Fixed ammonium in antarctic rocks and soils and a possible cause of underestimation

pp. 397-399. 1991 Rioted in Great Britain. All rights reszwcd

003&0717;91 53.00 + 0.00

Soil Biol. Biochem. Vol. 23, No. 4.

Copyright C 1991Pergamon Pmaapk

SHORT COMMUNICATION

FIXED AMMONIUM IN ANTARCTIC ROCKS AND SOILS AND A POSSIBLE CAUSE OF UNDERESTIMATION L. G. GREENF~ELD Department of Plant and Microbial Sciences, University of Canterbury, Christchurch. (Accepted

IS October

New Zealand

1990)

of NH: held within the structures of primary silicate minerals (Baur and Wlotxka, 1972). This form of NH;. which resists KCl extraction and can only be released by an HF treatment. is called fixed NH: or non-exchangeable NH;. Soils, particularly those containing 2: I clay minerals

With the exception of Antarctica the occurrence and forms of N in rocks and soils in terrestrial ecosystems has been established (Stevenson. 1982). N occurs in organic and inorganic forms in soils and most sedimentary rocks. Igneous rocks contain only inorganic N mainly in the form

. P

1

bN

wes::e”

-

73%

7s’

Ross

Sea

n Fig. I. Sample locations in Antarctia. I. Signy Island; 2. Deception Island; 3. Cape Bird; 4. CianvooU Valley; 5, Inexpressible Island; 6. Mount Melbourne; 7. Mount Erebus; 8, Shapeless Mountain; 9. West Beacon: IO. Mount Nilson. 397

398

Short communications Tabk

I. &tails

of samoks collected

Table 2. .4mounts of 6x4 and cxchantptabk NH; in Antarctic rocks and soils

S-vk

No.

Material description

I

Sandy soil wtthm sorted stone ctrck at Jane Cal. moist. no visibk V~getatiOll

2

4

5 6

7

8

9 IO

II

I2

I3

I4 IS

Mica schist rock. periphery sorted stone circle at Jane Col, moist. no visibk vegetation Sandy soil, within sorted stone circk at Factory Bluffs. moist. vcgetatcd Mica schist rock. lateral moraine at Chwcll glacier, moist. no vegetation Sandstone rock, plateau beneath summit of West Beacon. dry no vegetation Sandstone rock, plateau beneath summit of West Beacon. dry. endolitic microbes within rock Quart&c rock. plateau beneath summit of West &acon, dry, no vegetation Siltstone rock. summit Shapeless Mountain. dry. no vegetation Sandy soil. valley floor near Garwood glacier, moist, syrcc vcgctation Quart& rock. terminal moraine Garwood glacier. dry. cndolithic violet pigmented bacteria within rock Quartzitc rock, lateral moraine Gnrwood glacier. dry. no organisms Granodioritc rock, summit unnamed ridge overlooking Gurwood glacier. dry. no ve8ctation Microgranite rock, outcrop rdjncent to sample I3 Dolcrite rock, v&y floor near Gamood glacier. dry, no vcg elation Quartz rock, same lwations as sample IS Diorttc rock, raised beach. Evnns Cove, dry, no vegetation Vesicular basalt rock, below Cape Bird ice cap, dry. no vegetation Scoria rock. from soliditied larva flow Pendulum Cove. wet. vcgctatcd Sandy soil (warmed). summit Mt Pond, active geothermal area. wet. vegetated Sandy soil (warmed), summit Mt Melbourne, active geothermal area. wet. vegetated Sandy soil (warmed) summit Mt Ercbus. active geothermal arca. wet. vegetated Granite rock. summit Mt Nilxn. Rockefeller Mountains. dry, no

S=vk

Total N (co 8-l)

Organic N

Fixed NH;-N

Excbangeabk NH;

I

281 f7

155

12656

0

2 3 4 5 6 7 8 9 10 II I2 I3 I4 IS I6 I7 I8 ::

477 + 9 122*7 706*10 266*6 17*5 101 * 8 77 * 9 l424*9 55 f 6 57 * 7 23 f 3 85 f 6 126 f 5 27 f 3 36 f 3 51 *3 102 *4 56 f 5 441*3 2100*5 2370 f 8

334 9 384 8 0 80 21 555 42 20 5 2

MO*6 88 f 5 322*4 224*6 15*5 17*3 35 f 6 837 f 10 II *4 36*4 17*4 80 f 3 119+3 24 f 3 35 f 3 48*2 81 53 7*4 9*3 36 0 3 f 33*4

No. I

Sandy soil. periphery sorted stone circle at Jane Col, moist, no visible VC@iUiOll

3

Locality

I

I

9

9

::

1 : 2 I4 0 22 1995

9 23 8

4

4

4

4 4

2

2

36 f 4

;z 69 71 I

Rocks and surface soils (O-5 cm) from the localities where samples were collected (Table I and Fig. I) were air dried, crushed or ground (5 min) to < 140 pm. Plastic gloves were worn during collecting and processing to reduce N contamination from hands. Exchangeable and fixed NH: were determined (Kccney and Nelson. 1982). Total N detcrminations were made using the Kccney-Brcmner HF modification of the Kjcldahl method to include fixed NH,+ (Brcmncr and Mulvancy. 1982). I have examined the possibility that grinding caused the rclcasc of fixed NH,’ from rocks and soils and its conversion to cxchangcable NH,‘. Samples wcrc leached with KCI to remove exchangeable NH,‘. Residues were water washed, air dried and ground in a vibratory pot mill for I4 h each day for 7 days (100 h total). The temperature inside the pots during grinding did not exceed 35°C. Following grinding, powdcrcd samples were taken for total N, exchangeable and fixed NH,* dctcrminations. All the samples contained fixed NHf (Table 2) cxcep~ sample 21. This sample together with samples 20 and 22 were from active geothermal areas. The proportion of total sample N prcscnt as fixed NH,+ in these samples was no Table 3. The effects of prolonged grinding on the release of fixed NH,’ from Antarctic rock and soils Ground 5 min eO.14 mm sample*

7

total soil N in the form of fixed NH,’ generally increases with soil depth from ca 10% in surface to ~30% in subsurface soils (Young and Aldag. 1982). Greenfield (1988) described the occurrence of fixed NH; in Antarctic rocks and Greenfield and Wilson (1981) fixed NH; in Antarctic soils. I have confirmed and extended these earlier findings to other continental and maritime Antarctic locations. During this work the possibility that grinding cauxd the release of fixed NH; was also examined.

I 3 6 3 I I 7

Values arc means f SE of duplicates.

6

contain fined and exchangeable NH:. This latter type of NH,’ is readily extracted with KCI. The proportion of the

2

2: 0 34 2 4 21 32 2 I

~

Ground IOOh ball-milled sample -

Sample

Fixed NH;

Fixed NH; (re g-‘1

I

l26&6 88 r 5 322 f 4 224 & 6 Is+5 17*3 35 + 6 II *4 80 f 3 81 k3 7*4

98 * 2 42 f. 2 263 f 2 202 f. 2 922 I4 ?: 2 25 f 2 7r2 722 I8 k2 Sk2

3 4 5 6 7 8 10 I3 18 19

Fixed NH; released by ball milling 28 46 59 22 6 3 IO 4 73 63 2

‘Samples shaken with 2 M KCI to mnovc exchangeable NH,+ before prolonged grinding. Values arc means * SE of duplicates.

Short communications

399

more than 2%. Sample 9. a siltstone rock. was collected from a freshly-exposed face beneath the surface of the rock outcrop after removal of shattered surface debris. This sample contained fossil Dicroidium leaves. It is not uncom-

aals. The rcsuks in this

mon to find high total N contents together with variable of tied NH,’ and organic N in palaeozoic shales and siltstones (Stevenson. 1962; Sullivan er al., 1979; Strathouse er of.. 1980). Samples I, 2. 4. 7. IO. 20. 21 and 22 contained appreciable quantities of organic N which exceeded their fixed NH: contents. This can be ascribed to plant- and microbially-derived organic matter. Samples I. 2, 4. 6, 7, IO, II. 12, 13. IS, 16. 17, 18 and 23 contained only small amounts of exchangeable NH; (< 7 p g g- ’ ) unlike the remaining samples which contained >21 pg g-‘. Following the 5 min crushing to reduce the samples to I40 pm considerable amounts of exchangeable NH; were detected in some rock samples, which had been leached with 2 M KCl to remove exchangeable NH; (unpublished). It can be seen (Table 3) that when samples free from exchangeable NH,+ were ball milled. varying proportions (mean 39%. range 10-91) of the fixed NHf contained in these samples were converted to exchangeable NH:. It is therefore possible that during the preparation of < I40 pm sized samples from orginal samples an amount of the fixed NH; in the original sample was converted to exchangeable NH;. This might explain the large amounts of exchangeable NH,’ present in several of the < l4Opm samples, e.g. samples 3, 5.8.9. 19.20,21 and 22 in Table 2. Although the possibility cannot be excluded that the release of “fixed” NH,’ when samples were ground to < 140 pm could be derived from the release of exchangeable NII,’ occluded in secondary minerals. Exchangeable NH,’ determinations on the original samples before crushing to < 140 pm indicated that, with the exception of sample 19. none contained more than 5 pg g-’ of exchangeable NII,‘. Sample 19 contained up 10 30 /dg g-’ of cxchangcable NH,’ and this probably originates from precipitation NH,’ becoming physically cntrappcd within this porous material. The possibility that some of the exchangeable NH,‘. arising during ball milling. originated from organic matter seems remote. It was found that mineral-free mixtures of microbes (algae. bacteria and fungi), mosses, lichens and defined compounds such as uric acid, urea, zein and glutamine did not cause increases in exchangeable NH; after 100 h of ball milling over those concentrations present in control mixlures. Since the bulk of the N in rocks occurs as fixed NH,‘. (Young and Aldag. 1982; this study) it seems reasonable to suggest that the fixed NH,’ present in developing soils originates from weathering of these rocks. The possibility cannot be excluded that NH,’ in atmospheric precipitation may react with soil and rock constituents to become fixed NH,+ (Young and Aldag. 1982; Nommik and Vahtras, 1982). My results demonstrate that fixed NH,’ occurs in a variety of rocks and soils in Antarctica in amounts and proportions similar IO elsewhere in the world. Young and Aldag (1982) suggest that surface soils contain about 10% of their total N in the form of fixed NH,’ with this value approaching 90% in subsurface soils. rocks and clay min-

Young and Aldag and soils.

propotions

paper show that igneous and sedimentary rocks from Antarctica contain 7-837 pg fixed NHf g-’ and that Antarctic soils contain 0-322pg fixed NH; g-l. These values are comparable to those reported by (1982)

for similar

but non-polar

rocks

AcknowledgemenrI--I thank the D.S.I.R. Antarctic Division. New Zealand and the U.S. National Science Foundation for logistic support over the period 1978-1987 and the Brit&h Antarctic Survey fo; similar support in 1987-1988. I thank Dn J. Adams. A. Camobell. 1. Campbell. K. Goh, J. Smellie and D. Wynn-Williams for critically reading the manuscript. REFERENCES Baur W. H. and WIotzka F. (1972) Nitrogen. In Hundbook of Geochemisrry (K. H. Wedepohl, Ed.), Vol. II/l. pp. 7-B-l-7-0-3, Springer, Berlin. Bremner J. M. and Mulvaney C. S. (1982) Nitrogen-total. In Mefhodr o/Soil Analysis. (A. L. Page. Ed.) 2nd Edn, Part 2. Monograph No. 9. pp. 595624. American Society of Agronomy. Madison. Greenfield L. G. (1988) Forms of nitrogen in beacon sandstone rocks containing endolithic microbial communities in Southern Victoria Land. Antarctica. Polurforschung 58, 21 I-218. Greenfield L. G. and Wilson G. J. (1981) New Zealand Antarctic Research Programme Report No. I, Immediate Scientific Report. University of Canterbury, pp. l-47. Keeney D. R. and Nelson D. W. (1982) Nitrogen-inorganic forms. In Me/hods of Soil Analysis (A. L. Page. Ed.) 2nd Edn, Part 2. Monograph No. 9, pp. 643-698. American Society of Agronomy. Madison. Nommik H. and Vahtrrs K. (1982) Retention and Axation of ammonium and ammonia in soils. In Nitrogen in Apiculturul SoiLv (F. J. Stevenson, Ed.) Monograph No. 22, pp. 123 -171. American Society of Agronomy, Madison. Stevenson F. J. (1962) Chemical state of the nitrogen in rocks. Geochimicu et Cosmochimicu Actu 26, 797-809. Stevenson F. J. (1982) Origin and distribution of nitrogen in soil and or&dnic forms of soil nitrogen. In Nitrogen in A~riculrural Soils (F. J. Stevenson, Ed) Monograph No. 22, pp. l-42 and 67-122. American Society of Agronomy, Madison. Strathouse S. M.. Sposito G.. Sullivan P. J. and Lund L. J. (1980) Geologic nitrogen: a potential geochemical hazard in the San Joaquin Valley, California. Journul o/Environ-

mentul Quuliry 9. 5460. Sullivan P. J., Sposito G.. Strathouse S. M. and Hansen C. L. (1979) Geologic nitrogen and the occurrence of high nitrate soils in the western San Joaquin Valley, California. Hilgurdiu 47. 1549. Young J. L. and Aldag R. W. (1982) Inorganic forms of nitrogen in soil. In Nirrogen in A~riculrurul Soils. (F. J. Stevenson. Ed.) Monograph No. 22. pp. 43-66. American Society of Agronomy, Madison.