Internacional Atomic Energy Agency

First Coordination Meeting on “Using Environmental Radionuclides as Indicators of Land Degradation in Latin

American, Caribbean and Antarctic Ecosystems”ARCAL, RLA5051

Review ReportARGENTINA

May 2009

ContributorsHugo VelascoMarcos RizzottoJimena Juri Ayub

Grupo de Estudios Ambientales Instituto de Matemática Aplicada San LuisUniversidad Nacional de San Luis-Conicet.

Ej. de los Andes 950- 5700 San Luis, Argentina

Argentina Situation

1. The state of soil erosion in Argentina.

2. Its effect on society and environment.

3. Advances in soil erosion monitoring (availability of datasets).

4. National Programmes focusing on soil erosion.

5. GEA experience in the use of fallout radionuclides for soil erosion studies.

• Agricultural production is one of the main factors that regulate the economy, through export of grains and meats.

• Although the soil is not receiving adequate care.

• Argentina presents the environmental changes typical of countries that are expanding their primary production on natural ecosystems .

• Agriculture and livestock in developed countries declines, while in Argentina Increases dramatically (Paruelo et al., 2004).

• This requires us to figure out how ecosystems work.

• The development of techniques based on radionuclide can be an effective strategy to meet this need.

1. The state of soil erosion in Argentina

• In 1993, nearly 50 million hectares were affected by moderate to severe water or wind erosion (FAO, 1993).

• At present, the number of affected hectares has grown to 60 million, with 650.000 more being added each year with varying degrees of soil erosion (SRA, 2006).

consequences of soil erosion in Argentina

• The area devoted to annual crops has expanded over the period 1988-2002 to an average annual rate greater than 0.27 %, at the expense of forests and natural grasslands (Orúe et al., 2007).

• In the decade 1983-1993 the economic losses due to soil deterioration, considering only the main agricultural region, totalled 700 million dollars per year (FAO, 1993).

• In the Humid Pampa losses occur between 40 and 50 % in some cases, for corn and soybeans (FAO, 1993 ).

consequences of soil erosion in Argentina

Surface eroded by province

Source: Atlas Argentino 2003. PAN (SAyDS)-INTA-GTZSecretaría de Ambiente y DesarrolloSustentable de la Nación.

2. Its effect on society and environment

• The effects of erosion occur at the source (field producer), and also away from the source (dams, rivers, lakes, etc.).

• At the source the phenomenon leads to the thinning of the topsoil. This effect decreases soil productivity.

• Outside the source sedimentation of particles take place. This effect causes damage and injuries, not so much to productivity, but rather to the infrastructure affecting urban populations, through the filling in of dams and canals, and increasing the cost of drinking water.

• One of the negative consequences of the conversion of natural land to crops is an increase in erosion processes associated with an increased rate of runoff.

• Higher rates of sedimentation and siltation.

• Eutrophication.

• Loss of capacity to regulate the hydrological regime.

• Increased flood intensity and frequency.

Desertification map

The erosion is directly related to desertification.

Of the 270 million hectares that make up the country, 60 million are affected by different processes and degrees of desertification.

Source: Programa de Acción Nacional de Luchacontra la Desertificación(PAN), 2002.

Surface eroded by province Desertification map

consequences of soil erosion in Argentina

3. Advances in soil erosion monitoring (availability of datasets)

• Is a universal equation of soil loss mainly by water erosion.

• Orúe et al., 2007, showed that 17% and 32% of studied basins present high and moderate risk of water erosion, respectively.

• It only provides information on the potential risk or erosion, and not any actual measure of it.

• Information difficult to access (spread, in spanish, for the most important agricultural regions).

• There is no a general database.

USLE (Universal Soil Loss Equation) method – Argentina

• Constitute the only references to date on the application of techniques of radioactive isotopes (137Cs) to estimate rates of soil removal.

• Use the Mass Balance Model 2 (Walling and He, 1997).

• They cover a narrow region of the country’s agricultural zone.

• The erosion / deposition rates from Mass Balance Model 2 are in the range

Bujan (2000 and 2003) – Pioneering works in Pampa Ondulada, Argentina

0 to -30 t ha-1 y-1 for erosion0 to 19 t ha-1 y-1 for deposition(2000)

These values matched well with the rates of erosion obtained by classical methods (stick).

Pampa ondulada

-11.5 to -36 t ha-1 y-1 for erosion(2003)

4. National programs focusing on soil erosion

a) Land Degradation in Drylands (LADA)

• Worldwide project developed by the Organization of the United Nations for Agriculture and Food (FAO).

• Aimed at assessing the extent of dryland degradation of the planet and the reasons for this phenomenon, as well as finding solutions.

b) Sustainable management of arid and semiarid ecosystems for the control of desertification in Patagonia

• Project of the Ministry of Environment and Sustainable Development, with implementation in the period 2006-2010.

• Aimed to combat desertification in the Patagonia in the framework of the United Nations Convention to Combat Desertification and Drought Mitigation (UNCCD).

c) Regional Network of benchmarks and indicators of desertification in Latin America and Caribbean (TPN1)

• Coordinated project between the Ministry of Environment and Sustainable Development and the Argentine Institute for Research in Drylands (IADIZA).

• Aimed to establish a monitoring and evaluation system of desertification and drought.

d) Sub-regional action program for sustainable development of the Gran Chaco Americano

• In the framework cooperation agreement between Argentina, Bolivia and Paraguay for the subregional action program for sustainable development of the Gran Chaco (Buenos Aires, 2008, Law 26383).

• Aimed to improve socioeconomic conditions of the inhabitants of the Gran Chaco Americano, and preserving, conserving and restoring the ecosystem, with actions to mitigate and reverse the degradation processes of shared natural resources.

5. GEA experience in the use of fallout radionuclides for soil erosion studies

• The GEA (Grupo de Estudios Ambientales) is working in radioecological research since 1992.

• Its contribution has been mainly in modeling the transfer of radionuclides in natural and semi-natural environments.

• It has no laboratory for the detection of radionuclides. The measures are carried out in laboratories of the National Atomic Energy Commission (CNEA), which limits the experimental work.

• In 2004 began with soil sampling activity in an area undisturbed belonging to INTA (137Cs, 226Ra, 40K).

• In 2007 began with the sampling of rainwater to determine 7Be.

40

30

20

10

00 1 2 3 4 5

Sitio A Sitio B

137Cs (Bq kg-1)

dep

th (

cm)

Measured Activity Concentration in soil (Bq kg-1)

0.00 0.02 0.04 0.06 0.08 0.10

50

40

30

20

10

00.00 0.02 0.04 0.06 0.08 0.10

Pro

fun

did

ad (

cm)

Sitio A - Punto A17D

s = 1,0 cm2 año-1

vs = 0,23 cm año-1

Sitio B - Punto B19Ds = 3,2 cm

2 año

-1

vs = 0,23 cm año-1

Concentración de actividad normalizada C t(z,t)/C0

137Cs

Activity Density calculated from measurements (kBq m-2) : 0.89 (A), 0.67 (B).With these values we calculated the deposition (1951-1960): 2.3 (A), 1.7 (B). In the range of known deposition values for the region.

0 10 20 30 40 50 600

20

40

60

80

100

120

140

160

Are

al a

ctiv

ity d

ensi

ty (B

q m

-2)

Rainfall (mm)

Linear fit (y = a + bx) a = 0.16 ± 0.34 b = 1.52 ± 0.07 R = 0.9290% Confidence bands a

min= -0.51; a

max= 0.85

bmin= 1.39; bmax= 1.66

rain collector

7Be

0

100

200

300

400

500

600

Act

ivity

dep

ositi

on (B

q m

-2)

DecNovOctSepAugJulJunMayAprMar

calculated soil activity content rainfall activity contribution

Jan Feb

The main results obtained by GEA can be seen in the website http://gea.unsl.edu.ar

• light (3 cm of soil lost): causes reductions in yields of wheat and maize in the order of 10 %.

• moderate (7 cm of soil lost): 30 % loss.

• severe (15 cm of soil lost): 60 % loss (1000 kg/ha of wheat, 1500 kg/ha of soybeans, 5000 kg/ha de maize; INTA, 2003).

• serious (>20 cm of soil lost): makes crop production impossible.

Pampean Region (the country’s most important agricultural - livestock area)

Water erosion

Livestock tending is likewise affected

We can observe that the areas around Sites A and B are cultivated.

INTA lands in San Luis, Sites A and B.

137Cs

Activity density (kBq m-2) calculated from measurements

20

15

10

5

00 1 2 3 4 5

137Cs (Bq kg-1)pr

ofu

nd

idad

(cm

)

Promedio P1 P2 P3

137Cs

Activity concentration (Bq kg-1) in disturbed soil

Technique of Berilyum-7 to calculate soil redistribution

Fallout beryllium-7 as a tracer in soil erosion investigations.W. H. Blake, D. E. Walling, Q. He, Applied Radiation and Isotopes 51 (1999) 599-605.

• Could be used to calculate soil redistribution for rain point events

• Methodology proposed by Blake et al., 1999

Technique of Cesium-137 to calculate soil redistribution

• Methodology proposed by Walling et al., 1999Use of 7Be and 137Cs measurements to document short and medium term rates of water-induced soil erosion on agricultural land.Walling D. E., Q. He, Blake W., Water Resources Research 35 (12)(1999) 3865-3874.

• With this technique average rates of erosion in large periods of time could be calculated, i.e. 10 years, 20 years.

• The same is valid for 210Pb.

a) Fallout beryllium-7 as a tracer in soil erosion investigations.W. H. Blake, D. E. Walling, Q. He, Applied Radiation and Isotopes 51 (1999) 599-605.

/( ) oh href

h

A C x dx A e∞

−= =∫

A: measured 7Be inventory (Bq m-2) at the sampling point

Aref: local 7Be reference inventory (Bq m-2)

ln( / )o refh h A A= −

If A>Aref then deposition has occurred. The depth of deposition h’ (kg m-2) is

This allows h to be calculated as follows:

' ( ) /ref dh A A C= −

Cd (Bq kg-1): 7Be concentration of deposited sediment.

hx=h

AAref

x=0

x=∞

} }