基于muddy-LOICZ模型的小清河河口及下游河段营养盐通量估算

Estimate of the budget of nutrients in the Xiao Qinghe River and estuary based on the muddy LOICZ model

基于2013年7月、9月小清河口及9月小清河下游河道分段营养盐数据,采用LOICZ及改进的muddy LOICZ生物地球化学收支模型,分析了小清河口及下游河道分区域的水体存留时间和营养盐收支。结果表明,小清河口夏、秋季水体存留时间分别为0.67 d和3.09 d,夏、秋季DIP平均收支分别为–2.96×103、–1.72×103 mol/d,夏、秋季DIN平均收支分别为–1.55×106、–0.77×106 mol/d。进一步分析表明,河口生产力旺盛,存在净生产过程,成为氮磷的汇,且磷汇通量要远远小于氮汇,存在强烈的反硝化反应的脱氮过程,说明该河口的低氧问题需得到进一步重视。不同的河道区域其生产力水平、呼吸作用、光合作用和硝化作用等强度等均有所不同,且在羊口镇附近有大量支流和生活排污进入,小清河下游流域的综合治理不能单一全篇而论,而应该针对不同的河道区域特点进行分别治理。需要注意的是,LOICZ模型为箱式模型,忽略物理过程的作用以及更详细的生物地球化学过程。

By uploading the nutrient concentration, salinity and suspended particulate matter in the Xiao Qinghe River （XQR） estuary （in July and September） and along the XQR （from WangDao, in July） into the classical LOICZ model and muddy LOICZ model, the residual time and nutrient budget in the estuary and the river box were calcu-lated. The estuarine LOICZ model result showed that the residual time of water mass in the estuary was 0.67 day and 3.09 days in July and September, respectively. The average budgets of DIP were –2.96 ＆#215; 103 mol/d in July and–1.72 ＆#215; 103 mol/d in September, and the average budgets of DIN were –1.55 ＆#215; 106 mol/d in July and –0.77 ＆#215; 106 mol/d in September, respectively. This indicated that the XQR estuary was the high productivity area to be the sink of N and P resulting from the contribution of biology and primary production. The flux of P was far less than that of N due to the phosphorus-limitation in the XQR estuary. The negative value of p-r of the XQR indicated the nitrogen metabolism in the estuary. The riverine LOICZ model demonstrated that many pollutants were from branch chan-nels and wastewater discharges into the XQR from the Yangkou community. It is of note to highlight here that the LOICZ model was a zero-order model that provides order of magnitude estimates of the fate of the nutrients, and that it is unable to mimic the subtle controls involved in estimating nitrogen fixation and denitrification, such as the effects of dissolved oxygen, carbon, and nitrate availability.