镍对蔬菜毒害临界值的研究

采用水培＋土培的方法研究了镍对蔬菜的毒害临界值。先采用水培法从18种福建常见蔬菜中筛选出对镍毒害的高敏感蔬菜，再通过土培试验确定土壤镍对高敏感蔬菜的毒害临界值。结果表明，在水培条件下镍对蔬菜生长存在低浓度的刺激效应和高浓度的抑制效应。综合表观症状和蔬菜地上部生物量降低20％的效应浓度值（EC20）确定清江白（Brassica chinensis L．）和蕹菜（Lpomoea aquatica Forsk．）为镍毒害的高敏感蔬菜。以蕹菜为指示作物的土培试验表明，随着镍添加量的增加，蕹菜地上部生物量显著下降。以土培条件下蕹菜地上部生物量降低10％为依据，确定土壤有效镍毒害临界值为2．21mg·kg^-1（DTPA提取）；根据野外采集的菜园土壤DTPA提取镍和全镍的回归关系，求得土壤全镍毒害临界值为43．67mg·kg^-1。

Study on the threshold values of Ni toxicity to vegetables

The threshold values of Ni toxicity to vegetables were studied by water culture followed by soil culture experiments. Wa-ter culture was performed to select the most sensitive vegetable species to Ni toxicity among 18 vegetable species commonly culti-vated in Fujian province. The most sensitive vegetable species was then tested by soil culture experiments in order to determine the threshold values of Ni toxicity. The results showed that there were hormesis effects at low Ni concentration (0.1 mg·L~(-1)) and toxic effects when the Ni concentrations were higher in water culture. Based on the apparent symptoms and the EC_(20) values (effective concentration causing a 20% inhibition of shoot biomass) of each species, Qingjiang pakchoi (Brassica chinensis L.) and water spin-ach (Lpomoea aquatica Forsk.) showed to be the most sensitive vegetables. In the following soil culture experiments with water spinach, no obvious hormesis effects were found. The shoot biomass of water spinach significantly decreased as the Ni added to the soils increased. Based on the EC_(10) (effective concentration causing a 10% inhibition of shoot biomass) of water spinach under soil culture experiment, the threshold value of available soil Ni was 2.21 mg·kg~(-1) (DTPA-extractable). The corresponding threshold value of total soil Ni estimated from the regression between total soil Ni and DTPA-Ni of the vegetable soils collected from the fields was 43.67 mg·kg~(-1).