| The specific regional ecological environment has created the unique eutrophication mechanism of Erhai.The TN and TP of the overlying water are low,but the??DON?and DON/TDN value?33.2%67.1%?are relatively high,moreover the organic matter pollution of sediment is serious.During the growth period of algae and other organisms,the interface activity of DON is an important supplement to overlying water and nitrogen pools.This paper focuses on the two interfaces of sediment-water and particle-water in Erhai.The DON release characteristics were studied by dynamic simulation and static culture,and establishes its relationship with human activities in the basin The distribution characteristics of??SPM?and their relationship with DON.The nitrification-denitrification process at particle-water interface was simulated by acetylene inhibition method.The migration and transformation rules of DON at the interface were analyzed,and the characteristics and environmental significance of DON in Erhai were discussed from the interface perspective.?1?The sediment-water interface research results was as follows:?1?Therelease kinetics of DON could be well simulated by first-order kinetics equation.The maximalDON release amount from each area followed the pattern:northern>southern>middle,ranging from 24.387 to46.949mg/kg.Moreover,the first and the largest releasing components were the protein-likecomponent and humic-like component?76%?respectively.The increased of pH or DO decreased would promoted the release of DON.By established the relationship between the parameters of spectrum characteristics and release,the content ratio of protein-like to humic-like substances P?I+II,n?/P?III+V,n?can also be taken as the indirect indicator of the release amount ofsediment DON.?2?The maximum releaseand release rate of columnar sediments are similar:30cm>40cm>50cm>10cm>20cminthenorthandsouth,and10cm>20cm>30cm>40cm>50cm in the middle.The release characteristics of DON from columnar sediments can well indicate the basin change.Before 1970s,DON release was stable.Significant increase was released from1970 to 1990,and the release began to stabilize after 1990.Similarly,the potential risk of DON release could be predicted by changes in overlying water environment?pH,DO,etc.?and human activities?GDP,planting area and nitrogen fertilizer?.?2?The particle-water interface research results are as follows:?1?The distribution characteristics of??SPM?was:summer?5.408±0.861?>autumn?4.919±0.728?>winter?3.267±0.471?>spring?2.107±0.318 mg/L?,north and south is smaller than middle?6.56 mg/L?,and decline as the water depth increases.The distribution of algal-derived SPM is easily affected by both environmental factors and endogenous metabolism:the northern is mainly affected by rivers,the central has stronger microbial activity,and the southern was easily disturbed.Within a certain range,increased water temperature,pH>8.98,and lower DO could lead to increased??SPM?.in addition,S2 can be used as a key component of nutrient for algae uptake to stimulate lake eutrophication,to a certain extent,it can be used as indicators of??SPM?in Erhai.?2?The nitrification rate of the particle-water interface was north?0.0403?>medium?0.0256?>south?0.0018 ppm/?h·L??The concentration of N2O conforms to the logistic model.It's showed the rhythm of"slow to fast to slow",and the maximum rate at third hours.Establishedthe relationship of??SPM?and the nitrogen of overlying water,logKd value of DON?6.12±0.47?is higher than that of DIN?5.70±0.48?,it shows that DON interacts more with particles..The spatial and temporal variation between dissolve and particle nitrogen affects the SPM distribution,and DON can be used as a nitrogen source to produce more suspended particles. |
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