城市雨水对生菜产量品质与重金属含量的影响

作为都市农业灌溉用水,城市雨水对农产品食品安全和营养品质的影响深受关注。论文收集自然雨水(T1)、屋顶雨水(T2)和路面雨水(T3),静置沉淀后配置营养液进行水培生菜种植,测量生物产量、生理指标(叶绿素含量、净光合速率、根系活力)、营养指标(可溶性糖、可溶性蛋白、维生素C、硝酸盐)和元素含量(Ca、Fe、Mg、Zn、As、Cd、Pb),结果表明:城市雨水重金属含量低于国家标准,可以作为农业灌溉用水;雨水栽培生菜比自来水栽培生菜长势弱、产量低,路面雨水栽培生菜产量最低,单株干质量仅为3.57 g;雨水降低了生菜叶绿素含量和净光合速率,提高了生菜根系活力,屋顶雨水生菜和路面雨水生菜根系活力分别为3.17和4.08 mg/(g·h),雨水栽培生菜的根冠比大于自来水生菜;雨水栽培生菜蛋白质、糖类和Vc含量不比自来水栽培生菜低,自然雨水生菜蛋白质质量分数4.97 mg/g,路面雨水生菜可溶性糖含量1.00%,路面雨水生菜Vc含量1.52 mg/g,分别为各项指标的最高值;供试生菜硝酸盐含量分别为5.62、5.48、6.04和7.04 mg/g,都超过了国家标准3.00 mg/g,这与试验采用1倍剂量营养液和采用硝酸调节p H值有关;雨水生菜有益元素Ca、Mg含量高于自来水生菜,Fe含量低于自来水生菜,雨水生菜总体品质略好于自来水生菜;自来水、自然雨水、屋顶雨水和路面雨水栽培生菜含As量分别为5.83、4.10、4.53和4.60μg/kg,含Cd量分别为0.76、0.78、2.59和1.37μg/kg,含Pb量分别为102.37、118.63、151.53和123.37μg/kg,远小于国家限量值,满足食品安全要求。总之,利用城市雨水作为都市农业灌溉用水,作物长势弱,产量低,但营养品质略好,食品安全,将城市雨水作为都市农业灌溉用水是可行的。

Influence of urban rainwater of city on yield, quality and heavy metal content of hydroponic lettuce

Rainwater has become a big problem of the city, because rainwater led to urban waterlogging, affect urban transport. Urban waterlogging is also a kind of hidden danger for urban residents. At the other side, government spends a lot of money to meet municipal water demand, for example the South-to-North Water Transfer Project. Many cities land subsidence caused by groundwater exploitation. Urban agriculture which used rainwater as irrigation water is an effective way for urban rainwater as resources. The safety of urban agricultural products irrigated by rainwater is attention focus, because urban rainwater is polluted by automobile exhaust, asphalt, cement and so on. This paper study the food safety and nutrient quality of lettuce irrigated by urban rainwater aims to explore the feasibility of urban rainwater as urban agricultural irrigation water. A hydroponics experiment was carried out from October 2014 to January 2015 in Hainan University. Four kinds of treatments were designed using hydroponic lettuce design with four replicates, respectively: hydroponic lettuce using tap water (CK), hydroponic lettuce using rainwater (T1), hydroponic lettuce using rooftop rainwater (T2), and hydroponic lettuce using road rainwater (T3). 3 times rainwater from rainwater, rooftop rainwater of office and road rainwater were collected from October in 2014 to January in 2015. The rainwater was mixed respectively, allowed to stand for precipitating impurities, was used as nutrient solution water. Lettuce was cultured in tap plastic pipe. Plant height, leaf number, physiological indexes (chlorophyll content, net photosynthetic rate, root activity), nutritional indexes (soluble protein content, soluble sugar content, vitamin C content, nitrate content), and element (Ca, Fe, Mg, Zn, As, Cd, Pb) content in the lettuce mature stage under different rainwater nutrient solution and tap water nutrient solution were measured. The results show that heavy metal content of rainwater is lower than national agricultural irrigation water standards, urban rainwater is safety to be used as urban agriculture irrigation water. As content of lettuce was respectively 5.83 (CK), 4.10 (T1), 4.53(T2), 4.60μg/kg (T3), Cd content of lettuce was respectively 0.76 (CK), 0.78(T1), 2.59(T2), 1.37μg/kg (T3), Pb content of lettuce was respectively 102.37(CK), 118.63(T1), 151.53(T2), 123.37μg/kg (T3). They were less than the national limit values (As content 500μg/kg, Cd content 200μg/kg, Pb content 300μg/kg), the lettuce meet the food safety requirements. Proteins content, sugars content and vitamin C content of lettuce cultivated in rainwater was not lower than that in rainwater; Ca, Mg content of lettuce cultivated in rainwater is higher than that in tap water, Fe content of lettuce cultivated in rainwater is less than that in tap water. The quantity of lettuce cultivated in rainwater is better than that in tap water. Chlorophyll content and net photosynthetic rate of lettuce cultivated in rainwater is lower than that cultivated in tap water. Root activity of lettuce cultivated in rainwater was increased. Root-shoot ratio of lettuce cultivated in rainwater was respectively 0.19(T1), 0.11(T2), 0.12 (T3), they were bigger than that cultivated in tap water(0.08). Lettuce cultivated in rainwater has worse growth power and lower biomass yield than lettuce cultivated in tap water. Lettuce biomass yield cultivated in road rainwater is lowest in three kind of lettuce cultivated in rainwater. In short, the urban rainwater and the agricultural produces cultivated by urban rainwater is safety, and the quality of agricultural produce cultivated in urban rainwater is better. At the same time, crop irrigated by urban rainwater grows weak and has lower yield. Experiments on lettuce demonstrate that urban rainwater is used as urban agriculture irrigation water is feasible.