Geology Reference
In-Depth Information
100
4
A
5
1
5
3
7
2
60
22
7
6
11
40
14
5
2
1
20
0
40
B
30
20
10
0
Figure 8 Organic wastewater contaminants by general use category. Emerging organic
contaminants in US streams, as reported by the US Geological Survey
159,160
,
can be broken down into 15 categories. A shows the frequency of detection, and
B shows the fraction of the total measured concentration (%). The number of
compounds in each category is shown above the bars in A
(Reprinted with permission from ref 159,
r
American Chemical Society,
2002)
groups, frequently occurring (atrazine, chlortoluon, isoproturon,
MCPA, mecoprop, simazine) and commonly occurring (2,4-D, dicam-
ba, dichlorprop, dimethoate, linuron, 2,4,5-T). A major seasonal source
of insecticide in freshwaters is sheep dipping. With organophosphorus
compounds, which themselves replaced the more persistent organo-
chlorine insecticides such as lindane, now falling out of favour because
of health risks to users, the use of synthetic pyrethroids as alternatives
