Scholarly article on topic 'GIS-based dairy-industry sludge application plan in Galiza (NW Spain)'

GIS-based dairy-industry sludge application plan in Galiza (NW Spain) Academic research paper on "Agriculture, forestry, and fisheries"

CC BY-NC-ND
0
0
Share paper
Academic journal
Procedia Environmental Sciences
OECD Field of science
Keywords
{"agro-environmental indicators" / "dairy-industry sludge" / "GIS based model" / "site suitable" / "socio-economic factors"}

Abstract of research paper on Agriculture, forestry, and fisheries, author of scientific article — Emilio Carral, Marcela Bello, M. Elvira López-Mosquera

Abstract A site-specific dairy-industry sludge application plan (GIS-based) has been development in Vilalba municipality, Galiza (NW Spain). Sites suitable for sludge application were identified using GIS based weighted linear combination (WLC) model. The degree of land suitability for dairy sludge was determined using a range of environmental, agronomic and socio-economic factors: water runoff and groundwater risk of pollution, heavy metals input to system, proximity to watercourses and potable water sources, presence of sensitive areas (protected and flooded land), land use, soil depth, plot suitability for mechanisation, distance from human settlements and main roads, and sludge spread cost were included in the model.

Academic research paper on topic "GIS-based dairy-industry sludge application plan in Galiza (NW Spain)"

Available online at www.sciencedirect.com

SciVerse ScienceDirect PfOCSCl ¡C

Environmental Sciences

Procedia Environmental Sciences 9 (2011) 27 - 32

Ecological engineering: from concepts to applications

GIS-based dairy-industry sludge application plan in Galiza (NW

Spain)

Emilio Carrala' Marcela Belloa, M. Elvira López-Mosqueraa

aEscola Politécnica Superior, Universidade de Santiago de Compostela, 27002 Lugo, Galiza-Spain

Abstract

A site-specific dairy-industry sludge application plan (GIS-based) has been development in Vilalba municipality, Galiza (NW Spain). Sites suitable for sludge application were identified using GIS based weighted linear combination (WLC) model. The degree of land suitability for dairy sludge was determined using a range of environmental, agronomic and socio-economic factors: water runoff and groundwater risk of pollution, heavy metals input to system, proximity to watercourses and potable water sources, presence of sensitive areas (protected and flooded land), land use, soil depth, plot suitability for mechanisation, distance from human settlements and main roads, and sludge spread cost were included in the model.

©2011PublishedbyElsevier Ltd.Selection and/or peer-review under responsibility of Laboratory "Biochemistry and ecology of continental environments Keywords: agro-environmental indicators; dairy-industry sludge; GIS based model; site suitable; socio-economic factors

1. Introduction

In many parts of the world, ever-increasing quantities of sludge are being generated in the treatment of domestic, urban and industrial wastewaters, and the storage and disposal of this sludge is an increasingly serious problem. This type of sludge is of highly variable composition, but generally has high concentrations of fertilizer elements, so that their use as agricultural fertilizers is often seen as an attractive disposal option [1]. However, such use may have more or less serious drawbacks for environmental quality and public health, due to the often considerable presence in sludge of heavy metals, toxic organic compounds, salts and/or pathogens [2]. In Spain, the dairy sector produces an estimated total of 26,210 tonnes of BOD5 per annum, equivalent to 9,233 tonnes of suspended solids [3]. Galicia (NW Spain) produces more than 40% of the total national milk output, and processes more than 25% of this production. In the municipality of Vilalba - Galiza, the dairy production, processing and packaging industry is very important. To allow accurate evaluation of the value of dairy sludge for fertilization it is necessary to identify and characterize the sites to which the sludge will be applied. All the types and levels of information considered in the present report (runoff and groundwater risk of pollution, heavy metals input to system, proximity to watercourses and potable water sources, presence of protected natural areas, soil cover/use, soil depth, mechanisation parcel suitability, distance from human settlements-main roads, and field sludge spreading distance from dairy industry) were usefully integrated into a geographical information system (GIS). It was suitably designed and sufficiently accurate to constitute a powerful tool for both long-term planning and week-to-week decision-making by the managers of the sludge disposal programme.

Corresponding author. Tel.: +0-34-982223996; fax: +0-34-982285926. E-mail address: emilio.carral@usc.es.

ELSEVIER

1878-0296 © 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of Laboratory "Biochemistry and ecology of

continental environments

doi:10.1016/j.proenv.2011.11.006

2. Study area and factors description

The study area, Vilalba Council, extending through 379 km2, is located in North-East part of Lugo Province (Galiza - NW Spain), and has an important economic activity based on milk production (processing and packaging). Bioclimatological, soil, geomorphologic and land use/occupancy factors have an important role for agricultural/economic activities. They must also be taken into account to determine the suitable lands for sludge spread. The study area is characterized by a warm temperate regime, with an average annual temperature about 11.5°C, with an average daily minimum of 6.2°C and maximum of 24°C. The average annual rainfall is 1,176 mm and the average annual potential evapotranspiration is 616 mm. Soils are humic or gleyic Cambisols (FAO classification). The morphology of the land is dominated by plain form, very suitable for crop production (less relevant are hill slope or mountains). By other way, the significative presence of floodplain goes to temporal restrictions for agriculture activities.

The primary information source used to build the GIS was 1:5.000 official topographic maps. Slope and hypsometric models of the study area were derived from a digital elevation model (DEM), following standard methods. Soil use and cadastral maps (1:25.000, 1:5.000) was acquired from Laboratorio do Territorio-U.S.C [4]. All data sets (derived and original) were pre-processed using ArcView 3.2 Geomedia Professional.

The factors determining the land capability to received sludge are diverse in their nature and origin. The interaction of environmental, agronomic, social and economic factors will determine these capabilities. Indicators are needed for the quantitative spatial description/assessment of the factors that contribute to determining the site restriction to sludge application over the studied area. The model was based on weighted linear combination processes. Factors were arranged in order of importance and a pair- wise comparison was done, assigning different weights for different indicators, according to their influence on the suitability for sludge reception. Currently legal normative in relationship with to protected areas location and heavy metals soil content limits were used, too. Value ranged between 0 and 12, with -1 score for excluded areas (Table 1).

Table 1. Factors and indicators used in the model and their weights

Factor Indicator Weight Maximum Relative

value weight

Sensitive zones Area of sludge application 6 12 0.24

Surface water pollution Water runoff/ slope 5 10 0.20

Soil flooded risk Hydromorphic level 4 8 0.16

Economic Distribution costs 3 6 0.12

Nutrient extraction Land use 2 4 0.08

Groundwater pollution Soil parental material 2 4 0.80

Soil depth Soil depth 1 2 0.04

Air pollution Area of sludge application 1 2 0.04

Mechanization Soil slope 1 2 0.04

2.1. The sensitive zones factor

Several zones must be protected and these areas are excluded from sludge spread program. Areas protected and regulated under EU Habitats directive [5] were excluded for sludge disposal. Fluvial system and potable water sources must be preserved from diffuse pollution. In this way, zones around 20 m distance from watercourses and 80 m from water sources were established as excluded zones [6].

e.e. Hmmoy amomi eeeomeo fmeoec

Emilie Varoal et rl /maovedio Eneirmnmental Seiannns e (CCI 1(27 n(2

Legal restrictions established for sludge and soil heavy metal content were used [7]. Neither sludge nor soil heavy metal content is over legal limits [8,9]. All study area is suitable for sludge application in relationship with this criterion.

e. 3. Oucfmar wmorcp/iiuol/e fmao/c

Potential sludge runoff was established from soil slope characterization. The relationship between soil slope classes and potential runoff rates were established by the Spanish Ministry of Civil Engineering recommendations [10]. The slope classes help to calculate the "vulnerability" to leaching and runoff processes.

e.4. O/li- fie/drafmao/c

Soil drainage characteristics and topographic position in the landscape are the two main factors determining the presence of flooded areas. These watershed areas, during the flood time, must be avoided in sludge application program and in other liquid organic amendments [11]. Different levels of sludge spread restriction were defined following Boixadera and Teira [12], taking into account hydromorphic level values.

e.5. Nuoclreo rxocmaol/e fmao/c

In the agronomic and environmental senses, it is very important to establish a relationship among crop needs and the power of organic amendments fertilization. This is necessary, for a good economic and environmental performance of fertilizer applications. The nutrient extraction is different for diverse crops or soil use [13], and Spanish regulations defined different minimum times between organic amendments application and crop recollection [7]: respectively three weeks and ten months for swards-croplands and horticultural crops. Under these considerations different restriction levels were defined in relationship with soil use.

e. 6. Gc/uedwiOrcp/iiuol/e fmao/c

Hydraulic conductivity is an important indicator for estimation the percolation level through soils profiles and the estimation of groundwater table depth. The soil permeability coefficient is in relationship with geological background, soil porosity, etc, and all these factors conditioned the organic amendments use [11]. Following Castelao and Díaz-Fierros [14] (soil profiles description for the study zone), Dunne and Leopold [15] (geology-hydraulic conductivity relationships (Table 2), and Boixadera and Teira [12] (restriction level for sludge application in relationship with hydraulic conductivity), it is possible establish a relationship between geological characteristics and the restriction level to sludge application for groundwater pollution risk evaluation.

Table 2. Relationship between soil parental material and hydraulic conductivity

Soil parental material Hydraulic conductivity (cm/h)

Granitic 12.5

Consolidated soil 6.3

Quaternary sediments 2.6

Tertiary sediments 0.2

e. 7. O/li drpoh fmao/c

The depth of soil to which the roots of a plant can readily penetrate, in order to reach water and nutrients, influences the yield from a crop. By other way, soil depth shows how thick the soil cover is, and determines the soil volume useable to sludge disposal. Soil depth was estimated by means of digging pits for soil classification and soil sampling and the references from Castelao and Díaz-Fierros [14]. Following Boixadera and Teira [12] restriction levels were defined.

2.8. Mechanization factor

Agricultural equipment and machinery are the indispensable part of agricultural activities, and the soil slope determines the possibilities of sludge transportation and disposal. Different slope classes are in relationship with degree of optimal mechanization performance [16].

2.9. Atmospheric pollution factor

The sludge spread risk consequences for human settlements are in relationship with odours and air pollution by pathogens. In this way, excluded areas were defined under two different criteria: suitable areas for sludge spread must be far away 100 m from human settlements and 20 m far away from mainly roads [6].

Table 3. Indicators weight

Indicator (factor) Restriction level Indicator weight

Area of sludge application (sensitive zones)

Inside Excluded -1

Outside Low 12

Soil slope-% (water runoff)

0-8 Low 10

8-16 Moderately 5

16-30 High 0

30-65 Excluded -1

Hydromorphic level-cm (soil flooded risk)

0-25 High 0

55-60 Moderately 4

> 60 Low 8

Land use (nutrient extraction)

Arable High 2

Grassland Moderately 3

Forest Low 4

Human settlements Excluded -1

Soil parental material (ground water pollution)

Granitic Low 4

Consolidated soil Moderately 3

Quaternary sediments Moderately 2

Tertiary sediments High 0

Soil depth-cm

< 30 High 0

30-80 Moderately 1

> 80 Low 2

Soil slope classes-% (transportation performance)

0-10 Low 2

Emilia Carral et al. 0 Procedin Environmantal Sniences 9 (0011)27-32

10-20 Moderately 0

20-35 High 0

35-50 Forest land -1

> 50 Marginal land -1

Area of sludge application(atmosphericpollution area)

Inside Excluded -1

Outside Low 2

Distribution costs classes-duro

16-22 Low 6

22-44 Moderately low 4

44-88 Moderately 2

>88 High 1

2.12. dconomic factor

The cost for sludge distribution is a compendium of sludge tank load cost, transportation and spread cost, and is in relationship with the time spent in these activities, and the distance between dairy factory and stakeholders parcels. The distance criterion was established from a regression model between real distance (Dr) for forty parcels and their Euclidean distance (De), and then, extrapolated to the remaining of the study area (Dr = 1.391 . De, n= 40,

r2 = 0.87).

For all the factors and their indicators above defined, different qualitative and quantitative appreciations were assigned in relationship to sludge disposal possibility (Table 3).

3. Estimation of land suitable

As a result of normalization, all values stored in the maps are made suitable for aggregation. The spatial index (Si) of land suitability is calculated using multicriteria evaluation (MCE) procedures and the Weighted Linear Combination (WLC) technique: Si = £ P Vmi where

Si= Weighted combination

P = weight for each indicator

Vmi = maximum value for each indicator.

Different partial multiple maps for each variable were first released, and them, incorporated into a final suitable map. The degree of suitability were expressed on this map over a non-dimensional range of 0 to 100 before classifying them into three suitable classes using the equal internal function available within Arc View GIS.

4. Conclusions

Sites suitable for dairy-sludge application in Vilalba Municipality - Galiza (NW Spain) were identified (Fig. 1). An exclusion zone: 2,160.5 ha / 22.6 % (protected natural areas, exclusion distance from human settlements, roads, streams and potable water sources), and three suitable classes were defined: Class 0: high restriction to sludge application (313.4 ha / 8.3 %, sludge spread is only possible some years). Class 1: intermediate restriction: (781.8 ha / 18.2 %, sludge application is only possible in dry season). Class 2: moderate restriction (6,300.5 ha / 65.9 %, sludge application is possible over all year under established agronomic dose). Having established the sites of disposal, the management plan should include procedures for site monitoring. In this sense, previous studies about both soil quality and grassland forage production using experimental plots were done. We have monitored a total of 12 grass/clover swards over a 1- to 4-year period, in comparison with equivalent swards in the same area receiving mineral NPK fertilizer or cattle slurry. Our results show that dairy sludge application did not increase heavy metal levels in soil or plant either in the short or the medium term [8], as expected given the sludge low heavy metal

contents. Besides, the high Na content and the high electrical conductivity of sludge suggest that their continuous application could lead to salt accumulation in the soil. However, soil salinity did not reach detrimental levels for soil physical properties and crop growth with a dose of 80 m of sludge ha-1 [17].

Fig. 1. Map of Vilalba municipality, showing site restriction for dairy sludge disposal

Acknowledgments

Financial support by FEDER (project 1FD97-0334), and Lactalis-Leche de Galicia (contract 1997/CE317). References

[1] L.E. Sommers, J. Environ. Qual., 6(1997)225.

[2] E.G. O 'Riordan, V.A. Dodd, and G.A. Fleming, Irish J. Agr. Food Res., 33(1994)41.

[3] MOPTMA, Propuesta de límites de vertido a aplicar a la industria agroalimentaria de acuerdo con la Directiva 91/271/CEE, Ministerio de Obras Públicas, Transporte y Medio Ambiente, Spain, 1994.

[4] http://laborate.usc.es.

[5] Xunta de Galicia, DOGA, 118(2001)8176.

[6] http://www.xunta.es.

[7] B.O.E. Real Decreto 1310/90, (1990)262.

[8] M.E. López-Mosquera, C. Moirón, and E. Carral, Resour. Conserv. Recy., 30(2000)95.

[9] M.E. López-Mosquera, R. Barros, M.J. Sainz, E. Carral, and S. Seoane, Soil Use Manage., 21(3)(2005)298.

[10] M.O.P.U, Medio Ambiente en España, Monografía de la Secretaría General del Medio Ambiente. Madrid, 1998.

[11] R. Lea, W.C. Tierson, and A.L. Leaf, Forest Sci., 25(4)(1979)597.

[12] J. Boixadera, and M.R.Teira, Aplicación agrícola de residuos orgánicos, Universidad de Lleida, Spain, 2001.

[13] L.Ryszkowsk, Agr. Ecosys. Environ., 27(1-4)(1989)107.

[14] A. Castelao, and F. Díaz-Fierros, Os solos da Terra Cha, Tipos, xénnese e aproveitamento, Servizo de Publicacións, Deputación Provincial de Lugo, Spain, 1992.

[15] T. Dunne, and L.B. Leopold, Water in environmental planning, W.H. Freeman and Co., San Francisco, USA, 1978.

[16] F. Díaz-Fierros, E. Benito Rueda, and R. Perez Moreira, Catena, 14(1987)189.

[17] M.E. López-Mosquera, M.J. Bande, and S. Seoane, Edafología, 7(2000)73.