Benzo[a]pyrene is a high-molecular-weight polycyclic aromatic hydrocarbon highly recalcitrant in nature and thus harms the ecosystem and/or human health. Therefore, its removal from the marine environment is crucial. This research focuses on benzo[a]pyrene degradation by using enriched bacterial isolates in consortium under saline conditions. Bacterial isolates capable of using benzo[a]pyrene as sole source of carbon and energy were isolated from enriched mangrove sediment. These isolates were identified as Ochrobactrum anthropi, Stenotrophomonas acidaminiphila, and Aeromonas salmonicida ss salmonicida. Isolated O. anthropi and S. acidaminiphila degraded 26% and 20%, respectively, of an initial benzo[a]pyrene concentration of 20 mg/L after 8 days of incubation in seawater (28 ppm of NaCl). Meanwhile, the bacterial consortium decomposed 41% of an initial 50 mg/L benzo[a]pyrene concentration after 8 days of incubation in seawater (28 ppm of NaCl). The degradation efficiency of benzo[a]pyrene increased to 54%, when phenanthrene was supplemented as a co-metabolic substrate. The order of biodegradation rate by temperature was 30°C > 25°C > 35°C. Our results suggest that co-metabolism by the consortium could be a promising biodegradation strategy for benzo[a]pyrene in seawater.
Leachate from Ampar Tenang landfill was characterized and then treated with ferric chloride. Treated leachate was used at different dilution levels as biofertilizer for the cultivation of Brassica rapa L. (leafy vegetable). A treatment with inorganic fertilizer at the same N-equivalent as the leachate, and a control (water) were also included. Physical growth parameters (leaf length, leaf width, stem height) and harvest parameters (total number of leaves, root length and dry weights of different plant parts) were determined. The dry-weights of leaf, root and stem in (both) treatments had significantly higher biomass over the control. B. rapa receiving 25%DTL had the highest specific growth rate for leaf length (0.53 mm/d) and leaf width (0.39 mm/d). Heavy metal accumulations in B. rapa grown with leachate and in B. rapa bought from the market were compared with the permissible concentration limit of FAO/WHO. Inorganic fertilizer did not give a better fertilizing effect in terms of plant yield and growth than the leachate treatments according to this study, but heavy metal accumulation makes the leachate unfit for fertilization of edible plants like Brassica rapa L.
HOW TO CITE:Alaribe FO, Agamuthu P. Fertigation of Brassica rapa L. using treated landfill leachate as a nutrient recycling option. S Afr J Sci. 2016;112(3/4), Art. #2015-0051, 8 pages. http://dx.doi.org/10.17159/ sajs.2016/20150051 Optimising nutrient availability and minimising plant metal contamination are vital in sustainable agriculture. This paper reports experiments in which treated leachate was used at different concentrations with predetermined N content for fertigation of Brassica rapa L. (leafy vegetable). An inorganic fertiliser, with N content equivalent to the leachate amount, was also prepared, as well as a control. Growth (leaf length, leaf width and stem height), harvest parameters (total number of leaves, root length and root dry weight) and specific growth rates (mm/day) were determined for three consecutive seasons. The dry weights of leaves, roots and stems in the leachate treatments were within the ranges of 1.95-3.60 g, 1.18-3.60 g and 0.33-1.37 g, with biomasses of 1.75 g, 1.14 g and 0.2 g, respectively, which were higher than those of the control. B. rapa L. fertigated with 25% diluted treated leachate recorded high specific growth rate and a leaf length of 0.53 mm/day and 0.23.17±0.58 cm, respectively (%N=0.023; p<0.05). The maximum permissible mineral concentration set by the Food and Agricultural Organization of the United Nations/World Health Organization (FAO/WHO) was compared with that of the grown plants. Treated leachate can increase plant nutrient content.
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