Tani F H, Barrington S
Department of Agricultural and Biosystems Engineering, Macdonald Campus of McGill University, 21 111 Lakeshore, Ste Anne de Bellevue (Québec) H9X 3V9, Canada.
Environ Pollut. 2005 Dec;138(3):548-58. doi: 10.1016/j.envpol.2004.06.004.
To evaluate the environmental risks of irrigating crops with treated wastewater, a study was undertaken to quantify heavy metal uptake by 4-week old buckwheat (Fagopyrum esculentum L.) plants during 18 days of irrigation with 8 different Cu and Zn solutions under two transpiration rates (TR). At 4 weeks, potted buckwheat plants were transferred into one of the two growth chambers, offering either a high or low vapour pressure deficit (VDP) for, respectively, a high or low TR. Triplicate pots received one of the 8 irrigation treatments containing one of two Zn levels (0 and 25 mg/L) combined with one of four Cu levels (0, 5, 10 and 15 mg/L). Daily TR were measured by weighing the evapo-transpired water lost from the planted pot, less was the evaporation loss measured from triplicate non-planted pots. After 0, 6, 12 and 18 days of treatment, the stems and leaves of three randomly selected plants were harvested and after 18 days, the roots were harvested to determine Cu and Zn uptake. The treatments did not affect TR in terms of dry plant mass, indicating the absence of toxic effects. Irrigating with Zn, without Cu, increased dry biomass production, whereas the lowest biomass occurred with 15 and 30 mg/L of Cu with and without 25 mg/L of Zn, respectively, because higher applications of heavy metal significantly reduced soil pH. Plant Cu and Zn uptake increased with TR. With higher levels of Cu, Zn uptake by buckwheat was significantly reduced, while Zn had a slight but non-significant impact on Cu uptake. Previously and in a study exposing wheat plants to the same conditions, Cu significantly increased Zn uptake, while Zn had a slight but insignificant negative effect on Cu uptake. The buckwheat roots contained the greatest levels of Cu and Zn, indicating their role in moderating heavy metal uptake. Also, both Cu and Zn had a synergetic effect on each other in terms of root levels, and a similar observation was made in the earlier similar experiment using wheat plants. Irrigating a buckwheat crop with treated wastewater, with more natural Cu and Zn levels of 0.08 mg/L, could be quite beneficial without endangering the quality of the crop and acidifying the soil pH. The most concentrated experimental solutions contained 300 times more Cu and Zn, to obtain measurable differences.
为评估用处理后的废水灌溉作物的环境风险，开展了一项研究，以量化4周龄荞麦（苦荞麦）植株在两种蒸腾速率（TR）下用8种不同的铜和锌溶液灌溉18天期间对重金属的吸收情况。在4周时，将盆栽荞麦植株转移到两个生长室之一中，分别为高或低蒸腾速率提供高或低的蒸汽压亏缺（VDP）。一式三份的花盆接受8种灌溉处理之一，其中包含两种锌水平（0和25毫克/升）之一与四种铜水平（0、5、10和15毫克/升）之一的组合。每天的蒸腾速率通过称量种植花盆中蒸发散失的水分来测量，减去从一式三份未种植花盆中测量的蒸发损失。处理0、6、12和18天后，随机选择三株植物的茎和叶进行收获，18天后收获根系以测定铜和锌的吸收情况。这些处理在干植物质量方面不影响蒸腾速率，表明没有毒性作用。只用锌灌溉而不添加铜会增加干生物量产量，而分别在有和没有25毫克/升锌的情况下，15和30毫克/升铜处理时生物量最低，因为较高的重金属施用量会显著降低土壤pH值。植物对铜和锌的吸收随蒸腾速率增加。随着铜水平的提高，荞麦对锌的吸收显著降低，而锌对铜的吸收有轻微但不显著的影响。之前在一项将小麦植株置于相同条件下的研究中，铜显著增加了锌的吸收，而锌对铜的吸收有轻微但不显著的负面影响。荞麦根中铜和锌的含量最高，表明它们在调节重金属吸收方面的作用。此外，在根部水平上，铜和锌对彼此都有协同作用，并且在早期使用小麦植株的类似实验中也有类似观察结果。用处理后的废水灌溉荞麦作物，其中铜和锌的自然含量为0.08毫克/升，可能非常有益，而不会危及作物质量和使土壤pH值酸化。最浓缩的实验溶液中铜和锌的含量高出300倍，以获得可测量的差异。
