Ba. Among all microelements taking on banding distribution Sr and Zr contents in the high tidal flat are higher than its contents in the middle or low tidal flat, while the reverse distribution for other microelements. Thirdly, the space distribution can be divided into two types: I type for estuarine zone and II type for littoral zone, which might be controlled by the estuarine terrain. This is similar to the land-use distribution of the tidal flat. Fourthly, the transitional elements of quaternary periodicity have the best correlativity with the chalcophile elements. Sr has the best correlativity with Ba, but it has the better correlativity with others. Nb has the best correlativity with Y, but it has the worst correlativity with others. All microelements can be divided into 3 combinations: the first combination contains Zn, Mn, Rb, Co, Cu, V, Ni and so on, which is consisted of siderophile elements and chalcophile elements; the second combination has Sr and Ba, which has correlation with potassium mineral; the third combination has Nb and Y , which has correlation with thin clay mineral. According to rock types and mineral composition, Liaohe river drainage area can be divided into four provenances which contribute to the sediment in outfall area. Through chemical mass balance method(CMB), contributing models of four provenances are established, and then the contribution ratio of four provenance to the deposition area is calculated, respectively for 76.08% (II), 17.10% (IV), 5.58%(I), 1.24%(III).Concentrations of heavy metals in tidal sediments of the Shuangtaizi estuary lie in the mid range for Chinese estuary. Assessment results show that metal pollution levels of Zn, Cu and Pb only belong to low pollution level in the Sandaogou area, but in the other research areas for mid pollution level; metal pollution level of Cd belongs to a little high pollution level in the Zuanjingpingtai and Sanjiaozhou areas, but in the other research areas for mid pollution level; metal pollution level of As belongs to mid pollution level in all the research areas. Comparing with ecology risk index(RI), we can find that a little high potential ecology risk of heavy metals in the tidal flat lies in the Guanniaotai, Zuanjingpintai and Sanjiaozhou areas, but other areas for mid potential ecology risk level.Generalizing the investigating data of Suaeda heteroptera plant community, we find that it is a little obvious that Suaeda heteroptera plant community affect the accumulation and distribution of heavy metals in the tidal flat.In conclusion, according to investigation and sample testing, this paper systemically analyzes the feature of composition and space distribution of grain size in the tidal sediments, generalizes the physical behavior of tidal soil, studies the features and regulations of elements content, space distribution, symbiosis, accumulation, transport and origin in the supergene geochemical environment, evaluates the present pollution level of heavy metals and the potential ecology risk level, and disclosures that Suaeda heteroptera plant community affect the accumulation and distribution of heavy metals in the tidal flat.