Hemp-Based Phytoaccumulation of Heavy Metals from Municipal Sewage Sludge and Phosphogypsum Under Field Conditions

Wiesław Szulc,Monika Skowrońska,Stefan Russel,Dariusz Zielonka,Beata Rutkowska

doi:10.3390/agronomy10060907

Wiesław Szulc, Monika Skowrońska + Show 3 more

Open Access

https://doi.org/10.3390/agronomy10060907

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Abstract

The aim of this study was to evaluate the ability of three hemp cultivars to accumulate heavy metals under sewage sludge (SS) and phosphogypsum (PG) application. The field study was carried out from 2014 to 2016 on Luvisol (loamy sand) in Poland. The experiment scheme included five treatments—T0: the control without fertilization, T1: 170 kg N (nitrogen) ha−1 from sewage sludge, T2: 170 kg N ha−1 from sewage sludge and 100 kg ha−1 of phosphogypsum, T3: 170 kg N ha−1 from sewage sludge and 500 kg ha−1 of phosphogypsum, and T4: 170 kg N ha−1 from sewage sludge and 1000 kg ha−1 of phosphogypsum. It was found that the application of municipal sewage sludge enriched the soil with the bioavailable forms of heavy metals to the greatest extent and contributed to the highest increase in their contents in vegetative and generative organs of hemp plants. These parameters showed a phosphogypsum dose-dependent decline, which could hinder the phytoextraction process. The greatest extractions of heavy metal(loid)s (HMs) from the soil treated with SS and PG were achieved by the Tygra variety, which had the highest bioconcentration factor (BCF) and biomass yield.

Highlights

Heavy metal(loid)s (HMs) include both biologically essential (e.g., Fe, Co, Cu, Cr, Mn, Ni, and Zn) as well as non-essential (Cd, Pb, Hg, and As) elements
Industrial hemp absorbs a wide range of heavy metals in vegetative and generative parts, in different concentrations (Figure 1), making it suitable to be considered in soil remediation processes
Sewage sludge application contributed to significant increases in heavy metal(loid)s (HMs) contents in both vegetative parts except Zn and Cu and generative organs except Cd, when compared to the values obtained in the T0 treatment (Figure 1)

Summary

Introduction

Heavy metal(loid)s (HMs) (i.e., elements with an atomic density greater than 4–6 g cm−3 ) (with the exception of As, B, and Se) include both biologically essential (e.g., Fe, Co, Cu, Cr, Mn, Ni, and Zn) as well as non-essential (Cd, Pb, Hg, and As) elements. Both groups are toxic to plants at excessive concentrations. In the European Union, more than 10 million tons of SS dry matter (10 to 15 kg per person) are generated annually. This is expected to increase to 15 million tons

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