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10028-18-9, 13940-83-5, 7718-54-9, 7791-20-0, 13462-88-9, 7789-49-3, 13138-45-9, 13478-00-7, 7786-81-4, 10101-98-1, 7785-20-8, 13770-89-3, 14708-14-6, 13520-61-1, 3349-06-2, 6018-89-9, 6018-92-4
This assessment was carried out by staff of the National Industrial Chemicals Notification and Assessment Scheme (NICNAS) using the Inventory Multi-tiered Assessment and Prioritisation (IMAP) framework. The IMAP framework addresses the human health and environmental impacts of previously unassessed industrial chemicals listed on the Australian Inventory of Chemical Substances (the Inventory). The framework was developed with significant input from stakeholders and provides a more rapid, flexible and transparent approach for the assessment of chemicals listed on the Inventory.
The environmental risks associated with industrial uses of eighteen water soluble nickel(2+) salts are considered in this assessment. These nickel salts are used for the production of other industrial chemicals, metal plating, and research. The risk assessment of these chemicals has been carried out as a group because all eighteen nickel salts are very soluble in water and they can all potentially release nickel(2+) ions into water. This provides a common source of toxicity for each of the chemicals in this group. For the purposes of assessment, the chemicals have been sub-grouped into nickel salts of strong inorganic acids and nickel salts of short-chain carboxylic acids. This assessment provides reference information on the environmental fate and effects of ionic nickel which may be released into the environment from the industrial uses of other nickel containing substances listed on the Inventory. The environmental risks of these remaining nickel substances will be assessed separately.
CAS RN 7786-81-4 Chemical Name Sulfuric acid, nickel(2+) salt (1:1) Synonyms nickel sulfate anhydrous nickel sulfate Molecular Formula NiSO Molecular Weight (g/mol) 154.76 CAS RN 10101-98-1 Chemical Name Sulfuric acid, nickel(2+) salt (1:1), heptahydrate Synonyms nickel sulfate heptahydrate Molecular Formula NiSO .7H O Molecular Weight (g/mol) 280.86 CAS RN 10028-18-9 Chemical Name Nickel fluoride (NiF ) Synonyms nickel fluoride nickel(2+) fluoride nickel difluoride Molecular Formula NiF Molecular Weight (g/mol) 96.69 CAS RN 13940-83-5 Chemical Name Nickel fluoride (NiF ), tetrahydrate Synonyms nickel fluoride tetrahydrate nickel difluoride tetrahydrate Molecular Formula NiF .4H O Molecular Weight (g/mol) 168.75 CAS RN 7718-54-9 Chemical Name Nickel chloride (NiCl ) Synonyms nickel chloride Molecular Formula NiCl Molecular Weight (g/mol) 129.60 CAS RN 7791-20-0 Chemical Name Nickel chloride (NiCl ), hexahydrate Synonyms nickel chloride hexahydrate Molecular Formula NiCl .6H O Molecular Weight (g/mol) 237.69 CAS RN 13462-88-9 Chemical Name Nickel bromide (NiBr ) Synonyms nickel bromide Molecular Formula NiBr Molecular Weight (g/mol) 218.53 CAS RN 7789-49-3 Chemical Name Nickel bromide (NiBr ), trihydrate Synonyms nickel bromide trihydrate Molecular Formula NiBr .3H O Molecular Weight (g/mol) 272.55 CAS RN 13138-45-9 Chemical Name Nitric acid, nickel(2+) salt Synonyms nickel nitrate Molecular Formula Ni(NO ) Molecular Weight (g/mol) 182.71 CAS RN 13478-00-7 Chemical Name Nitric acid, nickel(2+) salt, hexahydrate Synonyms nickel nitrate hexahydrate Molecular Formula Ni(NO ) .6H O Molecular Weight (g/mol) 290.79 CAS RN 14708-14-6 Chemical Name Borate(1-), tetrafluoro-, nickel(2+) (2:1) Synonyms nickel tetrafluoroborate nickel fluoroborate nickel bis(tetrafluoroborate) Molecular Formula Ni(BF ) Molecular Weight (g/mol) 232.30 CAS RN 7785-20-8 Chemical Name Sulfuric acid, ammonium nickel(2+) salt (2:2:1), hexahydrate Synonyms ammonium nickel sulfate hexahydrate Molecular Formula (NH ) Ni(SO ) .6H O Molecular Weight (g/mol) 394.99 CAS RN 13770-89-3 Chemical Name Sulfamic acid, nickel(2+) salt (2:1) Synonyms nickel sulfamate Molecular Formula Ni(SO NH ) Molecular Weight (g/mol) 250.85 CAS RN 13520-61-1 Chemical Name Perchloric acid, nickel(2+) salt, hexahydrate Synonyms nickel perchlorate hexahydrate Molecular Formula Ni(ClO ) .6H O Molecular Weight (g/mol) 365.69
CAS RN 3349-06-2 Chemical Name Formic acid, nickel(2+) salt Synonyms nickel formate nickel(2+) formate nickel diformate Molecular Formula Ni(HCO ) Molecular Weight (g/mol) 148.76 CAS RN 373-02-4 Chemical Name Acetic acid, nickel(2+) salt Synonyms nickel acetate Molecular Formula Ni(CH CO ) Molecular Weight (g/mol) 176.78 CAS RN 6018-89-9 Chemical Name Acetic acid, nickel(2+) salt, tetrahydrate Synonyms nickel acetate tetrahydrate Molecular Formula Ni(CH CO ) .4H O Molecular Weight (g/mol) 248.84 CAS RN 6018-92-4 Chemical Name 1,2,3-Propanetricarboxylic acid, 2-hydroxy-, nickel(2+) salt (2:3) Synonyms nickel citrate trinickel dicitrate Molecular Formula Ni (C H O ) Molecular Weight (g/mol) 544.30
Based on the available information, all of the nickel salts in this group are solids under ambient conditions. The anhydrous and hydrated forms of nickel salts in this group are chemically equivalent in aqueous solution. However, they can have some significantly different properties as solids. For example, the rate of dissolution of anhydrous nickel sulfate in unbuffered water is several orders of magnitude slower than that for nickel sulfate hexahydrate. The chemicals in this group are used industrially as very water soluble sources of dissolved nickel(2+) ions. An important example is metal plating where high concentrations of dissolved nickel salts (such as nickel sulfate) are required for some common aqueous plating bath formulations. The typical characterisation of the nickel salts in this group as very water soluble is supported by the following water solubility data that are reported as the mass of the anhydrous nickel salt dissolved in a fixed mass of water (100 g) at the specified temperature: Chemical CAS RN Water Solubility (g/ 100 g H O) nickel fluoride 10028-18-9 2.6 (25°C) nickel chloride 7718-54-9 67.5 (25°C) nickel bromide 13462-88-9 131 (20°C) nickel nitrate 13138-45-9 99.2 (25°C) nickel sulfate 7786-81-4 40.4 (25°C) ammonium nickel sulfate hexahydrate 7785-20-8 6.5 (20°C) nickel perchlorate hexahydrate 13520-61-1 158.8 (25°C) nickel acetate tetrahydrate 6018-89-9 16 (20°C)
According to industry information obtained for this assessment, nickel sulfate, nickel chloride, and nickel sulfamate are used in the domestic metal plating industry. Nickel sulfate is also an intermediate in processes used to refine nickel ores at some nickel refineries operating in Australia. Nickel nitrate is reported to have uses in metal pre-treatment solutions that are used to manufacture coil extrusion products. No specific Australian use, import, or manufacturing information has been identified for the other chemicals in this group.
Nickel metal accounts for 95% of the total consumption of nickel, where approximately 85% is used in the manufacture of stainless steel and other alloys. The nickel chemicals in this group constitute a small proportion of the total global consumption of nickel. Nickel sulfate is used in the highest volume (15 000 tonnes per year) based on estimates from the European Union Risk Assessment Report (EU RAR) on nickel. Some of the chemicals in this group have significant uses in the metal finishing industry for processes such as metal plating and anodising. Quantitative use data are available for nickel chloride, nickel sulfate and nickel nitrate in the EU. Nickel sulfate and nickel chloride are used primarily for plating (89% and 71%, respectively) and the production of catalysts (11% and 29%, respectively). Furthermore, nickel sulfate and nickel chloride (and their hydrated forms) are the most commonly used nickel salts in nickel plating formulations. Nickel nitrate is mainly used for the production of catalysts (50–74%) and in the manufacture of Ni-Cd batteries (10–50%). While quantitative use data are not available for the remaining chemicals in this group, the nickel salts of strong inorganic acids are mainly used in catalyst production and for specific metal finishing applications. For example, nickel sulfamate is commonly used for plating when a functional coating is required (e.g. in electroforming). Similarly, for the nickel salts of short-chain carboxylic acids in this group, their main industrial use is also expected to be for specialised metal finishing applications. For example, nickel acetate is used as a sealing agent in anodising processes.
Nickel and nickel compounds are subject to reporting under the Australian National Pollutant Inventory (NPI). Under the NPI, emissions of nickel and nickel compounds are required to be reported annually by facilities that use or emit more than 10 tonnes of nickel or nickel compounds, burn more than 2000 tonnes of fuel, consume more than 60 000 megawatt hours of electricity (excluding lighting and motive purposes), or have an electricity rating of 20 megawatts during a reporting year. Emissions may be intentional, accidental or incidental releases arising through industrial processes. Diffuse emissions data are updated much less frequently than facility data. In Australia, high reliability default guideline values for nickel in freshwater and marine water have been determined. The freshwater guideline values have been adjusted to account for the effects of water hardness on the toxicity of nickel in aquatic systems. The current default guideline value for nickel in low hardness water is 11 micrograms of nickel per litre (μg Ni/L) which will protect 95% of species in a slightly-moderately disturbed freshwater ecosystem. The 99% protection level for nickel in marine waters (7 μg Ni/L) is currently recommended for slightly-moderatelydisturbed marine ecosystems.
For irrigated soil, a cumulative contaminant loading limit (CCL) trigger value has been set at 85 kilograms of nickel per hectare (kg Ni/ha). Nationally, an upper limit on nickel contamination in Grade C1 biosolids has been recommended (60 mg Ni/kg dry weight). Grade C1 biosolids can be applied in an unrestricted manner to all lands excluding sensitive sites.
The chemicals in this group are not currently identified as Persistent Organic Pollutants, ozone depleting substances, or hazardous substances for the purpose of international trade.
Nickel chloride, nickel chloride hexahydrate, nickel nitrate, nickel nitrate hexahydrate and nickel sulfate are listed as OECD High Production Volume (HPV) chemicals. The chemicals are produced at a level greater than 1000 tonnes per year in at least one member country of the OECD. Nickel chloride, nickel nitrate and nickel sulfate have been sponsored for assessment under the Cooperative Chemicals Assessment Programme (CoCAP). The Screening Information Dataset (SIDS) Initial Assessment Meeting (SIAM 27) found that all three chemicals are candidates for further work based on the chronic toxicity of bioavailable forms of nickel in the environment.
Chemicals containing nickel are listed as a broad class of compounds (‘Oxidic, sulphidic, and soluble inorganic nickel compounds’) under Schedule 1 (the Toxic Substances List) of the Canadian Environmental Protection Act 1999 (CEPA 1999). Nickel chloride, nickel nitrate, nickel sulfate, nickel sulfamate and nickel acetate are listed on the Canadian Domestic Substances List (DSL). These nickel salts were all categorised as Persistent (P), not Bioaccumulative (not B), and Inherently Toxic to the Environment (iT ) during the Categorization of the DSL. These five chemicals are also prioritised for further assessment under the Chemicals Management Plan (CMP).
Fifteen chemicals in this group have been pre-registered for use in the European Union under the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) legislation. Seven of these fifteen nickel salts have undergone the full registration process.
Most of the chemicals in this group (10 substances) are listed on the inventory of chemicals manufactured or processed in the USA, as published under the Toxic Substances Control Act 1976 (TSCA).
In Australia, the most significant industrial use for the nickel chemicals in this group is in the metal finishing industry for applications such as metal plating. This use pattern is therefore considered to provide the most likely pathway for emission of the nickel chemicals in this group to the environment. However, it should be noted that emissions of nickel from nickel plating will likely constitute a very small proportion of total anthropogenic nickel emissions compared to other known sources such as the combustion of fossil fuels and nickel mining, smelting and refining operations. The significance of any emissions of nickel from industrial applications of nickel chemicals must also consider the speciation and quantities of nickel which occur naturally in all compartments of the environment. The aqueous plating baths used in nickel plating contain high concentrations of ionic nickel and release of nickel(2+) ions to waterways and wastewater streams is therefore the environmental release scenario of most concern in this assessment. Nickel can be present in the vapour emitted from so-called electroless nickel plating solutions. However, such discharges are expected to be captured by extraction systems. The release of nickel to wastewater is most likely to occur during the disposal of spent plating bath solutions. However, disposal of electroplating bath solutions is very rare and does not occur directly to sewers as facilities must meet stringent standards for discharges of heavy metals in trade wastes. Electroless nickel plating has greater potential for emissions than electrolytic plating as the solutions used in the former technique have a finite lifetime. During normal plating operations, minor releases can also occur from a) drag-out (the solution lost from the bath when the plated article is removed), and b) wash-off (when the plated article is rinsed, the drag in material will be diluted in the rinse bath which is subsequently removed in the rinse effluent). Based on data collected in Australia, 40% of nickel that enters a sewage treatment plant (STP) is removed from wastewater by adsorption to sludge which may be applied to land as biosolids. Removal rates for nickel in STPs in the range 9–59% have been reported internationally. Therefore, emissions of nickel(2+) to both environmental surface waters and soils are considered as part of this assessment. The ammonium, fluoride, chloride, bromide, sulfate, and nitrate ions present as constituents of some salts in this group are ubiquitous, naturally occurring inorganic species. The use of the chemicals in this group is not considered likely to alter the background concentrations of these ions in the environment and their environmental fate and effects is not further considered in this assessment.
The behaviour of the nickel(2+) ion is strongly dependent on the chemistry of the environmental compartment into which it is released. The nickel(2+) ion is known to form only relatively weak complexes with halide and simple carboxylate anions in aqueous solution. Dissolution of the salts in this group in water will therefore result in dissociation into the nickel(2+) di-cation and the respective anions. The fully dissociated nickel di-cation is present in water as the hexaaquanickel(2+) complex ion, [Ni(H O) ] . This complex cation is a very weak acid and dissolved ionic nickel will therefore not undergo significant hydrolysis under typical environmental conditions. In natural waters (pH 5–9), nickel(2+) ions may adsorb to Fe/Mn oxides or dissolved organic matter (DOM), or form complexes with inorganic ligands (OH , SO , Cl or NH ). These interactions produce a complex mixture of nickel species and compounds that are largely determined by the chemistry of the aquatic compartment. In aquatic systems, > 90% of nickel is associated with particulate matter or sediments. However, this distribution between phases is affected by pH. At pH > 6, nickel(2+) readily adsorbs to suspended organic matter or precipitates with iron and manganese hydroxides. Conversely, in acidic waters (pH < 6), adsorption of nickel(2+) to organic matter plays a minor role and ionic nickel is relatively mobile. In soils (and soil solution), nickel can exist in many forms and its speciation will be determined by many site-specific factors including soil type, abiotic factors (e.g. pH) and the presence of complexing ligands (humic acid), soil organic matter, DOM, clay and iron hydroxides, and silica and hydrous oxides. Nickel can be removed from the soil solution and become less bioavailable following adsorption to clay particles, iron and manganese hydrous oxides and DOM. Over time, bioavailability can decrease following the adsorption of nickel to soil components and the formation of insoluble precipitates (e.g. in double layered hydroxide soils). It is noted that the amount of nickel that can be leached from soils does not always correlate with the total nickel concentration. For example, in some Australian soils that contain naturally high concentrations of nickel, < 2.5% of the total amount of nickel can be leached from the soil using strong extraction techniques. Depending on soil type, nickel can be relatively mobile in soil and is considered more mobile than other di-valent heavy metal ions (e.g. lead, cadmium, zinc). In general, the mobility of nickel is greater in acidic soils (pH 4.4– 6.6) compared to alkaline soils (6.7–8.8). In addition to soil pH, other key factors that determine the mobility of nickel in soil are soil type and cation exchange capacity (CEC). The concentrations of organic matter and extractable nickel are also important factors. Overall, the solid-solution partitioning of nickel in soil has a complex dependence on soil properties, but is mainly determined by soil pH, CEC and the concentration of both clay and DOM. Recently, the partition coefficients (K values) for nickel in 500 soils with varying physical and chemical properties were measured as part of a large-scale European geochemical survey. The median log K value (2.74) was in close agreement with that reported previously (2.08).
The nickel cation is not considered to be subject to abiotic transformation, except as discussed above. The tetrafluoroborate anion (BF ) hydrolyses in water in a stepwise manner to give hydroxyfluoroborates, then boric acid. These degradation products are naturally ubiquitous in the environment.
The nickel cation is not considered to be subject to biotransformation. Perchlorate anions (ClO ) occur naturally in the environment and are relatively stable. Due to their negative charge, perchlorates do not readily partition to soil. The precise degradation processes for perchlorates in aquatic systems have not been determined. However, laboratory studies suggest that the most likely route is throughreduction by anaerobic microbial organisms. During this step-wise process, ClO is reduced to chlorate (ClO ) followed by chlorite (ClO ) and finally to chloride (Cl ). Abiotic factors are unlikely to contribute to degradation of perchlorates in aquatic systems. The distribution of sulfamates in the environment is limited; however, they are believed to be a component of the organic sulfur fraction in soils. The concentrations of sulfamate in soils are therefore expected to be regulated by geochemical processes. The carboxylic acid components of the chemicals in this group are naturally occurring organic acids that undergo rapid biodegradation in the environment. For example, citric acid (CAS RN 77-92-9) has been found to undergo 77% degradation in 14 days in a study conducted in accordance with OECD Test Guideline (TG) 301C.
Nickel does not bioaccumulate to a significant extent in aquatic or terrestrial organisms. The exception to this is nickel hyperaccumulator plants which actively accumulate nickel in plant leaf tissue (≥ 1000 μg Ni/g) by uptake of nickel from the soil. Several aquatic plant species have the ability to remove nickel from water. However, such species typically do not meet the criteria necessary to be classified as hyperaccumulators. For other aquatic organisms, the highest accumulators of nickel appear to be certain species of marine bivalves. Although data are limited for the biomagnification of nickel, most studies indicate that biomagnification does not occur in aquatic or terrestrial food chains. Assessment of nickel bioaccumulation and biomagnification is complicated by the fact that nickel is an essential micronutrient for many species of microorganisms, plants and many higher animals. Furthermore, conventional measures of bioaccumulation as applied to organic chemicals are not appropriate for metal ions. These measures do not consider the potential for metals to accumulate in specific tissues, the physiological mechanisms available to organisms to regulate internal metal concentrations, and the influence of environmental factors. The carboxylic acid components of the chemicals in this group are not expected to pose a bioaccumulation hazard as they are naturally occurring, ubiquitous organic acids that are water soluble and readily biodegradable.
The nickel salts considered in this assessment do not undergo long-range transport. The nickel(2+) ions released from the salts in this group may have some mobility in surface water due to complexation by dissolved organic matter and/or synthetic chelating agents present in wastewater. However, nickel released to water will eventually become bound to sediment. In soil, nickel is relatively immobile, except in soils with low pH where there is an increased potential for transport through the soil compartment. Nickel compounds that are emitted to the atmosphere can associate with particulate matter and be transported over long distances through the atmosphere when associated with these particles. This emission pathway is not relevant for the known industrial uses of the nickel salts in this group and will therefore not be considered in this assessment.
A PEC was not calculated for the chemicals or their ionic components addressed under this assessment. The background concentrations of nickel in the environment vary widely, but are usually low. In Australian soils, background concentrations range from 1.4 to 55 mg Ni/kg, where agricultural soils have intermediate background levels (21.9 mg Ni/kg). No reliable or current data were identified for background concentrations of nickel in Australian freshwaters. The mean concentration in European freshwaters is 3.3 μg Ni/L. The most likely source of emissions of nickel chemicals in this group is from their use in nickel plating operations. The concentrations of nickel in electroplating and electroless plating baths range from 60 to 84 g Ni/L and approximately 8 to 10 g Ni/L (respectively). The concentration of nickel in spent electroless bath solutions is approximately 5 g Ni/L. Depending on the size of the plant and the viability of implementing recovery measures, nickel may be recovered from waste solutions and re-used within the plant. However, if recovery is incomplete, a proportion of nickel may be released with the treated effluent. No specific data regarding nickel emissions to wastewater from metal plating facilities in Australia were identified for this assessment. However, the concentration of nickel in Australian wastewater entering STPs is in the range 4 to 11 μg Ni/L. Wastewater treatment is expected to remove up to 40% of the total quantity of nickel that enters an STP. Given this rate of removal and measured concentrations of nickel in wastewater, the concentration of nickel in treated effluents discharged to surface waters is expected to be < 10 μg/L. This estimated concentration of nickel in treated effluent is comparable with findings in Europe. In the EU, approximately 1370 kg of nickel is released each year from plating operations. This includes emissions directly to surface waters (e.g. Sweden and Italy) and to wastewater streams (e.g. UK and Germany). Downstream of the discharge point (3 km), measured nickel concentrations have been recorded between < 5 μg/L and 8 μg/L. As a result of wastewater treatment, approximately 40% of nickel in wastewater influent will partition to biosolids. The average nickel concentration in Australian biosolids is 32 mg/kg and the National contaminant limit for Grade C1 biosolids (lowest level of contaminants) is 60 mg Ni/kg (dry weight). This contamination threshold is only applied when specific State guidelines have not been developed. In South Australia and Western Australia, nickel was removed from the list of contaminants to be monitored in biosolids as current nickel concentrations were deemed unlikely to significantly perturb background soil concentrations (21.9 mg Ni/kg).
The environmental effects of the nickel salts in this group will be determined by the release of nickel(2+) ions into the environment. The effects of the chemicals in this group have therefore been assessed collectively by reference to the extensive ecotoxicity data available for ionic nickel. The assessment of the aquatic toxicity of ionic nickel in this assessment distinguishes between “total nickel” (Ni ) and “dissolved nickel” (Ni ) exposure concentrations where possible. The dissolved nickel concentration is usually a more reliable indicator of the concentration of bioavailable forms of nickel in solution and provides a more useful toxicity indicator value for comparative hazard evaluation and risk assessment. The dissolved nickel concentration is the concentration of nickel that remains in water following filtration of a water sample through a 0.45 μm filter. The dissolved nickel fraction includes many simple ionic nickel species such as the [Ni(H O) ] cation, and other (typically low to moderate molecular weight) inorganic and organic complexes of the nickel(2+) ion. The speciation of nickel in the dissolved fraction can vary greatly depending on the chemistry of the water in which the nickel ion is dissolved.
Bioavailable forms of nickel(2+) are very toxic to aquatic life in short and long term exposures. The toxicity of ionic nickel to aquatic organisms varies considerably between species and is strongly influenced by water chemistry.
The following acute median lethal concentrations (LC50s) and median effective concentrations (EC50s) for model organisms across three trophic levels are presented together with relevant water chemistry parameters. The acute toxicity values for fish are based on total nickel concentrations, rather than dissolved nickel, as the LC50 values were similar in this case: Taxon Endpoint Method Fish 96 h LC50 = 270 μg Ni /L Pimephales promelas (fathead minnow) age < 1d CaCO = 12 mg/L, pH = 7.3, DOC = 0.9 mg/L 96 h LC50 = 3500 μg Ni /L Pimephales promelas (fathead minnow) age < 1d CaCO = 102 mg/L, pH = 8.8, DOC = 8.6 mg/L Invertebrates 48 h EC50 = 35 μg Ni /L Ceriodaphnia dubia (daphnid) CaCO = 108.4 mg/L, pH = 7.95, DOC = 5.02 mg/L Taxon Endpoint Method 48 h EC50 = 183 μg Ni /L Ceriodaphnia dubia (daphnid) CaCO = 131.6 mg/L, pH = 7.51, DOC = 23.6 mg/L Algae 72 h EC50 = 483 μg Ni /L Pseudokirchneriella subcapitata CaCO = 116 mg/L, pH = 6.35, DOC = 6.62 mg/L 72 h EC50 = 1630 μg Ni /L Pseudokirchneriella subcapitata CaCO = 178 mg/L, pH = 7.37, DOC = 25.8 mg/L The acute toxicity of nickel to freshwater organisms varies at both the interspecies and intraspecies level. Differences in intraspecies acute nickel toxicity can be attributed to abiotic and biotic factors including water hardness, pH and dissolved organic carbon (DOC). In addition, fish age is also an important factor influencing toxicity where older fish are more tolerant than younger fish.
The chronic toxicity of nickel(2+) to freshwater and marine species was critically evaluated for the compilation of water quality trigger values for environmental contaminants in the Australian and New Zealand Guidelines for Fresh and Marine Water Quality. Only studies that considered the complex relationship between water chemistry and toxicity were considered, and no-observed effect concentration (NOEC) equivalent values were derived. The calculated values were corrected for water hardness and converted to a uniform hardness of 30 mg CaCO /L. These values are reported below for a fish and invertebrate species. Chronic toxicity values for additional fish and invertebrate species are also given below together with values for algae and an aquatic plant species. For tests that did not specify dissolved or total nickel concentrations, it was assumed that exposure concentrations referred to total nickel in solution (Ni ): Taxon Endpoint Method Fish 28 d LC50 = 18.5 μg Ni /L Oncorhynchus mykiss (rainbow trout) CaCO = 30 mg/L, pH = 6.3– 7.7, DOC (not reported) 32 d NOEC = 57 μg Ni /L Pimephales promelas (fathead minnow) CaCO = 102.6 mg/L, pH = 7.4, DOC = 0 mg/L (estimated) Invertebrates 5–30 d EC50 = 67 μg Ni /L Daphnia magna (water flea) CaCO = 30 mg/L, pH = 6.3– 7.7, DOC (not reported) 10 d EC10 = 9.0 μg Ni /L Ceriodaphnia dubia (daphnid) CaCO = 15 mg/L, pH = 6.56, DOC = 6.36 mg/L Algae 72 h EC10 = 90 μg Ni /L Pseudokirchneriella subcapitata CaCO = 116 mg/L, pH = 6.35, DOC = 6.62 mg/L Freshwater Plant 7 d EC10 = 36 μg Ni /L Lemna minor (common duckweed) CaCO = 96 mg/L, pH = 7.6, DOC = 7.1 mg/L In addition to these chronic toxicity data from single species laboratory tests, a freshwater microcosm study with a community of algae, zooplankton, and snails showed that gastropods (snails) are sensitive to nickel. In this study, no snails were found in microcosms after 12 weeks of continuous exposure to 48 μg and 96 μg Ni /L. The population density of snails was the most sensitive end-point monitored in these microcosms and the NOEC for chronic effects under these conditions is 12 μg Ni/L. The chronic toxicity of nickel is strongly dependent on the bioavailability of nickel(2+) which is influenced by the following three key parameters: pH; water hardness; and concentration of DOC. In general, nickel toxicity is greatest in waters with alkaline pH, low water hardness and a low concentration of DOC. For example, the European Risk Assessment of nickel compounds found that the most sensitive exposure conditions occurred in waters with a pH of 7.7, 48 mg CaCO /L and 2.5 mg DOC/L. Nickel toxicity to fish and invertebrates decreases with pH over the whole pH range of natural waters. At low pH, H ions compete with nickel(2+) for the biotic ligand surfaces of exposed aquatic organisms (e.g. fish gills). In algae, toxicity decreases at high pH as well as low pH. For some freshwater invertebrates, the effect of pH on nickel(2+) ion toxicity is more important in chronic exposures than acute. Nickel toxicity decreases with increasing water hardness due to competition of other divalent cations (e.g. Ca and Mg ) for binding sites on the biotic ligand. This effect is linear down to water hardness levels of approximately 20 mg CaCO /L. The presence of DOC reduces nickel toxicity to all species across all pH ranges and water hardness values. The mitigating effect of DOC on toxicity is more pronounced at higher pH levels in softer waters. The dissolved nickel(2+) concentration alone is generally not a sufficient indicator of aquatic toxicity as abiotic factors strongly influence nickel bioavailability as discussed above. The mechanisms by which these factors affect toxicity are well understood and as a result, a bioavailability-based approach has been implemented in Europe for setting Environmental Quality Guidelines for nickel. Biotic ligand modelling (BLM) takes into account a) the affect of abiotic factors on aqueous speciation, and b) the competition between nickel(2+) and other cations for binding to the biotic ligands of aquatic organisms. Nickel BLMs can be used to normalise toxicity test results that are carried out in different water conditions provided that critical water chemistry parameters have been characterised.
Bioavailable forms of nickel(2+) can have some toxic effects on sediment-dwelling organisms. The chronic toxicity of nickel is influenced by several physico-chemical properties of sediments including total organic carbon (TOC), total recoverable iron, the concentration of acid-volatile sulfides (AVS) and CEC. These characteristics of sediments can mitigate the toxicity of nickel to sediment-dwelling organisms. Chronic toxicity values for the effects of nickel on sediment-dwelling invertebrates have been obtained for amphipods, insects, oligochaetes and mussels. Based on a worst-case scenario (low sediment AVS and TOC), a 28 d EC20 of 149 mg Ni/kg was obtained for the amphipod Hyalella azteca . Under the same exposure conditions, the most tolerant sediment-dwelling species were midges ( Chironomus riparius and Chironomus dilutes ) and mussels ( Lampsilis siliquoidea ), where the no-observed effect concentration (NOEC) exceeded the highest nickel concentration (> 762 mg Ni/kg). An intermediate toxicity value was found for the freshwater oligochaete, Lumbriculus variegates (worm) (EC10 = 554 mg Ni/kg).
Bioavailable forms of nickel(2+) are toxic to terrestrial organisms. The bioavailability and toxicity of nickel in soil is strongly influenced by soil properties, especially cation exchange capacity. Soil Quality Guidelines (SQG) have been derived for nickel in Australian soils. The guidelines were derived from NOEC and EC10 values for plants, microbial processes and invertebrates exposed to nickel in the form of nickel metal, nickel sulfate, nickel chloride, nickel nitrate or nickel carbonate (CAS RN 3333-67-3). Over 330 toxicity data points were available, with the majority relating to microbial processes and enzymes. The lowest NOEC/EC10 values for nickel toxicity to plants, microbial processes and invertebrates are 26.9 mg Ni/kg ( Spinacia oleracea , spinach), 81.3 mg Ni/kg (nitrification) and 103 mg Ni/kg ( Eisenia veneta , earthworm), respectively (geometric mean values).
The primary environmental effects of the chemicals in this group are expected to be caused by the release of nickel(2+) ions. Given that the focus of this assessment is the release of nickel to wastewater streams and aquatic environments, existing guideline values for nickel in soils and aquatic systems were considered. In place of a PNEC for the soil compartment for nickel(2+), the
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