Total phosphorus and its main forms: dissolved mineral, dissolved organic, particulate organic and particulate mineral in the vertical water column of three subalpine lakes of various types in Italy, has been estimated during the winter-vernal season. The range of variation in the phosphorus content in these waters was as follows: total phosphorus 16 ± 2860 μg/1 PO4, dissolved mineral phosphorus 4 ± 1040 μg/l PO4, dissolved organic phosphorus 1 ± 160μg/l PO4, particulate organic phosphorus 0 ± 290 μg/l PO4 and particulate mineral phosphorus 1 ± 100 μg/l PO4, Generally the content of total phosphorus and dissolved mineral phosphorus (phosphates) increased with the degree of eutrophy with the depth and with the progress of the vernal season towards the summer stagnation time. The amount of phosphates increased in water with the depletion of oxygen, both in the verical water column and with the progress of stagnation time. The amounts of dissolved organic phosphorus decressed with the depth of the vertical water column whereas the dissolved mineral phosphorus increased. The development of the particulate organic phosphorus stratification in the vertical water column was clearly visible in the eutrophic lake. The quantities of total phosphorus and its main component, dissolved mineral phosphorus, decreased evidently from January to May in all three lakes, mostly in the eutrophic lake. The reason of this decrease is sorption by lake sediments and to a certain degree sedimentation of phosphorus sorbed by ferric hydroxide. The increase of dissolved mineral phosphorus and that of total phosphorus in the vertical water column and with the progress of summer stagnation had as a reason the liberation of phosphorus from sediments, and not so much decomposition of sedimentating plankton or dissolved organic phosphorus. The share of single (mean) values of phosphorus forms in the total phosphorus was as follows: In the oligotrophic lake the share of particulate mineral phosphorus was extremely high in March (21% of the total), probably because of the inflow of the melting waters from the drainage area. The development of vertical stratification in waters of three subalpine Italian lakes at the end of the vernal season (May) indicates the quantitative prevailing of dissolved mineral phosphorus with its increase with the depth and domination of dissolved organic phosphorus in the trophogenic zone. 相似文献
The Songhua Lake in the Northeast China is chosen as a study case in this paper. Monitoring of samples and analysis 18 indexes
related to the eutrophication in the Songhua Lake had been conducted in 2002–2004. Ecological risk assessment methods are
employed here. The study results showed that total phosphorus and total nitrogen were main risk factors to impact on the eutrophication
of the Songhua Lake, and influence of the phosphorus on the lake eutrophication was larger than that of nitrogen. Algal growth
potential test was also conducted to validate the results. High phosphorus and high nitrogen concentrations were mostly distributed
in Huifahekou and Jiaohe sites of the Songhua Lake. Threshold values of total phosphorus, total nitrogen and Chl-a concentrations
from dose-effective examination were 0.065 mg/L, 0.843 mg/L, and 11.90 μg/L, respectively. The probability of the eutrophication
appeared in the Songhua Lake was 0.69, of them, risk-free type area was 19.21% of total lake area, slight risk type area was
30.10%, middle risk type area was 16.50%, heavy risk type area was 25.8%, hyper risk type area was 8.39%. In order to control
the eutrophication in the Songhua Lake, maximum permission discharges of total phosphorus and total nitrogen to the lake would
be 2,123.78, 7,018.82 t/a, respectively. 相似文献
Managed aquifer recharge (MAR) provides means to remove natural organic matter (NOM) from surface waters. Recent studies have explored the degree of NOM removal in groundwater. In this study, we further elaborate the NOM removal at a lakeside natural bank infiltration site that functions as a surrogate for MAR. Our objective was to quantify the carbon budget in the aquifer based on concentration measurements of dissolved (in)organic carbon, and the molecular changes in NOM using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). According to the carbon budget, only 25% of the dissolved carbon entering the aquifer was organic, and it predominantly originated from lake water. Of the inorganic majority, on average 40% was produced in the vadose zone above the groundwater table, 31% in the lake bank, 22% in the aquifer as a result of degrading organic matter of lake water, and 7% in the lake. Seasonal concentration variations suggested that the lake bank was the main carbon source in the summer, increasing the carbon concentration of infiltrating lake water, that is, 3.0 mg/L to 7.9 mg/L. FT-ICR MS results showed 4960 to 5330 individual compounds in lake and groundwater. NOM removal in the aquifer was selective: the relative abundance of oxygen-containing species decreased from 75 to 31%, while the relative abundance of sulfur-containing species increased from 15 to 57%. The average molecular weights of both species remained unchanged. The study highlighted the role of lake bank processes and sulfur-containing species in groundwater quality. 相似文献
