Changes of spatial distributions in copper and lead in Shenzhen surface soil over a 20-year period.

Fifty-two surface soil samples from agricultural, forest, and grassland sites were collected from the Shenzhen municipal area for determination of copper and lead levels. The spatial dependence of the measured results was quantified using semivariogram modeling, and structural changes in copper and lead in Shenzhen surface soil were analyzed during the past 20 years from the late 1980s to 2009. The resulting semivariogram direction of copper was from northwest to southwest, while that of lead was from east to northwest. [ABSTRACT FROM AUTHOR]