[Primary study on enacting the lake nutrient control standard].

It is important precondition to enact viable lake nutrients control standard for lake control and management. Now China is shortage of study on nutrients control standard considering of the regional and nutrient difference. In this paper, five-step method for nutrient control standard is built following the principle of commonality, possibility and practicability. The monitoring data from 1994 to 2005 were divided into six groups according to chlorophyll-a content. Every group is a representative of one grade, oligotrophication, mesotrophication, low eutrophication, middle eutrophication, high eutrophication and extro-eutrophication respectively. In every group, total nitrogen, total phosphate and transparency were analyzed by frequency method, and 50% frequent values were applied. Results came out that the nutrient control standard for Taihu lake is as follows: Chlorophyll-a content were < 1.6 mg x m(-3), 1.6-10 mg x m(-3), 10-26 mg x m(-3), 26-64 mg x m(-3), 64-160 mg x m(-3), > 160 mg x m(-3). Transparence is 0.7 m, 0.4 m, 0.3 m, 0.3 m, 0.3 m and 0.25 m. Total phosphate is 0.03 mg x L(-1), 0.04 mg x L(-1), 0.06 mg x L(-1), 0.09 mg x L(-1), 0.12 mg x L(-1), 0.18 mg x L(-1). Total Nitrogen is 0.6 mg x L(-1), 1.7 mg x L(-1), 2.2 mg x L(-1), 3.2 mg x L(-1), 4.2 mg x L(-1), 6.2 mg x L(-1). This study would offer the experience for enacting nutrient control standard in the other lake region of China, also would offer the theoretic support for eutrophication control in China.