Evaluation of Chromium Contamination in Tomato Farms (Case study: Western Hormozgan Province)

Metals and metalloids with a density greater than 5 g.cm-3, are recognized as heavy metals. These elements are almost thermally stable and non-biodegradable, resulting in high persistence and accumulation of toxic levels in the environment. Some heavy metals like chromium could be distributed as a result of anthropogenic activities like transportation, mining and industries, which may be toxic to human and plants even at low concentrations. For instance, Chromium may be accumulated in human tissues, resulting in some killing diseases. Modelling and monitoring of heavy metals in soil, water bodies and vegetation are vital techniques to developing remediation strategies. Hormozgan province has more than 14000 ha under tomato cultivation with a total yield production about 630 tons. A relatively large part of these farms are located in Western Hormozgan, adjacent to the busy roads and industrial sites, which makes them important to be evaluated for heavy metals pollution in both soil and plant. The present study was undertaken to investigate some soil physical and chemical properties as well as chromium content in soil and tomato plant tissues in farms of western Hormozgan province in Iran.

The study was conducted during 2015-2017 in three main regions of tomato cultivation in western Hormozgan. Some industries including an oil refinery, a gas company and medical hospitals were located relatively near the studied farms. However, traffic activities on the busy roads parallel to the studied farms could be the main reason for soil heavy metals pollution. We studied the soil chromium concentration, as well as the uptake and distribution of chromium in different organs of tomato plants in nine heavy metal polluted farms in western Hormozgan. In addition, two important contamination indices of bio concentration factor (BCF) and translocation factor (TF), were calculated for chromium in all studied farms. All data were subjected to analysis of variance and means comparison was performed by Duncan̕s Multiple Range Test.

The results showed that chromium concentration was higher than the critical level (2 mg.kg-1) in almost all examined soils. All the studied farms were adjacent to the factories, hospitals and busy roads. Therefore, the location could be considered as the main reason for soil, water and plant pollution. Plant accumulation of Chromium was also as follows: fruit peel-1 dry weight) that could cause serious health problems in human body. More than one third of fruit chromium content was accumulated in the peel, showing a practical suggestion to reduce chromium entrance into the human body through separating the peel from the pulp before consumption of tomato fruits. The results also showed that increasing soil salinity reduced plant potential for soil chromium extraction, despite of the significant enhancement of soil available chromium concentration resulting from increasing salinity level in soil saturation extract. Furthermore, bio concentration factor declined as a result of soil salinity increasing, because the rate and intensity of chromium uptake by the plant was lower than those of soil chromium content increase in saline conditions.  

The results showed that tomato has a considerable potential for chromium uptake in polluted soils. Neighboring industries and roads were recognized to be the main reasons for high chromium contents in the studied soils in fields of Hormozgan province. Thus, it is highly recommended to establish tomato fields far from crowded roads, factories and industrial sites.AcknowledgmentThe present manuscript was prepared as part of a research collaboration between "Hormozgan Agricultural and Natural Resources Research and Education Center" and "Hormozgan University of Medical Sciences". We are so grateful for the supports.