scholarly journals Evolution of the content of total suspended particulates and of the metals, lead, zinc, cadmium, copper, iron and manganese, in the atmospheric aerosol from Cartagena, for the period 1995–2000

2009 ◽  
Author(s):  
María del Carmen Martínez Arroyo

The mechanism of metallic friction, in air, has been investigated for loads ranging from 0.003 to 10000 g. The metals studied include platinum, gold, silver, copper, tin, lead, zinc, cadmium, magnesium, aluminium and chromium. The earlier work of Whitehead has been extended and simultaneous measurements made of the frictional force and the electrical resistance between the sliding surfaces. The results show that with most metals the natural oxide layer is sufficient to prevent metallic contact at very small loads. The degree of protection depends on a number of factors, such as the surface roughness, the thickness of the oxide film and in particular on the relative hardness of the oxide and the metal substrate. When sliding occurs solely on the oxide layers the friction is not necessarily less than that observed when appreciable metallic contact occurs. The surface damage is, however, greatly diminished on account of the reduced metallic interaction.


2011 ◽  
Vol 184 (11) ◽  
pp. 6789-6798 ◽  
Author(s):  
Wenxin Wang ◽  
Yinlong Zhang ◽  
Shuiliang Wang ◽  
Chinbay Q. Fan ◽  
Hui Xu

2018 ◽  
Vol 5 (11) ◽  
pp. 781-797
Author(s):  
Paul Chinedu Echi ◽  
Daberechi Ndudim Okpechi ◽  
Janet Azu Urum ◽  
Izuchukwu Samson Arukwe

Ibaka Estuarine in Mbo, Nigeria, has little or no information on its basic properties, therefore its water samples were studied from March to June 2018 in three different stations and compared with International Standards to evaluate its physic-chemical properties as well as heavy metal contents. The physic-chemical properties studied include pH, salinity (g/L), EC (μs/cm), turbidity (NTU), total suspended solids (mg/L), total dissolved solids (mg/L), dissolved oxygen (mg/L), BOD5 (mg/L), and chemical oxygen demand (mg/L). In addition, some metal concentrations of manganese, iron, copper, lead, zinc, cadmium, chloride and magnesium were determined by atomic absorption spectroscopy (AAS). The range of metal concentrations manganese (0.08-0.12 mg/L), copper (0.05-0.09 mg/L), lead (0.01-0.03 mg/L), iron (1.86-4.66 mg/L), zinc (0.68-1.16 mg/L), cadmium (0.04-0.08 mg/L), chloride (675.0-791.25 mg/L), magnesium (10.66-14.30 mg/L). The study infers that anthropogenic pressure plays damaging role to its properties in addition to general health implication of high values for Fe, Zn, Cd, Cl and Mg which exceeded international standard.


2006 ◽  
Vol 63 (5) ◽  
pp. 567-577 ◽  
Author(s):  
E.E. Ukpebor ◽  
J.E. Ukpebor ◽  
P.O. Oviasogie ◽  
J.I. Odiase ◽  
M.A. Egbeme

2006 ◽  
Vol 14 (3) ◽  
pp. 169-186 ◽  
Author(s):  
Eiliv Steinnes ◽  
Andrew J Friedland

This review focuses on the long-range atmospheric transport of metals to organic-rich surface soils (mostly 50–90% organic matter) in the temperate, coniferous, and boreal zones of North America and Europe. From various air-pollution related measurements (air, precipitation, moss, peat cores) Pb and Zn are known to be transported long distances in the air in large amounts. Arsenic, Cd, Hg, Sb, and Se are also typical representatives of long-range transported air masses, and there is evidence that Ag, Bi, In, Mo, Tl, and W belong to this group of elements. Through the use of “environmental archives” such as ice and peat cores it has become evident that long-range transport of pollutants and associated contamination of natural surfaces is not just a recent phenomenon. There is compelling evidence for widespread enrichment of surface soil horizons in Pb from long-range transport, and many studies support enrichment of Zn. Mercury is also generally elevated by anthropogenic emissions over natural levels in organic-rich surface soils, whereas results for Cd are less conclusive. There is evidence that As, Se, Ag, Mo, In, Sb, W, Tl, and Bi all are subject to some enrichment in organic-rich surface soils from long-range atmospheric transport, but studies are still few for most of these elements. With the exception of Pb, little is known about residence times of the elements in the organic-rich surface horizon, and more research is needed on this topic. Further studies are desirable on the temporal and spatial trends in supply of the above elements, which are poorly known in large parts of the northern temperate zone.Key words: natural soils, metals, long-range atmospheric transport, organic matter, lead, zinc, cadmium, mercury.


2009 ◽  
Vol 66 (1) ◽  
pp. 126-134 ◽  
Author(s):  
Ye-Tao Tang ◽  
Rong-Liang Qiu ◽  
Xiao-Wen Zeng ◽  
Rong-Rong Ying ◽  
Fang-Ming Yu ◽  
...  

Sign in / Sign up

Export Citation Format

Share Document