| Guanzhen Stream is one important branch of downstream region of Nanfei River in Hefei suburban, the combination of sewage, industrial waste water and vegetable wash-water affected water quality,so nitrogen and phosphorus pollution is quite serious. Based on the trunk stream and two main tributaries upstream of Guanzhen Stream as the object, set up eight sampling points, collecting water samples and surface sediment samples from month to month, resoluting space-time variation of different forms of phosphorus in sediments, as well as the bio-availability of phosphorus and release risk in sediments,and exploring the adsorption characteristics of phosphorus in sediment.summary of achievements is presently as follows:(1) pH is in 7.71 to 9.02 range in sediment,ORP ranges from-948 to-245mv,which has strong reducibility;EC is within 291 to 1139μs·cm-1.Correlation study shows that in addition to the EC, the temperature and the indicators are closely related;NH4+ and NO3 have a significant negative correlation.The overlying water pH ranges of 7.60 to 9.43, ORP is in -705 to-72mv range, also performance for reducing;EC is within the scope of 629 to 1023 ms·cm-1,which shows various ion content;COD is range of 46.33 to 161.53 mg·L-1, exceeds bid badly,generally high concentrations of nitrogen and phosphorus,the maximum TP concentration is up to 3.63 mg·L-1.(2) The contents of TP in the sediments ranged from 1430.10 to 1941.26 mg·kg-1.The rank order of various forms of phosphorus content is as follows:OP>Fe-P>Ca-P>De-P>Al-P>Oc-P>Ex-P.Bioavailable phosphorus (including Ex-P,A1-P and Fe-P) accounts for 26.84% of TP, generalized bioavailable phosphorus (including Ex-P,Al-P,Fe-P and OP) accounted for 70.80% of TP.(3) Ex-P content is in range of 5.93 to 48.92mg·kg-1, the peak appears in the sample point 3,the minimum value is in the sample point 7;at first each point of Ex-P content increased gradually over time,and Ex-P content is generally lower after march and April.Al-P content is in range of 52.57 to 138.48 mg·kg-1;The maximum is in the sample point 7 and the minimum appeared in the sample point 2.A1-P content showing a trend of first increases and then reduce,the maximum value appeared in January or February.Fe-P and OP are similar about the change of temporal-spatial, the peak appears in December to February, and the lowest number in June and July;As one of the inert phosphate, the change of Oc-P content is small,the mean is at 50 to 100mg·kg-1.Oc-P weakly impact on the environment;Ca-P and De-P are part of calcium phosphate, which belongs to nature is relatively stable.(4) Fast phosphorus adsorption mainly occurred within the first 3h in sediment, slow adsorption is from 3 to 12h.Dynamic adsorption fitting results show that the false secondary dynamics model is suitable for simulation of phosphorus adsorption in sediment of Guanzhen Stream;According to the results of the thermodynamic fitting,Langmuir isotherm equation for phosphorus adsorption simulation effect is better in sediment.Sampling points which the adsorption quantity is larger have June, July and August.EPCo ranges from 0.058 to 0.154 mg·L-1, higher than general rivers and lakes.TP standard index is greater than 1, there is a big potential harmfulness to the environment. PSI range of 16.33 to 16.33[mgP·(100g)-1]·(umol·L-1)-1, compared with other rivers and lakes, phosphorus release risk is relatively large in sediment of Guanzhen Stream, and release risk of spring and summer is higher than that in autumn and winter. |
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