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Sediment toxicity

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Experimental data on the toxicity of Boron orthophosphate (CAS 13308-51-5) to sediment organisms are not available. However, based on the results of short-term and long-term aquatic toxicity studies, toxic effects of the substance on sediment organisms are not expected.

Boron is an essential element for animals, human and plants. Boron will normally occurs in low concentrations (U.S. EPA 1975), e.g. in natural freshwater ecosystems, surface water concentrations are usually less than 0.1 mg/L and concentrations of more than 1 mg/L will be rarely exceed (United States Department of the Interior 1998). The chemical form of boron found in water is dictated by pH and other constituents (Sprague 1972), but in most freshwater systems (pH<9) non-dissociated boric acid will occur (Hem 1970, Maier and Knight 1991).

Boron is released to the environment slowly in low concentrations by weathering processes. There are only a few data available quantifying boron releases from industrial sources. But estimations show, that more boron will be released by natural weathering to the environment worldwide than by industrial sources (Butterwick et al. 1989).

Phosphate is the most common form of phosphorus source, which is an essential nutrient for all life forms, and is the eleventh-most abundant mineral in the earth's crust. Phosphate itself does not consider toxic to sediment organisms. However, in the aqueous environment nutrient enrichment (eutrophication) by the addition of phosphate can be a problem in some circumstances. In particular increased phosphate loads to surface waters may be a problem when the conditions are such that P is a growth-limiting factor. The effects of eutrophication can range from ecosystem modifications changes in balance between different species or communities), through to algal blooms and in extreme cases (through decomposition of plant biomass leading to oxygen depletion) collapse of the ecological community.

To avoid such effects, limiting phosphate emissions to surface water via industrial wastewater are regulated in the Council Directive 96/61/EC concerning integrated pollution prevention and control. This states that phosphates have to be taken into account for fixing emission limit values for industrial wastewater. In order to meet the requirements it may be necessary to add a treatment step for phosphate removal from industrial wastewaters before these waters are released to the aqueous environment.

References:

Butterwick, L.N. De Oude, and K. Raymond (1989). Safety assessment of boron I aquatic and terrestrial environments. Ecotoxicol. Environ. Safety 17: 339-371.

Council Directive 91/271/EEC of 21 May 1991 concerning urban waste-water treatment

Hem, J.D. (1970). Study and interpretation of the chemical characteristics of natural water, 2d ed. U.S. Geological Survey Water-Supply Paper 1473.

Maier, K.J., and A.W. Knight (1991). The toxicity of waterborne boron to Daphnia magna and Chironomus decorus and the effects of water hardness and sulfate on boron toxicity. Arch. Environ. Contam. Toxicol. 20: 282-287.

Sprague, R.W. (1972) The ecological significance of boron. U.S. Borax Research Corporation, Anaheim, California. 58p.

United States Department of the Interior (1998) Guidelines for Interpretation of the Biological Effects of Selected Constituents in Biota, Water and Sediment. National Irrigation Water Quality Program Information Report No. 3.

U.S. EPA (United States Environmental Protection Agency). 1975. Preliminary investigation of effects on the environment of boron, indium, nickel, selenium, tin, vanadium and their compounds. Vol. 1. Boron. U.S. Environmental Protection Agency Rep. 56/2- 75-005A. 111pp. Cited In: Eisler, 1990.