The trophic states of 35 reservoirs were investigated in the region of Chongqing,Southwest China.The results showed that the concentrations of nutrients and chlorophyll a were high and organic pollution and transparen...The trophic states of 35 reservoirs were investigated in the region of Chongqing,Southwest China.The results showed that the concentrations of nutrients and chlorophyll a were high and organic pollution and transparence(SD) were low in the water body.The concentrations of total nitrogen(TN) range from 0.52 mg/L to 5.94 mg/L and those of total phosphorus(TP) range from 0.002 mg/L to 0.598 mg/L.Chemical oxygen demand(COD) ranges from 0.75 mg/L to 9.3 mg/L and SD ranges from 0.48 m to 3.2 m.There was a significant positive correlation between COD and chlorophyll a,but a significant negative correlation between SD and chlorophyll a.In terms of the integrated nutrition state index,the eutrophication states of the reservoirs were assessed.Of the investigated reservoirs,about 22 reached the grade of eutrophication.Only one reservoir was in the state of oligotropher,the rest were in the state of mestropher.Integrated nutrition state indices range from 25.4 to 74.5.The storage capacity of nutrients in the reservoirs was calculated.The stored TN,TP and COD were about 4731,206 and 10259 t,respectively.The main pollution sources are industrial and domestic wastes.With the development of aquaculture,the contamination level increases gradually.展开更多
The influence of the short storage periods at different temperatures on the concentrations of extractable soil cations (Ca<sup>2+</sup>, Mg<sup>2+</sup>, Na<sup>+</sup> and K<sup...The influence of the short storage periods at different temperatures on the concentrations of extractable soil cations (Ca<sup>2+</sup>, Mg<sup>2+</sup>, Na<sup>+</sup> and K<sup>+</sup>) and anions (Cl<sup>-</sup>, SO<sub>4</sub>-</sup> and PO<sub>4</sub>-</sup> ) has been investigated in nine soil samples from Nile river terraces at River Nile State, North of Sudan (17.82289 to 17.82389N and 33.99974 to 34.02127E). Each soil extract is divided into three treatments: i) control (immediately analyzed);ii) storage for 10 days and;iii) storage for 30 days. Each treatment is replicated three times: i) storage at 10°C;ii) storage at ambient laboratory temperature (25°C) and;iii) storage at 45°C in incubator. Statistical analysis of results reveals that significant difference are found at level (P -</sup> and PO<sub>4</sub>-</sup> (0.043, 0.002, 0.001, 0.021, 0.004 and 0.001) respectively at 25°C and 45°C and storage periods of 10 and 30 days. In contrast, significant difference is also found at level (P -</sup> concentrations are significantly decreased when the storage period exceeds 10 days and temperature more than 25°C. Depending upon our study results;we conclude that, all extractable inorganic nutrients are clearly affected by storage periods at various temperatures, exception of Na<sup>+</sup>. Most cations and anions are increased significantly with increased of storage period and temperatures. We therefore highly recommend that the extractable inorganic soil nutrients should be rapidly analyzed in order to obtain accurate results;otherwise, the time between extraction and analysis should be carefully recorded which may help considerably interpreting data from various studies.展开更多
文摘The trophic states of 35 reservoirs were investigated in the region of Chongqing,Southwest China.The results showed that the concentrations of nutrients and chlorophyll a were high and organic pollution and transparence(SD) were low in the water body.The concentrations of total nitrogen(TN) range from 0.52 mg/L to 5.94 mg/L and those of total phosphorus(TP) range from 0.002 mg/L to 0.598 mg/L.Chemical oxygen demand(COD) ranges from 0.75 mg/L to 9.3 mg/L and SD ranges from 0.48 m to 3.2 m.There was a significant positive correlation between COD and chlorophyll a,but a significant negative correlation between SD and chlorophyll a.In terms of the integrated nutrition state index,the eutrophication states of the reservoirs were assessed.Of the investigated reservoirs,about 22 reached the grade of eutrophication.Only one reservoir was in the state of oligotropher,the rest were in the state of mestropher.Integrated nutrition state indices range from 25.4 to 74.5.The storage capacity of nutrients in the reservoirs was calculated.The stored TN,TP and COD were about 4731,206 and 10259 t,respectively.The main pollution sources are industrial and domestic wastes.With the development of aquaculture,the contamination level increases gradually.
文摘The influence of the short storage periods at different temperatures on the concentrations of extractable soil cations (Ca<sup>2+</sup>, Mg<sup>2+</sup>, Na<sup>+</sup> and K<sup>+</sup>) and anions (Cl<sup>-</sup>, SO<sub>4</sub>-</sup> and PO<sub>4</sub>-</sup> ) has been investigated in nine soil samples from Nile river terraces at River Nile State, North of Sudan (17.82289 to 17.82389N and 33.99974 to 34.02127E). Each soil extract is divided into three treatments: i) control (immediately analyzed);ii) storage for 10 days and;iii) storage for 30 days. Each treatment is replicated three times: i) storage at 10°C;ii) storage at ambient laboratory temperature (25°C) and;iii) storage at 45°C in incubator. Statistical analysis of results reveals that significant difference are found at level (P -</sup> and PO<sub>4</sub>-</sup> (0.043, 0.002, 0.001, 0.021, 0.004 and 0.001) respectively at 25°C and 45°C and storage periods of 10 and 30 days. In contrast, significant difference is also found at level (P -</sup> concentrations are significantly decreased when the storage period exceeds 10 days and temperature more than 25°C. Depending upon our study results;we conclude that, all extractable inorganic nutrients are clearly affected by storage periods at various temperatures, exception of Na<sup>+</sup>. Most cations and anions are increased significantly with increased of storage period and temperatures. We therefore highly recommend that the extractable inorganic soil nutrients should be rapidly analyzed in order to obtain accurate results;otherwise, the time between extraction and analysis should be carefully recorded which may help considerably interpreting data from various studies.
