Heavy Metal Toxicity In Aquatic Ecosystem And Species

For a long time, there are many factors that destroy the aquatic environments. The environment and health effects has been going down lately, especially aquatic environments because of heavy metal toxicity. The freshwaters have always started off with low concentrations of heavy metals. Even though the toxicity is base concentrations in the water, some metals are essential to organisms. Talking about heavy metals, there’s a range of them; it could be anything from Hg, Cd, to Cu,W, Zn, these types metals are part of the fast growing innovative technology and invention on the market.

The industries try so hard to get rid of waste that led them to have no other option but to dump it back into the ecosystem, even though they thoroughly try to find plausible ways to get rid of metals. Even though industries follow the environmental laws that are put upon them, the protective measures are still not enough to keep heavy metal out of fresh waters. These industries electroplate their wastewaters that contain tons of heavy metal, which then goes through a hydrographic system. This type of process diffuses these metals in pollutants, right into the ecosystem of our waters. The metals either get settled in the depths of the water or be taken into by aquatic species. This endangers the species through two ways, right directly from the aquatic environments or indirectly by food chain. When species take up these metals it reaches high concentrations right into their tissues. The accumulation of metals in their system can show how much metal levels are in the waters through long term, however these levels are based on fish’s size, sex, feeding habits, and environment.

In the aquatic environment the negative factors outweigh the positive with heavy metal toxicity. Tungsten is one of the main metals that cause great damage, its concentration of tungsten differentiates from ground waters and surface waters. Tungsten doesn’t just appear in aquatic environments by chance, manufacturers, miners, and other industrial activities are the leading cause to disruption in aquatic environments.

Tungsten and many other metals are spread throughout the ecosystem by entering through riverine, estuarine, and many other ecosystems, they come in through discharge of industrial wastewater and sewage, storm water runoff, and acid mines. Tungsten can come across to the streams or lakes are by people hunting near these grounds, fishing, smelting and metal facilities, hazardous waste landfills, and lastly agricultural. All these factors can affect the waters by running it through the waters. When tungsten is found in waters, it is neutral at alkaline natural waters, however once waters are lower than 6 in pH; it gets unsafe. Tungsten is one of many metals that are being distributed in the water that has great effects on fish life, food chain, and humans. Some place being affected by it is US, Asia, and UK. In finding out the process of how much, and how did it get there, Taiwan has managed to research about this greatly.

Taiwan figures out contamination by collecting samples of the sediments in the river by using buckets that are pre-cleaned, and bringing it back to the laboratory for filtration. To filter out these ions using polycarbonate filters while pre-weighting the sediments. They tried to analyze for dissolvement of ions. When they collected the filtration, they used acid digestion and pop it in the microwave to look for the solid samples.

In analyzing the samples by taken, they filter it by the pre-weight then use polycarbonate filters, which allows them to acidify and use HNO3 to change the concentration. They found out that when taking account of their concentrations and averaged it with global ocean average concentrations, having tungsten in water was much higher. This finding allows them to also assume that tungsten and some other metals in some zones can be diluted from breaking off sediments or sedimentary concentrations base on a bundle of aluminum. In the difference in other metals in the stream, tungsten affects aquatic organism, as well as being a toxin to aquatic biota. They assume that there are damages to fish’s gill epithelium by tungsten. In the aquatic ecosystem, the heavy metals concentration and dilutions are based on the influence of industries, river runoff, history of eroded sediments, and pollutants that make up the difference in the system.

Tungsten was not one of the most abundant heavy metals that were in the aquatic ecosystem, but as time progressed people have started to replace lead with tungsten. In turn to make better environment choices, they replaced ammunition, fishing weights, and other types of lead caused a great increasement in tungsten. Replacing lead to tungsten was believe to cause less environment pollution, they have thought that changing to tungsten would be non-toxic. It turns out that tungsten is very toxic and carcinogenic, as well as being very mobile in environments.

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When tungsten is found in waters, it is neutral at alkaline natural waters, however once waters are lower than 6 in pH; it gets unsafe. There is still a lot of unknown, even though knowing tungsten gets polymerized into monomers to become tungstate oxyanion in waters. This is subjective to change in low tungsten concentrations, temperature, pH, and ionic strength. The unknowns are based on their biogeochemistry in low temps, groundwater flow, which may or may not affect the fishes or the people who eat or drink these waters.

Since there are no known logical correlations between the biogeochemical reactions of tungsten in all these aspects, they used aquifers in groundwater surface levels to check for pH, redox sensitive indicators to understand this process of the system vs the contamination being made. They looked at tungsten in solid form as well as filtered tungsten and testing the sample collected. They also looked at tungsten speciation and toxicity, it shows that when tungsten is at a neutral pH and with other ions it can create several polytungstates, which is different than monotungstates (sodium tungstate). The polytungstates are more toxic and is a form of redox and acidic properties that can cause oxidative stress.

Some other factors that make up the tungsten in aquatic ecosystem is the nanomaterials being tossed into the waters. This has been a recent problem because of the buildup in making a lot of products has been using nanomaterials. The species being affected by this are daphnia, zooplanktons, isopod and mostly filter feeders. The nanoparticles of tungsten can appear on the surface level and as well as the bottom of the waters, this can rapidly accumulate over time. The accumulation can move by currents and waves as well as effect population size and throughout different ecosystems. Since these tungsten nanoparticles can be small particles or clumps of small particles together, they have found that species have been taking in the smaller particles. The exposures of these toxic metals have called a reduction in survival rate and their reproduction rate base on how fit they are in the ecosystem. This comes back to the big problems of having a big risk factor to the food chain, which effects the fishes and then humans.

In having all these heavy metal toxicities and the changes in the aquatic ecosystem base on these factors of tungsten, many species have been affected by the changes. Some effected by these changes in aquatic ecosystems is daphnids, algae, and zebrafish. The algae are especially sensitive to these changes in toxicity. Not only are species affected but so are the plants in these aquatic environments.

There are a lot of efforts in cleaning up the aquatic ecosystems with different resources, and till this day they are still finding new ways to eradicate the damage that they are making in the aquatic ecosystem for the animals and people. One big way to remove heavy metal is sorption. There have been studies to show that removing aqueous tungstate from waters base on sorption. However, the studies have shown that sorption does not efficiently take out all or even most of the tungsten in the system. Since tungsten has a strong affinity to iron, they have found using iron-bearing minors to take out tungsten. Another way to take out tungsten or any other heavy metals in the system have looked into using Iowaite.

Iowaite is Fe based layered double hydroxide or better known yet to be called LDH. This kind of method comes right from the labs. LDH’s layered structure and weak interlayer bonding. They also have the characteristics of a large surface area, high anion exchange capacity, and good thermal stability. Some of the ions they use in the removal of tungsten is boron, selenite, and phosphate. The rate of LDH to sorption removal is by 10% higher, which is a better way to remove tungsten. To better increase LDH from taking up tungsten is to having it increase in temperature, pH about 3 to 11. In these conditions is the best and favorable way to removal tungsten. These conditions are adequate because the effects are base on how the attraction between the negative charges and positive charges between tungsten and iowaite layers. Also, the complexity of their inner sphere due to electroactivity with iron’s. This has been one of a few great ways to treat and remove tungstate from any aquatic or nonaquatic ecosystems.

There are still some unknowns in looking at how nanoparticles tungsten is affecting species through short term effects. As well as long term effects on different species. They also haven’t tested in many more various conditions in aquatic ecosystems, that would be the next step into making a better hazardous free ecosystem too. They could research more about absorptions in other places as well. There is still a need to remove different types of tungsten, but overall there is a good way of removing some major percentages of tungsten from aquatic environments.