Spatial Distribution Of Organic Phosphorus And Relationship With Water Environment Factors Of Taihu Lake

As a major component of the phosphorus in water, Organic phosphorus play an important role inaquatic ecosystem. It is meaningful to intensify the study about the space distribution of organicphosphorus in water and the relationship with environmental factor, which provides the basis forunderstanding well about biogeochemical cycles of phosphorus and its role in eutrophic lakes. The typicaleutrophic lake–Taihu Lake is the study object in the paper. it analyzes systematically the organicphosphorus composition characteristics of the Taihu Lake with the technology of31phosphorus nuclearmagnetic resonance (31P-NMR), on the basis of determining the optimal solution on enrichment of organicphosphorus. And it uses the software GIS10.0to reproduce the character of the spatial distribution aboutthe component of organic phosphorus, and the software SPSS17.0to study the relationship between thecomponent of organic phosphorus of water and the environmental factors, Lastly, the results of the researchare as follows:(1) In the simulated experiment, different volumes of water in Taihu is used. Taking consider of thefactors, such as pH, the choice of the extraction agent, the amount of the aluminum compound added andthe way to add. The optimal program for the enrichment of dissolved organic phosphorus will bedetermined as follows: By comparison with the rate of aluminum salt precipitation on phosphorus in wateras pH is3、4、5、6、7、8and9, The aluminum salt precipitation rate is highest when the pH is6~7; Theflocculent precipitate is shock extracted with1MNaOH、the1MNaOH+0.1MEDTA、1MNaOH+0.05MEDTA、0.5MnaOH、0.5MNaOH+0.1MEDTA and0.5MNaOH+0.05MEDTA respectively, and the bestextraction agent is0.5MNaOH+0.1MEDTA through comparing with the extraction rates;0.1、0.2and0.3gram aluminum salts were added to250mL water samples respectively and1,2,3and4gram aluminumsalts were added to20L water samples respectively, and the highest precipitation rate occurred in thesituation of adding0.3gram aluminum salts to250mL and3gram to20L water samples; aluminum saltswere added one step (add3g aluminum salts in20L water) and two-step (adding1.5g firstly, then24hourslater adding another1.5g aluminum salt in20L water), by comparison with the spectrum of organicphosphorus composition, As a result,the effect of the latter is better.(2) The dissolved organic phosphorus is mainly distributed in northwest of Taihu Lake which is seriously polluted, and less distributed in clean East Taihu Lake. Dissolved organic phosphorus are mainlymade up of phosphate monoesters、phosphate diesters and phosphonates. The content range of phosphatemonoester is0.799~7.03μg/L, which mainly exists in Zhushan Bay and Western Taihu. Along thedirection of northwest-southeast, the content of phosphate monoester gradually decreased. Its content inEastern Taihu is at the least; The content range of phosphate diester is from0.069to2.942μg/L, mainlydistributed in Meiliang Bay north of Wuli Lake, the lowest content existed in the junction betweenMeiliang Bay and Zhushan Bay and South of East Taihu Lake; The content range of phosphonate is from0.066to1.482μg/L, the highest content of phosphonates is in Meiliang Bay, Zhushan Bay and West TaihuLake, and the lowest content is in East Taihu Lake; The content of poly phosphorus in samples13,14and20were0.298,0.628and0.291μg/L respectively, The dissolved polyphosphate can be only detected inthe southern side of the western Taihu and the west of the East Taihu Lake.(3) The particulate organic phosphorus of Taihu lake are mainly distributed in the northern ZhushanBay of Taihu and along the west bank of Taihu Lake. It is made up of phosphate monoeaster and phosphatedieaster. The content range of phosphate monoeaster is from0.615to6.506μg/L, it is mainly distributed inthe northern Zhushan Bay, less in central and southern Taihu Lake, the content in east and the west bank ofTaihu lake is lowest; The content range of phosphate dieaster is from0.095to2.639μg/L, it is mainlydistributed in west bank of Taihu Lake, the weat of Weat Mountain,and the west of East Taihu Lake, it hasnot been detected in the East Taihu Lake and Xukou Bay; The content of phosphonate in sample3,6,7,10,11,16, and21of are0.67、1.553、0.311、0.226、0.137、0.158and0.287μg/L respectively, the phosphonateis detected in other lakes except South TaiHu and Zhushan Bay; The content of polyphosphorus in sample1、5、7、14、16and17are0.058、0.373、0.622、0.215、0.412and0.545μg/L respectively, mainly distributedin the boundary of Meiliang Bay Zhushan Bay and the east of Xukou Bay, It isn’t detected in East TaihuLake and the west of Taihu Lake.(4) The correlation relationship of the dissolved and particulate phosphate monoeaster and TN、DTN、TP、 DTP、PO3-4、COD、chlorophyll a and TLI is significant (significant level α=0.01). the phosphatemonoeaster is closely associated with the environmental factors, and this relationship has nothing with theform. The dissolved phosphate dieaster isn’t related with the indexes above. Particulatephosphate diesterand TN、DTN、TP、COD and TLI are significantly correlated under the significant level α=0.01, the relationship between particulate phosphate dieaster and DTP、PO3-4、and chlorophyll are significantlycorrelated(significant level α=0.05). dissolved phosphate dieaster is more stable than the particulate, isalmost not influenced by external environment factors. The dissolved phosphonate with TN、DTN、TP、DTP、PO43-、COD、and chlorophyll a is correlated significantly at the level of0.01, and the correlationbetween phosphonate and TLI is significant(significant level α=0.05). It demonstrates that the phosphatemonoester and dissolved phosphonate are both potential biological phosphorus, get involved in the cycle ofphosphorus in water, which is related with the nutritional level of the lake closely.(5) The correlation coefficient of phosphate monoeaster and phosphonate as the components ofdissolved organic phosphorus at the significant level of0.01is0.727, phosphate dieaster、monoeaster andphosphonate are not related. The correlation coefficient of phosphate monoeaster and phosphonate as thecomponents of particulate organic phosphorus is0.599(significant levels α=0.01). That is to say that thephosphorus transformations among particulate phosphate esters are more evident than the dissolved.Therelationship between dissolved and particulate phosphate monoesters or diester are significantlyassociated(significance level α=0.05). The correlation coefficient between dissolved phosphate diester andparticulate phosphate monoesters is0.324, the relationship between dissolved and particulate phosphatediester is irrelevant. The dissolved phosphonate and the particulate phosphate monoester are significantlyassociated (significance level α=0.01). and the correlation coefficient between which and particulatephosphate is0.411. It shows that the phosphorus conversion among dissolved phosphate monoester,phosphonates and particulate phosphate easters, and the latter transformation is more complex.