长江口营养盐浓度变化及分布特征

根据2003年11月(枯季)和2004年8月(洪季)对长江口的2次现场调查,分析探讨了长江口的营养盐浓度变化及分布特征.结果表明,长江口水体3种不同形态的溶解无机氮中,以NO3--N含量最高,洪、枯季分别占溶解态无机氮的92.8%～97.7%和84.3%～98.4%.洪季NO3--N和NH+-N含量高于枯季,洪季与枯季NO2--N含量接近.洪、枯季长江口ρ(PO43-P)平均值分别为0.014和0.016 mg/L,接近国家海水一类标准.洪、枯季N3--N和PO3-4P含量均是由长江口内向口外近海逐渐降低,而NH4+-N含量则表现出相反的空间分布规律,即口外高于口内.通过计算长江口营养盐比值发现,枯季长江口氮、磷供应充分,不存在磷受限的情况,而洪季长江口水体受到磷的限制. 

The Characteristics of Nutrients Distribution in the Yangtze River Estuary

The variations in the concentration and distribution of nutrients in the Yangtze River Estuary were investigated based on the data obtained during field observations in November 2003(dry season) and August 2004(wet season).The results showed that the concentrations of nitrate were much higher than those of nitrite and ammonia,which accounted for 92.8%～97.7% and 84.3%～98.4% of dissolved inorganic nitrogen in wet and dry seasons,separately.Nitrate and ammonia showed higher concentrations in wet season than in dry season.Nitrite,however,gave the similar concentration levels in both seasons.The average concentrations of phosphate were 0.014 and 0.016(mg/L) in wet and dry seasons separately,which attained the first standard level of seawater,according to the national standard of seawater quality.For both seasons,the concentrations of nitrate and phosphate decreased from inside the estuary to outside the estuary,which displayed the opposite spatial variations with ammonia.Based on the results of nutrient ratios,it was suggested that the nutrients supply was sufficient in dry season and thus phosphate was not a limiting factor for phytoplankton growth in the Yangtze River Estuary.However,the primary production in the Yangtze River Estuary might be limited by phosphate in wet season.