Experimental Study On The Spatial Distribution Of Nutrient Salts In The Ice Of Lake Wuliangsuhai And Their Release Processes During Melting

Some water bodies have been gradually eutrophiced due to phosphorus and nitrogen contamination. As a result of this, some lakes and wetlands could not play an important role as before in the environment.Lakes located in the north of China have a quite long frozen period. To getting better understanding on the nutrient salts distribution in the ice and release processes during melting, water and ice sampled were sampled during the frozen period in Lake Wuliangsuhai and lab physical modeling experiments were carried out.The analyzed results of the field samples showed that ice took about 30.5% of the total lake water amount in January 2011 in which the ice was frenzied upto the maximum thickness. During the frozen period of time, the concentrations of the most nutrient salts in the beneth water body were higher than that of before freezing. The concentrations of the most nutrient salts were higher within the top and the bottom layers of the ice. The concentration of soluble orthophosphate varied randomly with lower concentrations between 0.01 mg/L and 0.09mg/L. The proportion of nitrate and nitrite nitrogen in the beneth water body was less than that of before freezing.The lab physical modeling experiments support the analyzed results of the field samples results about the distribution charecterestics of the nutrient salts. Compared with -15℃,the nutrient concentration is higher of -25℃treatment.The results of from the experiments also showed that the concentrations of the nutrient salts before freezing did not affect the trend of the nutrient salts release. However, pH before freezing did affect the release amount of nutrient salts during melting to some extend. The released amount of TP was higher in high pH than in neutral and low pH, that of TN is higher in both low and high pH, that of DIP, DTP and nitrite is higher in low pH, and that of nitrate is higher in high pH. The concentrations of the nutrients were higher for -15℃treatment than that of -25℃treatment at the beginning stage of melting.