The Study On Spatial-temporal Characteristics Of Water Quality And Water Environment Quality In Jinhai Reservoir

Jinhai reservoir is one of the important water resources in the Yellow River Diversion Project into Hohhot city that the quality of the water is closely related to the health of the citizens in the urban area as well as the production and development in the society. A water sampling was collected every month from June,2012 to May,2013 to conduct indoor monitor on the water quality index and identify the phytoplankton species, make the analysis of temporal and spatial variation on the water quality of the reservoir based on the experimental data, study the structural characteristics of the phytoplankton and evaluate the water environment quality, which works out the following conclusions:(1) The TN content in Jinhai reservoir is comparatively higher than the annual averaged water surface Ⅲ-class standard with Nitrogen pollution; while the NH3-N content excesses the standard in winter and keeps comparatively lower concentration in other seasons; the concentrations of DO、TP、CODMn in the whole year is comparatively low and match the water quality requirement. The content of nitrite is comparatively lower for its unstable components while the content of nitrate is comparatively stable with lower variation. The average water temperature all over the year is 13 ℃, the average pH value is 8.16, the annual average SD value is comparatively lower and the Chl-a content is increasing dramatically in winter while it is relatively stable in other seasons. In conclusion, the annual water quality in Jinhai reservoir is comparatively good, but based on the seasonal comparison analysis, many indexes are comparatively higher in winter, which indicates the water quality in winter is comparatively bad and easily polluted.(2) According to the analysis on the spatial variation features of the water quality index in winter (freeze up period), the head concentrations of the TN and TP values are comparatively higher, the middle concentrations of them are moderate and the end concentrations of them display the lower tendency; the CODMn concentration value indicates the tendency of higher in southeast and lower in northwest while the eastern NH3 value in the middle of the reservoir is higher and gradually lower to the west area; the overall distribution trend of the Chl-a value is the highest in the head reservoir, moderate in the middle reservoir and smallest in the end reservoir, while the overall distribution of DO values shows the increasing trend from the inlet to the outlet of the reservoir. It obtained comprehensive:water quality indicators concentration decreased (contrary DO), the water had significantly improved by precipitation and purification of Jinhai reservoirs. After species identification, phytoplankton community structure characteristics was:green algae-diatoms type based, both cyanobacteria-Euglena-dinoflagellates-Cryptophyta-golden algae type in Jinhai Reservoir, the monitored species of the phytoplankton in winter is only 14, which accounts for 31.11% of the total amount; the higher density value of the phytoplankton is almost in the middle vertical sampling and the right vertical sampling since the density of the phytoplankton in the left vertical sampling area is comparatively smaller, among which, water fluidity is an important elements determining the density of the phytoplankton.(3) It discovers by principal component analysis that the four major components represent the previous 11 water quality indexes, among which, the first component is closely relative to temperature, permanganate index, total nitrogen, ammonia nitrogen and nitrite; the second component is total phosphorus, dissolved oxygen and chlorophyll a, the third component is pH value and nitrate while the fourth component is closely related to transparency.(4) The single-factorial evaluation, Nemero pollution index method and fuzzy synthetical marking method are adopted to evaluate the current condition of the water quality in Jinhai reservoir, and the three evaluation results have the communality and the distinctiveness. Through the comprehensive analysis, the current condition of the water quality in Jinhai reservoir is comparatively good, which has archived the surface water Ⅲ-class water quality standard from the overall perspective. However, some months still meet the pollution to some extent, which corresponds to the seasonal variation characteristics of the water environment factors and needs relative solutions timely.