Spatial Distribution, Adsorption/Release Characteristics, and Environment Influence of Phosphorus on Sediment in Reservoir

Abstract

Sediment gradually accumulates at the bottom of reservoirs after decades of running. To explore the influences of sediments on the water quality of reservoirs, the spatial distribution, adsorption/release characteristics, and environment influence of sediment pollutants should be analyzed. In this paper, the spatial distributions of phosphorus (P) and P fractions in the Biliuhe reservoir (river valley reservoirs) sediments were investigated. The adsorption and release characteristics of sediments P were studied in the experiment, while its environmental influence was analyzed too. The results indicate that the concentration of P in sediments was higher at the dam and the Zhongling site, while lower at other entrances of the reservoir and the smallest in the water-level fluctuating zone. Total Phosphorus (TP) varied from 355.46 to 764.57 mg/kg. Inorganic Phosphorus (IP) was the main form of TP in sediments, making up a proportion of 56-75%, while the correlation coefficient of P bound to Al, Fe, and Mn oxides was 0.922. Hydroxide (Fe/Al-P) was the main form of IP, which accounted for 46-83% with a correlation coefficient of 0.888. The maximum adsorption capacity calculated by Langmuir model was between 714.29 and 3333.33 mg/kg. The adsorption efficiency obtained by the Freundlich model was within the range of 0.40-1.42, which indicated that P adsorption was more difficult in the water-level fluctuating zone. The critical adsorption and release concentration range was 0.1-0.2 mg/L for the majority of the sampling points. The amount of P released in 24 h (the initial concentration of TP in the overlying water was 0 mg/L) accounted for 1.15-4.16% of TP in sediments, which was higher than the average concentration in the reservoir. It is concluded that the sediment is the potential pollution source. The relationship between the change of environmental factors and the release of sediment contaminants should be considered in the future.

Effects of Sediment Chemical Properties on Phosphorus Release Rates in the Sediment-Water Interface of the Steppe Wetlands

“…As for the W–A, its establishment time was short (completed in 2013); the pollutant accumulation was still lower. Meanwhile, because of the decrease of the water flow rate and disturbance, the increase of settlement is more favorable to the adsorption of phosphorus [ 55 , 56 ]. This might indicate that the W–A had a higher ability to maintain stability than the W–R when the environmental factors change, e.g., temperature changes.…”

Seasonal Release Potential of Sediments in Reservoirs and its Impact on Water Quality Assessment

“…The nutrients in the water column, such as the total nitrogen (TN), total phosphorus (TP), and ammonia nitrogen (NH 4 + –N), may exceed third level of the National Surface Water Quality Standards of China (GB3838-2002) at times, resulting in the risk of water eutrophication [26]. The TN and TP contents in sediments have reached 2725 mg/kg and 571mg/kg after nearly 30 years of operation [27,28]. Compared with other similar reservoirs in China, the sediments have a higher release risk for nitrogen and phosphorus.…”

Alteration in the potential of sediment phosphorus release along series of rubber dams in a typical urban landscape river

“…Fe, Al and Ca) 57 . We need to examine this further to clarify whether the absence of Ca-related interactions in this study is related to the presence of different Ca fractions that do not readily react with P. The fact that the TP contents in sediments fluctuated with distance downstream is also not consistent with our expectations as the sediment TP should be lower in the downstream than in the upper area due to cascading retention 34,35 . We assumed the only P input was the upstream river, however the lack of pattern in the contents suggests that there were additional external sources of pollution.…”

“…Previous researches have demonstrated that there are differences of physicochemical properties of sediments and water column between reservoirs and free-flowing river systems. For instance, studies have shown that there was more P in sediments near reservoir dam than in sediments of the upper river 34,35 , and sediment BAP increased from the reservoir inlet to the reservoir dam 36 . It was also reported that sediments had higher contents of clay (finer grain size) 37 and OM 38,39 in dammed rivers than in natural rivers.…”