Blog Update #10 - Pain and a paper

Eleanor Faith Holland

The blog has been on hold for a while. But I have always intended to keep on writing. There has been some major changes in where I live and work and most recently our lovely 6 year old daughter Eleanor passed away. There has been much pain but there is much celebration too for our special girl. My wife Becky and I are in feelings of loss. That said, we want to celebrate the life of our daughter who demonstrated so much strength in so many ways. A service will be held at St Peter’s Cathedral in Armidale at 2pm on Monday (19th December).

 

Coming to Christmas it is a subdued feeling at our home and my birthday was yesterday as well so I didn’t feel like celebrating. However, there was something I was excited to see. A confirmation that a paper that I was a co-author of has been accepted to the journal Science of the Total Environment (Santos et al 2016). I was only a minor co-author but there is something about having your name up there that caters for ones ego.

The highlights of the article are:

• We assess groundwater recharge through a pervasive layer of floodplain muds.
• Modelled groundwater flow paths were consistent with tritium dating.
• The clay layer did not prevent recharge because of macropores and cracks.
• Fine-grained floodplain soils do not necessarily protect underlying aquifers from pollution.
• Combining multiple techniques gives more confidence in recharge estimates.

The article can be found here:

 

http://dx.doi.org/10.1016/j.scitotenv.2016.11.181

References

*Santos, I.R., Zhang, C., Maher, D.T., Atkins, M. L. Holland, R. Morgenstern, U & Li, Ling. 2016. Assessing the Recharge of a Coastal Aquifer using Physical Observations, Tritium, Groundwater Chemistry and Modelling, Science of The Total Environment, Available online 15 December 2016, ISSN 0048-9697, http://dx.doi.org/10.1016/j.scitotenv.2016.11.181.

A Rock of Gibraltar Range National Park - Part 2

Dandahra Creek Leucogranite

This post is a follow-on from an earlier post which can be read here.

The Dandahra Creek Leucogranite is mainly composed of granite which is depleted in dark (mafic) minerals. The crystals are of very similar size and medium to coarse grained. The crystals are mainly quartz with feldspars and occasional biotite mica. The term Leuco- simply refers to the light colour and lack of mafic minerals. There are also small amounts of other minerals that are disseminated through the rock these include the mineral zircon which is used for dating.

The dating of the Dandahra Creek Leucogranite was only conducted in the last couple of years. It is an example of using multiple techniques together to get an answer. The mineral Zircon is formed in magma chambers of granite and granite-like composition. This is a very stable mineral. Zircon locks up uranium in small amounts and this uranium undergoes radioactive decay to lead. By measuring the proportions of uranium to lead it is possible to determine how long ago the zircon had formed. In the past in some cases the whole zircon crystal have been used to determine the ratio. However, this method has some complications.

Not all of the zircon crystals in rocks show the same age. In the case of the Dandahra Creek Leucogranite some seemingly having much older ages. These crystals are actually inherited from the parent rock. The stability of the zircons means that they have not fully melted in the magma chamber. Often a good way to determine if a zircon is older than the magma chamber is to look at the shape and determine whether there has been any melting of the edges of the crystal. However, sometimes it is very hard to tell because the zircon often builds itself up again with an old core and a new crystal face.

To overcome the problem of age zoning in zircon crystals an alternative method was developed measure the ratio of lead and uranium. A high accuracy ion beam is aimed at the different portions of crystal. The ion beam vaporises the elements in that tiny area. The vapour is then measured for the abundance of each element and then the ratio of elements can be calculated. This is called the Sensitive High Resolution Ion Micro Probe or SHRIMP.

SHRIMP was a method developed right here in Australia. It is regarded as one of the most reliable ways to analyse microscopic crystals to determine when and how they formed. The need for the special machine came from dating the Rocks that make up the oldest parts of Western Australia which are the oldest in the world. It has no become a recognised tool around the world (Ireland et al 2008). There are 20 SHRIMP analysers around the world with four built in the last couple of years in Japan, China and Poland. Like Wi-Fi, the Hills-Hoist and Pavlova it is another example of Australian scientific ingenuity.

The age of the intrusion given for the Dandahra Creek Leucogranite using the SHRIMP method is 237.6 Ma (plus or minus 1.8Ma). This makes it the youngest example of the Stanthorpe Suite of Granites (Chisholm et al 2014) and nearly the youngest in the whole Standthorpe Supersuite (Thanks for the correction rockdoc!).

References.Bibliography:

*Chisholm, E.I., Blevin, P.L. and Simpson, C.J. 2014. New SHRIMP U–Pb zircon ages from the New England Orogen, New South Wales: July 2012–June 2014. Record 2014/52. Geoscience Australia

*Clarke, Peter J. & Myerscough, Peter J. 2006. Introduction to the Biology and Ecology of Gibraltar Range National Park and Adjacent areas: Patterns, Processes and Prospects. Proceedings of the Linnean Society of New South Wales

*New South Wales National Parks and Wildlife Service 2005. Gibraltar Range Group of National Parks (Incorporating Barool, Capoompeta, Gibraltar Range, Nymboida and Washpool National Parks and Nymboida and Washpool State Conservation Areas) Plan of Management. February 2005. ISBN 0 7313 6861 4

*Ireland, T.R., Clement, S., Compston, W., Foster, J. J., Holden, P., Jenkins, B., Lanc, P., Schram, N. & Williams, I. S. (2008), "Development of SHRIMP", Australian Journal of Earth Sciences V55 p937–954

Baseline CSG methane in groundwater

A friend recently let me know that a paper that one of his students wrote for the Journal of Hydrology had been published. I had a very minor involvement in the formative stages of the paper which came about indirectly as a result of the protests of many local people about potential coal seam gas (CSG) and other natural gas types in the region. The paper (Atkins et al 2015) is essentially the results of a data collection exercise but has some interesting techniques and findings about the baseline concentrations of gas in groundwater bores in the Richmond Valley area.

Methane concentration for different geological environments
(after Atkins et al 2015)

91 water samples were collected from government and private bores in geological units overlying the target CSG geological formations in the Clarence-Moreton Basin (e.g. the Walloon Coal Measures). These units were quite diverse and ranged from sedimentary rocks of the Piora Member of Grafton Formation and the Kangaroo Creek Sandstone (recently reclassified as the Orara Formation), basalt lava flows of the Lismore, Astonville and Kyogle Basalts and Quaternary aged alluvium including coastal sands and riverine sedimentary environments.

Special glass water sample containers were used to collect the samples. These were then injected with a carbon dioxide and methane free gas to create a clean “air bubble”. The methane and carbon dioxide naturally dissolved in the water will then come into equilibrium with the “air bubble”. The resulting gas from the bubble can then be extracted and the concentration and isotopic composition of the carbon in the two compounds determined by an electronic analyser. The isotopic signature can then be assigned to recent biological formation (biogenic) or geologically derived (thermogenic) origin.

The end result was annoyingly quite not straight forward. The concentration of methane showed no obvious relationship to the chemistry of the groundwater. However there was a relationship between geological units. Methane concentration was very low in the basalt aquifers and relatively higher than the Clarence-Moreton basin sedimentary rocks and much higher in the Quaternary alluvium of the Richmond River valley floodplain and coastal sands systems. So there was more methane in some of the aquifers that were the less likely to be connected to any CSG formations! Quite counter-intuitive.

The isotopic signatures did not really help clear up this confusion very much. There appeared to be a large thermogenic component to the coastal sands and flood plain aquifer systems sometimes at concentrations greater than the formations that should be the thermogenic CSG source. Why? It was noted by some CSIRO scientists working in the Great Artesian Basin that sometimes biogenic gas can be oxidised and then be chemically reduced back to methane and this process favours the thermogenic isotopes (Day et al. 2015). So, It gives the impression of thermogenic gas.

This means that the methane gas concentration is related to the biological activity in and around the aquifer. The shallowest groundwater systems are the most connected with surface water and biological processes and therefore these have the highest concentrations of methane. The Clarence-Moreton Basin sediments are not connected with the CSG and natural gas rich formations.

This means that if companies like Metgasco do commence gas operations in the area there is a statistical background that can be used to compare if anyone becomes concerned about methane in their water bores. Interestingly, it also shows that methane in groundwater is probably not a good method to search for natural gas in the region. It might apply to other areas like the Great Artesian basin but apparently there are good barriers between CSG and non-aquifers in the Northern Rivers. This is good news since if something does go wrong it is now more easy to identify if it has impacted upon any groundwater.

References/bibliography:

Atkins, M.L., Santos, I.R. & Maher, D.T. 2015. Groundwater methane in a potential goal seam gas extraction region. Journal of Hydrology: Regional Studies. V4.
Day, S., Ong, C., et al. 2015. Characterisation of regional fluxes of methane in the Surat Basin, Queensland. CSIRO report EP15369

An excellent outcome from atmospheric atomic bomb testing

Human ingenuity surprises me again and again, especially the efficiency in which we can annihilate each other. During the 1940’s and 1950’s the superpowers were focused on increasing the efficiency in the way they could destroy everyone on the planet. It was a very worthy goal (yes that was a joke) and to achieve maximum efficiency they needed to conduct atmospheric tests of their bombs. Sometimes, unforeseen obvious benefits other than the benefits of death and destruction of humanity can arise.

I have recently been thinking about groundwater in the Richmond River area for which I have been consulting sections of a PhD thesis written by Leonard Drury in 1982 (Drury 1982). Drury's comprehensive thesis included qualitative identification on the age of groundwater in aquifers in the Richmond River by using an unstable isotope of hydrogen called tritium. Hydrogen is an atomic component of water (the H in H2O) but hydrogen actually comes in three natural forms based on the number of neutrons are in the nucleus of the hydrogen atom. These different forms are called isotopes. Hydrogen naturally has one neutron or less commonly two neutrons (called deuterium) and very rarely three neutrons (called tritium). In nuclear explosions the third isotope tritium, is created at concentrations much higher than the background. The reason why tritium is rare naturally is that it is only formed in the upper atmosphere but is unstable and loses the extra neutrons to become a smaller isotope over a period of time.

Half of the tritium in a given amount of water (or whatever) decays over a period of 12.5 years (this is called a half-life). Which means that over 25 years there is only a quarter of the original tritium left, 37.5 years one eighth, 50 years one sixteenth etc. Since tritium is not naturally occurring there is no practical use to measure for tritium unless you can introduce it into a system as a tracer and then measure its behaviour. This means that a large ‘slug’ of tritium was created during the 1940’s and 1950’s during atmospheric nuclear testing. Therefore if you can look for tritium in groundwater and if it is not present you can assume that that groundwater has been in existence for more than 50 years, i.e. it was present in the ground before any nuclear tests. If you detect tritium in several locations in an aquifer the relative abundance of the tritium will give an indication of the age of the water and whether mixing is occurring between old groundwater and new groundwater. It won’t give you an exact date but it will let you know a lot about behaviour of an aquifer.

The trouble is time is running out. The half-life of tritium means that as time goes on the ability for us to accurately measure the smaller amount of the isotope means that one day we won’t be able to use this as a technique. I was aware that time was running out on using tritium as an effective groundwater tracer but I was not aware how soon. I have had a few chats with an academic at Southern Cross University one of which was about using tritium, he said we actually only have about 5 or 10 years left to which I jokingly suggested to him that we should reset the tritium clock with some more atmospheric nuclear explosions! To which he informed me that actually there appears to be some more tracers that can be used following the Fukushima Nuclear Accident.

Bibliography/References:

*Drury, L.W. 1982. Hydrogeology and Quaternary Stratigraphy of the Richmond River Valley, New South Wales. University of New South Wales, PhD thesis.
*Moran, J.E. & Hudson, G.B. 2005. Using Groundwater Age and Other Isotopic Signatures to Delineate Groundwater Flow and Stratification. University of Illinois.
*U.S. Geological Survey (USGS), 2004, Stable Isotopes and Radiochemicals, in National Field Manual for the Collection of Water-Quality Data, Chapter A5 Processing of Water Samples. USGS Techniques of Water-Resources Investigation

Why you won't find CSG here now

As you might have noticed there has been an occasional blog post that I’ve done dealing with coal seam gas matters in a cursory manner. I’ve been asked again and again by many people to explain aspects of the industry and the environmental issues associated with it. I’ve worked in coal exploration and in an environmental capacity before and I know a moderate amount about gas extraction too but I’m afraid I don’t have all the answers. Caution is needed especially given the highly political nature of the subject now. Therefore, I don’t really want to weigh into the subject, but I’ll have a very quick comment or two just to really outline the big picture. In the last week I cautiously commented in the Northern Star online twice as the avatar ‘GeologyRod’ just to correct a couple of mistakes people have made. I’ve also written one letter to the editor cautioning about how to interpret water chemistry. Given the heated debate, I’m not sure I will do so again!

From what I understand of the coal seam gas industry and the geology directly applicable to the area I am not as concerned about the industry doing damage to groundwater sources or surface water as some. From my contaminated land experience, I do however; see two potentially serious environmental problems. These are failure of well casings causing local cross-connection of poor and good quality water (and gas) and the disposal of poor quality production water (salinity is the biggest problem, as the chemicals potentially used can easily be treated but salt is hard to get rid of).

Considering a risk assessment approach (using the possible outcome and likelihood of that outcome) provides many scenarios with only the two mentioned above displaying an elevated level of risk (in my very hastily developed opinion). The nature of the geology of the southern Clarence-Moreton Basin is such that regional scale ground water contamination touted as a problem by many is probably of negligible risk, though this may occur elsewhere in eastern Australia in places like the Surat and Gunnedah Basins. However, local groundwater contamination (with a chance of affecting someone’s water supply bore) is probably on the moderate to high side. The disposal of salty water poses a moderate risk to the environment through adversely affecting large areas of pasture which might be irrigated or a moderate to high level if discharged untreated directly to fresh water streams.

Both of the matters outlined above are difficult to deal with and not knowing about the ins and outs of operators in the region I don’t know how the companies are going to mange these problems. This is ignorance on my part. I can only assume that this has been considered in detail (a legal requirement) so that the management of these problems is adequate.

This is my opinion only and given that opinions can get one in trouble I won’t be commenting on any other matters CSG related for quite some time. I really don’t like getting involved in political matters and it is easy to be carried into them. I hope I haven't been carried into them too far already. If you want to know a bit more about the technical side of coal seam gas extraction and the pollution risks there are some good fact sheets put out by the CSIRO linked to here. Maybe that is why I like rocks so much, they don’t argue with you (too much).

But back onto happier topics. I’ve been most excited by some new information that has come my way, one a University of New South Wales thesis by Leonary Drury on the Richmond Valley stratigraphy, groundwater, dating and much more, and the other is the preliminary geophysical data package released by the NSW geological survey. I’ll be blogging on these topics (plus others) in the coming months.