| Bosten Lake was once China’s largest inland freshwater lake. Also, it was the most important water source for the Yanqi Basin, the banks of Qongquehe, and the Tarim River. Since the 1950’s, the increasing development of industry and agriculture has caused the water quality to deteriorate. Aiming at the current eutrophication status of Bosten Lake, TN was selected as the indicator for the eutrophication level. The locations that were measured were the East of the Kaidu River, drainage canals, and the Qongque River. The time frame that the data was collected was from the year 2005 to the year 2011 and during the months of May and September. For the results, we calculated the income and the outcome of the TN content for the lake, in addition to the net income of the TN content. On the other side, we based on the data of the concentration of the TN using the terrain of the basin of the lake and the method of Thiessen polygons to analysis the distribution of spatial and temporal distribution for TN stocks and its variations. Finally, we contrasted the net income and the variation of the TN stocks, estimating the range of the total TN content, and evaluating the limits of the two methods. These results can be a more precise basis for the nitrogen balance and be a scientific basis for eutrophication controlling. The criteria set above helped to produce the following information:(1) Income from the eastern part of the Kaidu River into the lake: Data collected in the month of May from the years 2006 to 2009 showed that the average income of the TN content to be 67.66 t. This was a great change. The highest level was recorded at 122.75 t and the lowest level was at 7.12 t. Data collected in the month of September for the same years showed the average income of the TN content to be 96.51 t. The highest level was set at 141.08 t and the lowest level was set at 67.92 t. There was no obvious difference in the income of the TN content between the months of May and September. The increase of the income of the TN content was determined to be from the water from the eastern of the Kaidu River.(2) Income from drainage canals into the lake: Data for the highest and the lowest income of the TN content was collected during the months of May and September from the years 2005 to 2011. The highest level was recorded in the year 2010(15.31t) and the lowest level was in the year 2006(5.39t). This data showed that May’s income was lower than September’s income for all of the canals. The Nanzong canal was the most obvious data, with the difference being about 80 t. Among the five main canals, the Nanzong canal and the Shengli canal had the most content of TN. The proportional increase was Nanzong with 54% and Shengli with 25% for the five main canals during the month of September. This TN content was caused by the concentration of the canals.(3) Output along the Qongque River from the lake: The income of the TN content was 46.39 t on average in the month of May, where the highest level was in the year 2007(95.45t) and the lowest level was in the year 2009(17.68t). The income of TN content averaged out to be 14.7t; at the same time the highest level was in the year 2009(19.13t) and the lowest level was in the year 2007(11.34t). The month of May turned out to have a higher level of income of TN content than in September. The amount of TN content was positively correlated with the amount of water.(4) The stocks of TN in 17 areas: The stock of 17 samples was lower in the month of May 2009 than that in May 2010. From this, the sample 16 was the most obvious one, with the stock of TN being 584.68 t higher in the year 2010 than in the year 2009. The stocks of TN were decreased year by year in September beginning in the year 2008 to the year 2010. Among this data, the sample 4 was the one that was the most obvious, with the stock level for the year 2008 being recorded as 945.36 t, then it decreased to 505.73 t in the year 2010. In addition, the stock in the month of May was much lower than that in the month of September for the same year. In the middle of the lake(sample 4, 16 and 15) was recorded to be the highest TN stock in all the samples for all the years. The lowest three sample areas were recorded in the north-west of the Huangshui Area(sample 7 and 9) and the exit of the Qongque River. The main reason for this was that in the middle of the lake there is a larger water area(lower concentration of TN) and the other areas had a smaller water area(higher concentration of TN)..(5) The difference between the net income of TN and the stocks of TN in the lake: The stock of TN in May 2009 was recorded at 2600.9t, while in May 2010 it was recorded at 5141.84 t. The stock was increased by 2540.94 t during this period. The stock of TN in September 2008 was recorded at 6036.71 t, while in September 2009 it was recorded at 5456.44 t. The stock was decreased by 580.27 t during this time period. Then from September 2009(5456.44t) to September 2010(4497.76t) the stock decreased even more, which was by 958.68 t. From May 2009 to September 2009, according to the content of TN, the net income was 430.49 t, while the stock of the lake was recorded at 2855.54 t by the Thiessen polygons. Of course, both of these had the limits of themselves, just like the former didn’t consider the fact of non-point sources and the Sediment release. In addition, the latter was hard to measure than the Sediment release. The highest and the lowest levels were set as 6042.16 t and 3871.37 t respectively for the months of October and May, which had a huge variation of TN stock between them. |
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