根据2012年9月对莱州湾西南部海域及其毗邻10条河流的调查结果，以及近30年来关于莱州湾海域表层水营养盐的调查资料，报道了各条河流和近海海域的营养盐状况及该海域营养盐的长期变化趋势，结果表明：（1）10条主要调查河流的总溶解态氮（TDN）平均含量在1.82~10.66 mg/L 之间，其中有8条河流超过河流总氮劣五类水质标准，6条河流硝态氮（NO3-N）含量高于氨氮（NH4-N）。（2）所调查的5个近海断面中小清河口近海断面、虞河口近海断面及溢洪河口近海断面的 DIN 平均含量超过海水无机氮第四类水质标准；除小清河口近海断面外其余近海断面活性磷（PO4-P）含量均属一类海水水质。（3）部分断面营养盐含量在河口混合区淡水端升高，可能与咸淡水混合动力作用相关；莱州湾西部区域营养盐含量高于南部区域，南部的堤河氮、磷含量极高；原油开采活动可能是影响附近水体中营养盐含量及形态的重要因素。（4）从20世纪80年代初至90年代中期，莱州湾表层水无机氮平均含量经历了由低到高的变化，到90年代后期已属劣四类海水水质；无机磷平均含量在该时段呈降低趋势，但到90年代后期也保持在较高水平，随后又波动下降。（5）所调查的莱州湾近海区域整体处于磷限制潜在富营养状态；氮磷摩尔比（N：P）在所考察的大部分时段内高于 Redfield阈值（16），净营养盐收支呈磷减少而氮增加的总体变化趋势，近年来磷限制程度有所减缓。%Dissolved nitrogen and phosphorus in surface waters of the southwestern nearshore area of the Laizhou Bay and the adjacent 10 rivers that it connects with were surveyed in September 2012 and the long-term variation trends of them were studied based on the historical data of the past 30 years. The main findings are as follows: (1) The average total dissolved nitrogen concentrations of the 10 rivers ranged from 1.82 mg/L to 10.66 mg/L, most of which exceeded the river-water standard Grade V of China. (2) The average dissolved inorganic nitrogen concentrations in 3 transects (Xiaoqinghe river transect, Yuhe river transect, Bailanghe river transect) of the 5 surveyed nearshore transects exceeded the seawater standard Grade IV of China (0.5 mg/L); the average active phosphorus concentrations in 4 sections of the 5 surveyed nearshore sections were below the seawater standard Grade I of China. (3) The nutrient concentrations in the upper reaches of some estuaries maintained a high level, which maybe correlate to intense mixing of seawater and freshwater. The nutrient concentrations in the western part of the studied area were higher than those in the bottom part of the Bay. The nutrient concentrations of the Dihe River in the bottom part of the Bay were especially higher. Crude oil mining activities may affect nutrient content and morphology of the neighboring aquatic body. ( 4) The average concentration of inorganic nitrogen in the Laizhou Bay experienced a transition from a low level to a high one, which was worse than the seawater standard Grade IV of China after the year of 1995. (5) Since the late 1980 s, phosphorus has been in the nutrient limiting phytoplankton growth in the Laizhou Bay, and the molar ratios of nitrogen and phosphorus were higher than Redfield threshold ( 16) for most of the survey period, but the extent of phosphorus limitation has eased relatively in recent years.
展开▼
