Environmental Engineering Reference
In-Depth Information
per is utilised as the principal biocide. Copper exhibits antifouling activity
against organisms such as barnacles, tube worms and the majority of al-
gal fouling species. However, several algal species (e.g.
Enteromorpha
spp.,
Ectocarpus
spp.,
Achnanthes
spp.) show marked physiological tolerance to cop-
per. In order to achieve protection against these tolerant species, a number
of booster biocides are used in conjunction with copper to control copper-
resistant fouling organisms [24]. Organic booster biocides that have recently
been used in the UK include chlorothalonil, dichlofluanid, diuron and Ir-
garol 1051 (Irgarol), and, less frequently, Kathon 5287, maneb, TCMS pyridine,
2-(thiocyanomethylthio)benzothiazole (TCMTB), thiram, zineb, ziram and
zinc pyrithione.
Irgarol is highly effective against freshwater and marine algae. It be-
longs to the
s
-triazine group of compounds which act as photosystem-II
inhibitors, with the inhibition of photosynthetic electron capture and trans-
port in chloroplasts as their biochemical mode of action [25, 26]. Diuron, one
of the major urea herbicides in use since the 1950s, also inhibits photosyn-
thesis. It is predominantly used on land for general weed control on noncrop
areas. Chlorothalonil and dichlofluanid are protective fungicides widely used
in agriculture, with a wide range of action against a number of organisms.
Chlorothalonil is highly toxic to fish and aquatic invertebrates, but is not
phytotoxic [27, 28]. Dichlofluanid is one of the most widely used antifouling
biocides in the country [29]. However, it has been detected in saline coastal
waters at concentrations higher than in freshwaters, suggesting that its use
in antifouling products may be of significance [30]. Kathon 5287 is a highly
effective, broad-spectrum biocide. It is an isothiazolone compound which is
licensed for use as an active component in antifouling products in the UK and
elsewhere. It was the first organic booster biocide to be registered for use by
the USA EPA. A number of other booster biocides are also used in antifouling
Table 1
Physiochemical data for selected antifouling biocides
Mol Wt
Vapour
Aqueous
log
K
ow
Melting
Refs.
pressure
solubility
point
(g m
-3
)
(
◦
C)
(Pa)
Irgarol
253.37
0.00001488
7
2.38
130
[26]
Diuron
233.10
0.00041
36.4
2.85
159
[36]
Chlorothalonil
265.92
0.0013
0.6
2.64
250.5
[27]
Dichlofluanid
333.2
0.000133
0.006
3.7
106
[37]
Sea-Nine 211
/
213.3
0.0004
0.0065
2.85
0.01
[38]
Kathon
TCMTB (Busan)
238.4
1
0.00033
3.3
<
- 10
[39]
Zinc pyrithione
317.68
0.000133
77.96
2.13
262
[38]
Zineb
275.8
<
0.00001
10
≤
1.3
157
[40]
