Toxicity Assessment of Waste From Mechanical Processing of Polymers by Biotesting

Abstract

Background. Biotesting allows us to take into account the complex relationships between soil, pollution and living organisms, as well as to determine the impact of minimum concentrations of pollutants on ecosystems. It is more informative than determining the minimum concentration values.

Objective. We are aimed to analyze the phytotoxicity assessment of sludge from mechanical processing of polymer mixtures extracted from solid household waste.

Methods. The object of the study is waste from mechanical processing of polymer mixtures, represented by sludge after washing of crushed polymers, that is composed of particles of polymers of various compositions ranging in size from 0.5 to 2.7 mm (87.3 to 92.6 % of the total amount), as well as residues of paper labels from 7.4 to 12.6% of the total amount. The assessment of phytotoxic effects was carried out by vegetative methods in accordance with ISO 17402-2008, ISO 17126-2005a, ISO 22030:2005b, ISO 11269-1:2012a, MP 2.1.7.2297-07 "Guidelines. Justification of the hazard class of production and consumption waste by phytotoxicity". The contamination levels of the test samples were assessed according to ISO 11269-2:2002 and MR 2.1.7.2297-07. Biotesting was carried out on the following types of plants: watercress, mustard, wheat, corn, soy, barley. The study of the content of heavy metals (Pb, Cu, Cd, Zn, Ni) was carried out by atomic absorption method with a spectrophotometer of the CAS-120.1 type. The obtained results were processed using traditional statistical methods applying licensed computer programs Microsoft Excel and StatSoft STATISTICA 10.0.1011.0.

Results. The studied sludge does not have a negative effect on the process of germination of watercress, mustard, corn. The level of phytotoxic effect of sludge on the germination of soybeans and barley was within the permissible range and did not exceed 3.33 %. When assessing the vegetative properties of the studied plants, it was found that in the process of growing corn, wheat, barley and soy, the sludge does not have a phytotoxic effect. When the concentration of added sludge changed, the phytotoxic effect on the length of the roots and stems of watercress and mustard was medium (cress) and weak (mustard). The study of the migration of heavy metals present in the growth substrates and their accumulation during the growth and development of plants showed an insignificant content of heavy metals in plants in all the studied samples with different sludge content. The lead content is 1.83 times higher compared to the control samples and 2.13 times higher compared to the samples on "conditionally clean"  soiland 14% lower compared to the norms of SRN 42-123-4089-86 "MAC of heavy metals and arsenic in food raw materials and food products".

Conclusions. The assessment of the phytotoxic effect of the sludge obtained in the process of mechanical processing of polymer raw materials has established that it is rational to determine the phytotoxicity of this type of sludge on the germination process and vegetation changes of plants on the most sensitive crops, such as cress and mustard. The mobile forms of lead that migrates from plant substrates and sludge into plants and accumulates in them are determined. Migration of bound forms of heavy metals copper, nickel, cadmium and zinc has not been established.