内蒙古农业灌区夏、秋浇的氮磷流失变化

通过对内蒙古农业灌区引黄灌溉的2次主要大规模灌溉（夏浇、秋浇）的跟踪监测,研究了农业灌区的氮磷流失情况.分析了2次灌溉期的各引水渠和排水渠中总氮（TN）、氨氮（NH4＋-N）、硝氮（NO3--N）、总磷（TP）、溶解性无机磷（DIP）、溶解性有机磷（DOP）、颗粒磷（PP）的变化情况.研究表明：夏浇时,由于植物吸收、灌水量小等因素,基本不产生污染.而秋浇期间,由于灌水量大、土地裸露成为非点源污染产生的主要时期.在对第8排域的TN、TP的连续监测中发现,排干沟中的总氮总磷含量基本维持在4.16mg.L^-1和0.1725mg.L^-1,且氮为主要的污染控制因子;排干沟中的N/P为24,排入乌梁素海中极易引起水华发生.结合河套农业灌区的自然条件、耕作方式等因素,综合分析了河套灌区在夏浇及秋浇时期的非点源污染产生过程及污染特点.为该地区非点源污染管理和控制提供科学依据.

Nitrogen & phosphorus losses caused by the summer & fall irrigation runoff in the agricultural irrigation area in Inner Mongolia

Nitrogen and phosphorus losses in the Hetao agricultural irrigation area in Inner Mongolia, caused by summer and fall, irrigation, were traced and monitored. Water quality indices such as TN, NH+4-N, NO-3-N, TP, DIP, DOP, PP were examined in both the head races and the offtakes during the two irrigation events. The results showed that almost no nitrogen or phosphorus pollution occurred during summer irrigation due to factors such as the small volume of irrigation water and rapid plant uptake. In contrast, non-point source pollution occurred mainly during the fall irrigation, because in this period the volume of irrigation water was large and the land was bald. According to the data obtained by continuous water quality monitoring for 20 days, the concentration of TN and TP were almost 4.16 mg·L-1 and 0.1725 mg·L-1 and the main pollution factor was nitrogen. The ratio of TN to TP was 24, which might result in a water bloom when it reaches Wuliangsu Lake. The paper explores the characteristics of the non-point source pollution in the Hetao agricultural irrigation area under certain climate conditions and fertilization modes, and the data is expected to be helpful to evaluate and control the agricultural non-point source pollution in this area.