Abstract
Contaminated soils can cause a potential risk into the health of the environment and soil as well as the quality and productivity of plants. The objectives of our study were to investigate the integrative advantageous effects of foliar ZnO nanoparticles (NPs) (60 mg Zn NPs L−1), rice straw biochar (RSB; 8.0 t ha−1), cow-manure biochar (CMB, 8.0 t ha−1), and a combination thereof (50% of each) on sunflowers grown in agricultural land irrigated with polluted wastewater for the long term (≈50 years). The availability of heavy metals (HMs) in soil, HMs accumulation in whole biomass aboveground, growth, productivity, and quality characteristics of the sunflower were investigated. The combination treatment significantly minimized the availability of HMs in soil, and, consequently, substantially lessened the uptake of HMs by the sunflower, compared to treatments of ZnO NPs and control (i.e., untreated soil). The application of the combination treatment reduced the availability of Pb, Cr, Cu, and Cd in the soil by 78.6%, 115.3%, 153.3%, and 178.5% in comparison to untreated plots post-harvest, respectively. Compared to untreated plots, it also reduced the Pb, Cr, Cu, and Cd in plant biomass by 1.13, 5.19, 3.88, and 0.26 mg kg−1 DM, respectively. Furthermore, combination treatment followed by biochar as an individual application caused a significant improvement in sunflower productivity and quality in comparison to untreated soil. For instance, seed yield ha−1, 100-seed weight, and number of seeds per head obtained from the combination treatment was greater than the results obtained from the untreated plots by 42.6%, 47.0%, and 50.4%, respectively. In summary, the combined treatment of NPs and both RSB and CMB is recommended as a result of their positive influence on sunflower oil quality and yield as well as on minimizing the negative influences of HMs.
Highlights
Terrestrial soil contamination by heavy metals (HMs) has become a serious environmental problem worldwide as a result of anthropogenic activities [1,2,3,4,5,6,7,8,9]
Compared to the untreated plots post-harvest, the combination of different treatments reduced the availability of Pb, Cr, Cu, Cd, and Ni in the soil by 78.6%, 115.3%, 153.3%, 178.5%, and 193.7%, respectively
The combination treatment, which included cow-manure biochar (CMB), rice straw biochar (RSB), and Zinc oxide (ZnO) NPs, significantly improved the soil characteristics in terms of reducing toxic metals availability, lessened the uptake of toxic metals in the biomass, enhanced growth and physiological characteristics, increased yield, and improved quality of the sunflowers grown in soil irrigated with long-term wastewater when compared to each individual treatment
Summary
Terrestrial soil contamination by heavy metals (HMs) has become a serious environmental problem worldwide as a result of anthropogenic activities [1,2,3,4,5,6,7,8,9]. HMs and metalloids can cause irretrievable harm to ecological systems, animals, and human health [3,7,8]. Soil contamination with toxic metalloids and HMs such as arsenic (As), lead (Pb), cadmium (Cd), chromium (Cr), nickel (Ni), copper (Cu), and zinc (Zn) has meaningfully increased in recent decades due to the sewage wastes, agricultural pesticides, chemical fertilizers, and industrial waste application [2,3,8,11]. The dispersion of toxic HMs in agricultural lands are irrigated with wastewater, and, in plant biomass or edible parts, can pose a contamination for the food chain with hazardous consequences to both animals and humans [3,8,12,13]
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