The ruecir of52100 steel ita boziiadary lzcbricalion conditioiu is sented. Subsequently, wear test results are discussecl with cw~trolled by theforittation ofiao~~hoinogeneozcs, l/iitafibu. Wheia the help of models which bring to light the import.;tnce of tricres~lphosphate is zu.ed cu. a71 antiwear ccdditive, the buildzg of corrosive wear in the test.lhefilit~ i s dzte lo a chemiccll reaction process involving the bearing suif[lce caiad the lzibricar~t on or near the bearing szrtface. LITERATURE SURVEYA pl~ne-on-plane-type tribometer using a 521 00 steel specimen For a complete understanding of the mechanism of action wcu used lo detehine the rate of wear and lo follow the develobment of TCP, three q~lestions of funclamental importance must offiliru by the w e ofl/&e eleclrical contact resistnnce method. The be answered: First, what are the processes by which the reslllls the chemical analysis of t,Le additive is destroyed? Second, what is the nature of the (polnrograPhic method), sur/ace analpis ofthefilm (AES and nonhomogeneous films? Third, what are their tribological properties (antiwear properties and rheological behavior)? XPS spectroscopies) andfinally with the surface topography (surface In the investigations carried out in the last 40 years to replicas and electron tmnsmission spectroscopy). elucidate the mechanism of action of TCP, several points Dlo-itrg the itrlld wear test, several phases of wear are evidenced or explanations have been developed: attd lhe obse,ved relation wilh TCP decomposition suggests a cor--chemical polishing (1)-(4) rosive wecar model proposed in the discussion. Explanations of observed pheizomet~~a (ire offered. (ECR increase, wear reduction,filin fi)rttl~ltiol~).

This study reports the chemical bioavailability of several potentially toxic elements (Zn, Pb, Cd, As, and Sb) in contaminated Technosols from two former smelting and mining areas. Though these elements have long been recognized as potentially harmful elements, understanding of their toxicity and environmental behavior in Technosols developed on former mining and smelting sites are more limited, particularly for As and Sb. Surface soils were sampled from metallophyte grassland contaminated with Zn, Pb, and Cd located at Mortagne-du-Nord (North France) and from a former mining settling basin contaminated with As, Pb, and Sb located at la Petite Faye (Limoges, France). Various selective single extraction procedures (CaCl2, NaNO3, NH4NO3, DTPA, and EDTA) were used together with germination tests with dwarf beans whose shoots were analyzed for their potentially toxic element concentrations after 21 days of growth. The extraction capacity of the potentially toxic elements followed the order EDTA > DTPA > NH4NO3 > CaCl2 > NaNO3 for both studied areas. Pearson's correlation coefficient analysis between the concentrations of potentially toxic elements accumulated in bean primary leaves or their mineral mass with their extractable concentrations showed a positive significant correlation with dilute CaCl2 and nitrate solutions extraction procedures. In contrast, for all studied elements, except Pb, the complexing and chelating extractants (EDTA and DTPA) exhibited poor correlation with the dwarf bean leaves concentrations. Moreover, results showed that the 0.01 M CaCl2 extraction procedure was the most suitable and provided the most useful indications of metal phytoavailability for studied elements.

Biochar is a potential candidate for the remediation of metal(loid)-contaminated soils. However, the mechanisms of contaminant-biochar retention and release depend on the amount of soil contaminants and physicochemical characteristics, as well as the durability of the biochar contaminant complex, which may be related to the pyrolysis process parameters. The objective of the present study was to evaluate, in a former contaminated smelting site, the impact of two doses of wood biochar (2 and 5% w/w) on metal immobilization and/or phytoavailability and their effectiveness in promoting plant growth in mesocosm experiments. Different soil mixtures were investigated. The main physicochemical parameters and the Cd, Pb, and Zn contents were determined in soil and in soil pore water. Additionally, the growth, dry weight, and metal concentrations were analyzed in the different dwarf bean plant (Phaseolus vulgaris L.) organs tested. Results showed that the addition of biochar at two doses (2 and 5%) improved soil conditions by increasing soil pH, electrical conductivity, and water holding capacity. Furthermore, the application of biochar (5%) to metal-contaminated soil reduced Cd, Pb, and Zn mobility and availability, and hence their accumulation in the different P. vulgaris L. organs. In conclusion, the data clearly demonstrated that biochar application can be effectively used for Cd, Pb, and Zn immobilization, thereby reducing their bioavailability and phytotoxicity.

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