The Effects Of Urban Riparian Zone Structure On River Water Quality In Beijing

Riparian buffer as an important transitional zone between highland and river, the river water quality and water quality improvement function plays an important role. However, due to the particularity of urban riparian zone, excessive use of hardening slope protection and retaining wall revetment engineering measures to make it more focused on the effect of flood control drainage, such as it ignores the function of ecological measures with vegetation and soil.et. As a result, many urban riparian zone were gradually losing the ecological function.Though, in recent years, the ecological restoration measures has gradually got the attention, but they have been few quantitative study about the function of improve water quality of ecological restoration in urban riparian zone, Therefore this study use experiment and model to compensate for the loss.From July to October in 2013, the experimental study on Beijing Yongding river shows that there were obvious seasonal variations in the concentrations of these nutrients and DO.For the majority of sites, the water quality could not meet the requirement for the surface water standard class IV in the most sampled periods. The NH4+-N concentration was lower where the amount of hydrophytes was relatively large, In the growing seasons, the stronger growth coverage of hydrophytes led to the higher DO and NO3--N concentrations, but the lower TP concentrations; while later growing period, much more litters contributed to higher TP and lower DO concentrations. The convex river bank could enhance the DO and NO3--N concentrationsand reduce the NH4+-N concentration. In short, changing the structure characteristics of riparian zone such as bank material, abundance of hydrophytes, and curvilinearity of river banks also had great effects on water quality in the Yongding river.REMM model was used to simulate the effects of ten different types of riparian buffer on the retention of nutrients in surface runoff in Mencheng-Lianshi Lake from March to November in 2013. The results showed that whole of these riparian buffers in Yoingding river of Beijing could effectively intercept inorganic nitrogen (IN) and phosphorus (IP) in the runoff and the retention efficiency for IP was significantly higher. Therefore, riparian buffers have the intercept runoff pollutants, which can indirectly improve river water quality. First of all, the retention efficiency of riparian buffer was relatively low, due to rainfall amount and intensity. Secondly, retention efficiency for Ammonia nitrogen (NH4+-N) was positively influenced by width and bare soil area of riparian buffer. Retention efficiency for nitrate nitrogen (NO3--N) was positively influenced by width, herbaceous vegetation coverage and the difference between nutrients in the soil more in Summer; as for soluble inorganic phosphorus (IP), width of riparian buffer is the most influence factors. Thirdly, the law of REs of three cross sectional zones (zone1, zone2, zone3) perpendicular to the river in riparian buffer was that zone3 was the middle, zone1 was the minimum and zone2 was the maximum, with seasonal variation for NH4+-N and NO3--N, but zone1 was middle, zone2 was minimu and zone1 was maximum for IP. Biological and physical structure in different zones of each riparian buffer all affect the retention efficiency of nutrients.This study could provide quantitative theory support of ecological restorationa measures for the future urban riparian. For the management of urban riparian, it could also provide theoretical basis and implementation suggestions.