**3.1.2 Analytical procedure**

160 Environmental Monitoring

A total of 127 wild birds, including Anatidae (n=65), seabirds (n=17), common cormorants (*Phalacrocorax carbo*, n=30), Ardeidae (n=10) and others (n=5) was used in the present study. The categories of birds included the following species: the Anatidae included spotbill duck (n=19, *Anas poecilorhyncha*), wigeon (n=15, *Anas penelope*), pintail (n=11, *Anas acuta*), mallard (n=7, *Anas platyrhynchos*), common teal (n=6, *Anas crecca*), gadwall (n=2, *Anas strepera*), common shoveler (n=2, *Anas clypeata*), wood duck (n=1, *Aix sponsa*), garganey (n=1, *Anas querquedula*) and tundra swan (n=1, *Cygnus columbianus*). The seabirds included greater scaup (n=6, *Aythya marila*), tufted duck (n=6, *Aythya fuligula*), Eurasian pochard (n=3, *Aythya ferina*), common scoter (n=1, *Melanitta nigra*) and great crested grebe (n=1, *Podiceps cristatus*). The Ardeidae included black-crowned night heron (n=3, *Nycticorax nycticorax*), little egret (n=3, *Egretta garzetta*), intermediate egret (n=2, *Egretta intermedia*), cattle egret (n=1, Bubulcus ibis) and great egret (n=1, *Egretta alba*). The others included eastern turtle dove (n=1, Streptopelia orientalis), common kestrel, (n=1, *Falco tinnunculus*), sparrowhawk (n=1, *Accipiter nisus*), peregrine falcon (n=1, *Falco peregrinus*) and Eurasian woodcock (n=1, *Scolopax rusticola*). As shown in Fig. 3, the birds were collected from various areas in Japan.

Fig. 3. The wild birds and collection areas used in this study. Number in brackets indicated

Most of the wild birds were collected as part of another National Investigation conducted by the Environment Agency in Japan (the present; Ministry of the Environment in Japan) in

**3. A new index for investigation of contamination by multiple elements** 

**3.1 Materials and methods** 

the number of samples.

**3.1.1 The wild birds used in the present study** 

Samples of kidney were removed from the birds, and about 200 mg of each sample was put into a Pyrex tube (Corning, USA), and dried in an oven at 70℃ to determine the dry weight of the sample. The appropriate volume of HNO3 : HClO4 (1:1, Wako Pure Chemical, Ltd., Japan) was added to the dried samples, and the samples were digested at 180℃. The contents of various elements in the kidneys of the birds were analyzed using inductively coupled plasma emission spectrometry (ICP-AES, FTP08, Spectro A.I., Germany). The eight target elements were: Cd, Cr, copper (Cu), lithium (Li), Mo, titanium (Ti), Tl and V. The standard additional method was employed for the analysis. The detailed methods of sample preparation and the analytical procedure have been described previously (Mochizuki et al., 2002b).
