Phosphorus release rates from sediments and pollutant characteristics in Han River, Seoul, Korea.
ABSTRACT The Han River is 469.7-km long and drains a 26219-km(2) watershed. The sediments in the river are highly polluted due to inputs from upstream tributaries as well as partially treated municipal wastewaters that are discharged to the river. The water quality and strategy for control are important because the river is the primary drinking water supply for the City of Seoul, as well as being a major source for irrigation and industrial water. The Jamsil submerged dam partitions the river to isolate an upstream area for drinking water, but also captures sediments. Samples from four sites were studied to determine sediment pollutant concentrations and phosphorus release rates. Phosphorus tends to desorb from sediments when the concentration of overlying water is less than 1.4 mg/l. Water column P concentrations range from 0.04 to 0.1 mg/l, which suggests that sediments will act as a P source. In a series of batch experiments, P was released at approximately 15-20 mg/m(2)week in the winter (1-5 degrees C) and as much as 90 mg/m(2)week in the summer (20-24 degrees C), and is also a function of pH and dissolved oxygen concentration. The sediment total phosphorus concentration, which averages 833 mg/kg, is evenly distributed among non-apatite-P (33%), apatite-P (32%) and residual-P (34%). An equilibrium model is proposed to describe release rate.
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ABSTRACT: Flooding can have a major impact on riverside plant communities, and this is likely to be especially important in monsoonal climates, where large floods occur after heavy rain. In urban areas where riparian vegetation remnants are the only vegetation of conservation interest remaining, understanding the impacts that floods have on these ecosystems is needed to inform their future conservation. Accordingly, we assessed the impact of a flood caused by Typhoon “Ewiniar” on the soil seed bank of five plant communities of the only remaining fragment of high-quality riverine habitat within the Seoul city stretch of the Han River (South Korea). We surveyed the seed bank composition of the five dominant plant communities before and after the flood. We also measured selected soil physico-chemical properties in each community. We used univariate and multivariate methods to examine the effect of the flood on both seed bank and soil physico-chemical properties. Flooding resulted in variable deposition of sediment within the plant communities; four communities varied from 14.6 to 18.8 cm but the fifth (dominated by Miscanthus sacchariflorus) had much less sediment (4.8 cm). The physico-chemical properties of the surface soil also changed after the flood, with the sediment particle size being the most affected. The species richness and composition of the seed bank suffered significant changes after the flood. In both cases there was a homogenization process, with was also impinged on species with different life-forms (annuals and perennials). Our results suggest that an extreme flood can affect the riparian vegetation seed bank by removing wetland plant species and allowing common and ruderal species to establish. There may also be different interactions between the different plant communities in terms of sediment capture and this translates into altered soil conditions and seed banks. These results are of use to conservation policy-makers aiming to conserve a native flora within severely modified urban rivers, and these remnant areas can provide an important seed source of wetland plants to aid restoration of riparian ecosystems.Ecological Engineering 09/2014; 70:102 - 113. · 3.04 Impact Factor
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ABSTRACT: Cyanobacterial blooms frequently occur in freshwater lakes, subsequently, substantial amounts of decaying cyanobacterial bloom biomass (CBB) settles onto the lake sediments where anaerobic mineralization reactions prevail. Coupled Fe/S cycling processes can influence the mobilization of phosphorus (P) in sediments, with high releases often resulting in eutrophication. To better understand eutrophication in Lake Taihu (PRC), we investigated the effects of CBB and temperature on phosphorus cycling in lake sediments. Results indicated that added CBB not only enhanced sedimentary iron reduction, but also resulted in a change from net sulfur oxidation to sulfate reduction, which jointly resulted in a spike of soluble Fe(II) and the formation of FeS/FeS2. Phosphate release was also enhanced with CBB amendment along with increases in reduced sulfur. Further release of phosphate was associated with increases in incubation temperature. In addition, CBB amendment resulted in a shift in P from the Fe-adsorbed P and the relatively unreactive Residual-P pools to the more reactive Al-adsorbed P, Ca-bound P and organic-P pools. Phosphorus cycling rates increased on addition of CBB and were higher at elevated temperatures, resulting in increased phosphorus release from sediments. These findings suggest that settling of CBB into sediments will likely increase the extent of eutrophication in aquatic environments and these processes will be magnified at higher temperatures.PLoS ONE 03/2014; 9(3):e93130. · 3.53 Impact Factor
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ABSTRACT: The purpose of this study is to evaluate the possibility of nutrient release at up and downstream of Kangchun weir, upstream of Yuju and Ipo weir in Namhan River. For this survey, we measured basic characteristics of the sediments (water content, ignition loss, TOC, TP, SRP, TN, phosphorus fractionation) and conducted nutrients release experiments under both aerobic and anaerobic condition. The overlying water from the sediment-water column was analyzed for nutrients (i.e. TP, -P, TN, -N, -N) everyday for 18days. Result of soil texture experiment showed that sediments are Sand. SRP concentration before the release experiment was different with the value after the release experiment. According to this result, we can find that there were more activated release processes in anaerobic condition. -P increased from 1 to 8 days and remained at the maximum value (7~8 days) afterward. The rapidly increase of -P was observed from 1 to 2~3 days whereas the TP continuously increase from 1 to 18 days. The -P release rate calculated by up to 7~8 days data highly correlated with initial SRP concentration with =0.8502. -N release rate appears constantly decreasing trend as -5.7~-3.08 , otherwise the -N release rate, by-product of a organic matter decomposition using nitrate as electron acceptor, was 0.57~2.41 . Substantial portion in TN can be induced by organic nitrogen which originated from the tributary passing through non-point pollutant source. Compared with other similar researches, phosphorus and nitrogen release rates obtained in this study can be considered as relatively low values. Since this study targeted the sediments accumulated by one time of flooding season, there are limitation to generalize theses results. Therefore, it is necessary to consistently monitor and investigate the accumulation of nutrients in the sediment for understanding the effect of weir construction on the overlying water quality.Journal of Korean Society of Environmental Engineers. 08/2013; 35(8).