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2020 seems to have been a particularly bad year for wildfires globally. Major fires that commenced in Australia in 2019 continued into the first few months of 2020. They were followed by wild (or biomass) fires in many other parts of the world, from the Amazon to the Arctic and from central Africa to California, and other states in western/northwestern US. Wildfires have a multiple of causes, of course, but climate conditions are often a major contributing factor. Perhaps unsurprisingly, an August 2020 paper in the journal Environmental Research Letters, available here, finds climate change to be important in increasing the likelihood of extreme late summer/autumn wildfire conditions across California. The authors note that a cocktail of environmental conditions (high temperatures, low rainfall, strong winds) have enabled the ignition and spread of wildfires. They use climate models to project future conditions, and find that continued climate change will further lengthen the period during which extreme fire weather occurs, and hence the most devastating wildfires (assuming there is still biomass left to burn!).

Given that major wildfires are perhaps even more likely, rather than less, in coming years – as a result of climate change but also as humans and their sources of ignition penetrate deeper into forested and peat lands, now is probably a good time to evaluate the effectiveness of our response. Here I would like to focus, in particular, on the chemicals that are used to limit the spread or reduce the intensive of wildfires ~ fire suppressant and retardant chemicals, in other words. These are the often brightly coloured substances that get air-dropped on and around wildfires – they are to fighting wildfires what chemical dispersants are to dealing with oil spills at sea. Just as we have begun to question the efficacy of chemical dispersants when dealing with a major oil spill it is probably useful to enquire about fire suppressant and retardant chemicals, and in particular whether they do more harm than good.

There are several types of fire suppressant (generally applied to a fire to reduce its intensity) and retardant (used to reduce the chances of a fire starting or spreading once started) chemicals. Fire suppressants generally reduce the temperature of the fire – water sprayed onto burning vegetation is an example, as are chemical foams. Foams are wetting agents that allow water to penetrate a surface more effectively, thereby allowing its more efficient use in suppressing a fire.

Fire retardants (e.g. Phos-Chek) are most often used in the creation of fire breaks – their application is aimed at reducing the combustibility of vegetation ahead (i.e. in front) of an advancing fire. They are therefore designed to persist in the environment rather than to degrade immediately. The most common retardants are a combination of water and either ammonium sulfate [(NH4)2SO4] or diammonium phosphate [(NH4)2HPO4] mixed with additives to thicken, reduce spoilage during storage and colour the liquid. The latter give fire retardants their bright colours – so that it is possible to see which parts of the landscape have already been treated, but also (I guess) to look good on the TV …. Retardants also include other elements to help reduce combustibility, including antimony, chlorine, bromine, boron. Chlorine and bromine are used in what are known as “halogenated retardants”.

Generally retardants are regarded as being non-toxic to humans and large mammals, at least in low concentrations. However, their toxicity to aquatic life, even at low concentrations, has long been known (e.g. Dietrich, 2013). Although retardants are meant for terrestrial use (spraying on forest and other combustible biomass) they can end up being washed into or inadvertently sprayed over aquatic ecosystems. Further, the toxicity of some of the chemicals used may be enhanced by the heat of, or through mixing with emissions from, the wildfire. At high temperatures, some halogenated retardants can form extremely toxic dioxins, for example.

And then there are the environmental effects of spraying ammonium sulfate and diammonium phosphate over large areas of vegetation and soil. Both are ammonium-based fertlizers, and therefore likely to result in environmental eutrophication and acidification. Ironically, depositing large amounts of fertilizer is likely to boost productivity in vegetation that survives the fire – resulting in increased loadings of highly-combustible litter, potentially adding to the intensity of any burn during the next fire-season ….

Given the current extent and intensity of wildfires and the likelihood that conditions that predispose biomass to burning will become more extensive, frequent and intense in coming years, chucking chemicals that only add to environmental pollution and its harmful effects at the problem seems neither desirable nor sustainable.

Much has been written over the past few months about the the relationship with the COVID-19 pandemic and air quality. Based on past experiences – e.g. the so-called Spanish Flu pandemic of 1918-1919 caused by a H1N1 virus – we know that the symptoms and effects of respiratory illnesses are made worse by poor air quality. We have feasible mechanisms that explain the link too – air pollution facilitates both the ability of a pathogen (such as a virus) to invade a human body, by damaging the epithelial cells that line the respiratory tract, and, once in, proceed to modulate the host’s immune response. Thus it is perhaps not so surprising that studies (e.g. by Wu et al.) have revealed a link between poor air quality and a high incidence of the most severe cases of and highest death rates due to COVID-19. Of course there are likely to be other factors at play too that are also linked to poor air quality, such as poverty, poor diet, inadequate access to health facilities etc. Therefore it is perhaps best to see poor air quality as an amplifier of the effects of existing inequalities.

A lot has also been written about the positive effects on air quality of lock-downs around the world in response to COVID-19. Reduced industrial activity and reduced travel (particularly in airplanes) have contributed to reduced pollution emissions, including those to the atmosphere. As a result, clear skies have been reported in many places where such experiences had become the subject of distant memories. But these positive effects are likely to be short-term, and unlikely to outlive lock-downs, as is already evident in some places that have seen something of a recovery in economic activity in recent weeks. They also come at a huge economic cost too, which itself will have profound, negative health effects ~ and could also reverse some of the pre-COVID-19 successes in dealing with some of the more intractable environmental problems, such as climate change, as governments focus more on the future health of national economies rather than existing international obligations. A recent article in Nature Sustainability (see here) focused on China makes the point very well that while lock-downs resulted in improvements in air quality those improvements were relatively small, were least in warmer, sub-tropical parts of the country (where a large proportion of China’s population and industry is located but where consumption of polluting fossil fuels for heating is generally lower) and came at huge economic cost. Hu et al., the authors of the study, go on to opine that the same improvements in air quality, but over the long term, could be made at a much lower cost through the implementation of anti-pollution measures targeted at individual large emitters of air pollutants.

Fortunately, when relatively short-term variations in air quality – due to, for example, lock-downs associated with disease pandemics or major sporting events such as the Beijing Olympics of 2008 – are placed in the context of air quality measurements over the longer-term, it seems that air pollution and its health effects have been reduced throughout much of China since 1997. The date 1997 is significant in China because it shortly precedes the Chinese Government’s declaration of war on air pollution in its capital, Beijing (see UN report here).

According to research recently published last month (August 2020) by Yin et al in Lancet Planetary Health it seems that improvements in air quality as a result of reductions in fine particulate matter (PM2.5) in the atmosphere have occurred across China since 1997 following implementation of a series of national and regional control measures. For example, the National Air Pollution Prevention and Control Action Plan was introduced in 2013, and this has led to widely observed reductions in ambient concentrations of PM2.5. Improvements in air quality, including indoor air quality, have also followed a ban on the use of coal for domestic heating and cooking.

Population-weighted mean ambient PM2·5 concentration in provinces of China in 1990 (A) and 2017 (B) (from Yin et al 2020)

Despite these improvements, however, the vast majority of people in China (about 80% according to Yin et al) still live in areas where air quality does not meet even the most basic World Health Organisation (WHO)’s recommended levels, and mortality rates linked to poor air quality although on the decline in many parts of the country remain high overall (over a million premature deaths due to air pollution in 2017, according to Yin et al). Major differences in mortality rates linked to air quality remain within China, presumably reflecting differences in socio-economic conditions, access to health facilities etc, with 12 provinces actually showing an increase in mortality rates over the ca 30-year long study.

China and indeed many parts of the world now stand at something of a crossroads with regard to air quality. Will recent improvements in air quality, either linked to COVID-19 related lock-downs or to policies and regulations implemented over the longer-term, be maintained into the future? Or will potentially highly polluting and health-threatening fossil fuels once again be returned to as the convenient engine of global economic growth, as they were following World War II? Such a return may now be taking place in China (see here).

Here are the student blogs for the Semester one AY2020-2021 version of GE3246 Environmental Pollution (August to November 2020):

Here are the student blogs for the Special Term version of GE3246 Environmental Pollution (June/July 2020):

The latest data on atmospheric concentrations of greenhouse gases (GHGs) released by the World Meteorological Organization (WMO)’s Global Atmosphere Watch and published in the 25 November 2019 issue (issue #15) of the WMO Greenhouse Gas Bulletin make for chilling reading. Issue #15 can be accessed at the bottom of this post.

The data for 2018 show an increase in concentrations for three key GHGs, carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) over 2017 levels (Table 1). For two of the GHGs (CH4 and N2O) the rate of increase 2017-2018 is greater than the average rate of increase over the preceding decade, while for CO2 the increase is around the average rate of change for that same period. Positive radiative forcing attributed to the three key GHGs has increased markedly since pre-industrial times (pre-AD 1750). Thus radiative forcing attributed to increased concentrations of CO2 has increased by 147%, CH4 by 259%  and N2O by 123% since pre-AD 1750.

Table 1: Global annual surface mean abundances (2018) and trends of key greenhouse gases from the GAW global GHG monitoring network. Units are dry-air mole fractions with 68% uncertainties shown. The data are based on an average of several stations around the world. There are relatively few stations for tropical latitudes.

Emissions of CO2, CH4 and N2O can persist in the atmosphere for relatively long periods. They are also therefore commonly referred to as “long-lived GHGs” (LLGHGs). One other group of pollutants are also considered as LLGHGs, the ozone-depleting chlorofluorocarbons (CFCs) together with hydrochloroflurocarbons (HCFCs), hydrofluorocarbons (HFCs) and sulphur fluorides, such as “deep voice gas” mentioned previously on the Environmental Pollution blog (see here ). Although atmospheric concentrations of CFCs have stabilised and even reduced in the last decade or so since implementation of the Montreal Protocol, levels of HCFCs, HCFCs and sulphur hexaflouride (SF6, deep voice gas) have increased (HCFCs were meant as an interim replacement for CFCs, with HFCs intended to replace HCFCs) (Figure 1). According to the WMO Greenhouse Gas Bulletin, radiative forcing of all LLGHGs combined has increase by 43% since 1990, with the 2018 level corresponding to an equivalent CO2 mole fraction of 496 ppm!

Figure 1: Changing atmospheric concentrations of halocarbons (CHFs, HCFCs and HFCs) and SF6.

Issue #15 of the WMO Greenhouse Gas Bulletin also refers to some neat work involving the measurement of different isotopes of carbon. Carbon in the environment occurs in the form of three isotopes ~ 12C (the most common), 13C and 14C (the least common). Establishing the relative ratios of these isotopes in the atmosphere provides an indication of the source of the carbon, and knowing the source can help explain the most likely cause of increased concentrations of carbon-containing GHGs in the atmosphere (notably CO2 and CH4). The figure at the top of this blog and repeated below as Figure 2 illustrates changes in anthropogenic (human) emissions, the atmospheric concentration of the 13C isotope and CO2 and the 14C content of the atmosphere since the mid-18th century. Some of the data are from direct measurements, whereas the earlier data relating to atmospheric composition are from carbon preserved in ice cores and tree rings. The figure shows that as human emissions of CO2 have increased (panel a) so too have concentrations of CO2 in the atmosphere (panel c). At the same time, both the relative proportions of 13C and 14C have declined. This is because CO2 emitted from the burning of fossil fuels is relatively rich in 12C, and massive emissions of 12C-enriched CO2 from the burning of coal and oil in particular have caused a relative decline in the proportion of the 14C and 13C isotopes in the atmosphere (the massive spike in atmospheric 14C around the beginning of the 1960s relates to the atmospheric detonation of atomic bombs). Variations in relative concentrations of the three carbon isotopes provide additional evidence that a large part of the increased CO2 in the atmosphere is from the burning of fossil fuels, and is therefore human in origin.

Figure 2: Variations CO2 emissions and atmospheric concentrations, and in relative proportions of 13C and 14C isotopes.

Finally, issue #15 of the WMO Greenhouse Gas Bulletin highlights the interesting trends shown by CH4 concentrations in the atmosphere. Following rapid increases during the 1980s and 1990s, atmospheric concentrations stabilised during the early 2000s. The stabilisation appears to have been short-lived, however, as by the late 2000s levels had started to rise rapidly again (Figure 3). Approximately 60% of CH4 emissions are linked to human activity (e.g. cattle farming, rice agriculture, and the burning of fossil fuels and living biomass – e.g. forests and peatlands). Once again isotopic measurements can help determine the source of CH4 in the atmosphere. Despite this, the cause(s) of the plateau and the renewed increase in atmospheric concentrations is(are) a focus of much debate among scientists at present.

Figure 3: Globally averaged CH4 mole fraction (a) and its growth rate (b) from 1984 to 2018.  The red line in both panels is the monthly mean with the seasonal variation removed. The figure is based on observations made at 127 stations globally.

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Hà Tĩnh Province in northern central Vietnam, economically one of the poorest parts of Vietnam, has been heavily featured in the news of late, after the bodies of 39 people – many thought to be from the province – were found in the refrigerated trailer of a lorry in Waterglade Industrial Park, about 25 miles east of central London. Following the tragedy much attention has focused on the criminal gangs and risks involved in people trafficking, and on poverty in parts of central Vietnam.

Hà Tĩnh Province, north-central Vietnam

Much less attention has been paid to the role of environmental disasters as a possible reason why the economically-marginalised might risk their own lives and the future of family members who they leave behind ~ the latter through borrowing the relatively large amounts of money (several times an annual income in rural central Vietnam) demanded by people-traffickers, with stay-behind-relatives left to pay-off any outstanding migrant loans.

Reuters “Postcards from a poisoned coast” report released towards the end of last week (29 October) highlights the role that pollution and other drivers of environmental change might have played in the disaster that befell the 39 migrants. While in no way excusing people trafficking and the criminals that profit massively from it, the report highlights that many rural livelihoods in Hà Tĩnh and surrounding provinces have been made all the more precarious of late by frequent environmental disasters. An increasingly precarious livelihood is a potential trigger in deciding to risk being trafficked for the promise of a better life far away. The Formosa Steel plant, owned by Taiwan’s Formosa Plastics, in Hà Tĩnh Province was in 2016 the source of one of Vietnam’s worst environmental disasters. The disaster involved the discharge of toxic waste directly into adjacent areas of sea via “a submerged pipe belonging to the Formosa corporation, 1.5km in length, buried under the seabed“. Hundreds of tons of fish died as a result, and this loss and resultant bans on the sale of fish because of concerns over food safety disrupted fishing and related livelihoods in at least four provinces in central Vietnam, including Hà Tĩnh Province. Tourism was also severely impacted. The increased poverty that resulted affected more than 200,000 people. Locals took to the streets to demand action and compensation, with protests resulting in a government crackdown and the arrest of prominent protestors and journalists.

Eventually Formosa offered compensation, but later the same year (2016) was caught dumping around 260 tons of untreated dry waste at different spots in Hà Tĩnh Province. Cyanide was detected in some of the analysed samples of waste.

As pollution-related disasters  – including those linked to climate change (itself in part a consequence of pollution) – become more frequent occurrences we can expect refugees from such catastrophes to be all the more numerous. People trafficking is likely to become yet more lucrative as demand for a better life somewhere else increases.

Happy Diwali (Deepavali)!

No doubt Diwali will be celebrated across the world, as are many important events on the calendar, through the setting off of lots of fireworks. The spectacles produced are brilliant, of course ~ but they are costly, and not only in terms of the cost of the fireworks and the impacts on our pets. Fireworks are also highly polluting and have the potential to impact negatively environmental quality and our health.

Aside from the littering caused by all those spent fireworks – no surprises there, what goes up has to come down – ever wondered what all those bright colours are formed from? They are formed from the high temperature combustion of compounds containing heavy metals (“heavy metal salts”). Sparkling green colours are produced by barium chloride, blue is produced by copper chloride. Strontium carbonate is used to produce red fireworks, calcium chloride ~ orange fireworks, sodium nitrate ~ yellow fireworks. Purple fireworks are typically produced by use of a mixture of strontium (red) and copper (blue) compounds. The list goes on and on ….

Combustion also yields other pollutants, notably fine particulate matter (including PM10 and PM2.5, but no doubt even finer particles too), sulfur dioxide (SO2), persistent organic pollutants (PoP) polycyclic aromatic hydrocarbons (PAHs) and highly toxic dioxins. None of these are good for us. And that is not all, of course we have developed fireworks that make louder bangs and travel to higher altitudes in the sky. This is all based on chemistry and chemical reactions, but also involves some very old technology – gunpowder, which is believed to have been invented in China over 1000 years ago! Thus as Licudine et al. (2012) reported in the journal Public Health Reports, based on their study of air pollution linked to new year firework celebrations on Hawaii (see paper linked below), “chlorates or perchlorates can be used to achieve noise levels equivalent to trinitrotoluene and result in more violent explosions than traditional nitrates … Lead (Pb) salts are widely used as igniters to initiate fireworks explosions. Manganese (Mn) and Mn dioxide serve as fuel and oxidizer for brighter lights, chromium (Cr) is used as a burn rate catalyst for propellants,and nickel (Ni) acts as an electric firing device for fireworks.” The health effects of heavy metals are well-known, and many of the emissions from fireworks persist in the environment long after the spectacle of the display is over. The authors go on to state that “perchlorates have been associated with thyroid problems, and toxic byproducts (e.g., dioxins) could be produced as a result of atmospheric reactions between metal oxides and organic fuels.”

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Licudine et al. (2012) is not the only study on fireworks as a source of environmental pollution. In fact there have been many such studies. One of these investigated air quality in Delhi, India, during the Diwali celebrations. Delhi is already one of the world’s most polluted cities, particularly during the Northern Hemisphere autumn and winter months (which is when Diwali takes place) when local weather conditions and the burning of fossil fuels and biomass for heat, transport and cooking conspire to produce some of the poorest air qualities ever recorded globally. The study by Peshin et al (2017 – and see link below to the paper) recorded substantial increases in SO2, nitrogen dioxide (NO2) – a greenhouse gas and cause of environmental acidification, ozone (O3), fine particulate matter (including black carbon, or soot) and trace metals during firework displays associated with Diwali celebrations.

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Similar findings have also been reported for Jamshedpur in the east Indian state of Jharkhand, suggesting that firework-related pollution is a widespread problem in India during Diwali celebrations (Ambade, B. The air pollution during Diwali festival by the burning of fireworks in Jamshedpur city, India. Urban Climate 26, 149-160). The setting-off of firecrackers is highlighted in this article as a particularly rich source of pollution, as it is here (for Delhi) and here (for China).

An even more recently published article – just out in the Journal of Cleaner Production, emphasises that “[r]ecreational fireworks use causes some of the most extreme urban particulate matter pollution: Hourly peaks over 1000 ug/m3 PM10 have been measured during the Chinese New Year and Indian Diwali festivals …. [f]ireworks plumes can be detected over a long range, between regions and countries, in the form of elevated particulate matter (PM10 and PM2.5) and water-soluble potassium … [i]n Western Europe, fireworks celebrations have contributed to significant annual atmospheric metal emissions, to the urban background of trace metals, and to a localized perchlorate pollution in surface and groundwater” (Andradottir and Thorsteinsson, 2019). Unfortunately this article is not available for public download, but it is accessible via NUS’s excellent library in digital form: Andradottir, H.O. and Thorsteinsson, T. (2019) Repeated extreme particulate matter episodes due to fireworks in Iceland and stakeholders’ response. Journal of Cleaner Production, 236, 11711.

One of the points raised by Andradottir and Thorsteinsson (2019) is the “passiveness” of the general public when it comes to the pollution and health risks of firework displays. The authors of the paper claim that this in part stems from a lack of awareness of the link to pollution. The authors argue that the general public should be made more aware and that the purchasing of less environmentally damaging fireworks should be encouraged (for example, Disney uses fireworks that are propelled by compressed air rather than gunpowder – why cannot others follow suit?).

We need also to be mindful of the costs of producing and transporting fireworks to their point of use, and the risks posed to those involved in their manufacture. An estimated 90% of the world’s fireworks are manufactured in China – often in rural areas, with women predominantly involved in actually making the fireworks, handling dangerous chemicals with little formal training. Accidents happen, often with lethal consequences – as is evident from the webpage linked here. Accidents are also commonplace in Sivakasi, the city in Tamil Nadu that is commonly regarded as India’s “fireworks capital“. Whoever thinks about the conditions fireworks are produced under, and what health-threatening substances and practices those involved in the manufacture of fireworks are exposed to, when purchasing fireworks or going along to a display? Do we really think that those toxic substances used in manufacturing never leak out into the environment even before the fireworks are used? And what about all that packaging that comes with fireworks – where does that all end up?

It could be argued that what we are actually celebrating through our firework displays is our reckless disregard for our environment, for the economically marginalised and, ultimately, for ourselves.

By now students on GE3246 are probably either bored or confused by my seemingly constant references to pH, acid deposition, acidification and their role in environmental pollution and its effects. The truth is, pH, and more particularly variations in pH, has a major part to play in discussions concerning environmental pollution; changes in pH can be an effect (a result) of pollution. Moreover, pH variations can influence the amount of human and ecosystem harm caused by other chemicals in the environment, such as heavy metals, but also impact the availability of nutrients essential to the fertility of soil and hence to plant growth and crop productivity. Already in GE3246 we have discussed acid deposition – its sources and effects. A major source is air pollution in the form of carbon, sulfur and nitrogen oxides [CO₂, SO₂ & NO] released from power stations etc. Ammonia (‎NH₃), associated with traffic pollution and the misuse of fertliizer, is also a source of acidification pressure. These gases combine with moisture in the atmosphere to form acid and when deposited go on to cause acidification of lakes and rivers and the ocean. In the lecture this coming week we will add the acidification of soils and its effects to this list ….

Environmental acidification occurs naturally, of course, particularly where the underlying geology is base-poor. Humans have through their activities made the situation far worse, however, by causing anthropogenic (or cultural) acidification.

So what is pH and how is it linked to environmental acidification and anthropogenic acidification in particular?

The Danish scientist S. P .L. Sørensen first introduced the term pH (though he denoted it as p_H) to mean the amount (or power) of hydrogen (H⁺) ions (protons) in a solution. If a solution (e.g. lake or ocean water, or even the water between individual particles of soil, known as soil pore water) becomes more or less acidic, the concentration of H⁺ ions becomes stronger or weaker. Acidity (or its converse alkalinity) is the amount of hydrogen and hydroxide (OH^–) ions present in solution, or relative concentrations of these. As acidity increases, the amount of H⁺ ions increases while levels of OH^– ions decline. The table below shows the reciprocal relationship between H⁺  and OH^– ions.

Note that the pH scale ranges from 0 to 14.  Solutions with a pH less than 7 are generally referred to as acidic, while those with a pH greater than 7 are basic or alkaline. A pH of 7.0 is taken to be neutral, because the H⁺ and OH^– ions balance one another. It is perhaps worth pointing out that temperature directly effects pH. An increase in temperature causes ionisation to proceed at a higher rate than at lower temperature, causing more H ions to be freed from water molecules ( H2O ⇌ 2H⁺ + OH^– ). It is also worth pointing out that pH is the negative log of the molar hydrogen ion concentration (-log₁₀[H⁺], or [H⁺] = 10^-pH). What that means in English is that as pH falls, acidity increases, and a pH fall of 1.0 unit represents a 10x increase in acidity (or 10 x more H⁺ ions)!

So how is pH linked to anthropogenic acidification and its environmental effects, such as coral and forest death?

Hydrogen ions are highly positively charged (the ⁺ indicates that). Hence acids can be highly reactive and corrosive (ever spilt battery acid on your clothes?). OH^– is also highly reactive, hence strong alkaline solutions, such as bleach, are highly caustic (common bleach is Sodium hypochlorite, NaClO, composed of one sodium (Na) atom, one chlorine (Cl) atom and one oxygen (O) atom.). Heavy metals are also positively charged (positively charged atoms are known as cations – e.g. copper (Cu²⁺), magnesium (Mg²⁺), manganese (Mn²⁺),  lead (Pb²⁺), zinc (Zn²⁺)), in fact most inorganic contaminants are positively charged (or cations). Many nutrients that plants required (e.g. Potassium, K⁺, Calcium, Ca²⁺) are also cations. This sounds confusing, but some metals, including some heavy metals (copper, iron, zinc etc), are classed as nutrients at low concentrations (i.e. they are micro-nutrients) but are toxic at higher concentrations. As mentioned in an earlier lecture, the dose makes the poison (although hopefully everyone realises by now that this is a gross over-simplification).

Acidification has direct effects on biota. Generally however its effects are less direct, and take place through the effects on concentrations of heavy metals, water transparency, availability of nutrients, including calcium carbonate (CaCO3), the material for coral exoskeletons. The infografic below shows how key aquatic organisms may be lost as the pH of their habitat becomes more acidic.

Acidification impacts soils through changing the availability of chemical elements, some of which can be harmful to biota and have negative impacts on agricultural productivity. Soil particles, organic matter etc, tend to be negatively charged – and therefore they can hold (adsorb) cations on their surface (when something is adsorbed on a surface it is basically adhered, or stuck/glued, to the surface). Soils differ in this ability – known as Cation Exchange Capacity (CEC), depending on their texture (e.g. proportion of clay, silt and sand sized particles, amount of organic matter). Generally  organic-rich, finely textured soils have have high CEC – they are sticky as far as nutrients and other cations go – and are therefore often relatively “fertile”, and good for agriculture. Coarse-grained (with a high proportion of sand-sized particles) soils with low organic matter content tend to have low CEC, and any nutrients present may be easily lost to leaching and flooding of the soil. The schema below shows how the finest plant roots (root hairs) interact with surrounding soil particles and soil pore water, and the cations attached to negatively-charged soil particles.

Note that in order to obtain essential nutrients (cations) from soil a plant must pump out H⁺ ions. These H⁺ ions are swapped for the cations (such as K⁺ and Ca²⁺). For an excellent, short video on the Cation Exchange process between plants and soil/soil pore water (and the influence of soil texture) – see here. More on the influence of soil texture is available via the short video linked here.

Interestingly, the video explaining Cation Exchange linked above states that the vast majority of cultivated soils are negatively charged but some soils, mostly in the tropics, are positively charged. We’re in the tropics – so which soils are positively charged? The answer is those soils that are ancient and that have been subjected to intense and deep weathering over a long period of time. As a result of prolonged, intense weathering clay minerals disintegrate, losing their silicon (Si) in the process. As a result, the weathered soil has a lower negative charge (and may even have a positive charge), and thus a lower CEC. This reduced CEC is one of the reasons why lateritic soils in the tropics are less fertile than their younger, less intensively weathered counterparts in more temperate latitudes.

Increased acidity (increased concentration of H⁺ ions) results in many more H⁺ ions in the soil pore water competing with dissolved cations for attachment sites on soil particles. Because the H⁺ ions are generally more reactive they tend to attach to vacant attachment sites on soil particles and displace already attached cations of, for example, heavy metals. The latter are then dissolved in the soil pore water where they are much more biologically available, and can be taken up by plants through their roots. In solution, heavy metals such as Aluminium (Al) bind with phosphorus fertilizers (generally in the form of Phosphate, PO₄), forming – for example, AlPO₄, which is a form of phosphate that plants cannot use (cannot take up). Hence fertilizer applications to acid soils are often ineffective, and farmers must first find a way of neutralising the acidity (generally by liming, the application of quicklime, CaO).

The pH of solution also influences solubility of heavy metals. Generally heavy metals are in solution in acidic water. At higher pHs (strongly alkaline), the OH^– ions bind with the heavy metal cations forming solid compounds, which precipitate-out (they form “precipitates”). Varying the pH of wastewater, reservoir water etc entering water treatment plants is the main way of removing heavy metals from large volumes of water that are then used for human consumption, irrigation etc., as mentioned in an earlier lecture.

I’ve been enjoying reading my copy of Eleanor Herman’s excellent book “The Royal Art of Poison: Filthy Palaces, Fatal Cosmetics, Deadly Medicine, and Murder Most Foul“, a review of which can be found here. Chapter 3 “Dying to be Beautiful  Dangerous Cosmetics” has been particularly fascinating, in part because in addition to some rather startling revelations about the lengths people went to in the past to make themselves what they and others at the time considered beautiful, and then stay beautiful, the chapter also raised some questions that are relevant to GE3246. One of these is whether we are any more knowledgeable now about the true personal and wider costs of our luxury consumption. Luxury consumption is geared to meeting our wants, rather than our needs. Luxury consumption is largely avoidable (it is not necessary) – but it also involves the use of valuable resources (including energy, water etc) in their production and transport, thereby denying others of those resources, and generates pollution. Everything we consume causes pollution- it comes with embodied pollution, in other words. In some cases, our luxury consumption actually does us harm. Certainly the problems it causes – often in distant parts of the world – can end up causing food insecurity, water shortages, harmful pollution etc for others. But more about all that later in GE3246 ….

Back to The Royal Art of Poison. You can actually view a short and very enjoyable video summary of Chapter 3 of Eleanor Herman’s book here. I enjoyed the account (in the book) of how Queen Elizabeth the First (QE 1), who died at what was then the ripe old age of sixty-nine in 1603, had led a generally healthy life, at least according to standards at the time. For a member of royalty, she ate healthily and exercised often ~ she was, apparently, fearful of ending up like her father, the morbidly obese King Henry VIII. Unfortunately QE 1 contracted smallpox during her 20s, and this left scars on her body and face. Not only were blemishes considered unattractive at the time, they were also considered “proof of God’s displeasure” – even manifestations of sexual urges and desires. QE 1 seems to have been so-encouraged to apply, liberally, a ceruse, a pigment that contained highly poisonous white lead and often arsenic too, to cover her blemishes. Unfortunately the lead leached into the body through the skin, and this is thought to have caused QE 1 to lose her hair, become less active (lead poisoning causes muscle paralysis) and to suffer declining metal acuity and major swings in her mood. It also likely corroded her skin, causing QE 1 to have to apply even more ceruse, thus kick-starting a positive cause-effect-cause cycle involving ever thicker applications of ceruse. Herman argues that rather than simply aging, heavy metal poisoning may have contributed to mood swings, odd decisions (such as to have her friend Robert Devereux executed) and depression that characterised the last years of QE 1’s life, and ultimately her death.

Herman describes other cases, a notable one of which is that of Diane de Poitiers, the mistress of French King Henri II, who died in 1566. De Poitiers was commonly regarded as one of the most beautiful women of her time. She went to extraordinary lengths to stay youthful looking, including bathing in assess’ milk, to remove body hair and prevent the signs of aging, and taking an elixir that was meant to promote a youthful complexion. The elexir contained gold – and gave a person who drunk it a white skin because the gold caused anemia. Gold is a heavy metal and anemia can be caused by heavy metal poisoning. The elixir that De Poitiers took was meant to be used sparingly ~ no more than once a month (even back in the 16th century people knew that excessive use was not good for you), but it is thought that De Poitiers took the elixir once a day over many years. She accumulated so much gold from the elixir that when her remains were discovered centuries later the soil in which she had been buried was heavily contaminated with gold that had leached from her body as it decayed!

Of course, we’re much more mindful consumers these days – aren’t we? I am not sure that we are. We still use urine in face creams (pee is a great moisturiser, apparently) just as folk did in the 16th century, and heavy metals (e.g. titanium dioxide) in sunscreens and other cosmetics. And botox injections are popular. These involve injecting a toxin produced by the gram positive bacterium Clostridium botulinum. The same toxin causes the potentially fatal illness Botulism.  Botulism through normal routes (e.g. food poisoning – especially from eating fish that has not been properly stored or cured/fermented and canned foods that have “gone off”) is now relatively rare. Although we are told that the cosmetic use of botox is generally safe, because of the relatively low concentrations used, different people are likely to have different levels of sensitivity, and deaths do occur (including one in Singapore earlier this year – see here).

For an excellent account of current cosmetic use – and the toxins involved, many linked to petrochemicals – see the short video here. The video “examines the pervasive use of toxic chemicals in our everyday personal care products, from lipstick to baby shampoo” and is by The Story of Stuff Project, a project dedicated to mindful consumerism and de-materialisation.

Perhaps if we are willing to risk our own health through our luxury consumption we shouldn’t be surprised that we are also willing – at the same time – to risk the health of our planet.

A more mindful approach to consumerism would seem to be needed – perhaps urgently. There is now guidance out there to help us to be more mindful, or literate, consumers. See, for example, the Campaign for Safe Cosmetics webpage.

Several news agencies are today reporting research that appears to suggest that, in addition to everything else, air pollution may cause (or contribute to) baldness. More precisely it seems that fine particular matter in the air that we breathe may cause hair loss. One article goes further and suggests that men living near busy roads are particularly vulnerable!

The American Association for the Advancement of Science (AAAS) is also reporting the finding through its EurekAlert! website ~ see here.

The research described was presented at the 28th EADV Congress in Spain earlier this week and found that fine particulate material in the air can interfere with a body’s production of proteins (β-catenin, cyclin D1, cyclin E and CDK2) that are responsible for hair growth and hair retention.

The lead researcher on the study, Dr Hyuk Chul Kwon (Future Science Research Centre, Republic of Korea) opined “[w]hile the link between air pollution and serious diseases such as cancer, COPD [Chronic obstructive pulmonary disease] and CVD [Cardiovascular disease] are well established there is little to no research on the effect of particular matter exposure on the human skin and hair in particular. Our research explains the mode of action of air pollutants on human follicle dermal papilla cells, showing how the most common air pollutants lead to hair loss”.