Occurrence

Water Quality

Ambient Water Quality Criteria for Colour in British Columbia: Technical Appendix

2. Occurrence

2.1 Natural Sources

The natural colouration of aquatic systems can be pleasing to the eye. Humans associate pristine systems with deep blues or the turquoise colour seen, for example, in glacial lakes. Colloidal CaCO₃ scatters light in the greens and blues to give these lakes their characteristic colour. Forest streams often appear very dark or brownish-yellow. For example, the relatively undisturbed Yacoun River and its tributaries on Graham Island, British Columbia have a true colour varying from 13 to 922 true colour units (TCU), (Nijman 1993). This is due to the allochthonous inputs into the system composed of, for example, humic/fulvic acids, phenols, tannins and, saponins (Nijman 1993; also Midgley and Schafer 1992). These can form organo-metal (iron/aluminum) complexes responsible for staining of water (Mitchell 1990). Water may take on a seston colour that, if anoxic, harbours cyanophytic bacteria imparting a blue-green appearance to the water. In aerated waters, algal or bacterial blooms may occur that cause a green or red colouration.

Colouration of an aquatic system depends on many factors some of which are in flux or in a continuous state of dynamic equilibrium. For example, heavy rains will enable the transport of organic material, nutrients and minerals into aquatic systems. Colour values increase with increasing dissolved organic matter concentrations (Heikkinen 1994). Lake turnover will re-suspend organic material making it available for primary productivity and seston colour. If lakes are associated with wetlands, these will increase the colouration of lakes. For example, Seymour Lake in the interior of British Columbia is more highly coloured (mean = 50 TCU) than several nearby lakes (means = 8.3-20 TCU) likely because it is a bog lake (Boyd et al. 1985). The breakdown of vegetative matter, particularly Sphagnum (peat moss), releases dissolved tannins and lignins into the water causing a brown colouration. Wet meadows or herbaceous, seasonally-flooded wetlands contribute more to lake water colour than do cattail marshes (Detenbeck et al. 1993).

Studies of aquatic systems in British Columbia have shown that apparent colour is often closely matched to seasonal flow patterns. Annual freshets, for example, can cause marked increases in turbidity and reductions in water clarity, particularly in glacier-fed streams (e.g., Webber 1996a,b,c; Wipperman and Webber 1996). As a result, seasonal variations in apparent colour in British Columbia aquatic systems can be dramatic. For example, apparent colour in the Salmon River at Hyder was shown to range from the detection limit of 5 TCU to a maximum of 160 TCU during the period 1982 to 1995 (Webber 1996c).

Figure 2 is a schematic illustration of the possible mechanisms that have an influence on the colour of an aquatic system. Lake colour in Figure 2 is a function of allochthonous inputs, autochthonous production and re-suspension or internal loading (Häkanson 1993). These factors are in turn linked to physical, chemical and biological features of the drainage area and of the lake. A similar scenario could be used for aquatic systems other than lakes. The Figure indicates some of the complexities in the determination of the natural sources of colour in aquatic systems.

2.2 Anthropogenic

Anthropogenic activities can have a profound effect on the colour of aquatic systems (Parker and Sibert 1976; Shields and Sanders 1986; Mitchell and McDonald 1995; Weis et al. 1989). Of perhaps greatest concern in British Columbia, are forest management practices (Hatfield Consultants Ltd. 1994; Butcher 1992; Taylor 1994; Nordin and Holmes 1992). Forest management practices can cause increases in water colour as a result of increased soil erosion due to construction of infrastructure and harvesting of trees, discharge of highly coloured effluents, and leaching of wood debris, both in situ and from nearby storage sites (Butcher 1992; Taylor 1994; Nordin and Holmes 1992; Forsberg 1992).

Figure 3 illustrates the profound influence that discharges of coloured effluent from pulp mills can have on ambient water colour, even in relatively large rivers such as the Fraser River. In September, 1986, true colour immediately downstream of the Northwood Pulp and Timber diffuser at Prince George on the Fraser River was 45 TCU compared to upstream values of 5 TCU (Hatfield Consultants 1994). At 4.7 km downstream, true colour had decreased to 15 TCU. Values immediately downstream of the Canadian Forest Products at Prince George diffuser increased to 105 TCU and remained elevated (65 TCU) 5.6 km downstream. Aerial photographs clearly show that the colour component of the effluents from these kraft mills persists for at least 2 km downstream of their diffusers.

The Weyerhauser pulp mill has been shown to cause a dramatic increase in water colour in the Thompson River between the confluence of the north and south sections of the river and Kamloops Lake (Nordin and Holmes 1992). The effluent from the mill is brown and often has monthly mean values for true colour of 2000 SWU or higher. Public concern over colour has been expressed for the lower Thompson River.

Figure 2. Schematic illustration of variables accounting for colour in an aquatic system (adapted from Håkanson 1993)

since the early 1970s, and led to a colour reduction program by Weyerhauser beginning in 1980. Despite the reduction program, the available data indicate a fairly consistent increase in mean colour values during the low flow period of 2 to 7 SWU between upstream and downstream stations (North and South Thompson in comparison with Savona or Walhachin).

Figure 3. True Colour (TCUs) Chart

Another mill causing serious increases in water colour in British Columbia is the Celgar Mill on the Lower Columbia River (Butcher 1992). Local residents prefer not to swim between Celgar and Castlegar because of the discolouration of water from Celgar's effluent discharge. The Celgar effluent has a dark brown colour (750 - 2360 TCU during 1988 to 1990) that originates in the separated lignin fraction, especially the humates that combine with the extracted tannins. Data from 1983 and 1984 indicate that downstream true colour values (to Kootenay River confluence) ranged from 9 to 58 SWU compared to upstream values of <5 SWU. Celgar is currently undergoing a plant modernization that is predicted to reduce effluent colour by 62%. Even with this reduction, the colour increase in the Columbia River is expected to be 18 TCU in winter and 16 TCU in summer at the edge of the initial dilution zone. Sunken log debris near the Celgar woodroom also causes a darkening of water colour due to release of organic constituents from the wood (see also Lan et al. 1995).

In northern British Columbia, dark leachates from woodpiles of trembling aspen have been observed. A field study by Taylor (1994) revealed that the leachate initially had a dark amber colour that darkened further with age as a result of decomposition of the organic component (overall range = 220 to 1550 SWU). Given the large quantities of aspen currently harvested (500,000 m³/year) and stored in the open in British Columbia, there is the potential that this source could significantly augment true colour of nearby aquatic systems.

Other sources of dissolved contaminants in British Columbia and elsewhere could include, for example, surfactants, dyes, and wood preservation chemicals all of which could potentially be contributing to colour in aquatic systems. Surfactants are used in a wide variety of products including pesticide formulations, paints and detergents. These chemicals are not under regulation because they are considered to be "inerts" and are difficult to analyze. They absorb strongly in the blue colour range and can contribute to colour measurements as a result.

Dyes are water soluble or water dispersible organic substances used by the colourant industry (Brown 1987). There are potentially thousands of products that contain dyestuffs and although the probability of most of these getting into aquatic systems is very low, some can be detected in aquatic systems. In areas outside of British Columbia, triphenylmethane blue (acid blue toilet flush), has been found in rivers at a concentration of 1.7 g/L (Richardson and Waggott 1981) and food and cosmetic dyes (acid blue 9, acid violet 17, Quinoline yellow, acid red 51, 87 and 92, and N-benzyl-N-ethylaniline sulfonic acid) were found in wastewater treatment plants in the mg/L concentration range (Borgerding and Hites 1994).

Of considerable importance are the wood preservation facilities in British Columbia. Compounds used in heavy duty wood preservation such as copper chromated arsenicals and those used as anti-sapstains (TCMTB) are highly toxic to aquatic life and contribute to the colouration of water.


	Water Quality Ambient Water Quality Criteria for Colour in British Columbia: Technical Appendix 2. Occurrence 2.1 Natural Sources The natural colouration of aquatic systems can be pleasing to the eye. Humans associate pristine systems with deep blues or the turquoise colour seen, for example, in glacial lakes. Colloidal CaCO₃ scatters light in the greens and blues to give these lakes their characteristic colour. Forest streams often appear very dark or brownish-yellow. For example, the relatively undisturbed Yacoun River and its tributaries on Graham Island, British Columbia have a true colour varying from 13 to 922 true colour units (TCU), (Nijman 1993). This is due to the allochthonous inputs into the system composed of, for example, humic/fulvic acids, phenols, tannins and, saponins (Nijman 1993; also Midgley and Schafer 1992). These can form organo-metal (iron/aluminum) complexes responsible for staining of water (Mitchell 1990). Water may take on a seston colour that, if anoxic, harbours cyanophytic bacteria imparting a blue-green appearance to the water. In aerated waters, algal or bacterial blooms may occur that cause a green or red colouration. Colouration of an aquatic system depends on many factors some of which are in flux or in a continuous state of dynamic equilibrium. For example, heavy rains will enable the transport of organic material, nutrients and minerals into aquatic systems. Colour values increase with increasing dissolved organic matter concentrations (Heikkinen 1994). Lake turnover will re-suspend organic material making it available for primary productivity and seston colour. If lakes are associated with wetlands, these will increase the colouration of lakes. For example, Seymour Lake in the interior of British Columbia is more highly coloured (mean = 50 TCU) than several nearby lakes (means = 8.3-20 TCU) likely because it is a bog lake (Boyd et al. 1985). The breakdown of vegetative matter, particularly Sphagnum (peat moss), releases dissolved tannins and lignins into the water causing a brown colouration. Wet meadows or herbaceous, seasonally-flooded wetlands contribute more to lake water colour than do cattail marshes (Detenbeck et al. 1993). Studies of aquatic systems in British Columbia have shown that apparent colour is often closely matched to seasonal flow patterns. Annual freshets, for example, can cause marked increases in turbidity and reductions in water clarity, particularly in glacier-fed streams (e.g., Webber 1996a,b,c; Wipperman and Webber 1996). As a result, seasonal variations in apparent colour in British Columbia aquatic systems can be dramatic. For example, apparent colour in the Salmon River at Hyder was shown to range from the detection limit of 5 TCU to a maximum of 160 TCU during the period 1982 to 1995 (Webber 1996c). Figure 2 is a schematic illustration of the possible mechanisms that have an influence on the colour of an aquatic system. Lake colour in Figure 2 is a function of allochthonous inputs, autochthonous production and re-suspension or internal loading (Häkanson 1993). These factors are in turn linked to physical, chemical and biological features of the drainage area and of the lake. A similar scenario could be used for aquatic systems other than lakes. The Figure indicates some of the complexities in the determination of the natural sources of colour in aquatic systems. *2.2 Anthropogenic* Anthropogenic activities can have a profound effect on the colour of aquatic systems (Parker and Sibert 1976; Shields and Sanders 1986; Mitchell and McDonald 1995; Weis et al. 1989). Of perhaps greatest concern in British Columbia, are forest management practices (Hatfield Consultants Ltd. 1994; Butcher 1992; Taylor 1994; Nordin and Holmes 1992). Forest management practices can cause increases in water colour as a result of increased soil erosion due to construction of infrastructure and harvesting of trees, discharge of highly coloured effluents, and leaching of wood debris, both in situ and from nearby storage sites (Butcher 1992; Taylor 1994; Nordin and Holmes 1992; Forsberg 1992). Figure 3 illustrates the profound influence that discharges of coloured effluent from pulp mills can have on ambient water colour, even in relatively large rivers such as the Fraser River. In September, 1986, true colour immediately downstream of the Northwood Pulp and Timber diffuser at Prince George on the Fraser River was 45 TCU compared to upstream values of 5 TCU (Hatfield Consultants 1994). At 4.7 km downstream, true colour had decreased to 15 TCU. Values immediately downstream of the Canadian Forest Products at Prince George diffuser increased to 105 TCU and remained elevated (65 TCU) 5.6 km downstream. Aerial photographs clearly show that the colour component of the effluents from these kraft mills persists for at least 2 km downstream of their diffusers. The Weyerhauser pulp mill has been shown to cause a dramatic increase in water colour in the Thompson River between the confluence of the north and south sections of the river and Kamloops Lake (Nordin and Holmes 1992). The effluent from the mill is brown and often has monthly mean values for true colour of 2000 SWU or higher. Public concern over colour has been expressed for the lower Thompson River. Figure 2. Schematic illustration of variables accounting for colour in an aquatic system (adapted from Håkanson 1993) since the early 1970s, and led to a colour reduction program by Weyerhauser beginning in 1980. Despite the reduction program, the available data indicate a fairly consistent increase in mean colour values during the low flow period of 2 to 7 SWU between upstream and downstream stations (North and South Thompson in comparison with Savona or Walhachin). Figure 3. True Colour (TCUs) Chart Another mill causing serious increases in water colour in British Columbia is the Celgar Mill on the Lower Columbia River (Butcher 1992). Local residents prefer not to swim between Celgar and Castlegar because of the discolouration of water from Celgar's effluent discharge. The Celgar effluent has a dark brown colour (750 - 2360 TCU during 1988 to 1990) that originates in the separated lignin fraction, especially the humates that combine with the extracted tannins. Data from 1983 and 1984 indicate that downstream true colour values (to Kootenay River confluence) ranged from 9 to 58 SWU compared to upstream values of <5 SWU. Celgar is currently undergoing a plant modernization that is predicted to reduce effluent colour by 62%. Even with this reduction, the colour increase in the Columbia River is expected to be 18 TCU in winter and 16 TCU in summer at the edge of the initial dilution zone. Sunken log debris near the Celgar woodroom also causes a darkening of water colour due to release of organic constituents from the wood (see also Lan et al. 1995). In northern British Columbia, dark leachates from woodpiles of trembling aspen have been observed. A field study by Taylor (1994) revealed that the leachate initially had a dark amber colour that darkened further with age as a result of decomposition of the organic component (overall range = 220 to 1550 SWU). Given the large quantities of aspen currently harvested (500,000 m³/year) and stored in the open in British Columbia, there is the potential that this source could significantly augment true colour of nearby aquatic systems. Other sources of dissolved contaminants in British Columbia and elsewhere could include, for example, surfactants, dyes, and wood preservation chemicals all of which could potentially be contributing to colour in aquatic systems. Surfactants are used in a wide variety of products including pesticide formulations, paints and detergents. These chemicals are not under regulation because they are considered to be "inerts" and are difficult to analyze. They absorb strongly in the blue colour range and can contribute to colour measurements as a result. Dyes are water soluble or water dispersible organic substances used by the colourant industry (Brown 1987). There are potentially thousands of products that contain dyestuffs and although the probability of most of these getting into aquatic systems is very low, some can be detected in aquatic systems. In areas outside of British Columbia, triphenylmethane blue (acid blue toilet flush), has been found in rivers at a concentration of 1.7 g/L (Richardson and Waggott 1981) and food and cosmetic dyes (acid blue 9, acid violet 17, Quinoline yellow, acid red 51, 87 and 92, and N-benzyl-N-ethylaniline sulfonic acid) were found in wastewater treatment plants in the mg/L concentration range (Borgerding and Hites 1994). Of considerable importance are the wood preservation facilities in British Columbia. Compounds used in heavy duty wood preservation such as copper chromated arsenicals and those used as anti-sapstains (TCMTB) are highly toxic to aquatic life and contribute to the colouration of water.