Arsenic (As) contamination is one of the major factors that contribute to environmental pollution, and it plays havoc with sustainability of crop production. Nano-hydroxyapatite (nHAP) can be an effective phosphorus (P) source to cope with As toxicity. The mitigating effects of variable P sources on As toxicity in rice, sunflower, and maize grown in an alkaline soil were evaluated. Arsenic was applied at 0 and 20 mg kg-1, and P was applied at 0, 50, and 500 mg kg-1 in the forms of triple superphosphate (TSP) and nHAP. In addition, the same amount of phosphoric acid was also used in the sunflower and maize experiments with the other P sources. The structural and functional properties of nHAP were determined by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. Stunted growth was observed in rice, and less in sunflower; maize remained unaffected by As toxicity. In the presence of As, TSP and nHAP at their high doses (500 mg kg-1) significantly increased the rice dry weight compared with the control (0 mg kg-1). The As concentration in rice was decreased by approximately 25% in the presence of 50 mg kg-1 TSP and 500 mg kg-1 nHAP. The P treatments had no significant effect on the As concentration in sunflower, whereas the As concentration in maize was increased by 500 mg kg-1 TSP. In the absence and presence of As, nHAP at 50 mg kg-1 significantly increased rice P concentration, whereas in the presence of As, 500 mg kg-1 TSP significantly increased P concentration in rice compared with the control. Arsenic had no significant effect on sunflower P concentration, while the maize P concentration was decreased in the 0 mg kg-1 P treatment. It can be concluded that TSP and nHAP were effective in alleviating As toxicity in rice and sunflower. Comparative studies are further needed to determine the long-term effects of TSP and nHAP on prevention of As toxicity in field conditions.
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