Mercury in basil (Ocimum basilicum) grown simultaneously with shrimp (Litopenaeus vannamei) by aquaponics

Abstract

The accumulation, mass balances, and potential health risks associated with the presence of Hg were evaluated in basil cultivated simultaneously with shrimp by aquaponics (∼1.7 g L−1). Two aquaponic (well water (WW) and diluted seawater (DSW)) treatments and one hydroponic control (hydroponic solution (HS)) were examined. The trend of Hg accumulated in basil tissues was roots > leaves > stems. No significant differences (p > 0.05) were found between aquaponic treatments. Mercury concentrations in the edible basil tissues were below the maximum allowable levels (0.2 mg kg−1) for vegetables established by international guidelines (WHO, 2007; CREU, 2018). The mass balances evidenced that most Hg (> 99%) entered the aquaponic system through the input water, while the main output route (> 90%) was through the zeolite used in plants. Mercury inorganic speciation in water was similar between WW and DSW treatments. The dominating speciation was HgCl2 (50%), which is a bioavailable form that biota can use. In the HS treatment, the chemical speciation was different as it formed complexes mainly with ammonia. The health risk index for Hg was < 1.0, which indicates that the population exposed to the consumption of basil grown with shrimp would not be at risk.