Wellington College BaCoN Michaelmas 2023 by Wellington College

BaCoN Summer 2023

It’s not an Oxygen tank! By Dr. O’Loughlin “Love is Like Oxygen, You get too much, you get too high. Not enough and you're gonna die. Love gets you high.”

Sweet, 1978

A slight pet hate of any Scuba diver is when someone refers to it as an Oxygen tank on our backs. Most divers dive with compressed air (with the water removed) and some dive on Nitrox which is enriched air to 32% (EAN32) or 40% (EAN40). There are also some weird mixes (Heliox, Trimix, Heliair etc) and understanding what you need is literally life and death.

First some physics – When scuba divers breathe underwater, we are breathing gas from the tank at the ambient pressure. For every 10m down you go (in sea water), you add on 1 atm to the pressure so that we breathe gases at the following pressures: Surface: 1 atm, 20m down = 3 atm and 40m down = 5atm. That is the deepest that most recreational divers go. Oxygen is clearly needed to maintain vital bodily functions and at the surface we breathe air containing 21% oxygen at 1 atm. This gives us a partial pressure of oxygen pO2 of 0.21 (21% x 1 atm). As the lyric above suggests, too much oxygen is bad for us and can cause us to experience a range of unpleasant symptoms, but for a diver the most worrying is a seizure through Central Nervous System toxicity. On the surface, you would probably survive, or be able to lower your exposure to the oxygen, but underwater you can’t change your gas mix easily and the result of the seizure often prevents you from making good decisions or managing your equipment correctly.

Not An Oxygen Tank! We set our dive computers to warn us if our pO2 exceeds 1.4atm if you want to err on the safe side, or 1.6atm for a slightly elevated risk but acceptable for most divers. So, when does this get exceeded? If we dive on air, we reach 1.4atm when the ambient pressure is 6.7 atm or 57m down. As this is deeper than most recreational divers go, it is not a major concern for divers on air.

But there are other effects of breathing compressed air and “The Bends” is probably the most well known and is largely caused by too much nitrogen in your blood. So whilst there are disadvantages of having too much Oxygen in your tank, there are also advantages and I always dive on EAN32 – this reduces my nitrogen load, and makes me less likely to get the bends, hence I can dive more times per day and I get less tired. But I now have to be careful about my pO2. If I have 32% Oxygen in the tank, I exceed 1.4atm at 34m and so need to stay shallower than that to avoid going deeper than this limit. Luckily, I’m not doing the calculations as I enjoy watching the manta rays, my dive computer knows it all and does the sums for me, beeping helpfully if I approach the limit, but we need to understand why.

Two other interesting scenarios. A recompression chamber, used to treat patients suffering from the bends takes people to an effective depth of 18m on 100% Oxygen. How is this safe as this gives a pO2 of 2.8 atm – far above the safe limit? As you are already at a hospital, with a doctor in the chamber with you and you’re not underwater, the effect of a seizure is not so bad and the medical advantages of getting the Nitrogen out are more important. All a matter of relative risks.

The final point is a response to that initial question, why not 100% Oxygen? Well, that would limit my depth to 4m down and that hardly seems worth it.

BaCoN Summer 2023

A Brief Glimpse Into the World of Sea Otters By Mr. Allum There are 13 surviving species of otter in the world to this day, and the diversity amongst these 13 is astounding; the smallest species of otter will grow to 0.6m as an adult (Asian small-clawed otter species) and the largest up to 1.8m (held by the aptly named Giant River Otter species). The weight difference is again equally astounding; the smallest species weighing as little as 1kg, whilst sea otters (particularly the males) weigh in the heaviest at about 45kg, with a record of 54kg having been observed!

So where would you expect to find these magnificent sea otters? Being Marine mammals, you’ll only find them in coastal waters, typically within 1km of the shore, where they rely upon the ecosystems of the ocean to support themselves, living in thick kelp forests, rocky coastlines, and even in barrier reefs in some circumstances. They are unique in that they do not rely upon blubber to keep themselves warm in the water, and instead rely upon their exceptionally thick fur. This fur is the thickest of any animal and is designed to trap a layer of air between their skin and outer fur to provide them thermal insulation. This fur is so important to them, they spend most of their time, when awake and not hunting, grooming themselves to keep their fur in top condition.

Sea Otters

Sea otters, like almost all otters, enjoy fish and seafood the most, using their front paws to catch their prey – another unique feature for this marine mammal! But how do they crack open that tasty, but spiky urchin, or even those “tough as nails” clams? With the help of their favourite rock – sea otters are known (and if you didn’t know, now you do) for carrying a rock in a small pouch underneath it’s forelegs, which it has picked out as the rock that they will use to smash open any tasty treats that need a bash.

Whilst they are independent foragers/hunters, they are very social creatures when it comes to resting – they tend to rest in single-sex groups, and the collective name for resting otters in a group is called a raft. To prevent themselves from drifting out to sea, they’ll wrap themselves in kelp, anchoring them in place.

During the mid-1700s and early 1800s, sea otters were hunted for their luxurious fur; their fur was at one point one of the most valuable in the world. By 1903, sea otter pelts could fetch as much as $1,125 ($38,782.20 or £30,995.29). In 1911, Russia, Japan, the US, and Great Britain (for Canada) imposed a moratorium (a ban) on the harvesting of sea otters – it was estimated that there was only 1000 to 2000 sea otters left. Since then, the population has rebounded to about 2/3rds of its historic levels, being a huge success for conservation. However, they’re still listed as endangered to this day due to the dangers of parasitic infection, and anthropogenic (humaninduced) hazards such as oil spills, and illegal hunting. With human intervention, we can ensure that these majestic animals live on and provide benefits to the marine ecosystems.

Further reading on how otters trap air in their fur 5

BaCoN Summer 2023

The Role of Seagrass in our Ecosystem By Vivi (Hn) You’d think that seagrass is just some annoying string that you get caught in whilst swimming, or just food that fish and turtles eat. But no, it actually plays an incredibly vital role in the ecosystem, much more than you would think. Being crucial parts of the marine ecosystem due to their productivity level, sea grasses provide food, habitat, disease cures, and nursery areas for numerous vertebrate and invertebrate species, as well as fight against climate change. Seaweed could play a vital role in the sustainable future of our planet; it has a low carbon footprint, doesn’t require fresh water, needs minimal land-based infrastructure, and can be used in several industries. These include food, agriculture, cosmetics, pharmaceuticals, and biofuels. Seagrass captures carbon up to 35 times faster than tropical rainforests and, even though it only covers 0.2% of the sea floor, it absorbs 10% of the ocean’s carbon dioxide each year, making it a powerful weapon in the fight against climate change. Through photosynthesis, the seaweed will use sunlight to grow and capture carbon dioxide from the atmosphere. Scientists believe that seaweed cultivation may be an effective measure against climate change. Not just an annoying piece of string anymore, is it? It is crazy to think that such seemingly insignificant plants can have such great importance. Seaweed has been removing carbon dioxide from the atmosphere for at least 500 million years. Recent studies suggest that seaweed continues to aid humanity by sequestering 173 million metric tons of carbon dioxide annually. The average square kilometre of seaweed can sequester more than a thousand metric tons. It can help offset emissions by replacing more greenhouse-gas-intensive products like animal-based foods and be planted in the deep sea for the purpose of carbon sequestration.

The Importance of Seagrass

Seagrass serves as a valuable nutrition source for many marine animals. Their leaves and stems provide food for herbivores like sea turtles, manatees, parrotfish, surgeonfish, sea urchins, and pin fish. Moreover, post-mortem, sea grasses provide food for decomposers like worms, sea cucumbers, crabs, and filter feeders. People are beginning to realise just how vital this food source is for marine preservation and action is beginning to be taken. The Uk has just announced that they are planting over 50,000 seeds, and over the course of the project, are hoping to plant over five million, off the coast of Wales. Seagrass is also essential as 80,000 fish and more than a million invertebrates may coexist in a 10,000 m2 area of seaweed patches, according to WWF. Many fish we consume, such as cod, plaice, and pollock, as well as endangered species like seahorses, depend on seagrass as an underwater conservatory. Lastly, green, red, and brown algae have been shown to have useful therapeutic properties in the prevention and treatment of neurodegenerative diseases, including Parkinson’s, Alzheimer’s, multiple sclerosis, and other chronic diseases. Traditional Chinese medicine uses hot water extracts of seaweeds in the treatment of cancer. Additionally, the Japanese and Chinese cultures have used seaweed salad to treat goitre and glandular problems since 300 BC. The Romans used seaweeds in the treatment of wounds, burns, and rashes. Many of these medical properties are believed to stem from the fact that seaweed contains antioxidants, which protect the body from oxide radicals and reduce inflammation at the cellular level.

BaCoN Summer 2023

Basking Sharks in the UK By Honor (Ap) Surprisingly, the Basking Shark (Cetorhinus maximus) is a frequent visitor of the UK’s shoreline. Basking sharks are the largest sharks in the UK seas and the second biggest fish in the world. They can grow to 12 m which is as long as a double-decker bus. Adult basking sharks weigh an average of 10,200 pounds (about the same as five rhinos). Although having previously been mistaken for sea monsters, basking sharks are very gentle at heart. They are, in fact, one of the few sharks that pose minimal risk to humans. Despite their gaping mouth, giving them a shocking appearance, they really use this to filter zooplankton and small crustaceans out of the water which is later pushed through the gills. From May to September, they can be seen in locations such as Cornwall, the Isle of Man, and the Inner Hebrides. They are however classified as endangered on the IUCN red list. This is because of their fragile diet. With more extreme storms and unpredictable weather patterns, the currents change, and the plankton moves with them. The sharks themselves are of grey colour with a large triangular dorsal fin that appears above the water when feeding. When their mouths are closed, they also have a large snout. Their fearful appearance, however, has caused very little research into them for many years, but now through satellite tracking, they can be seen to migrate long distances in the winter traveling to as far as Florida and the Caribbean from our shores. They are also under threat as they are frequently killed for their fins, skin, and liver oil. These creatures are very special and are significant visitors in the UK. Therefore, as much as possible should be done to protect these incredible animals.

BaCoN+ Summer 2023

Managing Marine Micro-Pollution By Eric (M)

The ocean is a vast and enigmatic domain on Earth that holds various resources and

species such as fish, shellfish, oil, and natural gas. It plays a critical role in regulating the global climate and environment by absorbing carbon dioxide and controlling temperature. Nevertheless, the ocean is currently facing numerous challenges and threats, including overfishing and pollution caused by human activities, leading to severe harm to its ecological environment. Marine pollutants, such as heavy metals, microplastics, organic compounds, and persistent organic pollutants (POPs), are among the most concerning issues related to the ocean. Studies have shown that POPs are prevalent in the global marine environment, with abnormal levels even detected in organisms in the Mariana Trench, the deepest part of the ocean. POPs possess endocrine-disrupting properties that can severely impact the health of biological organisms. Moreover, they are lipophilic, accumulating in organisms, and amplifying through the food chain. The "Yusho Rice Bran Oil Incident" that occurred in Japan in the 1970s is an example of the harm caused by POPs, where more than 30 people died and over 1,600 people suffered from skin diseases after consuming rice bran oil containing polychlorinated biphenyls. To address the ecological risks of POPs pollution, a multi-perspective approach is necessary, including policy control and technological research and development. The development of efficient pre-discharge POPs treatment methods is crucial. There are various research foundations for pre-discharge POPs treatment methods, such as physical, chemical, and biological methods. Physical methods rely mainly on adsorption, which has low operational costs, but a high risk of secondary pollution. Biological methods utilize the metabolic ability of organisms to degrade POPs, with the advantages of low risk and cost-effectiveness but have a long processing cycle and low ability to treat complex POPs pollution. Chemical methods mainly use advanced oxidation technologies to generate reactive species to oxidize and degrade POPs, with the advantages of high processing efficiency and low risk of secondary pollution. Among the advanced oxidation technologies, peroxy-disulfate oxidation technology is a promising method due to its wide pH range, high ability to generate reactive species, and high mineralization rate of pollutants. Inspired by peroxy disulfate oxidation technology, scientists aim to develop a new catalyst with the ability to efficiently catalyze peroxy disulfate to generate reactive species. Considering that different POPs pollution has various electrophilic, hydrophilic, and lipophilic characteristics, the developed catalyst can be specifically designed to regulate different POPs pollution to meet the needs of complex POPs pollution treatment.

BaCoN+ Summer 2023

I participated in the preparation of a bimetallic iron-manganese catalyst in the laboratory that can activate peroxy disulfate to achieve the initial degradation of perfluoro octane sulfonate (PFOS). This catalyst utilizes the change in the valence state of iron and manganese to provide electrons to promote the breaking of the O-O bond of peroxydisulfate to generate reactive species, achieving the oxidation and degradation of PFOS. We performed the XPS characterization analysis and it was found that the use of the catalyst indicated a decrease in the manganese content in the catalyst, possibly due to its higher activity than iron, resulting in some iron being reduced to manganese in an ionic form and entering the solution. It can be inferred that manganese in the catalyst helps to reduce high-valent iron and enhances the catalyst's sustained catalytic ability. According to the results from XPS characterization, the catalyst before use contains a significant amount of Fe 0 with strong reducibility, which first catalyzes the generation of persulfate (SO 4-). Subsequently, the generated SO4- reacts with water to generate OH, which combines with the ironmanganese on the surface of the catalyst to form a metastable iron-manganese intermediate. Then, induced by the carbon-oxygen functional groups on the catalyst surface, HSO5- reacts with the low-valence iron-manganese intermediate through hydrogen bonding to generate SO4- and OH. This is also the reason for the relative content changes of different functional groups in the XPS characterization. As the reaction rate between iron-manganese and HSO5- is different, the electron density between iron-manganese with different valence states changes during the reaction, thus promoting electron transfer between them, which is one of the reasons why the catalyst has a high catalytic ability. According to the Fe spectrum in the XPS characterization, the relative content of Fe0 decreases significantly, while the relative content of Fe 3+ increases significantly. At the same time, according to the Mn spectrum in the XPS characterization, the absolute content of Mn decreases, and the relative content of Mn 3+ decreases significantly. This indicates that Mn3+ not only participates in the generation of active oxygen species but also serves as the primary electron donor-acceptor to regulate the electron density between iron and manganese, promoting the conversion of high-valent iron to low-valent iron. It should not be ignored that Fe0 can also act as an electron donor to reduce Fe3+ to Fe2+ and ensure catalytic activity. In addition to free radicals acting as oxidants to degrade PFOS, there may be non-free radical oxidation and degradation processes. When there is a sufficient concentration of OH, SO 4-, and O2- in the system, they can react with each other to generate 1O2 in the aqueous solution. With the combined action of free radicals and non-free radicals, PFOS is continuously degraded, even completely mineralized into CO2, H2O, F+, etc. The specific reaction equations involved in this process are shown below.

Managing Marine Micro-Pollution

However, the effectiveness of this catalyst against various competing ions in the environmental medium is yet to be determined, and its cost-effectiveness has not been calculated. As a result, there is still some way to go before a practical application can be achieved. Nonetheless, I am committed to further optimizing this catalyst in my future research to develop one potential path to achieve efficient treatment of POPs pollution before entering the sea.

Basic free radical substitution