青海湖新生湖滨带与主湖区水环境特征差异研究

DIFFERENCES IN WATER ENVIRONMENT CHARACTERISTICS BETWEEN THE NEWLY LAKESHORE ZONE AND THE MAIN LAKE AREA OF QINGHAI LAKE

文章研究对比了青海湖水位上升后形成的新生湖滨带与主湖区在不同季节的水环境特征差异。结果显示,在测定的14个指标中,高锰酸盐指数、总磷、浊度和电导率等指标在湖滨带与主湖区间存在显著空间差异,而pH、总氮、溶解氧饱和度、水温、溶解氧浓度、溶解性磷、溶解性无机氮、氨氮、亚硝氮和硝酸盐氮等指标无显著空间差异;但结合各指标的变异系数、季节变化和主成分分析的结果来看,所有指标在新生湖滨带都表现出更大的变异系数,6月湖滨带样点主要在溶解性营养盐指标方面离散,8月湖滨带样点主要在淹没土壤释放物质相关指标方面离散,两者可能分别受到生物残体分解和淹没土壤释放的影响。研究的结果表明,青海湖的新淹没湖滨带的水环境特征与主湖区存在明显差异。土壤释放、生命活动、风浪、水深和温度等因素共同塑造了青海湖新生湖滨带的水环境特征。上述结果提示了青海湖部分湖滨带区域的水环境特征有利于刚毛藻生长,同时也可能受到刚毛藻暴发影响。新生湖滨带对青海湖水生态系统的持续影响还需要在后续研究中进一步关注。

Qinghai Lake is located at the northeastern edge of the Tibetan Plateau and has important ecological values.Although the intensity of human activities in the catchment is low and there is relatively weak pollution,the water quality of Qinghai Lake has worsened significantly in recent years compared to the 1950s and 1960s.In recent years,some lakeshore areas of Qinghai Lake have experienced a proliferation of Cladophora.It is also accompanied by a continuous rise in the water level of Qinghai Lake since 2004.The large amount of newly lakeshore zone formed by the rising water level may be accompanied by soil nutrient release.However,there is a lack of specific knowledge about what specific differences exist between the water environment conditions in the newly lakeshore zone and the main area of Qinghai Lake,as well as the spatial and temporal patterns of water quality in the lakeshore zone area.Based on the field monitoring data of the lakeshore zone and the main lake area in different seasons,this study compares the diffe-rences between the water environment characteristics of the newly lakeshore zone and the main lake area after the rising water level of Qinghai Lake,and analyzes the causes and potential impacts.It could lay the foundation for further estab-lishing the correlation between the outbreak of Cladophora and the rising water level process of Qinghai Lake.In this study,water samples were collected in the lakeshore zone and the main lake area of Qinghai Lake in June and August 2020,respectively.Water environmental indicators such as water temperature(WT),conductivity(EC),pH,dissolved oxygen concentration(DO),dissolved oxygen saturation(DO%),turbidity(Turb),total phosphorus(TP),dissolved re-active phosphorus(SRP),total nitrogen(TN),nitrate nitrogen(NO_(3)-N),ammonia nitrogen(NH_(3)-N),nitrite nitrogen(NO_(2)-N),dissolved inorganic nitrogen(DIN),and CODMn were obtained by field measurements and laboratory analy-sis.In the main lake area of Qinghai Lake,pH ranged from 9.05-9.20,DO ranged from 6.78-8.30 mg/L,DO%ranged from 99.5%-111.4%,WT ranged from 9.3-16.9℃,EC ranged from 15.82-17.77 ms/cm,and turbidity ranged from 1.48-4.94 NTU,TP ranged from 0.009-0.136 mg/L,SRP ranged from 0.001-0.024 mg/L,TN was at 1 mg/L level,NO_(3)-N ranged from 0.09-0.25 mg/L,NH_(3)-N ranged from 0.10-1.10 mg/L,NO_(2)-N was between un-detected to 0.0048 mg/L,DIN was between 0.20-1.27 mg/L,COD_(Mn) was between 1.75-4.79 mg/L;While in the lakeshore zone,pH ranged from 8.76-9.46,DO ranged from 1.14-11.25 mg/L,DO%ranged from 15.7%-190.6%,WT ranged from 8.5-22.0℃,EC ranged from 0.85-18.82 ms/cm,and turbidity ranged from 2.09-196.00 NTU,TP was between 0.014-0.462 mg/L,SRP was between 0.002-0.044 mg/L,TN was at the level of 1.4 mg/L,NO_(3)-N was between 0.09-0.91 mg/L,NH_(3)-N was between 0.13-1.23 mg/L,NO_(2)-N was between undetected to 0.0099 mg/L,DIN was between 0.31-2.14 mg/L,CODMn was between 1.78-48.67 mg/L.Based on the significance of the spatial and temporal differences of the indicators between the main lake area and the lakeshore zone,water environment indi-cators involved in this study can be divided into four categories:there were no significant spatial and temporal diffe-rences in pH,TN and DO%;there were significant seasonal differences in WT,DO,SRP,DIN,NH_(3)-N,NO_(3)-N,and NO_(2)-N,but no significant spatial differences;there were significant spatial differences in turbidity and CODMn,and the spatial differences were the same in different seasons;there were also significant spatial differences in TP and EC,but the spatial differences were different in different seasons.Except for NO_(2)-N,the maximum values of coefficients of variation of water environment indicators were found in the lakeshore zone.Most indicators had higher coefficients of variation in August.The results of the principal component analysis suggested that the differences between different types of lakeshore zones might also be enhancing or weakening the influence of lakeshore zones on water environment indica-tors.The PCA plot shows that the distribution of sample sites in the lakeshore zone of Qinghai Lake disperse along dif-ferent principal component axes in different seasons.Therefore,the dispersion could be the cause or the result of the outbreak of the algal bloom in the lakeside zone of Qinghai Lake.The results of this study suggest that the water environment characteristics in some lakeshore zone areas of Qinghai Lake are favorable for the growth of Cladophora,which may be partly responsible for the outbreak of Cladophora.The continued impact of the new lakeshore zone formed by the rising water level on the Tibetan Plateau lakes represented by Qinghai Lake needs further attention in subsequent studies.