TABLE 1.

Some physicochemical parameters of the studied pristine soils.

Parameter	Kuwaiti soil	Lebanese soil	Egyptian soil	German soil
Soil type	Sandy	Loamy	Loamy	Loamy
Temperature (°C)∗	39	28	33	21
pH	6.5	7.1	8.2	7.5
Moisture (%)	10.5	5.1	13.3	41.7
Total organic carbon (%)	0.9	1.1	1.3	13.1
Total extractable	0.3	<0.1	0.1	<0.1
hydrocarbons (%)∗∗
Total nitrogen (%)	0.1	0.2	0.3	1.5
Ca (g kg–1)	26.7	7.4	5.9	19.4
Mg (g kg–1)	7.0	2.6	13.9	6.2
K (g kg–1)	0.5	2.0	5.2	0.7
P (g kg–1)	0.3	0.8	1.3	0.9
Cd (mg kg–1)	2.0	3.4	3.1	1.7
As (mg kg–1)	<0.1	<0.1	<0.1	<0.1
Pb (mg kg–1)	<1	<1	<1	<1
Hg (μg kg–1)	<0.2	<0.2	0.4	<0.2

^∗Maximum outdoor temperature in the last week of August, the time of sampling; ^∗∗with pentane.