[Seasonal variation of trophic states in backwater areas of tributaries in Three Gorges Reservoir].
After the Three Gorges Reservoir was storage water in June 2003, organic contamination, nutrient and biomass were determined in backwater areas of 13 tributaries in three seasons. Potassium permanganate index, chemical oxygen demand (COD), total nitrogen (TN), ammonia nitrogen (NH4+ -N),total phosphorus (TP) and chlorophyll a (Chl-a) value are 0.20-9.61 mg x L(-1), 4.58-42.0 mg x L(-1), 0.601-10.1 mg x L(-1), 0.044-6.82 mg x L(-1), 0.011-0.756 mg x L(-1) and 2.0-161 mg x m(-3) respectively.The water body of tributaries is polluted at various levels. The concentration of TN is abundant.The rate of TN and TP showed that a part of tributaries eutrophication are limited by TP. Utilizing the method of between-subjects effects tests, it is indicated that spatial and seasonal distribution of nutrient factors is different in diverse seasons.Chl-a value of backwater areas of tributaries is usually beyond upstream and concentration of Ch1-a in flood season is higher than that in normal and dry season. There was a significant positive correlation between Chl-a, nutrient and organic contamination. Utilizing the method of integrated nutrition state index,it assessed the trophic states degree of the studied area. The integrated nutrition state index ranged 35-72.All of the studied tributaries are beyond mesotropher. The degree of eutrophication in flood season is higher than that in normal and dry season.The degree of eutrophication is more serious than that before the Three Gorges Reservoir impoundment. The problem of eutrophication in tributaries of Three Gorges Area should be noticed.
College of Resource and Environment, Southwest University, Chongqing 400716, China. shengzsts@126.com
Sheng
S
Zhang
Chong-ming
CM
Li
Jian
J
Zheng
Ting-ting
TT
Liu
Fan-hai
FH
Zeng
Yong-chuan
YC
Fu
D002244:Carbon / Q000032:analysis; D002681:China; D002734:Chlorophyll / Q000032:analysis*; D000077194:Chlorophyll A; D004784:Environmental Monitoring; D005618:Fresh Water / Q000032:analysis*; D008433:Mathematics; D009584:Nitrogen / Q000032:analysis*; D009930:Organic Chemicals / Q000032:analysis; D010100:Oxygen / Q000032:analysis; D010758:Phosphorus / Q000032:analysis; D011196:Potassium Permanganate / Q000032:analysis; D045483:Rivers; D012621:Seasons; D014874:Water Pollutants, Chemical / Q000032:analysis*
D009930:Organic Chemicals; D014874:Water Pollutants, Chemical; D011196:Potassium Permanganate; D002734:Chlorophyll; D010758:Phosphorus; D002244:Carbon; D009584:Nitrogen; D010100:Oxygen; D000077194:Chlorophyll A