Levels of heavy metals in uncontrolled agricultural farms compared to regulated organic farms

Abstract

Over the last few years, soil pollution was observed to have increased rapidly, mostly due to anthropogenic sources. Heavy metal pollution has been seen to enter the food chain which has caused great concern due to the adverse affect to the health of the public wellbeing. Anthropogenic activities include livestock and agriculture soil pollution; sewage, waste production and disposal; infrastructure, transportation and urbinanisation; industrial activity; fireworks; mining and warfare. Conventional farmers use a number of pesticides and fertilizers containing heavy metals which unfortunately remain in the soils and water table, and eventually end up in the crops and food chain. The aim of the study was to evaluate the difference between the amount of heavy metals present in conventional and organic farms and to observe if there is a significant difference between the two types of farming. One hundred and one samples from around Malta and Gozo in 2019 were compared to two organic certified farms which confirmed through binomial testing that all ρ-values from the 101 samples compared with both controls, were less than the 0.05 level of significance stating that the district score differs significantly from the control value. Results showed that heavy metals where mostly found in the South-Eastern and South Harbour district. In the South-Eastern district, heavy metals found were vanadium at 64.25 mg/kg, manganese at 586.67 mg/kg, chromium at 45.93 mg/kg, selenium at 15.51 mg/kg and nickel at 21.90 mg/kg. In the Southern Harbour district, the heavy metals present were lead at 249.51 mg/kg, zinc at 251.33 mg/kg and copper at 95.15 mg/kg. The Northern district contained high concentrations of the heavy metals molybdenum at 12.09 mg/kg and arsenic at 7.93 mg/kg. In the Northern Harbour there is a high concentration of cadmium at 30.10 mg/kg. Cobalt was found highest in the Gozo and Comino district with a concentration of 15.8 mg/kg. The Finland standards were used to compare the results. Lead, cadmium, arsenic and zinc were to be found at high concentrations then the Finland standards, where the standards were at 60 mg/kg, 1 mg/kg, 5 mg/kg and 200 mg/kg respectively. Organic agricultural land proved to have lower concentrations of heavy metals than conventional agricultural land, which may be attributed to the lack of pesticide and chemical use.