The US and the EU BLM models for zinc are able to make predictions for safe concentrations based on test data for salmonid and warm-water fishes, invertebrates, and aquatic plants.
#Zn element ph free#
The model comprehensively considers various water factors and action for the free metal ion bio-ligands (And and Wood 2004 Clifford and McGeer 2009 Heijerick et al.
To address influence of the aforementioned physico-chemical water quality parameters on metal toxicity, a biotic ligand model (BLM) was developed to predict the toxicity of metals in the environment. At the same time, the criteria and standard values established by each country, according to toxicological data, were created under conditions when the pH values of different water bodies were in the range of 6–8, which is not in accord with the actual situations of water bodies. However, most of the current studies were carried out when the pH was in the range of 6–8, and they rarely addressed changes in the toxicity effect of zinc on aquatic species in acidic and basic water bodies (US EPA 2007). Some of the lakes or rivers may be acidic (pH 9) for a short time if they were polluted by industrial wastewater or influenced by algae blooms (You et al. There are also significant differences in the toxicity of metals in various water bodies. The pH values of the rivers and lakes in different regions of China are very different, and seasonal changes are also obvious (Fu et al. The toxicity of metals is significantly influenced by physical and chemical parameters of water quality such as hardness, pH, and temperature (Alsop and Wood 1999 Clifford and McGeer 2009 Ryan et al. Further, the influences of variations in natural water environmental factors on zinc toxicity were not considered. However, most research studies only considered the zinc toxicity effect on single species such as fish, benthic animals or phytoplankton. Due to the differences in the aquatic species, quantity, nutritional structure and other characteristics between China and European and American areas, Chinese investigators further studied the toxic effects of zinc on common Cyprinid fishes and other species exhibiting regional characteristics of China and Asia (Feng et al. 2003 Karntanut and Pascoe 2002 Mottin et al.
For example, the main research direction of European and American countries focused on the toxic effects on Salmonid fishes, shrimp, flea, hydroids and phytoplankton genera (Alsop and Wood 1999 Diamantino et al. Presently, much research has been conducted on aquatic toxicity effects of zinc. Thus, the potential toxicity of zinc to aquatic organisms in China should receive more attention (Wu et al. Therefore, the exposure risk to aquatic organisms due to zinc greatly exceeds that of other countries. In Songhua River in China, concentrations of zinc were from 0.92 to 70.81 mg/L (Liu et al. ( 2016) reported that concentrations of zinc in Tai Lake were detected to be 0.018–1.246 mg/L, and approximately 50.7% of the aquatic organisms were predicted to be affected by zinc. According to the statistics of the National Bureau of Statistics of China in 2016, China is the second largest country in the world with zinc reserves, extraction, import and consumption (Guo and Feng 2013). It is evident that aquatic organisms are much more sensitive to zinc concentrations in water than humans. According to the water quality criteria for zinc issued by the US EPA ( 2009), the criteria of zinc to protect freshwater aquatic organisms are 120 µg/L (short -term hazardous concentration) and 120 µg/L (long-term hazardous concentration), while the criteria for human health are 7400 µg/L (ingested potable water + edible aquatic organisms grown in the water) and 26,000 µg/L (edible aquatic organisms only). When the dose of zinc exceeds a certain amount, it may cause adverse effects to the organisms (Lindholmer 1974 Smirnova and MelNichenko 1997 Wadige et al. Zinc is widely distributed throughout the natural environment and is also an essential trace element for aquatic organisms and humans (Wang et al.
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