Perspective Chapter: The Toxic Silver (Hg)

In the late 1950s, residents of a Japanese fishing village known as “Minamata” began falling ill and dying at an alarming rate. The Japanese authorities stated that methyl-mercury-rich seafood and shellfish caused the sickness. Burning fossil fuels represent ≈52.7% of Hg emissions. The majorities of mercury’s compounds are volatile and thus travel hundreds of miles with wind before being deposited on the earth’s surface. High acidity and dissolved organic carbon increase Hg-mobility in soil to enter the food chain. Additionally, Hg is taken up by areal plant parts via gas exchange. Mercury has no identified role in plants while exhibiting high affinity to form complexes with soft ligands such as sulfur and this consequently inactivates amino acids and sulfur-containing antioxidants. Long-term human exposure to Hg leads to neurotoxicity in children and adults, immunological, cardiac, and motor reproductive and genetic disorders. Accordingly, remediating contaminated soils has become an obligation. Mercury, like other potentially toxic elements, is not biodegradable, and therefore, its remediation should encompass either removal of Hg from soils or even its immobilization. This chapter discusses Hg’s chemical behavior, sources, health dangers, and soil remediation methods to lower Hg levels

Depthprofile distribution of Cs and its toxicity for canola plants grown on arid rainfed soils as affected by increasing K-inputs

Radioactive cesium (Cs) is more likely to be trans-located via rainfall into surrounding environments. Upon Cs contaminated water reaching soil, Cs is retained on soil components, mainly organic matter and clay fraction. This study aims are i) comparing the relative ability of five arid soils, differing in their textural and chemical properties, to accumulate Cs when subjected to Cs-artificially contaminated rain droplets and ii) testing whether K fertilizer can decrease the uptake of Cs and its translocation within plants or not. A lab experiment was then conducted to simulate artificial rain droplets contaminated with 1000 becquerel (Bq) of Cs-134 L-1 precipitated on soil columns each of 10.5 cm inner diameter at a rate of 1.15 mL cm(-2) over a period of 2-months. At least 89% of Cs-134 accumulated within the uppermost 5-cm layer of these soils. Another greenhouse experiment was set to test the hypothesis which indicates that Cs uptake increases unexpectedly by supplying plants with K fertilizers. In this experiment, canola (Brassica napus L.) seeds were cultivated into three K-deficient soils (Typic Haplotorrent, Typic Haplocalcid, and Typic Torripsamment) which were contaminated with 100 mg Cs kg(-1) soil (stable-Cs was used instead of radioactive-Cs to designate its behavior on the long run). Canola plants were fertilized with 0, 80 and 120 mg K2SO4 kg(-1) soil. Results carried on Typic Haplotorrent soil confirmed the aforementioned assumption as K-addition increased Cd-uptake up to 40.1%. Contradictory results were achieved in the other two soils where Cs-uptake decreased by 21.5 and 15.3% in Typic Haplocalcid and Typic Torripsamment soils, respectively due to the application of the aforementioned dose of K. In the K non-amended soils, Cs shoot root translocation factor was > 1; yet, it was < 1 in response to K addition, regardless of its application rate

Feasibility of using natural mineral ores for removing Cs and Sr from contaminated water

Proper and economical treatments of wastewater are among the important and potential solutions to increase the water budget. Although mineral ores are barriers of potentially toxic metal contaminants; however to what extent, can these ores stand successfully for decontaminating waters polluted with Cs or Sr is the question of the current study. Therefore a trial was carried out on some of these ores i.e. kaolinite, montmorillonite, and illite, to investigate their effects as decontaminants for waters polluted with either 50 mu g Cs L-1 or 50 mu g Sr L-1. Results showed that sorption of Cs and Sr increased with decreasing the ratio of the applied sorbents to the quantities of contaminated waters. Such a finding was more obvious when the rate of the sorbent: water was only 1 g L-1. The highest sorption was attained by montmorillonite followed by kaolinite, then Illite. Thus, montmorillonite was selected to complete the sorption studies at a rate of 1 g L-1. Sorption of both Cs and Sr and consequently their removal efficiencies increased with increasing the pH of the sorbents-contaminated waters suspensions up to 7 beyond which significant reductions occurred. Also, increasing the temperature of the suspension resulted in significant increases in the removal efficiencies of the investigated sorbents. Only 120 min were enough to attain the highest removal efficiency. Moreover, Ca-salts could successfully substitute sorbed Cs and Sr on surfaces of the montmorillonite used previously for decontamination of these elements from waters. Accordingly, this mineral ore can be reused successively for further decontamination processes