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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - TESNinSAB (Fate and Toxic Effects of Silver Nanoparticles and Its Transformation Products in Soil Applied with Biosolids)

Teaser

Summary

Public health concerns have an impact for agri-food industry and so, Sewage Sludge Directive, SSD, includes standard values for pollutants to prevent the contamination of soil and not to lead to adverse effects on ecosystem and public. Recent studies showed that there is no need to revise the directive to include organic contaminants such as diclofenac, since they do not pose any considerable risk. However, risk assessment for nanomaterials is lacking. Silver nanoparticles (AgNPs) are among the most crucial nanomaterials with the production amount of 452 tons/year and 200 tons/year end up in wastewater treatment plants (WWTPs) , almost (>90%), in biosolids. Land spread of biosolids lead to the transfer of AgNPs and its transformation products to the soil environment. Therefore, addressing the fate and toxicity of AgNPs and its transformation products in the soil is essential for Environmental risk assessment (ERA). It is important to know the possible risks before a serious danger occurs for society when AgNPs are being widely used. The objectives of TESNinSAB project were including to understand the fate and effect of AgNPs and their transformation product Ag2SNP by considering the biosolid application in agricultural lands, the transformation ratio of AgNP, the organic matter content of soil and the aging of AgNPs in the environment.

Work performed

Biosolid application reduces the reproductive toxicity of Ag ions and Ag2SNP. Also, it is reducing the lethal toxicity of Ag ions. The partition of all Silver forms do not change with biosolid application. Majority of Ag is adsorbed on the soil and 1-5% of Ag enters to porewater and animal body. Higher organic matter content of soil can reduce the toxicity of Ag ions and Ag2SNP; however, the effect is similar for 0.8-2% organic matter content range and for biosolid application ratio between 500:1.5-500:6. The partition of silver also did not change depending on the higher organic matter content. The aging of AgNPs more than 12 months increases the reproduction toxicity. A preliminary risk assessment can be done by using the experimental results. The results were normalized to risk scores and score tables were created for the biosolid application case, for AgNPs and their transformation product Ag2SNP, and for the aging of AgNPs case. The results of the projects were presented in 5 international conferences, 2 seminars were given for Universities, 3 public engagement event was organized in High school and primary schools. I attended Fall Lab Walls activity in Brussesls and European Researcher Night in Turkey for 2 times.

Final results

According to the result, aging of AgNPs should be studied further in the future since there is a potential to increase the chronic toxicity significantly after 12 months of aging. Overall, toxic concentrations of AgNPs and its transformation product, Ag2SNP is lower than exisiting environmental relevant concentrations. For the near future, AgNP might not be posing a serious risk for soil environment; however, aging of AgNPs should be monitored strictly. For the long term, this study provided useful data to diagnose when the risk will start to increase and can help to take necessary actions on time to reduce possible environmental and human health risk.