两种种植体系下地下水硝态氮含量变化

Dynamic variation of nitrate-nitrogen content in groundwater under two different agricultural cropping systems

寿光作为全国闻名的保护地蔬菜产区,过量施肥的现象非常普遍。为了解集约化大棚蔬菜种植区地下水中硝酸盐的含量变化状况,于2003～2005年对寿光市大田(小麦-玉米)、大棚(一年两茬番茄)两种不同的种植体系下农田灌溉水和农村饮用水水井进行了定点跟踪监测。结果表明:大田区地下水中硝态氮的含量随着时间的变化波动很小,农村饮用水中硝态氮含量没有超标现象;随着时间推移,大棚区灌溉水井中硝态氮含量年内(从年初到年末)呈明显的上升趋势,年际间则存在有规律的波动并逐年升高;灌溉水中硝态氮平均含量普遍高于饮用水,浅层地下水明显高于深层地下水;无论大棚区还是大田区,井深不同对地下水的硝态氮含量影响差异很大,浅井中硝态氮的含量明显高于深井。大棚区农村饮用水硝态氮含量超标现象非常普遍,对国家饮用水标准(20mg·L-1)超标率最高达37.50%,平均为14.06%;对WHO推荐饮用水上限(10mg·L-1)超标率最高达56.25%,平均为42.19%,硝态氮最高含量45.60mg·L-1。集约化大棚蔬菜栽培模式已经对农村地下水造成了很大的硝态氮污染,饮用水中较高的硝酸盐含量已经对当地居民的健康构成了潜在的威胁。

In Shouguang, as a Chinese-famous production area of protected-land vegetables, the phenomenon of excessive fertilization is very common. To investigate nitrate-nitrogen （nitrate-N） variations of groundwater in intensive greenhousevegetable farmlands of Shouguang, a continual site-directed survey on farmland irrigation and countryside drinking wells was carried out under two different agricultural cropping systems. The cropping systems studied were wheat-corn cropping field and the greenhouses of annual two-stubble tomato during 2003-2005. The results suggested that with the passage of time, the variation of nitrate-N content was little in the main-field groundwater, and no exceeding limit was observed on the nitrate contents in drinking water of the countryside. However, in the greenhouse area, nitrate-N content in the well for irrigation during a year （fi＇om the beginning to the end） indicated the significant increasing tendency, and further more the annual change was regular and increasing. The average value of nitrate-N content in irrigation water was higher than in drinking water, and in shallow groundwater was obviously higher than in deep groundwater. Whether in the greenhouse area or main field area, the different well depth had great effect on nitrate-N content, that is to say, nitrate-N content in shallow wells was obviously superior to that in deep wells. The phenomenon of nitrate-N over standard was very common in countryside drinking water of greenhouse areas, and the maximum nitrate contents reached to 45.60 mg·L^-1 , and compared with Chinese drinking water standard （20 mg·L^-1 ） , the ratio of exceeding standard was up to 37. 50% and average at 14.06% ; as for drinking water upper limit recommended by world health organization （WHO） , the ratio of exceeding standard reached 56.25% and average at 42. 19%. It was concluded that cultivation pattern of intensive greenhouse vegetables resulted great pollution of nitrate-N to countryside groundwater, and the high nitrate content in the drinking water has composed a potential threat to the health of local population. Our results have good significance in the field of modern eco-friendly approaches in pollution ecology.