Radon exhalation study of manganese clay residue and usability inbrick production

Kovács, T., Shahrokhi, A., Sas, Z., Vigh, T., & Somlai, J. (2016). Radon exhalation study of manganese clayresidue and usability in brick production. Journal of Environmental Radioactivity.

Published in:Journal of Environmental Radioactivity

Document Version:Peer reviewed version

Queen's University Belfast - Research Portal:Link to publication record in Queen's University Belfast Research Portal

Publisher rights© 2016 Elsevier Ltd. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/which permits distribution and reproduction for non-commercial purposes, provided the author and source are cited.

General rightsCopyright for the publications made accessible via the Queen's University Belfast Research Portal is retained by the author(s) and / or othercopyright owners and it is a condition of accessing these publications that users recognise and abide by the legal requirements associatedwith these rights.

Take down policyThe Research Portal is Queen's institutional repository that provides access to Queen's research output. Every effort has been made toensure that content in the Research Portal does not infringe any person's rights, or applicable UK laws. If you discover content in theResearch Portal that you believe breaches copyright or violates any law, please contact openaccess@qub.ac.uk.

Download date:12. Feb. 2021

1

Radon exhalation study of manganese clay residue and

usability in brick production

Abstract

The reuse of by-products and residue streams is an important topic due to environmental

and financial aspects. Manganese clay is a residue of manganese ore processing and is

generated in huge amounts. This residue may contain some radionuclides with elevated

concentrations. In this study, the radon emanation features and the massic exhalation rate

of the heat-treated manganese clay were determined with regard to brick production. From

the manganese mud depository, 20 samples were collected and after homogenization radon

exhalation characteristics were determined as a function of firing temperatures from 100

to 750 ºC. The major naturally occurring radionuclides 40K, 226Ra and 232Th concentrations

were 607 ± 34, 52 ± 6 and 40 ± 5 Bq kg-1, respectively, comparable with normal clay

samples. Similar to our previous studies a strong correlation was found between the internal

structure and the radon emanation. The radon emanation coefficient decreased by ~ 96 %

from 0.23 at 100 ºC to 0.01 at 750 ºC. The massic radon exhalation rate of samples fired at

750 ºC reduced by 3 % compared to samples fired at 100 ºC. In light of the results, reusing

of manganese clay as a brick additive is possible without any constraints.

Keywords

Manganese clay, Heat-treatment, Radiation hazard, Radon, Emanation, Exhalation,

Building material

2

Introduction

The importance of the utilization of by-products and residue streams has grown over recent

decades due to the concern about sustainability of the human environment; of course, the

use of residues sometimes provides better financial solutions. The building industry seems

to be an appropriate solution as certain residues and waste materials have long been used

in the construction industry (Adam, 1994). The use of certain mining by-products such as

waste rock also has a past (Hooke, 2000). The use of other wastes, i.e. coal slag and fly-

ash has become frequent after the development of cement production (Blezard, 2004).

However, the use of these by-products has to be restricted in several cases as, on the one

hand, waste impairs the structural properties of the end-product (Ducman et al., 2007), on

the other hand, different contaminants dissolved and entered the environment causing harm

to the environment or to human health (Uhde et al., 2007).

The quantity and quality of additives usable in building materials has long been set out by

strict regulations. The radioactivity of materials usable in building materials is regulated

explicitly by the standards of only relatively few countries. However, some have been

established for many years: Hungary the regulation setting out the radioactivity limit of

building materials has been in effect since 1960 (no. 26/1960 Directive of Hungarian

Ministry of Construction).

Over recent years more and more studies have been published on the harmfulness of

NORM materials, and there has been no unified recommendation (regulation) on the

restriction of their use until recently, yet the newest EU-BSS (Council directive

2013/59/EURATOM, European Basic Safety Standards) emphasizes the restrictions

related to these materials. The reference level applying to indoor external exposure to

gamma radiation emitted by building materials, in addition to outdoor external exposure,

shall be 1 mSv per year.

In this study the potential usage of the residue of manganese ore mining in the building

industry, i.e. manganese clay, was investigated from a radiological point of view.

Manganese clay is the residue of manganese mining, it is not classified as a by-product as

it is listed as a secondary raw material (Farkas et al., 2004; Vigh, 2005). The underground

3

manganese ore mine in Úrkút, Hungary is one of the biggest European manganese mines

(Polgari et al., 2000).

Over recent decades 2.8 million tons of manganese clay has been deposited on the land

surrounding the mine covering a territory of 20 hectares (Szabo, 2006; Vigh, 2005). The

recent study of Vigh et al., 2013 investigated the radioactivity of a manganese clay. That

study showed that the activity concentrations of the primordial radioisotopes (238U, 226Ra, 40K) of different black shales (manganese clay) do not exceed average soil activity

concentrations. In the other study Kavasi et al., 2012, and Sas et al. 2015a investigated its

utilization as a building material, however, this study only considered the gamma dose and

did not include radon exhalation measurements. However, as several of our previous

surveys have proved the measurement of gamma dose or even that of 226Ra alone is not

suitable for the estimation of building material radiation dose as the majority of radiation

dose is provided by radon and its progenies (Somlai et al., 1997; 2006). The amount of

radon emitted greatly depends on the inner structure of the used building material (Somlai

et al., 2008, Sas et al., 2012, 2015b). Therefore, measuring radionuclide concentration is

insufficient for an accurate dose estimation and it is necessary to take into account the

processing used in the building industry to derive useful radon exhalation data.

According to NEN (Netherlands Standardization Institute) 5699:2001 EN standard entitled

Radioactivity measurement - Determination method of the rate of the radon exhalation of

dense building materials the exhalation rate (radon activity that diffuses per unit of time

from a material into the air surrounding the material, in Bq s-1) can be divided either the

area of the exhaling surfaces or by the mass, the areic (radon flux Bq m-2 s-1) and massic

radon exhalation rates (Bq kg-1 s-1). It is important to clarify that the areic exhalation can

be a characteristic parameter of investigated materials only if the sample thickness is

greater than the diffusion length of the radon belongs to investigated matrix. In case of

massic exhalation the sample thickness has to be very small against the diffusion length of

radon to estimate the radon exhalation without significant loss as a result of its decay inside

the matrix. This assumption can be used for comparison (Kovler et al., 2005) if the sample

thickness of porous material is less than 5 cm (López-Coto et al. 2009). Under this

4

circumstance all the radon has a chance to exhale and the massic radon exhalation rate can

be determined (Sas et al., 2015b).

From the aspect of building industry usage this parameter provides tangible information.

From the aspect of brick manufacturers, the maximum amount of by product that can be

added is important, and this may be driven by the amount of radon emitted. It is not easy

to comply with both requirements, the amount of radon emitted is simulated using complex

models in most cases (Risica et al., 2001). However, for modelling it is rather important to

identify the radon potential of materials. As already mentioned above radon emission is

considerably influenced by the inner structure of the building material (Sas et al., 2012;

2015b) or materials (Jobbagy et al., 2009) and for red mud it has been shown that specific

surface area and porosity greatly influence radon emission. However, both specific surface

area and porosity can be affected by thermal treatment of the material (Vigh, 2005; Sas et

al., 2015b).

Due to other major components of manganese clay (Seil et al., 1928) it is potentially useful

in brick productions. Thermal treatment (firing) is the basic treatment method of brick-

making and this has implications on the amount of radon emitted.

In this study the radon emanation characteristics of manganese clay were measured at

different temperatures identifying the optimum firing temperature in order to minimize

radon exhalation and provide useful data for later modelling and also for construction

companies, and information for authorities on the maximum amounts of additives.

Materials and methods

Sampling and sample preparation

The manganese mining is based on a sedimentary manganese deposit containing a very

fine grained, laminated ore of Jurassic age and the main ore minerals of rhodochrosite and

kutnahorite. Samples were taken from a waste depository site of Úrkút manganese mine

located near the village of Úrkút in the Balaton Upland region of Hungary (Figure 1).

5

Fig. 1- Location of the Úrkút manganese mine

In total 20 grab clay samples (about 10 kilograms) were taken from the difference part of

the depository site, the depository site is marked for environmental monitoring, after

removing the 70 cm thick upper layer (from 0 to 40 cm deep) and then each samples were

dried at room temperature then crushed and homogenized. For gamma spectrometry,

samples were crushed to under 0.63 mm in grain size and then dried in an oven at 105 °C

for 24 h to remove any moisture and to achieve mass constancy. The prepared samples

were weighed, sealed in aluminium Marinelli vessels of 600 cm3 in volume and stored for

at least 27 days in order to reach the radioactive equilibrium between 226Ra and its decay

products prior to counting using gamma spectrometry (Somlai et al., 2008).

Kovler et al., 2005 was found that the massic exhalation cannot be considered as

characteristic values of the tested materials, but can be used rather for comparison because

the massic exhalation rate should depend on some more factors, such as degree of

compaction and geometry (thickness of the layer, mainly) of the powder/granular sample.

If the sample thickness is much lower against diffusion length all emanated radon has a

chance to exhale from the matrix. In that case the massic exhalation can be a characteristic

value. This phenomena was examined by Sas et al., 2012 and it was found that the required

sample thickness should be thinner than 1 cm in the case of humid clayish materials to

avoid the diffusion inhibition effect of the sample thickness on radon exhalation. To

6

evaluate the effects of heat-treatment on morphological attributes, radon emanation and the

exhalation rate, about 1 kilogram of mixed homogenized manganese clay was moulded

into small spheres of 1-2 mm in diameter to ensure the required condition to measure the

massic exhalation rate. In case of massic exhalation the sample thickness has to be very

small against the diffusion length of radon to ensure the radon exhalation without

significant loss as a result of its decay inside the matrix (Sas et al., 2015b, López-Coto et

al. 2009). Then prepared samples were fired each of 100, 250, 350, 450, 550, 650 and 750

ºC for 24 hours (150 gram of prepared spherical samples for each temperature) (Sas et al.,

2012). Owing to occurred loss of mass uniformly 140 grams of each fired sample was

weighed and placed into glass emanation tubes, which were sealed and stored for 30 days

to achieve an equilibrium radon concentration (Jobbagy et al., 2009).

Internal structure related measurements

The relative densities were measured using Density Kit and the reference liquid (White

Spirit 150/200) with a density of 0.775 g cm-3 at 15 °C. A graduated glass body of defined

reference liquid volume (V1) was weighed in air and marked as M1; the samples were

dipped into the holder and placed on an ultrasound wave shaker for 30 minutes and then

the new volume and weight were recorded as V2 and M2. Then their density was calculated

by dividing ∆M by the reference displacement volume (Speight, 2015).

The porosity features and specific surface area were calculated by changing the absorbed

component of samples in a nitrogen gas tube under specific conditions (Jobbagy et al.,

2009). Total pore volumes from 1 nanometre to 15 micrometres were determined by

combining results from ASAP 2000 gas absorption (Micromeritics, U.S.A) and mercury

penetration (Micromeritics, U.S.A) methods.

Gamma spectrometry

A high resolution gamma ray spectrometer, using an ORTEC GMX40-76 HPGe

semiconductor detector with efficiency of 40 %, and an energy resolution of 1.95 keV at

7

1 332.5 keV was used to determine the concentrations of 40K, 226Ra and 232Th present in

the samples. The activity concentration of 40K was determined by the 1461 keV gamma

peaks, and for 232Th by the 911 keV gamma peaks of 228Ac, and the 2614 keV gamma

peaks of 208Tl. The 226Ra concentrations were determined by measuring the activities of

its decay product 214Pb using 352 keV gamma peaks (IAEA, 2007; Somlai et al., 2008).

Radon emanation and exhalation

For calibration and determining the efficiency of a Lucas cell, a certified Genitron EV

03209 calibration chamber, a RN2000A solid 226Ra source with an activity of 104 ± 0.4

kBq (Pylon Electronics Inc., Canada) and an AlphaGUARD PQ2000Pro radon monitor

(Saphymo Gmbh, Germany) as a reference were used.

The grab sampling method using Lucas scintillation cells (1 dm3 Lucas covered by

ZnS(Ag), MÉV Ltd., Hungary) and an EMI photomultiplier were used to determine the

radon concentrations.

The sample container (sealed glass tube) was broken inside a special breaker and radon-

free N2 gas transferred the evaluated radon gas to the Lucas cell. After transferring the

Lucas cells were stored for 3 hours to reach secular equilibrium between 222Rn and its

decay products. Each cell was measured for 3 × 2000 s. The calculated MDA was

determined by the Currie method (Currie, 1968). Radon concentration activity can be

calculated using Eq. (2) (Kovacs et al., 2003):

ARn-222 = N / (V×E×S×F×t×3) (2)

where ARn-222 is the activity of the 222Rn concentration (Bq m-3), N is the net count, V is the

volume of the scintillation cell in litres, E is the counting efficiency of the cell (cpm/dpm),

S is the decay correction factor for the time interval between sampling and measuring, F is

the transfer efficiency (0.95), t is the measurement time and 3 is the number of alpha

emitters under equilibrium conditions which are reached after 3 hours.

The radon exhalation rate in terms of mass was calculated using Eq. (3) (Sas et al., 2015b):

8

tMass et

tmVCE λ

λ−−⋅

⋅⋅⋅

=1

(1)

where:

• C = accumulated radon concentration [Bq m-3]

• EMass = massic exhalation rate [mBqkg-1 h-1]

• t = accumulation time [h]

• V = volume of the accumulation kit [m-3]

• m = mass of the sample [kg]

• λ = decay constant of radon [h-1]

The emanation coefficient of each investigated sample was calculated from obtained

massic exhalation results. (Kovler et al., 2005).

Results and discussion

The relative detection efficiencies and minimum detectable activities of gamma

spectrometry for 40K, 226Ra and 232Th were calculated as 1.2%, 2.4% and 1.4% and the

MDAs as 46, 1.3 and 2.3 Bq kg-1, respectively.

The concentration of 40K, 226Ra and 232Th in the manganese clay were determined in Bq

kg-1 as 607±34, 52±6 and 40±5, respectively. The concentrations of 40K and 226Ra with the

exception of 232Th were higher than the world average mean radionuclide concentration of

soils reported in UNSCEAR 2008 Annex B (226Ra: 32 Bq kg-1, 232Th: 45 Bq kg-1, 40K: 412 Bq kg-1) and RP112 (226Ra: 40 Bq kg-1, 232Th: 40 Bq kg-1, 40K: 400 Bq kg-1).

The morphological attributes of the clay are related to the firing temperature with the

exception of pore volume. The effects of firing on the samples in terms of different

temperatures show in Table (1).

Table 1- The modification of morphological attributes as a function of firing

temperature

9

Temperature (ºC)

Density (kg m-3)

100 4500 250 4400 350 4200 450 3800 550 4000 650 3600 750 3200

Increasing the firing temperature resulted in gradual decreases of specific surface area and

density decreased except at 550 ºC (Fig. 2.).

Fig. 2 Morphological modifications as a function of temperature

The efficiency and MDA of scintillation cells were calculated to be between 60 and 70 %

and 32 to 41 Bq m-3, respectively. A significant difference among firing temperatures was

observed for 222Rn exhalation and emanation rates and temperature (Table 2).

Temperature (ºC) 100 250 350 450 550 650 750 Massic exhalation (Bq kg-1 h-1) 76 67 74 30 51 46 3

Emanation factor 0.25 0.22 0.24 0.11 0.17 0.16 0.01

10

Table 2 – Radon concentration, exhalation rates and emanation factors for

manganese clay in terms of firing temperatures

In Fig. 3, the relationship between cumulative pore volume and exhalation rate and the

emanation factor are shown.

Fig. 3 The relationship between pore volume and radon concentration, exhalation

rate and the emanation factor

Fig. 4 shows Cumulative pore volume distribution of fired manganese clay. The obtained

results clearly proved that in the case of high temperature range the pore size distribution

significantly shifted towards bigger pore diameter compared with at low temperatures. As

a result, it can be stated that low emanation and exhalation rates at high temperatures can

be caused by the modified porosity features. Furthermore, it can be concluded that by

firing, the radon emanation and exhalation features can be significantly reduced, which can

ensure safer building material production from manganese clay in terms of a radiological

point of view.

11

Fig. 4 Cumulative pore volume distribution of fired manganese clay

__baIn the light of the obtained results it can be stated that similar behaviour was found

between presented results of manganese clay, previously studied red mud (Sas et al.,

2015b) and clay (Sas et al., 2012). In the case of red mud and clay study the exhalation

characteristic of heat-treated samples was obtained with accumulation chamber technique,

whilst in the case of currently presented study the radon exhalation results were obtained

with sealed glass tube technique. Despite of different methods the radon emanation and

exhalation decrement was observed in all cases around the high temperature range. In the

case of cumulative pore volume distribution of red mud also similarity was found. The

porosity changes of clay material were not investigated. The cumulative pore volume of

red mud and manganese clay has decreasing tendency in the function of increasing firing

temperature in both cases. Generally, the applied heat in the case of brick production is

around 800 °C, which means technological modification would not be required if these

material will be used for brick production.

Conclusions

12

This study characterized manganese clay in terms of major naturally occurring radioactive

materials, internal morphological modifications, and radon emanation and exhalation rates

as a function of firing temperature. The concentration of 226Ra and 40K presented in clay

were higher than the global average values, while the 232Th concentration was lower than

the global average. Results show a link between firing temperatures and changes in

morphological nature, and subsequently the radon emanation and exhalation rates. The

density, specific surface area and total pore volumes decreased as temperature increased.

The radon exhalation rate reduced by 97% from 75.7 to 2.4 mBq kg-1h-1. To change

properties of manganese mine slag waste as a by-product and reduce the radon exhalation

rate to eliminate health hazards for usage in the building and ceramic industries, firing at

750 °C is recommended. All in all, it can be stated that the high temperature treatment has

beneficial effect on internal structure of all type of investigated clayish materials, which is

favourable from building material production point. However, the application of by-

products (manganese clay and red mud) on its own can arise concerns from mechanical

point of view. On the basis of presented results, the possibility of the application of

manganese clay and also red mud as additive material is considerable, which justifies

further experiments of their clay-based mixtures focusing on mechanical and radiological

properties.

Acknowledgements

The author(s) would like to acknowledge the contribution of the COST Action TU1301.

www.norm4building.org.

References

Adam, J.P., 1994. Roman building: materials and techniques, Indiana University Press,

Bloomington. ISBN 0253301246

13

Blezard, G., 2004. The History of Calcareous Cements, in Hewlett, P.C. (Ed.), Leaʼs

chemistry of cement and concrete. 4. ed. Elsevier Butterworth-Heinemann, Amsterdam,

1–23.

http://www.sciencedirect.com/science/book/9780750662567 ISBN: 978-0-7506-6256-7

Council of the European Union (2014) Council directive 2013/59/EURATOM, European

Basic Safety Standards (BSS) for protection against ionising radiation Official Journal of

the European Union, L 13/1. http://eur-lex.europa.eu/legal-

content/EN/TXT/?uri=CELEX:32013L0059

Currie, L.A., 1968. Limits for Qualitative and Quantitative Determination – Application

to Radiochemistry, Anal. Chem. 40(3), 586-593. DOI: 10.1021/ac60259a007

Ducman, V., Kopar, T., 2007. The influence of different waste additions to clay-product

mixtures. Mater.Tech. 41(6), 289–293. http://mit.imt.si/Revija/izvodi/mit076/ducman.pdf

EN Standard Netherlands Standardization Institute (NEN) Radioactivity measurement

2001 Determination Method of the Rate of the Radon Exhalation of Dense Building

Materials, NEN 5699:2001 EN (2001),

https://www.nen.nl/pdfpreview/preview_113701.pdf

European Commission, 1999. Radiation Protection 112 - Radiological Protection

Principles concerning the Natural Radioactivity of Building Materials. European

Commission, Luxemburg, https://ec.europa.eu/energy/sites/ener/files/documents/112.pdf

Farkas, I., Vigh, T., 2004. A dúsítási maradékiszap termelésének és felhasználásának

tapasztalatai, BKL Bányászat, 137(6), 20-25. (In Hungarian)

http://www.ombkenet.hu/bkl/banyaszat/2004/bklbanyaszat2004_6_04.pdf

Hooke R.LeB., 2000. On the history of humans as geomorphic agents. Geology, 28, 843–

846

14

DOI: 10.1130/0091-7613(2000)28<843:OTHOHA>2.0.CO;2.

International Atomic Energy Agency, 2007. Update of X-ray and gamma ray decay data

standards for detector calibration and other applications. IAEA, Vienna, http://www-

pub.iaea.org/MTCD/publications/PDF/Pub1287_Vol1_web.pdf

Jobbagy, V., Somlai, J., Kovacs, J., Szeiler, G., Kovacs, T. 2009. Dependence of radon

emanation of red mud bauxite processing wastes on heat treatment, J. Hazard. Mater.

172(2-3), 1258-1263. DOI: 10.1016/j.jhazmat.2009.07.131

Kavasi, N., Vigh, T., Somlai, J., Kovacs, T., Sas, T., Nemeth, Cs., Ishikawa, T.,

Yonehara, H., 2012. Natural radioactivity of manganese clay in Hungary. in: Proceeding

of III. Terrestrial Radioisotopes in Environment: International Conference on

Environmental Protection. Pannon Egyetemi Kiadó, Veszprém. pp. 135-138. (ISBN:978-

615-5044-67-0)

Kovacs, T., Bodrogi, E., Somlai, J., Jobbágy, V., Patak, G., Nemeth, Cs., 2003. 226Ra and 222Rn concentrations of spring waters in Balaton Upland of Hungary and the assessment

of resulting doses. J. Radioanal. Nucl. Chem. 258(1), 191-194, DOI:

10.1023/A:1026299201984

Kovler, K., Perevalov, A., Steiner, V., Metzger, L.A. 2005. Radon exhalation of

cementitious materials made with coal fly ash: Part 1: scientific background and testing

of the cement and fly ash emanation J. Environ. Radioactiv. 82, 321-34.

DOI:10.1016/j.jenvrad.2005.02.004

López-Coto, I., Mas, J.L., Bolivar, J.P., García-Tenorio, R., 2009. A short-time method to

measure the radon potential of porous materials, Appl. Radiat. Isot. 67, 133–138,

Doi:10.1016/j.apradiso.2008.07.015

No. 26/1960 Directive of Hungarian Ministry of Construction

15

Polgári, M., Szabó, Z., Szederkényi, T., 2000. Manganese ores in Hungary: Manganese: a

review of research and exploration in Hungary (1917-1999): In commemroration of

professor Gyula Grasselly, MTA Szegedi Bizottság, Szeged (In Hungarian)

Risica, S., Bolzan, C., Nuccetelli C., 2001. Radioactivity in building materials: room

model analysis and experimental methods Sci. Total Environ, 272, 119-26.

DOI:10.1016/S0048-9697(01)00675-1

Seil, G.E., Heiligman, H.A., 1928. Use of Manganese in the manufacture of face brick, J.

Am. Ceram. Soc. 11, 241–248. DOI: 10.1111/j.1151-2916.1928.tb17023.x

Sas, Z., Somlai, J., Jonas, J., Szeiler, G., Kovacs, T., Gyongyosi, Cs., Sydo, T. 2012.

Radiological survey of Hungarian clays; radon emanation and exhalation influential

effect of sample and internal structure conditions, Rom. J. Phys 58, Supplement, 243-250.

http://www.nipne.ro/rjp/2013_58_Suppl/0243_0250.pdf

Sas, Z., Somlai, J., Szeiler, G., Kovacs, T., 2015. Usability of clay mixed red mud in

Hungarian building material production industry. J. Radioanal. Nucl. Chem. 306, 271-

275. DOI 10.1007/s10967-015-3966-z

Sas, Z., Szántó, J., Kovács, J., Somlai, J., Kovács, T., 2015. Influencing effect of heat-

treatment on radon emanation and exhalation characteristic of red mud, J. Environ.

Radioactiv. 148, 27-32. DOI:10.1016/j.jenvrad.2015.06.002

Somlai, J., Németh, Cs., Lendvai, Z., Bodnár, R., 1997. Dose contribution from school

buildings containing coal slag insulation with elevated concentrations of natural

radionuclides, J. Radioanal. Nucl. Chem. 218, 1-63. DOI: 10.1007/BF02033974

16

Somlai, J., Jobbágy, V., Németh, Cs., Gorjánácz, Z., Kávási, N., Kovács, T., 2006.

Radiation dose from coal slag used as building material in the Transdanubian region of

Hungary. Radiat. Prot. Dosimet. 118, 82-87. DOI: 10.1093/rpd/nci323

Somlai, J., Jobbagy, V., Kovacs, J., Tarjan, S., Kovacs, T., 2008. Radiological aspects of

the usability of red mud as building material additive J. Haz. Mat 150, 541-545.

DOI: 10.2478/s11600-013-0113-5

Speight, J.G., 2015. Handbook of Petroleum Product Analysis, 2nd Edition: John Wiley

& Sons. USA, ISBN: 978-1-118-36926-5,

http://eu.wiley.com/WileyCDA/WileyTitle/productCd-1118369262.html

Szabó, Z., 2006. Bakonyi Mangánércek Bányászata: Farkas József Bányamérnök

Emlékére. Mangán Bányászati és Feldolgozó Kft., Úrkút (in Hungarian).

http://epa.oszk.hu/01400/01466/00003/pdf/11.pdf

Uhde, E., Salthammer, T., 2007. Impact of reaction products from building materials and

furnishings on indoor air quality—A review of recent advances in indoor chemistry.

Atmos. Environ. 41(15), 3111–3128. DOI:10.1016/j.atmosenv.2006.05.082

United Nations Scientific Committee on the Effects of Atomic Radiation. UNSCEAR

2008 Sources and Effects of Ionizing Radiation, Annex B, UNSCEAR (2010) New York,

http://www.unscear.org/docs/reports/2008/09-86753_Report_2008_Annex_B.pdf

Vigh, T., 2005. Az úrkúti vas-mangán iszap kutatása és felhasználási lehetőségei,

Földtani Kutatás, 42(2), 12-16. (In Hungarian)

http://epa.oszk.hu/02700/02732/00020/12o.html ISBN: 963 03 9377 8

Vigh. T., Kovács, T., Somlai, J., Kávási, N., Polgári, M., Bíró, L., 2013. Terrestrial

Radioisotopes in Black Shale Hosted Mn-Carbonate Deposit (Úrkút, Hungary), Acta

Geophys. 61(4), 831-847. DOI: 10.2478/s11600-013-0124-2

17

18

List of Figures

Fig. 1- Location of the Úrkút manganese mine

Fig. 2- Morphological modifications as a function of temperature

Fig. 3- The relationship between pore volume and radon concentration, exhalation rate

and the emanation factor

Fig. 4- Cumulative pore volume distribution of fired manganese clay

List of Tables

Table 1- The modification of morphological attributes as a function of firing temperature

Table 2 - Radon concentration, exhalation rates and emanation factors for manganese

clay in terms of firing temperatures