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

The accumulation, mass balances, and potential health risks associated with the presence of Hg were evaluated in basil cultivated simultaneously with shrimp by aquaponics (similar to 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.

Automated summary

This study evaluated the accumulation, mass balances, and potential health risks of Hg in basil cultivated simultaneously with shrimp in an aquaponic system. The results showed that the aquaponic treatments did not significantly affect Hg accumulation, and the Hg concentrations in basil tissues were below the international guidelines. Mass balances revealed that most Hg entered the system through input water and was mainly eliminated through zeolite. The inorganic speciation of Hg differed slightly between treatments, but the health risk index indicated that the consumption of basil grown with shrimp would not pose a risk to the population.