Determination of Some Heavy Metals and Mineral Nutrients in Silybum Marianum (L.) Gaertner, Grown in the Industrial Area of Dilovasi-Kocaeli-Turkey
Silybum marianum (L.) Gaertner (syn:Carduus marianus L.) known as milk thistle, Marian thistle, Saint Marys thistle, Mediaterranean thistle and Scotch thistle in English is a bianneal plant with simple or branched, unwinged stems rising from a rosette. It has a discoid homogamous solitary capitula and the flowers are pink to purple in colour. The receptacle is flat and densely setose. Fruit is a brownish achene. It can climb up to elevations of 600 meters and can be found in roadside banks, ditches and fallow fields. This plant is a mediterranean element with a natural distribution in central and Northwestern Europe but also reaching as far as Iraq, Iran and Afghanistan. Milk thistle is considered an invasive species in North America, Australia and New Zealand where it has been introduced widely. This plant is widely distributed in Turkey and is a common sight in almost all regions below altitudes of 600 meters. Milk thistle is a medicinally important species being used for over 2000 years for the treatment of liver and gallbladder disorders in traditional medicine. The main active ingredient of milk thistle is silymarin and this chemical compound is proven to be effective as a natural remedy for liver and biliary tract diseases. Silymarin and its active in constituent silybin have been reported as natural antioxidants and lipid peroxidation inhibitors. Studies also suggest that they provide protection against genomic injury, increase hepatocyte protein synthesis, decrease the activity of tumor promoters, stabilize mast cells, chelate iron, and slow calcium metabolism. Our study area, Dilovası, where the plant samples were collected is a disrict of Kocaeli province with a population of 45.714 according to 2014 census and is not far from the metropolitan city of Istanbul. Its economy is largely dependent on industry and five organized industrial zones were established in the district covering roughly over 2200 hectares of area. The proximity of this district to the economical capital of Turkey resulted in a well-established and diverse industry in the area focusing in chemical products, paper, metallurgy, machinery and machine parts, electrical and electronic products, forestry, recycling, automotive spare parts, mining, coal and marble industries. As a result of this dense and busy industry the area is also marked as one of the most polluted districts of Turkey. Turkey has a very rich and diverse flora and Kocaeli is one of the provinces reflecting this diversity effectively. Dilovası Organized Industrial Area, hosts a wide variety of plants as a reflection of this rich flora. The area also comprises a wide variety of medicinal plants and local residents collect these plants for traditional medicinal purposes, ignoring the fact that the area is a dense industrial zone and the pollution levels are off the charts. Milk thistle, being one of the most abundant medicinal plants in the study area, is selected for evaluation of industrys impact on heavy metal levels in plant parts under and over the soil such as flowers, stem, root and leaves. Moreover, to determine the effects of accumulated heavy metals on mineral nutrition of plants the results were compared with control samples taken from Büyükada Island where, unlike Dilovası area, traffic and industry is completely absent. As a result of the measurements, the highest and lowest levels (mg.tkg-1 dw) of heavy metal and mineral elements measured in study and control locations is as follows: Al (192.533 root- 11.039 flower), B (130.038 root-11.305 stem), Ca (20,105.571 unwashed leaf-5,698.461 stem), Cd (3.601 root-0.124 stem), Co (4.441 root-0.237 stem), Cr (15.537 root-0.341 stem), Cu (139.900 unwashed leaf-20.037 stem), Fe (3,465.517 root-312.214 stem), K (29,641.173 root-7,002.208 stem), Mg (21,132.252 root-3,534.761 stem), Mn (273.604 root-23.629 stem), Na (1,546.681 root-133.537 stem), Ni (12.039 unwashed leaf-1.534 stem), Pb (43.987 unwashed leaf-1.206 stem) and Zn (284.530 unwashed leaf-32.206 stem). The results clearly display the devastating effect of industry on plant nutrient uptake and heavy metal accumulation levels. Heavy metal levels are found to be up to 24 times higher than control values for Cr, 10 times higher for Cd, 4 to 5 times higher for Al and B and significantly high for other evaluated heavy metals as well.
Keywords- Urban pollution, medicinal plant, traditional medicine, Heavy metal accumulation, Industrial effect