Metal uptake of tomato and alfalfa plants as affected by water source, salinity, and Cd and Zn levels under greenhouse conditions

Abstract

Irrigation with wastewater is a promising option to improve crop yields and to reduce pressure on freshwater sources. However, heavy metal concentrations in wastewater may cause health concerns. A greenhouse pot experiment was conducted in order to determine cadmium (Cd) and zinc (Zn) concentrations in sandy soil and plant tissues of tomato (Lycopersicon esculentum L.) and alfalfa (Medicago sativa L.). A 2 × 2 × 4 × 2 factorial treatment arrangement was utilized. Two water sources, fresh (FW) or treated wastewater (TWW), at two salinity levels (1 and 3 dS m(-1)) containing different levels of Cd and Zn were used. Samples were collected after a 90-day growth period. It was observed that the growth of both plants was depressed at the highest metal level (L3). Metal accumulation in plant parts increased with the increase of metal concentration and salinity in irrigation water. At low salinity, water source was the main factor which controlled metal accumulation, whereas, at high salinity, chloride appeared to be the principal factor controlling metal uptake regardless of water source. Metal translocation from roots to shoots increased in TWW-irrigated plants, even in the controls. Tomatoes accumulated Cd up to and above critical levels safe for human consumption, even though Cd concentration in irrigation water did not exceed the current recommended values. Therefore, food production in sandy soils may well pose a health hazard when irrigated with TWW containing heavy metals. Complexation with dissolved organic compounds (DOC) in TWW may be to be the principal factor responsible for increased metal uptake and transfer at low salinity, thereby increasing the risk of heavy metal contamination of food and forage crops.

Salinity affects pH and lead availability in two mangrove plant species

“…At higher salt concentrations there is an increase in the uptake of Cd, Zn and Pb in some plants, due to competition with other cations (Na + , K + , Ca 2+ , Mg 2+ ) for sorption sites. This could increase the formation of complexes with chloride anions, causing desorption of metals and their mobility (Fritioff et al 2005, Gharaibeh et al 2015. Additionally, some studies on sediments and different plant species show that higher salinity leads to a decrease in the mobilization and accumulation of Ni, Cu, Zn, Cd and Pb in plant tissues (Smolders and McLaughlin 1996, Riba et al 2003, Fritioff et al 2005, Leblebici et al 2011.…”

The Effects of Coexisting Elements (Zn and Ni) on Cd Accumulation and Rhizosphere Bacterial Community in the Soil-Tomato System

“…In this experiment, CdCl 2 •2.5H 2 O solution, ZnSO 4 •7H 2 O solution, and Ni(NO 4 ) 2 •6H 2 O solution were used as the sources of Cd, Zn, and Ni, respectively. The selection of Cd, Zn, and Ni contamination levels was mainly based on extreme pollution situations that have been reported earlier [37][38][39]. As shown in Table 1, the three experimental treatment groups comprised sub-treatments, as follows: (1) the Cd treatment group included four levels of Cd contamination (0, 1, 20, 50 mg kg −1 soil); (2) the Cd with Zn co-treatment group included four levels of Cd contamination (0, 1, 20, 50 mg kg −1 ) which were respectively supplemented with 1, 20, 50 mg Zn kg −1 soil; (3) the Cd with Ni co-treatment group included four levels of Cd contamination (0, 1, 20, 50 mg kg −1 ) which were respectively supplemented with 20, 80, 160 mg Ni kg −1 soil.…”

Effects of low‐molecular‐weight organic acids on the acute lethality, accumulation, and enzyme activity of cadmium in Eisenia fetida in a simulated soil solution

“…The simulated soil solutions were composed of 0.1 mmol/L Ca 2þ (as Ca(NO 3 ) 2 ), 0.1 mmol/L Mg 2þ (as MgSO 4 ), 1.0 mmol/L Na þ (as NaNO 3 ), and 0.1 mmol/L K þ (as KNO 3 ) at pH 6.0 AE 0.1 in deionized water. The simulated soil solutions were then spiked with Cd (as Cd(NO 3 ) 2 .4H 2 O), and equilibrated for 24 AE 0.5 h before the toxicity tests [24]. First, earthworms were exposed only to a series of Cd solutions at varying concentrations (0 mg/L, 5.6 mg/L, 11.2 mg/L, 16.8 mg/L, 22.4 mg/L, 28.0 mg/L, 33.6 mg/L, 44.8 mg/L, and 56.0 mg/L) to determine the LC50 value.…”