Citizen Science - Total Ammoniacal Nitrogen (TAN) Measurement, Part 1

 Although not part of the standard suite of tests performed by the Wye Alliance citizen science project, the measurement of 'ammonia' is important due to its toxicity towards aquatic life and as an indicator of pollution from sewage, agricultural run-off (fertilizers) and waste discharge from various sources (residential, commercial and industrial). Some groups within the Wye Alliance (e.g.Wye Salmon Association) have been monitoring ammoniacal nitrogen for a number of years; however, this analysis may be deployed more widely within the River Wye Catchment in the future.

Ammonia, NH₃, and its conjugate acid - the ammonium ion, [NH₄]⁴ - co-exist in water with the latter predominating in most natural water systems where the pH is typically between 6.5 and 8.5 (Figure 1). Ammonia is toxic to aquatic life even at concentrations below 1 ppm whereas the ammonium ion is less harmful. Ammonium ions are converted to toxic ammonia by increases in both pH (i.e. more alkaline) and temperature.

Figure 1: Effect of pH on Ammonia/Ammonium Equilibrium

The Nessler reaction is used to quantify the total ammoniacal nitrogen (TAN) in water. The colour-forming reagent (potassium tetraiodomercurate II) reacts with ammonia to form a yellow (Photo 2) to reddish brown (Photo 3) complex. The intensity of the colour is proportional to the concentration of the ammonia. The reaction is carried out under strongly alkaline conditions (pH >11) to convert all the ammonium ions to ammonia (see Figure 1). Values are reported as TAN ppmN; i.e. the nitrogen concentration in the water that is present as either ammonia or ammonium. To quantify the toxic free ammonia concentration in the original water sample, you will need to measure its temperature and pH and use an on-line calculator.

Test kits for ammonia come in various forms:

• Test strips (e.g. SimplexHealth) which are cheap and easy to use (just dip into the water) but less accurate as they rely on visual colour matching against a colour card
• Liquid reagent kits (e.g. API Ammonia Test Kit) where reagents are added to a water sample in a test-tube and the resulting colour is matched against a colour card. Possibly a little more accurate than the test strips but still subjective.
• Colorimeters such as the Hanna Checker Ammonia range where reagents (liquids or tablets) are added to the water sample in a cuvette and the colour intensity measured optically. Good accuracy at a reasonable price though more expensive than the first two options.

About a year ago, I bought a Hanna Low Range Ammonia Checker for use within our small group (the Belmont Testers) who regularly test the Newton Brook, a small tributary to the River Wye. The kit (Photo 1) comes with two glass cuvettes and two small bottles of reagent (Reagent A is a sodium hydroxide solution and Reagent B is a potassium tetraiodomercurate II solution) sufficient for 25 tests. I now buy the reagents in larger bottles sufficient for 100 tests as this is more economical.

Photo 1: Hanna Checker for Ammoniacal Nitrogen (0.0 to 3.0 ppmN)

The procedure is very simple:

• rinse the cuvette and cap three times with the sample
• fill cuvette to the 10 ml mark with sample
• switch on the Checker unit so that 'C1' is displayed, insert the filled cuvette, close the lid and  press the button (this is the sample blank)
• when 'C2' is displayed, remove the cuvette and add 4 drops of Reagent A, cap and mix for a couple of seconds
• add 4 drops of Reagent B, cap and mix for a couple of seconds
• put the cuvette back in the Checker unit, close the lid and perform a long press until 3:30 appears on the display
• 3 minutes and 30 seconds later, the result appears on the display
• finally, empty the contents of the cuvette down the toilet and wash with warm water followed by 3 rinses with distilled or de-ionised water.
• the cuvettes can be left to dry although I prefer to store them filled with distilled water

Below I've included a couple of photos showing how the intensity of colour changes with increasing TAN content.

 

Photo 2: Unreacted and Reacted Samples containing 0.3 ppm TAN

Photo 3: Reacted Sample (>3 ppm TAN)

In Part 2 we will look at some typical results obtained during our citizen science work.

Informal Logical Fallacies - #1 Basics

I've always been fascinated by the use of rhetorical devices, including informal logical fallacies, especially when they are used deliberately to mislead. Listen to any politician, religious apologist or any debate where there is real or imagined controversy (e.g. climate change) and you will always find examples of informal fallacious reasoning.

Logical reasoning is the process of using structured & rational thoughts/ideas/facts/rules/data/evidence to draw sound conclusions in the search for truth (i.e. the explanation that best describes reality). It is a form of critical thinking where one or more statements or facts (the premises) are used to reach a conclusion that is supported by the premises. The classic example is ...

Premise 1: All men are mortal

Premise 2: Socrates is a man

Conclusion: Socrates is mortal

This is an example of a syllogism (two premises and a conclusion) and the use of deductive reasoning. Logical arguments/reasoning require at least two premises (a major and a minor) but can have more; for example:

Premise 1: All humans are mortal

Premise 2: Socrates is a human

Premise 3: All mortal things eventually die

Conclusion: Therefore, Socrates will eventually die

For the conclusion to be valid, all the premises must be true. Logical fallacies can arise when either one or more premises are unsound or the conclusion does not rationally follow from the premises. For example:

Premise 1: All humans have two legs

Premise 2: I am human

Conclusion: Therefore, I have two legs

Logically, the argument is valid and I do, indeed, have two legs. However, the first premise is factually incorrect because some humans have fewer than two legs. Therefore, the conclusion will not be valid in all cases.

Here is another example of unsound logic where the premises are true but the conclusion is not valid because other types of bird (e.g. carrion crow) are also black

Premise 1: All ravens are black

Premise 2: The bird in this cage is black

Conclusion: Therefore, this caged bird is a raven 

So, a sound syllogism (logical argument) must be logically valid (i.e. the conclusion follows the premises) AND have true premises. The argument is unsound if it fails either of these two conditions.

It is not uncommon in debates, discussions, arguments and everyday conversations to be presented with only the conclusion (Socrates is mortal) without any supporting premises. The premises may be innocently omitted for brevity because the speaker assumes the premises are accepted as universal truths. The alternative is that the speaker is using the omission as a rhetorical device to hide their fallacious reasoning. Do not be afraid to ask for the premises to be explicitly defined so that you can verify their truthfulness.

For example, someone who does not believe that global warming is happening might say "climate change is a hoax!"

When you ask them for evidence to support that argument, they might offer ...

Premise 1: If the earth is warming, cold nights are a thing of the past

Premise 2: It was frosty last night

Conclusion: Therefore, climate change is a hoax!

The current scientific evidence does not indicate the immediate disappearance of the winter season so we will continue to experience cold weather and snowfall at the appropriate time of the year. Premise 1 is therefore false which makes the conclusion unsound.

View from the Rear Window - November 2025

 No-one is listening until you make a mistake - Stephen Wright

November (2025) was a bit of a strange month. There was plenty of sunshine but it also seemed to rain most days - sunshine and showers were the norm. Temperature-wise, the first half of the month (November 1st to November 15th) was extremely warm with a mean daily temperature of 12 ℃, some 5 ℃ warmer than normal! Temperatures returned to normal (daily average 6 ℃) for the second half of the month.

Storm Claudia hit Hereford on the 14th of the month with just over 22 mm of precipitation (Figure 2). Fortunately, we escaped the worst of the rain; c.f. Monmouth. Despite the (almost) one inch of rain deposited by Storm Claudia, the heaviest 24-hour rain event occurred a few days earlier on the 11th-12th November (Table 1).

This month's photo of the back garden (Photo 1) was taken on the 3rd November when there was plenty of autumn colour and before the autumn winds had removed the leaves.

Photo 1: The Back Garden on 3rd November 2025

Due to the popularity of last month's 'spot the wood pigeon', here is another test of your observational skills (Photo 2) ...

Photo 2: Spot the 'Woodie'

The rest of the daily garden photos for November 2025 are collated in Video 1 ...

Video 1: Daily Photos of the Rear Garden (November 2025)

Selected weather statistics from our backyard Davis Weather Station are summarised in Table 1. We had our first autumn frosts this month (seven of them), all during the cold spell (17th -26th November, Figure 1) when the mean daily temperatures were around 4 ℃. The other notable feature of November was the near 100 mm precipitation, well above average.

Table 1: Summary Weather Statistics for November 2025
Weather Parameter	Value	Dates
Average Monthly Temperature	9 oC
Maximum Monthly Temperature	17 oC	5th, 6th , 13th
Minimum Monthly Temperature	-4 oC	21st & 26th
Number of Air Frost Days	7
Number of Hot Days (> 25 oC)	0
Monthly Precipitation	99.2 mm
Greatest 24 h Precipitation	22.8 mm	11th - 12th
Number of Dry Days	7
Monthly Sunshine Hours (estimated)	53
Highest Wind Speed	47 km/h	14th
Heating Degree Days	285.5
Cooling Degree Days	0.0

Daily minimum and maximum temperatures for the month of November are shown in Figure 1. As noted above, the first half of the November were exceedingly warm, followed by about 10 days of below average temperatures with a return to warmer days and nights at the end of the month.

Figure 1: Min/Max Daily Temperatures (November 2025)

Figure 2 displays the daily sunshine and precipitation values for November. Rain fell on more than ¾ of the days, yielding 99.2 mm (approximately 4 inches) for the month as a whole. 60% of the monthly total fell over a six day period (9th - 14th) resulting in local flooding. In spite of all the rain, sunshine levels held up well especially during the cold snap.

Figure 2: Daily Rain/Sunshine Data (November 2025)

Figure 3 and Figure 4 show the November weather trends over the past 6 years (2020 - 2025). The mean November temperature (1991-2020 period) recorded at nearby Credenhill weather station is 7.3 ℃. Therefore, the mean November temperatures in Hereford itself (8 - 9 ℃, Figure 3) have been significantly warmer than the long-term average for the past 6 years.

Figure 3: Time Series of November Temperature Data (Hereford City)

November rainfall (Figure 4) has varied from about 5 mm to 100 mm over the past 6 years. The long-term average recorded at Credenhill is 68-69 mm; the past six years in Hereford have, therefore, seen one very dry November (2021), two below average (2020, 2023), one average (2024) and two well above average (2022, 2025) months. By comparison, sunshine levels have been remarkably constant.

Figure 4: Time Series Rain, Sunshine & Wind Data (Hereford City)

Figure 5, Figure 6, and Figure 7 are taken from the UK Met Office's monthly report for November 2025. For England and Wales, including Herefordshire (marked), November 2025 was warmer than the long-term average. The 1991-2020 November mean temperature at Credenhill (7.3 ℃) was 1.7 ℃ lower than my value (9 ℃, Table 1); i.e. at the upper limit indicated in Figure 5 (UHI and rounding effects?)

Figure 5: UK Mean Temperature Anomalies (November 2025)

England and Wales, including Herefordshire, had a wet month in November (Figure 6) in agreement with my backyard weather station (Table 1). Based on the Credenhill long-term rain data, my garden received about 150% of its normal rainfall in November. Some locations in Hereford (or just outside the city) received two, three or even four times as much rain than my back garden did during Storm Claudia. This would explain why Herefordshire, generally, received 175 - 200% of its normal November precipitation (Figure 6).

Figure 6: Relative UK Rainfall (November 2025)

Herefordshire (Figure 7) received above average (110% - 150%) sunshine during November 2025 and we certainly enjoyed a number of sunny days. Based on the evidence that sunshine levels were very average in November 2024, Figure 4 infers that sunshine levels in November 2025 were only 10% - 15% higher than normal.

Figure 7: Relative UK Sunshine Hours (November 2025) 

Jobs in the Garden

• Hot composting continues: finished compost added as mulch to the fruit beds
• Pick last of the aubergines and tomatoes in the polytunnel
• Harvesting beetroot, potatoes, turnips, chard and spinach
• Start clearing the polytunnel

Flora & Fauna in the Garden

• Blackbird (x2)
• Blue Tit (x3)
• Collared Dove (x1)
• Crow (x1)
• Dunnock (x1)
• House Sparrow (x11)
• Robin (x1)
• Starling (x12)

Photo 3: Starling Melee on the Bird Feeder

• Wood Pigeon (x3)

Not many photos from the garden this month ...

Photo 4: Gazania Plants on the Patio Table (Nov 6th 2025)

Photo 5: Cosmos in Pots (6th November 2025)

Photo 6: Salvia amongst the Autumn Colours (6th November 2025)

We were given a cutting of this Epiphyllum many years ago (20?) by a B&B landlady, Dinah, near Cleobury Mortimer. It flowers every year and we have passed cuttings onto family and friends.

Photo 7: Epiphyllum (indoor) - November 17th 2025

Finally, here is a short (2-3 minutes) video of the starlings attacking our bird feeder. Quality is not good because it was filmed through a glass windowpane in slo-mo. Can you count how many starlings there are? 

Video 2: Starling Melee