Distribution Characteristics of Phosphorus in Sediments of Dianchi

This paper takes the sediments of Dianchi Lake as the research object.The results show that the total phosphorus content in the sediments of Dianchi Lake is relatively high,and the spatial variation is large,ranging from 1,193.94 to 4,629.25 mg/kg.The spatial distribution characteristics of total phosphorus in the sediments of Dianchi Lake have obvious regional differences.The average content of total phosphorus in the sediments of Dianchi Lake is 2,184.39(+579.09 mg/kg),and the TP(Total Phosphorus)content in the areas over 60%of the lake is higher than 2,000 mg/kg,which is in heavily flat.By analyzing the distribution of phosphorus forms in surface sediments of different areas of Dianchi Lake,it can be concluded that the difference is significant.The relationship between the phosphorus contents of different forms is HCl-P>NaOH-rP>NaOH-nrP>Res-P>BD-P.Through summarizing the characteristics of different phosphorus distribution in the sediments of Dianchi Lake,this paper concludes that the sustained release of endogenous phosphorus load will be an important factor to delay the ecological health recovery time of Dianchi Lake and offset the effect of exogenous treatment.

Phosphorus forms and bioavailability of lake sediments in the middle and lower reaches of Yangtze River

Forms of phosphorus in sediments from 25 lakes in the middle and lower reaches of Yangtze River were analyzed by the sequential extraction procedure. Contents and spatial distrubution of algal available phosphorus (AAP) in sediments of Lake Taihu, the third largest freshwater lake of China, were also studied. Relationships between phosphorus forms in sediment and macrophytes coverage in sample sites, as well as phosphorus forms in sediments and chlorophyal contents in lake water were discussed. Exchangeable form of phosphorus (Ex-P) in surface sediments was significantly positive correlative to total phosphorus (TP), dissolved total phosphorus (DTP) and soluble reactive phosphorus (SRP) contents in the lake water. Bioavailable phosphorus (Bio-P) contents in sediments from macrophytes dominant sites were significantly lower than that in no macrophyte sites. In Lake Taihu, Ex-P content in top 3 cm sediment was highest.However, content of ferric fraction phosphorus (Fe-P) was highest in 4-10 cm. Bioavalilble phosphorus (Bio-P) contents in surface sediments positively correlated to Chlorophyll a contents in water of Lake Taihu with significant difference. Therefore, contents of Bio-P and AAP could be acted as the indicators of risks of internal release of phosphorus in the shallow lakes. It was estimated that there were 268.6 ton AAP in top 1 cm sediments in Lake Taihu. Sediment suspension caused by strong wind-induced wave disturbance could carry plenty of AAP into water in large shallow lakes like Lake Taihu.

农业流域中不同类型水塘沉积物磷素状态及其环境意义

通过对安徽巢湖六叉河小流域的多水塘系统进行采样和分析,测定了流域中不同类型水塘沉积物磷素赋存形态与分布特征,并对其环境意义进行了探讨.研究表明,水塘周边土地利用对沉积物磷含量具有重要影响,水塘沉积物全磷(TP)含量在286.3—651.3 mg·kg-1之间,村塘TP含量显著高于其他类型水塘,基本表现为村塘>河塘>山塘≈旱塘≈田塘;在TP中,铁铝结合态磷(Fe/Al-P i)和惰性磷(Residual P o)占主要地位(Fe/Al-P i,44.28%;Residual P o,37.74%),钙镁结合态磷(Ca/Mg-P i)和活性有机磷(Hu/Fu acids-P o)比例相对较小(Ca/Mg-P i,8.50%;Hu/Fu acids-P o,9.37%),易解吸磷(Exch-P i)所占比例最小,各水塘均不到0.20%;TP中的活性组分如Exch-P i、Fe/Al-P i、Hu/Fu acids-P o以及有效磷(Olsen P)、草酸浸提态磷(Ox-P i)等同TP均具有显著的正相关性(P<0.01),其他组分如Ca/Mg-P i和Residual P o与TP相关性不显著,水塘沉积物活性磷组分主要受控于外源输入,在水塘沉积物富磷化的同时,沉积物磷素的流失风险和潜在的生物可利用性均显著提高,因此在多水塘系统中,对水塘尤其是村塘的及时挖掘和疏浚是非常重要的.

Contributions of phosphatase and microbial activity to internal phosphorus loading and their relation to lake eutrophication

Phosphatase may accelerate the process of lake eutrophication through improving phosphorus bioavailability. This mechanism was studied in three Chinese eutrophic shallow lakes (Lake Taihu, Lake Longyang and Lake Lianhua). Phosphatase activity was related to the concentration of soluble reactive phosphorus (SRP) and chlorophyll a. Stability of dissolved phosphatase in reverse micelles may be attributed to molecular size, conformation and active residues of the enzyme.At the site with Microcystis bloomed in Lake Taihu, dissolved phosphatase activity was higher and more stable in micelles, SRP concentrations were lower in interstitial water, the contents of different forms of phosphorus and the amounts of aerobic bacteria were lower while respiration efficiency was higher in sediments. Phosphobacteria, both inorganic and organic and other microorganisms were abundant in surface water but rare in sediments. Therefore, internal phosphorus may substantially flux into water column by enzymatic hydrolysis and anaerobic release, together with mobility of bacteria,thereby initiating the bloom. In short, biological mechanism may act in concert with physical and chemical factors to drive the internal phosphorus release and accelerate lake eutrophication.