Mine Site Drainage and Environmental Impacts - Report Example

Running Head: MINE WASTE Mine Waste Name Course Lecturer Date MINE WASTE DRAINAGE AND ENVIRONMENTAL IMPACTS Introduction Mining is one of the major drivers of the global economy as it significantly supplies a great deal of raw materials for industrial and household consumption. Corresponding consequences in large scale mining is not only evidenced by the large amount of end products but also in large volumes of environmentally harmful waste products. This is because mining results in large volumes of waste rock that have to undergo extensive processing in order to obtain the valuable component. Whereas the procedures of metallurgical extraction and processing are time and resource intensive and also environmentally detrimental, they result in very small percentages of the valuable component (Hedin, 2006). The relevance of the mining is therefore questionable as the large amounts of unwanted products and their negative effects clearly outweigh its benefits. According to research, mine wastes account for the largest percentage of industrial wastes. As such, mechanisms have been developed to alleviate the impacts of the mining process towards the environment (Lottermoser, 2010). Unlike traditional mining which was characterized by excess wastes due to inefficiencies during processing, modern mining utilizes improved technology so as to minimize waste production. Additionally, new markets for mine wastes have been found whereby they are reused or recycled to create products of economical value. This essay discusses some of the issues underlying mine waste. The first part will tackle some of the dissolved constituents of drainage from mine sites and the precipitates they form. The second part will discuss some of the environmental impacts of these solutes and precipitates while the last will address ways of and managing and preventing the wastes from moving off the mining sites. The dissolved constituents of drainage from mine sites Base metal mines The principle base metals that are commonly extracted through mined are Zinc, Copper, Lead, Silver and Iron. Apparently, these metals are also classified among heavy metals which are known for their detrimental effects to the eco system. According to Duruibe et al (2007) heavy metals are leached and transported by acidic water downstream. Inside the rivers or lakes, the metals are methylated or acted upon by bacteria which yield organic forms such as dimethylcadmium and monomethylmercury (Senko et al, 2008). M + Organic matter H2O, bacteria CH3M and (CH3)2M Non-biological conversions that have been identified in mercury include; (Nengvhela et al, 2004) Hg2+ H2S(eutropic condition) HgS(less soluble) aeration Hg2SO4 (More soluble) CH3Hg+ (methyl mercury) Past experiments have reported that organic forms of these metals do have adverse and toxic effects and affect the quality of underground water. The release of these metals from mine wastes does is not necessarily accelerated by low pH as some of them such as Zn and Cd can also be dissolved in neutral pH of 6-7. Coal mines The metals primarily found in coal mine drainage are iron (II), Iron (III), Aluminum and Magnesium (Nugraha et al, 2009). Drainage of these metals into water bodies near the mine result into acidified drainage systems. Results from experiments carried out on such water systems indicate pH values as low as 2. In other cases, abandoned coal mines can expose sulfur to water and oxygen which can lead to formation of sulfuric acid through consequent hydrolysis and oxidation (Kim et al, 2002). Under controlled conditions of the drainage system, the dissolved species may precipitate. Examples of potential chemical reactions in acid mine drainage include ion exchange, acid neutralization, coprecipitation, preprecipitation and non-sulfide mineral dissolution. Acid mine drainage (AMD) are formed during the oxidation of iron-sulfide minerals like pyrites and result to formation of sulfuric acid. Pyrite is found in the sandstone strata, shale and seam adjacent to the coal beds. Once exposed to air and water during the process of mining, pyrite is oxidized to form sulfuric acid and ferrous sulfate. Moreover, the reaction can proceed to form ferric hydroxide and ferric sulfate (Gautama & Kusuma, 2008). The reactions below show the sequences of pyrite reactions; 2FeS2 + 7O2 + 2 H2O 2 Fe2+ + 4SO42+ + 4H+ 4Fe2+ + 7O2 + 4H+ 4 Fe3+ + 2H2O 4Fe3+ + 12 H2O 4 Fe (OH)3 + 12H+ FeS2 + 14 Fe3+ + 8H2O 15 Fe2+ + 2 SO42- + 16 H+ AMD reactions result to increased concentration of dissolved sulfate (SO42-), insoluble precipitate ferric hydroxide [Fe(OH)3] and acid (H+). The weathering process of pyrite has some microbiological component thus it can be accelerated by a bacterial species known as Thiobacillus ferroxidans (Sams & Beer, 2000). Secondary reactions of the sulfuric acid produced include reactions with adjacent rocks which erode to produce higher concentration of Al, Zn, Mn and other constituents found in mine drainage water. Products of pyrite oxidation join the receiving streams through sub-surface flow systems or infiltration of though the ground. Acid water that is produced form reactions of AMD can persist for a short time if there is adequate alkalinity to neutralize it. However, once the neutrality capacity has been exhausted, acidity accelerates and the PH declines rapidly. Neutralization of acids produced due to oxidation of pyrite can be achieved through the reactions of carbonates minerals such as dolomite (CaMg(CO3)2) and calcite (CaCO3) which are have been found to coexists in sulfide rocks (Jalu et al, 2012). This is shown in the equations below; CaCO3 + H+ Ca2+ + CO2 MeAlSiO4 (s) + H+ (aq) Mex+(aq) + Al3+(aq) +H4SiO4 (aq) + 3H- Where Me= Ca, Na, Mg, Mn and Fe Application of limestone in AMD systems is limited due to their slow dissolution and solubility relative to other basic agents. However, in order to enhance the ability of limestone to neutralize the water, passive-treatment systems have been developed. They include limestone diversion wells and limestone channels. The AMD process entails three basic stages: initiation, propagation and termination. The initiation stage occurs the moment the pyrite material is exposed to an oxidizing environment such as water and air. Acid levels are relative low at this stage. During the propagation stage acid formation is quite rapid thus the levels of acid are quite high. The termination stage is characterized by a sharp decline in acid concentration. Time associated to each of these stages is however not certain but usually occurs after years or decades. For instance, predictions indicate that propagation stage (during acid peak), occurs between 5 to 10 years after mining (Doye & Duchesne, 2003). Environmental impacts of mine wastes Acid mine drainage has adverse effects towards aquatic life. For instance, metal ions which penetrate into fish through the gills cause chronic and acute toxicity which results to impairment of their respiratory systems. Fish are also exposed to the harmful metals through ingestion of organic sediments that that are contaminated with these metals. Iron hydroxide, one of the basic products of the weathering process of sulfide oxidation, is an orange/red precipitate which forms several years after a stream has been affected by AMD. According to Jennings et al (2008), Iron hydroxide can physically form on the streambeds or on the surface of the stream surface and thus inhibit the growth of food item used by fish such as benthic macroinvertebrates as well s diminish availability of clean gravel for spawning (Beltman et al, 1999). Increased precipitates in water bodies have also been associated with avoidance behavior in fish. (Alvarez-Valero et al, 2008) observed reduced hatching success among the fathead minnow as attributed to increased amounts of small ferric hydroxide particles which form at low concentrations of iron. The small particles tend to clog the egg pores of these fish and thus induce suffocation. Adding into this (Kulbat et al (2003) suggested that the increased mortality rate of rainbow trout eggs is due to accumulation of ferric hydroxide particles on the surfaces of the eggs. Physical stress is yet another impaction of increased amount of ferric hydroxide in water bodies. In his study Lottermoser (2003) found out that benthic invertebrates use frequently used their mouths to push away particles of ferric hydroxide that come on their surfaces. Chemical precipitates in water have also been found to affect the diversity, abundance and distribution of aquatic life including fishes and benthic invertebrates. Sracek et al (2010) observed sudden increase in Al- and Fe-hydroxide precipitates that consequently led to drastic decline on the growth of diversity and abundance of periphytons along streams with high concentration of mine drainage. Fish and other aquatic animals also tend to move away from habitats that are contaminated to less contaminated environments. Agricultural soil irrigated using water from streams contaminated with heavy metal consequently becomes contaminated with the pollutant. As a result, plants take up the elements during germination and ultimately accumulate in the tissues of humans when it is ingested (Trueby, 2003). Furthermore, animals that graze in such contaminated plants or drink the water accumulate large volumes of the heavy metals in their tissues or milk if they are lactating. Human beings are in turn at the risk of accumulating the elements through consumption of the animals or plants. In fact, this is one of the leading causes of various biochemical disorders such as cancer (DeGraff, 2007). Management of mine wastes Limestone Drains Cravotta & Trahan (1999) maintains that AMD usually develop in waters with deficient carbonate minerals such as dolomite and calcite relative to the pyrite present. Acidity can be neutralized and pH increased by use of calcite which is the principle component in limestone. Additionally, it can increase concentration of Ca2+ and general alkalinity of the mine water (HCO3- + OH-) through the reactions: CaCO3 (s) + 2H+ Ca2+ + H2CO3* CaCO3(s) + H2CO3* Ca2+ + HCO3 CaCO3 (s) + H2O Ca2+ + HCO3- + OH- The rate of calcite dissolution is determined by HCO3- near the calcite surface, activities of Ca2+ and H2O, partial pressure of CO2 and pH. Generally, rate of dissolution decreases as partial pressure decrease and the activities of Ca2+ and HCO3_- and pH increase. Even so, the use of limestone in neutralizing mine waters has not been fully exploited which according to Rose et al (2003)is attributed to its slow rate of dissolution and solubility as compared to other alkaline agents. Moreover, the neutralization process using limestone is associated with “armoring” with Al3+ and Fe3+. Armoring refers to complete pacification and strong adhesion of ions by encrustation (Brown et al, 2002). However, passive systems that use limestone are rapidly gaining popularity because they relatively easy to construct, maintain and inexpensive. Treatment systems which include open limestone channels, anoxic limestone drains and limestone diversion channels have been proved effective in neutralizing AMD and downstream water in mining sites (Rose & Dietz, 2002). Anoxic limestone drains (ALDs) have been found particularly effective in providing sufficient alkalinity (Younger et al, 2002). By design, it is a buried trench filled with limestone and intercepts AMD waters before coming into contact with atmospheric oxygen (Cravotta & Watzlaf, 2002). ALDs are specifically designed to alleviate the problem of armoring. A reaction between CO2 and calcite enhances calcite dissolution and increases alkalinity. Thus, in order to ensure minimum gas flux, ALD are enclosed systems unlike diversion wells and limestone channels that are open to the atmosphere. One the effluent is treated in the ALD, it is released in the atmosphere which is them followed by the formation of Fe (OH)3 by the oxidation of Fe2+ to Fe3+ (Watzlafet al, 2000). Oxygen is excluded from the system to avoid in situ precipitation of Fe (OH)3. However, strict requirement to have minimal oxygen in ALD systems makes them inappropriate for the treatment of highly mineralized or oxic water, which is characteristic of water around mines (Ziemkiewicz et al, 2003). As a result, various designs of ALDs have been proposed. One of the proposed alternatives is to incorporate compost layers that carry out pretreatment of the AMD in order to reduce the concentration of AL3+, Fe3+ and O2. Removal of heavy metals by natural zoelites As earlier noted, mining is one of the major sources of heavy in the atmosphere. Park & Dempsey (2005) identified major pathways used by heavy metals to enter into aquatic ecosystems and include discharge of acid mine drainage, waste rock piles and polluted dust. This leads to oxidation of pyrite which increases acidity of the water thus encouraging solubilization of heavy metals such as Fe, Ni, Cr, Cu, Zn and Pb. Often, acid mine drainage waters are treated with alkaline agents such as fly ach and lime so as to precipitate metals as hydroxide. However, these methods have the disadvantage of low reaction rates, require continuous addition of reagents and produce large volumes of secondary waste (Jage et al, 2000). Use of low-cost natural zeolites is considered as a viable alternative. Unlike synthetic zeolites, the resistance of natural zeolites towards acidic solutions is relatively high (Yu & Heo, 2001). Clinoptilolite is the most abundant among the 40 known natural zeolites (Turkmen et al, 2001). The mineral is found in all parts of the world in areas with large mine sites. Clinoptilolite demonstrates some distinct properties such as low density and high selectivity for Sr2+, Cs+ and NH4+ and some heavy metals. These properties make it appropriate for the treatment of agronomical applications, contaminated soils as well as wastewaters (Moreno et al, 2001). Many studies have proposed the use of pretreated zeolite materials due to the fact that a homoionic structure is required in determination of isotherms as also to increase exchange capacity of zeolites (Nordstrom et al, 2000). Although practice requires discourages pretreatment procedures, desirable results are only achieved through pretreatment of the clinoptilolite (Cincotti et al, 2001). Inglezakis et al (2003) found out that the zeolite material can only take up heavy metals at low pH. However, little has been studied about the effect of grain size on the effectiveness of the zeolite. Wingefelderet al (2005) however tried to examine the effect of grain size on metal uptake and came up with the findings that are illustrated in the graphs below; As depicted by the graphs, grain size has very small effect on the uptake of heavy metals. In generals, fine grains tend to bind more heavy metals than courser grains especially during the initial stage of the experiment. This concurs with the findings of Hedstrom (2001), which showed no substantial difference in the uptake of heavy metals after 70hrs of application with the zeolite material. With regard to pH, Wingefelder (2005) found out that the pH of the solution has a significant effect on some heavy metals. For instane, the uptake of Pb went to almost completion (99.9%) at pH 5.5 and pH 2.2 while for Zn remoal rate was more efficient in a weakly acidic solution. Conclusion Mine wastes significantly contribute to the total water pollution. Heavy metals such as Zn, Cd, Pb, Ni and Fe are the predominant elements found in base metal mines. These elements are methylated to their organic forms by certain bacteria found in water. The organic forms are found to have adverse effects to aquatic life and to human beings. Principle metals found on coal mines on the other hand include iron, zinc and aluminum. Pyrite oxidation in coal mines results in formation of ferric hydroxide precipitate and sulfuric acid which caused further removal of the heavy metals from adjacent rocks. Mine wastes have adverse effects on the respiratory and reproduction systems of aquatic animals. In addition, it affects the diversity, abundance and distribution of these animals. Terrestrial animals grazing on contaminated grass or drinking contaminated water experience tissue damage and could potentially transmit these effects to human beings who feed on their meat. Limestone drains are the most common treatment procedures for AMD as they are less expensive, easy to construct and maintain. Limestone is added into the mine waste so as to increase pH and neutralize the water before being released into the environment. Use of natural zeolites provides an effective method for the removal of heavy metals. They are naturally occurring sorbents that bind heavy metals and become precipitated and removed from the water before it is released into the receiving stream. Clinoptilolite is the most common and abundant natural zeolite. Bibliography Alvarez-Valero, A., Perez-Lopez, R., Matos, J., Capitan, M., Nieto, J. S., & Caraballo, M. (2008). Potential environmental impact at Sao Domingos mining district (Iberian Pyrite belt, SW Iberian Peninsula): evidence from a chemical and mineral characterization. Environmental geology, 55 , 1767-1809. Beltman, D., Clements, W., Lipton, J., & Cacela, D. (1999). Benthic invertebrate metal exposure, accumulation and community level effects downstream from a hard mine site. Environmental toxicology and chemistry, 18(2) , 299-307. Brown, M., Barley, B., & Wood, H. (2002). MIne water treatment: Technology, application and policy. Dorchester: IWA publishing. Cincotti, A., Lai, N., Orru, R., & Cao, G. (2001). Sardinian natural zeolites for heavy metals and ammonium removal: an experiment and modeling. Chemical engineering, 84 , 275-282. Cravotta, C., & Trahan, M. (1999). Limestone drains to increase pH and remove dissolved metals from acidic mine drainage. Applied Geochemistry, 14(1999) , 581-606. Cravotta, C., & Watzlaf, G. (2002). Design and performance of limestone drains to increase pH and remove metals from acidic mine drainage. In Handbook of groundwater remediation using permeable reactive barriers (pp. 19-66). Elsevier science. DeGraff, J. (2007). Understanding and responding to hazardous substances at mine sites in the western United States. Boulder: Goelogical Society of America. Doye, I., & Duchesne, J. (2003). Neutralization of acid mine drainage with alkaline industrial residues: laboratory investigatio using batch-leaching tests. Applied goechemistry, 18 , 1197-1213. Duruibe, J., Ogwuegbu, M., & Egwurugwu, J. (2007). Heavy metal pollution and human bitoxic effects. international journal of physical sciences, 2(5) , 112-118. Gautama, R., & Kusuma, G. (2008). Evaluation of geochemical test in predicting acid mine drainage potential in coal surface mine. In N. Rapantova, & Z. Hrkal, Mine, water and the environment (pp. 271-274). Hedin, R. (2006). The use of measured and calculated acidity values to improve the quality of mine drainage datasets. Mine water and the environment, 25 , 146-152. Hedstrom, A. (2001). Ion exchange of ammonium in zeolites: a literature review. Journal of environmental engineering,127 , 673-681. Inglezakis, V., Loizidou, M., & Grigoropoulou, H. (2003). Ion exchnage of Pb, Cu, Fe and Cr on natural clinoptilolite:selective determination of influence of acidity on metal uptake. Journal of colloid interface science, 261(1) , 49-54. Jage, C., Zipper, C., & Hendricks, A. (2000). Factors affecting performace of successive alkalinity-producing systems. Proceedings of the 2000 national meeting of the American society of surface mining and reclamation, (pp. 451-458). Tampa. Jalu, K., Hideki, S., Takashi, S., & al, e. (2012). Physical and geochenical characteristics of coal mine overburden dump related to acid mine drainage generation. memoirs of the faculty of engineering, Kyushu university, 72(2) , 23-38. Jennings, S., Neuman, D., & Blicker, P. (2008). Acid mine drainage and effects on fish health and ecology: A review. Bozenman: Reclamation research group publication. Kim, J., Kim, S., & Choo, C. (2002). Seasonal changes of mineral precipitaotion from the coal mine draingae in the Taebaek coal field, South Korea. Geochemical journal, 37 (1) , 109-121. Kulbat, E., Qlanczuk-Neyman, K., Quant, B., & Haustein, G. (2003). Heavy metal removal in the mechanical-biological wastewater treatment plant "Wschod" in Gdansk. Journal of Environmental studies, 12(5) , 635-641. Lottermoser, B. (2003). Characterization, Treatment and environment impact . Berlin: Springer. Lottermoser, B. (2010). Mine wastes; characterization, treatment and environemntal impact. London: Springer. Moreno, N., Querol, X., Ayora, C., Fernadez-Pereira, C., & Jansses-Jurkoviciva, M. (2001). Utilization of zeolite synthesized from coal fly ash from purification of acid mine waters. Environment science technology, 35 , 3526-3534. Nengvhela, N., Strydom, C., Maree, J., & Greben, H. (2004). Chemical and biological oxidation of iron in acid mine water. Mine water environment, 23 , 76-80. Nordstrom, D., Alpers, C. P., & Blowes, D. (2000). Negative pH and extremely acidic mine water from Iron Mountain, Califoria. Environmental science technology, 34 , 254-258. Nugraha, C., Shimada, H., Sasaoka, T. I., & Manege, I. (2009). Waste rock characteristics at tropical coal mones area; A case study of PT Kaltim prima coal, Indonesia. International journal of teh Japanese Committe for rock mechanics, 5 . Park, B., & Dempsey, B. (2005). Heterogeneous oxidation of Fe(II) on ferric oxide at neutral pH and low partial pressure of oxygen. Environmental science technology, 39 , 6494-6500. Rose, A., & Dietz, J. (2002). Case studies of the passive treatment systems: Verticle flow systems. Porceedings of the 2002 national meeting of the American society of mining and reclamation, (pp. 776-797). Lexington. Rose, A., Shah, P., & Means, B. (2003). Case studies of Limestone-bed passive systems for manganese removal from acid mine drainage. Proceedings of the 2003 national meeting of the American society for mining and reclamation , (pp. 1059-1078). Billings. Sams, J., & Beer, K. (2000). Effects of coal-mine drainage on stream water quality in the Allegheny and MOnongahela River Basins Sulfate transport and trends. Lemoyne: U.S. Deparment of the interior. Senko, J., Wanjugi, P., Lucas, M., Bruns, M., & Burgos, W. (2008). Characterization of Fe(II) oxidizing bacteria activities and communities at two acidic appalanchian coalmine drainage-impacted sites. international society of microbial ecology, 2008 , 1-12. Sracek, O., Veselovsky, F., Kribek, B., Malec, J., & Jehlicka, J. (2010). Geochemistry, mineralogy and environmental impact of precipitated efflorescent salts at the Kabwe Cu-Co chemical leaching in Zambia. Applied Geochemistry, 25 , 1815-1824. Trueby, P. (2003). Impact of heavy metals on forest trees from mining areas. . International conference on mining and the environment III, . Ontario: Sudbury. Turkmen, M., Ulku, S., & technology, I. I. (2001). Removal of heavy metals from wastewaters by use of natural zeolites. Watzlaf, R., Schroeder, K., & Kairies, C. (2000). LOng-term performance of anoxic limestone drains . MIne watre environment, 19 , 98-110. Wingefelder, U., Hansen, C., & Schulin, R. (2005). Removal of heavy metals from mine waters by natural zeolites. Environmental science, 39 , 4606-4613. Younger, P., Banwart, S., & Hedin, R. (2002). MIne water: Hydrology, pollution, remediation. Dordrecht: Kluwer Academic publishers. Yu, J., & Heo, B. (2001). Dilution and removal of dissolved metals from acid mine drainage along Imgok creek, Korea. Applied geochemistry, 16 , 1041-1053. Ziemkiewicz, P., Skousen, J., & Sommons, J. (2003). LOng-term performnace passive acid mine drainage treatment systems. MIne water and the environment, 22 , 118-129. Read More

Moreover, the reaction can proceed to form ferric hydroxide and ferric sulfate (Gautama & Kusuma, 2008). The reactions below show the sequences of pyrite reactions; 2FeS2 + 7O2 + 2 H2O 2 Fe2+ + 4SO42+ + 4H+ 4Fe2+ + 7O2 + 4H+ 4 Fe3+ + 2H2O 4Fe3+ + 12 H2O 4 Fe (OH)3 + 12H+ FeS2 + 14 Fe3+ + 8H2O 15 Fe2+ + 2 SO42- + 16 H+ AMD reactions result to increased concentration of dissolved sulfate (SO42-), insoluble precipitate ferric hydroxide [Fe(OH)3] and acid (H+).

The weathering process of pyrite has some microbiological component thus it can be accelerated by a bacterial species known as Thiobacillus ferroxidans (Sams & Beer, 2000). Secondary reactions of the sulfuric acid produced include reactions with adjacent rocks which erode to produce higher concentration of Al, Zn, Mn and other constituents found in mine drainage water. Products of pyrite oxidation join the receiving streams through sub-surface flow systems or infiltration of though the ground.

Acid water that is produced form reactions of AMD can persist for a short time if there is adequate alkalinity to neutralize it. However, once the neutrality capacity has been exhausted, acidity accelerates and the PH declines rapidly. Neutralization of acids produced due to oxidation of pyrite can be achieved through the reactions of carbonates minerals such as dolomite (CaMg(CO3)2) and calcite (CaCO3) which are have been found to coexists in sulfide rocks (Jalu et al, 2012). This is shown in the equations below; CaCO3 + H+ Ca2+ + CO2 MeAlSiO4 (s) + H+ (aq) Mex+(aq) + Al3+(aq) +H4SiO4 (aq) + 3H- Where Me= Ca, Na, Mg, Mn and Fe Application of limestone in AMD systems is limited due to their slow dissolution and solubility relative to other basic agents.

However, in order to enhance the ability of limestone to neutralize the water, passive-treatment systems have been developed. They include limestone diversion wells and limestone channels. The AMD process entails three basic stages: initiation, propagation and termination. The initiation stage occurs the moment the pyrite material is exposed to an oxidizing environment such as water and air. Acid levels are relative low at this stage. During the propagation stage acid formation is quite rapid thus the levels of acid are quite high.

The termination stage is characterized by a sharp decline in acid concentration. Time associated to each of these stages is however not certain but usually occurs after years or decades. For instance, predictions indicate that propagation stage (during acid peak), occurs between 5 to 10 years after mining (Doye & Duchesne, 2003). Environmental impacts of mine wastes Acid mine drainage has adverse effects towards aquatic life. For instance, metal ions which penetrate into fish through the gills cause chronic and acute toxicity which results to impairment of their respiratory systems.

Fish are also exposed to the harmful metals through ingestion of organic sediments that that are contaminated with these metals. Iron hydroxide, one of the basic products of the weathering process of sulfide oxidation, is an orange/red precipitate which forms several years after a stream has been affected by AMD. According to Jennings et al (2008), Iron hydroxide can physically form on the streambeds or on the surface of the stream surface and thus inhibit the growth of food item used by fish such as benthic macroinvertebrates as well s diminish availability of clean gravel for spawning (Beltman et al, 1999).

Increased precipitates in water bodies have also been associated with avoidance behavior in fish. (Alvarez-Valero et al, 2008) observed reduced hatching success among the fathead minnow as attributed to increased amounts of small ferric hydroxide particles which form at low concentrations of iron. The small particles tend to clog the egg pores of these fish and thus induce suffocation. Adding into this (Kulbat et al (2003) suggested that the increased mortality rate of rainbow trout eggs is due to accumulation of ferric hydroxide particles on the surfaces of the eggs.

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