The effect of biosolid/soil composition on growth and uptake of zinc (Zn) by broccoli (Brassica oleracea var.) under greenhouse conditions

Abstract

Wastewater sludge (also known as biosolids) is commonly applied to agricultural and forestry land, offering the advantage of recycling nutrients and organic matter from the waste material back to the land. This study investigated the influence of biosolids on the uptake of Zn by broccoli (Brassica oleracea var.), a commonly consumed vegetable, grown in biosolid-amended soil compositions, by using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM/EDX). Broccoli was grown in soil amended with composted wastewater sludge at five different compositions (0, 25, 50, 75, and 100% wt/wt) treated with 100 ppm Zn at the beginning. Brassica oleracea var. (broccoli) plants from pot experiments were harvested after 30 days and Zn concentrations in plant parts (root, stem, and leaf) were analyzed by using flame atomic absorption (FAA) spectroscopy. Harvested biomass increased by 141–454% in comparison to the control (zero% wt/wt biosolid). The best growth was apparent at 25% (w/w)–75% (biosolid wt/wt), with Zn concentrations in plant parts found in the order [Zn]_root > [Zn]_shoot > [Zn]_leaf. SEM/EDX and FTIR spectral data show the presence of carboxyl functional groups that can bind Zn. The investigation shows that biosolids influence the yield and root-to-shoot-leaf transfer of Zn.