Journal of Environmental Quality 31:532-538 (2002)
© 2002 American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America
TECHNICAL REPORT
Ecological Risk Assessment
Industrial Impact on Marsh Soils at the Bahia Blanca Ria, Argentina
Maria Luisa Andrade*,a,
Maria Luisa Reyzabalb,
Purificacion Marceta and
Maria Jose Monteroa
a Dep. of Vegetable Biology and Soil Sciences, Ap. 874, 36200 Vigo, Spain
b Dep. of Agronomy, Universidad Nacional del Sur, Bahía Blanca, Argentina
* Corresponding author (mandrade{at}uvigo.es)
Received for publication August 1, 2000.
 |
ABSTRACT
|
|---|
The Bahía Blanca Estuary is located in southern Buenos Aires province, Argentina. The area is linked to a petrochemical industrial complex, whose raw materials and final products contaminate the surrounding areas via atmospheric pollution and effluents, which are dumped in the estuary waters. To establish the effects of the industrial waste disposal on the nearest coastal soils, 17 samples were taken at different distances from the loading dock and the outfall pipes of the industrial complex. Later, the physicochemical characteristics of the soil samples, their hydrocarbon contents, sulfides, sulfates, Zn, Cu, and Pb were analyzed and a comparison was made to control samples, which were not affected by the industrial outfall. Hydrocarbons, Zn, Cu, and Pb contents were found at levels that modified the physical and chemical characteristics of the soils. The resistance to penetration shows that the thinner the film of water that surrounds the particles or aggregates, the smaller the migration of organic micelle, which settle on the surface of the contact material. This is demonstrated by the degree of cohesion reached by the particles and the strong influence on the index of hydrophobicity. The high porosity shows that the continuity of the porous space of the soil matrix is impeded by the presence of pollutants, which generate areas that are highly limiting to water flow. The oxidation–reduction potential and the low concentrations of soluble forms of Cu and Pb compared with their concentrations precipitated as sulfides confirm the action of the pollutants.
|
INTRODUCTION
|
|---|
Bahía Blanca is a mesotidal estuary located in southern Buenos Aires province, Argentina. A system of northwest–southwest channels separated by islands, low-lying wide marshes, and tidal flats are the principal morphological features. A dense network of minor tidal channels and creeks extensively covers the tidal flats (Aliotta and Perillo, 1990; Gómez and Perillo, 1995).
The Bahía Blanca estuary port system is the most important in the country. Puerto Galvan is located on the northern coast and linked to a petrochemical industrial complex, whose hydrocarbon raw materials and final products contaminate the surrounding areas via atmospheric pollutants and effluents, which have been dumped in the estuary for almost 30 years. The industrial waste that reaches the sea through atmospheric precipitation and the introduction of urban waste are often responsible for the entry of heavy metals into the marine environment and their incorporation into the soils and sediments (Förtsner, 1989; Giordano et al., 1992; Hornung et al., 1989).
Tidal marsh soils are often characterized by low bulk densities, high organic matter content, and high sulfur content. The organic matter accumulated by superficial deposition of marsh grass detritus and the effluents is very important to the fate of trace metals (Griffin and Rabenhorst, 1989). The oxidation status of soils and sediments affects the distribution of some trace metals between bound, unavailable forms and soluble and available forms (Gambrell and Patrick, 1989; Gambrell et al., 1991).
The combination of anaerobic conditions and high organic matter content makes the salt marsh environment ideal for bacterial reduction of sulfate to sulfide (Pons and Van Breemen, 1982). This process of sulfidization plays an important role in the development of marsh sediments and in the control of heavy metal solubility.
This paper reports the influence of industrial pollution on the properties of soils in an estuarine environment. The objectives of this study are to determine the effect of hydrocarbons and waste dumping on the physical properties of soils, the heavy metal content and the relationship of the oxidation–reduction potential to the solubility of heavy metals, and the S-pyrite and sulfate contents.
|
MATERIALS AND METHODS
|
|---|
The sampling site extended 1700 m from the loading dock to the contaminant outfalls. Seventeen soil samples were taken (Thionic Fluvisols), one every 100 m (Fig. 1)
. The sampling sites were chosen to obtain a representative measure of the pollution conditions in the marsh.
Topsoil (0–30 cm) samples were collected using an Eijkelkamp (Giesbeek, the Netherlands) sampler and stored in polyethylene bags in darkness at 4°C. Six samples of each site were taken at each sampling point. Three samples from each site were air-dried, passed through a 2-mm sieve, mixed, and homogenized in the laboratory. Subsequently, three subsamples from each aggregate sample were taken.
In addition, nine undisturbed soil samples from the topsoil (0–30 cm) were collected from each site. Six of them were taken in steel cylinders and reserved for physical observations. The remaining three were collected using metal samplers (12 x 14 x 30 cm in height) for micromorphological observations. All samples were taken on the same day and transported in plastic boxes.
For micromorphological analysis, three thin vertical sections were made of each sampler, following the routine procedure of Murphy (1986), under a petrographic microscope. The terminology and concepts of Bullock et al. (1985) were used for the description and study of the thin sections.
The penetration resistance was determined in situ, using a cone-shaped probe, which is driven into the soil through consecutive falls of a given force. The resistance is recorded as the force necessary for the probe penetrate depths of 5, 10, 15, 20, 25, 30, 35, 40, 45, and 50 cm (Hartge and Bohne, 1985).
Redox potential (Eh) was determined in situ using a platinum electrode and a calomel reference electrode. The Eh was measured based on a standard hydrogen reference electrode.
Intrinsic permeability was measured using an air-entry permeameter placed on the top of steel cylinders with undisturbed soil samples (Bradford, 1986; Corey, 1986). Hydrophobicity was measured in undisturbed soils using the water drop penetration time method as described in Letey (1968)(1969) The <2-mm fraction was used for determining selected soil properties. The pH was measured by potentiometry, organic matter by the Walkley and Black (1934) method, and particle size distribution using the Boyoucos hydrometer method as described in Day (1965). Porosity was measured using the methods as described in Bradford (1986) and Corey (1986) and the salts content was evaluated by the method described in Page et al. (1982).
S-pyrite was determined starting from the difference among the iron extracted with hydrochloric acid and nitric acid (Tabatabai, 1982) and the adsorbed S–SO-24 was extracted with a solution that contains 0.1 M LiCl2 and P (500 mg L-1) (Tabatabai, 1982). Both were analyzed by turbidimetry with barium acetate.
The available content of Cu, Pb, and Zn was extracted by the DTPA method developed by Lindsay and Norwell (1978). The total concentrations were extracted by means of an acid digestion (nitric, hydrochloric, and hydrofluoric) in Teflon reactors in a microwave oven. This process was carried out in two phases of heating, plus one of cooling in between, which allowed a greater extraction than with only one phase. This two-phase procedure proved to be more successful, as indicated by Nakashima et al. (1988) and Marcet et al. (1997). The analysis of Cu, Pb, and Zn was carried out by an atomic flame absorption spectrophotometer.
The efficiency of the procedure of extraction and analysis was controlled by analyzing international standard reference material of sediment and soil from estuaries such as MESS-1 (10 repetitions for each element) from the Marine Analytical Chemistry Standards Program of the Canadian National Research Council (Ottawa, Canada), using the procedure as described in Marcet et al. (1997) and Andrade et al. (1997). MESS-1 is an estuarine sediment from the Gulf of San Lorenzo (Canada) characterized by a low average metal concentration, making the sediments an appropriate tool for the analytical control of the samples from the Bahía Blanca marsh. The confidence intervals of the obtained values were similar to those certified by the Canadian National Research Council (Table 1).
View this table:
[in this window]
[in a new window]
|
Table 1. Efficiency control of the metal extraction in the reference material (MESS 1). Data are the mean and standard deviation of 10 replicates. Precision is expressed as 95% tolerance limits.
|
|
Petroleum hydrocarbon content was determined by the procedure ISO/TR 11046(E) (1994), proposed by RIZA (1980, 1987) and Pennings (1987). The soil samples, obtained in the field and stored in darkness at a 4°C, were chemically dried with a hygroscopic salt, crushed, and extracted with 1,1,2-trichloro-1,2,2-trifluoroethane, adding magnesium silicate and shaking to remove the polar compounds. For quantitative determination, the extract was added to hexane and analyzed by gas chromatography. For detection, a flame ionization detector was used. The content of the sample was calculated using an external standard prepared with a mixture of n-alkane standard in accordance with ISO 3924.
The results obtained in all the analyses were the average of these three calculations and were expressed on a dry material basis. The data were statistically analyzed and the least significant differences (LSD) at the 5% level used to separate means. The relationship between the different variables was evaluated by a simple correlation and regression analysis.
|
RESULTS AND DISCUSSION
|
|---|
The observation of the thin sections from the control and the samples with lesser hydrocarbon content shows that these soils have a well-developed granular microstructure, consisting of coarse sand-sized round aggregates. Some of these had a vesicular intraaggregate microstructure, with 0.10- to 0.25-µm-diameter vesicles.
Based on observations in situ and the micromorphological study, the samples with greater hydrocarbon content (Samples 3, 5, and 6) show irregular crusts whose thickness varies between 2 and 30 cm, formed by aggregates of thin material collapsed and agglutinated with the components of the effluents, with vesicular microstructure, characterized by low porosity (0.2–0.6 m3 m-3). The crust is much more compact that the control soil and the soils with lesser hydrocarbon content. This crust was partly broken by vertical fissures every 0.5 to 1 cm on average. In places with elevated contents of Cu, S, and hydrocarbons the aggregation is high and the predominating color is dark, and a black crust with a high resistance to penetration (Tables 2 and 3; Sample 3) appears. There are also greenish crusts with a lesser aggregation, and a superficial dark crust with the same characteristics, lessening the aggregation of cohesion and resistance to penetration. The areas that have no crust formed by hydrocarbons show resistance to penetration values that are even smaller, while in the areas with superficial crusts the values are uneven. Depending on the degree of hydrocarbon decomposition, or on the time it was deposited, the crusts appears at different depths modifying the properties of the soil.
View this table:
[in this window]
[in a new window]
|
Table 2. Effect of the pollutant waste material on the soil physical properties. Values followed by different letters in each column differ significantly with p < 0.05.
|
|
View this table:
[in this window]
[in a new window]
|
Table 3. Effect of the pollutant waste material on the different chemical characteristics of the soils. Values followed by different letters in each column differ significantly with p < 0.05.
|
|
The observation of the thin sections showed that one of the most significant effects of the polluting waste on the affected soils is the great aggregation and agglutination observed among the particles, with a loss of macroporosity and an increase of the resistance to penetration (Table 2). The continuous use of hydrocarbons for almost 30 years has caused a heterogeneous hardening of the surface and/or a hard layer, which can be found at random up and down the coastline. Large patches with a high concentration of sludge with tar-like properties are commonly found where there is dumping of petroleum waste. This sludge has modified completely the properties and characteristics of the coastal soils. A dark contaminated layer appears either on the surface or under a thin clear soil layer.
The moisture front always reaches lower depths than the organic micelle, as it is retained by the soil. Therefore, different effects are produced by the tidal moistening and drainage cycles, which is due to the fact the hydrocarbons react in a very different way if the soil is relatively dry or saturated by water (Fig. 2) , as described by Fine and Yaron (1993), changing the distribution of the size of the pores.
View larger version (12K):
[in this window]
[in a new window]
|
Fig. 2. Variation of hydrophobicity with hydrocarbon content, including regression and correlation coefficient.
|
|
When the hydrocarbons penetrate the soils, the big pores are covered up because of the relocation of the particles. During the moistening process the fine particles, which are covered once again by hydrocarbons, regroup in the bigger pores, thereby reducing the number of big canals.
The blockage together with the fine particles acts as a bridge for the big particles, uniting the matrix of the contaminated soil, which loses freedom of movement for a new reorganization during the following moistening–drainage cycle (Marley and Hoag, 1986). This effect can be seen clearly with the data of resistance to the penetration (Table 2).
Based on micromorphological observations, the pore size distribution of Samples 3, 5, and 6 showed substantially more small pores than the others samples. This has been described by Brandt (1969), who indicates that when the soil is dry, the waste material penetrates deeply into it, contributing to the stickiness and coagulation of different-sized particles and uniting particles of a smaller diameter. The hydrocarbons settle on the relatively dry soils because they contain a thin water film surrounding the aggregates, which inhibits the migration of the hydrocarbons, giving rise to a superficial stickiness (Schwillw, 1984).
As the content and the thickness of the water film surrounding the aggregates increase, the hydrocarbons migrate toward the meniscus of water, resulting in a complex phenomenon where diverse physical and physicochemical factors intervene. These are the vapor pressure, the magnitude of net charge of the pollutant, and the angle of contact between the hydrocarbons and solid surface.
The observations in situ and the micromorphologic analyses show that a strongly aggregated layer appears a few centimeters under the surface of the most clear soils, whose thickness varies between a few millimeters to 20 to 30 cm. This crust modifies the properties of the soils. Therefore, the resistance to penetration (Table 2) has great spatial variability because of the heterogeneity of the crust formed, which is due to the different aggregation between the particles (Chen, 1992).
The influence of material waste dumping can be seen clearly, since in normal conditions the soils of the area would have no cohesion. As the sandy soil exhibits neither cohesion nor adhesion to any content of humidity there is no resistance to penetration for the ordinary porosities of this coastal soils according to Cosentino (1998).
The contaminated soils show properties that indicate the increased repellence soil water (hydrophobicity or resistance to water penetration) caused by the incorporation of pollutants. This resistance is measured by the time of penetration of the drop of water (Letey, 1969). This characterizes the stability of the repellence of soil water. The longer the drop of water remains on the surface without losing its spherical shape, the greater the repellence of soil water. This occurs in different samples (Table 2; Samples 1, 3, 5, 6, and 10). They show that the quantity of pollutant increases their hydrophobicity, which allows for establishment of a direct relationship between total organic C content and/or hydrocarbons and the time the drop remains on the contaminated surface.
The hydrophobicity of Samples 3, 5, and 6 corresponds with the contents of organic matter and hydrocarbons in them (Fig. 2). This effect is detected, though with lesser intensity in the Samples 1 and 10, while the control shows no sign of hydrophobicity (Table 2). Samples with hydrocarbon contents of more than 10% show a time of penetration that exceeds 2 h, while the time is less in those that have lower concentrations. Hydrocarbon content is significantly (P < 0.05) and positively correlated to hydrophobicity, resistance to penetration, and total content of Pb (Table 3 and Fig. 2–4)
.
View larger version (9K):
[in this window]
[in a new window]
|
Fig. 4. Variation of the total Pb content with hydrocarbon content, including regression and correlation coefficient.
|
|
View larger version (12K):
[in this window]
[in a new window]
|
Fig. 3. Variation of the resistance to penetration with hydrocarbon content, including regression and correlation coefficient.
|
|
The fluids that are not miscible in water and the pollutants adsorbed on particles in suspension that migrate along the outline are trapped in the soil by means of retention (Yaron et al., 1996). This leads to a random distribution of the pollutant in the affected area, which produces great spatial variability in the physical properties, depending on the predominant process.
Based on the observations in situ and in the micromorphological study, Samples 3, 5, and 6 displayed great aggregates or elastic unities with asphalt characteristics. This coincides with low porosity values and high hydrocarbon levels.
The soils affected by effluents crusts appear to be reduced based on the low SO-24 content adsorbed and the high sulfide levels. These soils also show high contents of Zn, Cu, and Pb (Table 3), which have modified the physical and chemical properties of the soils.
The relationship established between the oxidation–reduction potential and the total contents of S-pyrite, Zn, Cu, and Pb (Fig. 5–8)
show that when there is a larger reduction the metal and S-pyrite contents increase because they remain in the soil as precipitated sulfides.
View larger version (9K):
[in this window]
[in a new window]
|
Fig. 5. Variation of the S-pyrite content with redox potential, including regression and correlation coefficient.
|
|
View larger version (10K):
[in this window]
[in a new window]
|
Fig. 8. Variation of the total Cu content with redox potential, including regression and correlation coefficient.
|
|
View larger version (10K):
[in this window]
[in a new window]
|
Fig. 6. Variation of the total Pb content with redox potential, including regression and correlation coefficient.
|
|
View larger version (10K):
[in this window]
[in a new window]
|
Fig. 7. Variation of the total Zn content with redox potential, including regression and correlation coefficient.
|
|
However, the scarce quantity of S–SO-24 and those metals in soluble form shows that when oxidation is produced by the fluctuation of the tide, or desiccation, a great number of these metals will become easily soluble forms, which can affect waters, fauna, and flora, with the risk of entering the trophic chain.
So, the redox potential has a decisive effect on the amount of Pb, Cu, and Zn in insoluble form. Figures 6, 7, and 8 show that the highest concentrations occur under reduced conditions, gradually decreasing as these change to oxidant values. Gambrell et al. (1991) found that soluble heavy metals were hardly affected by the oxidation–reduction potential except at intermediate oxidation–reduction potentials similar to those found in the soils studied in this paper.
The effect of the pollutants on marsh soils was displayed by the resistance to penetration, hydrophobicity, the potential redox, and the low concentrations of Zn, Cu, and Pb in soluble form, against high total contents, precipitated as sulfides (Tables 2 and 3). The effects of the contaminant substances on the soils weaken from 1400 m away from the dumping point. Yet in the first 1300 m the spatial variations are great, appreciating the greater effects in the Samples 3, 5, and 6 (300, 500, and 600 m). Oscillations in pollutant spatial variations are caused because they often penetrate the soil indirectly through tidal oscillations.
Finally, it must be noted that at several points in the area there are very high total amounts of Pb, Zn, Cu, and hydrocarbons (Tables 2 and 3). This may seriously jeopardize the fauna and flora if the acidic conditions allow the total part of these contents to become soluble. It must be highlighted that according to data provided by Fuller and Warrick (1985) the Zn, Cu, and Pb concentrating in the contaminated soils are about 50 to 100 times greater than the content in uncontaminated soils (control). This will have a repercussion, in the near future, on the available amount of heavy metals and consequently the environmental quality of this area.
|
ACKNOWLEDGMENTS
|
|---|
The authors would like to thank Rocío Iglesias Alonso for his help in the laboratory.
|
REFERENCES
|
|---|
- Aliotta, S., and G.M.E. Perillo. 1990. Linea de costa sumergida en el estuario de Bahía Blanca, provincia de Buenos Aires. Rev. Asoc. Geol. Argentina 45:300–305.
- Andrade Couce, M.L., P. Marcet Miramontes, and M.J. Montero Vilariño. 1997. Origin and areal and vertical distribution of Cd and Cr in sediment cores in Vigo Ria (Spain). In R. Prost (ed.) Contaminated soils: 3rd Int. Conf. on the Biogeochemistry of Trace-Elements, Paris. 15–19 May 1995. Data\communic\111.PDF [CD-ROM computer file]. Colloque no. 85. INRA Editions, Paris.
- Bradford, J.M. 1986. Penetrability. p. 463–477. In A. Klute (ed.) Methods of soil analysis. Part 1. Physical and mineralogical methods. 2nd ed. Agron. Monogr. 9. ASA and SSSA, Madison, WI.
- Brandt, G.H. 1969. Water movement in hydrophobic soils. p. 91–115. In Water repellent soils. Univ. of California, Riverside.
- Bullock, P., N. Fedoroff, A. Jogerius, G. Stoops, T. Tursina, and U. Babel. 1985. Handbook for soils thin section description. Waine Res. Publ., Wolverhampton, UK.
- Chen, T. 1992. Understanding the fate of petroleum hydrocarbons in the subsurface environment. J. Chem. Educ. 69:357–359.
- Corey, A.T. 1986. Air permeability. p. 1121–1136. In A. Klute (ed.) Methods of soil analysis. Part 1. Physical and mineralogical methods. 2nd ed. Agron. Monogr. 9. ASA and SSSA, Madison, WI.
- Cosentino, D.J. 1998. Textura. p. 37–57. In M. Conti (ed.) Principios de edafología con énfasis en suelos argentinos. Orientación Gráfica Editora, Buenos Aires.
- Day, P.R. 1965. Particle size analysis. p. 545–567. In C.A. Black (ed.) Methods of soil analysis. Part 1. Agron. Monogr. 9. ASA, Madison. WI.
- Fine, P., and B. Yaron. 1993. Outdoor experiments on venting enhanced volatilization of kerosene components from soils. J. Contam. Hydrol. 12:355–374.
- Förtsner, U. 1989. Contaminated sediments. Lecture Notes on Earth Sci. 21. Springer–Verlag, London.
- Fuller, W.H., and A.W. Warrick. 1985. Soils in waste. Treatment and utilization. Vol. 12. CRC Press, Boca Raton, FL.
- Gambrell, R.P., and W.H. Patrick. 1989. Cu, Zn and Cd availability in a sludge-amended soil under controlled pH and redox potential conditions. p. 89–106. In B. Bar Yosef et al. (ed.) Ecol. Studies 74. Inorganic contaminants in vadose zone. Springer–Verlag, Berlin.
- Gambrell, R.P., J.B. Wiesepape, W.H. Patrick, and M.C. Duff. 1991. The effects of pH, redox and salinity on metal release from a contaminated sediment. Water Air Soil Pollut. 57/58:359–367.
- Giordano, R., L. Musmeci, and M. Ciorolli. 1992. Total contents and sequential extractions of mercury, cadmium and lead in coastal sediments. Mar. Pollut. Bull. 24:350–357.
- Gómez, E.A., and G.M.E. Perillo. 1995. Submarine outcrops underneath shoreface conected sand ridges, outer Bahía Blanca Estuary, Argentina. p. 23–37. In J. Rabassa and M. Salemne (ed.) Quaternary of South America and Antarctic Peninsula. A. Balkema Publ., Rotterdam, the Netherlands.
- Griffin, T.M., and M.C. Rabenhorst. 1989. Process and rates of pedogenesis in some Maryland tidal marsh soils. Soil Sci. Soc. Am. J. 53:862–870.[Abstract/Free Full Text]
- Hartge, K.H., and H. Bohne. 1985. Penetrometer measurements for screening soil physical variability. Soil Tillage Res. 5:343–350.
- Hornung, H., M.D. Krom, and Y. Cohen. 1989. Trace metal distribution in sediments and benthic fauna of Haina Bay, Israel. Estuarine Coastal Shelf Sci. 29:43–56.
- ISO/TR 11046(E). 1994. ISO standard compendium. Environmental soil quality. General aspects. Chemical and physical methods of analysis, biological methods of analysis. ISO, Geneva.
- Letey, J. 1968. Water drop penetration time. p. 6–10. In L.F. De Bano and J. Letey (ed.) Proc. of the Symp. on Water Repellent Soils. 6–10 May 1968. Univ. of California, Riverside.
- Letey, J. 1969. Measurement of contact angle, water drop penetration time and critical surface tension. p. 43–47. In Water repellent soils. Univ. of California, Riverside.
- Lindsay, W.L., and W.A. Norwell. 1978. Development of a DTPA soil test for zinc, iron, manganese and copper. Soil Sci. Soc. Am. J. 42:421–428.
- Marcet Miramontes, P., M.L. Andrade Couce, and M.J. Montero Vilariño. 1997. Efficacité d'une methode de digestion par microondes pour la determination de Fe, Mn, Zn, Cu, Pb, Cr, Al et Cd en sédiments. In R. Prost (ed.) Contaminated soils: 3rd Int. Conf. on the Biogeochemistry of Trace-Elements, Paris. 15–19 May 1995. Data\communic\055.PDF [CD-ROM computer file]. Colloque no. 85. INRA Editions, Paris.
- Marley, M.C., and G.E. Hoag. 1986. Induced soil venting for recovery restoration of gasoline hydrocarbons in vadose zone. p. 473–503. In Water Well Assoc. Am. Pot. Inst., Conf. on Petroleum Hydrocarbons and Organic Chemicals in Ground Water. Natl. Water Well Assoc., Houston, TX.
- Murphy, C.P. 1986. Thin section preparation of soil and sediments. AB Academic Publ., Berkhamsted, UK.
- Nakashima, S., R.E. Sturgee, S.E. Willie, and S. Bermon. 1988. Acid digestion of marine samples for trace element analysis using microwave heating. Analyst 113:159–163.[Medline]
- Page, A.L., R.H. Miller, and D.R. Keeney (ed.) 1982. Methods of soil analysis. Part 2. Chemical and microbiological properties. 2nd ed. Agron. Monogr. 9. ASA and SSSA, Madison, WI.
- Pennings, M. 1987. The influence of column choice and method of integration when determining mineral oil gas chromatographycally. ICW Note 1824. The Winand Staring Centre, Wageningen, the Netherlands.
- Pons, L.J., and N. Van Breemen. 1982. Factors influencing the formation of potential acidity in tidal swamps. p. 35–37. In H. Dost and N. Van Breemen (ed.) Proc. of the Bangkok Symp. on Acid Sulphate Soils. 18–24 Jan. 1982. ILRI, the Netherlands.
- RIZA. 1980. Quantification of the mineral oil content in extracts from environmental samples: Comparison of various standardized methods. Note 88.040x. RIZA, Lelystad, the Netherlands.
- RIZA. 1987. Quantitative determination of mineral oil in watersoil. Note 87.062x. RIZA, Lelystad, the Netherlands.
- Schwillw, F. 1984. Migration of organic fluids inmiscibles with water in the unsaturated zone. p. 27–48. In B. Yaron et al. (ed.) Pollutants in porous media. Springer, Berlin.
- Tabatabai, M.A. 1982. Analytical methods for sulphur. Proc. Conf. Int. Sulfur 82:1.
- Walkley, A., and I.A. Black. 1934. An examination of Degtjareff method for determining soil organic matter and a proposed modification of the chromic titration method. Soil Sci. 34:29–38.
- Yaron, B., R. Calvet, and R. Prost. 1996. Soil pollution. Processes and dynamics. Springer–Verlag, Berlin.
This article has been cited by other articles:
|
|
|
|
 
M. L. Andrade, E. F. Covelo, F. A. Vega, and P. Marcet
Effect of the Prestige Oil Spill on Salt Marsh Soils on the Coast of Galicia (Northwestern Spain)
J. Environ. Qual.,
November 1, 2004;
33(6):
2103 - 2110.
[Abstract]
[Full Text]
[PDF]
|
|
|
TOP
ABSTRACT
INTRODUCTION
