Abstract

The main objective of this study was to determine the effect of irrigation using three different types of waters, namely treated wastewater through membrane bioreactor (MBR) system, treated wastewater via intermittently decanted aerated lagoon (IDAL) process and tap water (TW) on soil pH and electrical conductivity (EC) under kikuyu grass production. No fertiliser was added during the study period (one year). Irrigation waters and water and soil samples extracted from different soil depths were analysed in laboratory. Considerable changes occurred in soil characteristics over the study period under various treatments. Soil pH increased more than 1 unit under irrigation with treated wastewater produced by the IDAL system while soil irrigated with treated wastewater from the MBR treatment system showed little change and TW irrigated soil evidenced a slight decrease when compared to pH at the beginning of the study. There was also a remarkable increase recorded for EC1:5 of top soils irrigated with treated wastewaters compared to the initial EC of the soil. The results from this study highlighted the benefits of irrigation with treated wastewater from the MBR system due to its lower cost of treatment compared to the IDAL process while providing additional nutrients such as nitrogen and phosphorus from the wastewater for plant growth.

INTRODUCTION

Treated wastewater is a reliable water source for reuse in various areas to confront water shortages (Pedrero et al. 2010). Using recycled water for irrigation can be beneficial in terms of preventing natural water resources contamination, saving water resources, saving wastewater treatment and recovering nutrients (Angelakis & Bontoux 2001; Rahman et al. 2016). The effect of treated and untreated wastewaters in different agricultural systems has been reported by many researchers around the world (Pettygrove & Asano 1984; Sheikh et al. 1987; Chakrabarti 1995; Gori et al. 2000; Manios et al. 2006; Castro et al. 2009; Costa et al. 2011; Pedrero et al. 2012; Minhas & Yadav 2015). Proper management of wastewater irrigation and regularly monitoring the soil parameters can ensure safe and successful usage of recycled water for irrigation over long periods (Qian & Mecham 2005; Rattan et al. 2005; Rusan et al. 2007; Xu et al. 2010; Rahman et al. 2015). Recycled water can be listed in different categories based on its chemical characteristics as a result of the level of treatments that wastewater goes through. In this study the effect of irrigation with two types of treated wastewaters produced under a membrane bioreactor (MBR) treatment process and an intermittently decanted aerated lagoon (IDAL) system on soil pH and electrical conductivity (EC) under kikuyu grass production was investigated. Tap water was used as the control water. Mean values of quality parameters for irrigation waters are considered. No fertilizer was used during the study.

Soil pH is considered as one of the most important parameters that can be affected when using recycled water for irrigation. Plant growth is affected by soil pH in different ways. Soil pH can impact nitrification, denitrification and glucose mineralization in the soil atmosphere (Tabatabai & Olson 1985). It has been reported that nitrogen mineralisation can be processed efficiently in the pH range of 5.5–7. Soil pH values below 5.5 can result in faster leaching of plant nutrients compared to soils with pH values of 5.5–7.0 (Ward 2015). On the other hand, soil pH values higher than 7 can limit the availability of some plant nutrients, causing a reduction in plant production. For example, phosphorus can be available to the plant mostly at a pH value between 6 and 7. Similarly, micro-nutrients such as iron, manganese, zinc, copper and cobalt are less available to the plant at a pH above 7 (Seelig 2000).

An inconsistent soil pH has previously been reported when different types of wastewater were used for irrigation. Those who reported the increase in soil pH attributed this to factors such as high pH values of effluent and availability of high levels of cations such as sodium, calcium and magnesium in irrigation waters (Schipper et al. 1996; Sparling et al. 2006; Gwenzi & Munondo 2008). On the other hand, other researchers reported a soil pH decrease as a result of wastewater application (Mohammad & Mazahreh 2003; Rattan et al. 2005) and this decrease was explained as a result of either acidic characteristics of sewage effluents or the process of nitrification in the presence of high amount of ammonium in the wastewater, which resulted in providing hydrogen ions in the soil. No significant effect on soil pH when irrigated with wastewater was recorded by Khan et al. (2008).

Another issue associated with the use of wastewater for irrigation is the addition of large amounts of salts to the soil because treated wastewater typically contains 200–300 mg/L of total dissolved solids (Muyen et al. 2011). Soils with saturated extract electrical conductivity (ECSE) over 4 dS/m, generally, are defined as saline soils. However, different plants depending on their salinity tolerance can be affected at half and twice this value of ECSE (Bernstein 1975).

Kikuyu grass (Pennisetum clandestinum) used in this study is known to have a moderate salinity tolerance up to 4 dS/m (Havilah et al. 2005) and can also grow well in soil with moderate acidity of pH 5–7 (Dickenson et al. 2004; Clark 2007). Kikuyu grass is a C4 tropical grass and is widely used in sports fields, as well as pastures, public areas and golf course fairways (Brede 2000; Fulkerson 2007). A large number of studies have been carried out in terms of kikuyu grass production with the application of fertilizer (Awad et al. 1976; Hacker & Evans 1992; Fulkerson et al. 1999; Gherbin et al. 2007; Botha et al. 2008).

The specific objectives of this study were (1) to investigate the effect of different types of treated wastewaters with significant differences among their main nutrients such as nitrogen and phosphorus on soil pH and (2) the impact of moderate level of salinity in treated wastewater in the presence of different levels of nutrients and salts on soil EC at different soil depth.

MATERIALS AND METHODS

Experimental design

Experimental set-up has been explained thoroughly in Shahrivar et al. (2019). Briefly, three identical stainless steel columns were filled with the pre-prepared soil of loamy sand texture. Initial physicochemical properties of the soil are given in Table 1.

Table 1

Selected physicochemical properties of the soil

Soil propertiesValue
Sand (%) 88.1 
Silt (%) 6.0 
Clay (%) 5.9 
Texture class Loamy sand 
Bulk density (kg/m31,340 
pH1:5 5.5 
EC1:5 (dS/m) 0.04 
Soil propertiesValue
Sand (%) 88.1 
Silt (%) 6.0 
Clay (%) 5.9 
Texture class Loamy sand 
Bulk density (kg/m31,340 
pH1:5 5.5 
EC1:5 (dS/m) 0.04 

The schematic set-up of the columns is illustrated in Figure 1. As shown in Figure 1, the columns regarding their size (450 mm diameter and 600 mm height) are considered as bigger columns compare to the other lab-scale lysimeters used for soil–plant studies. The GS3 sensors are able to measure bulk EC, volumetric water content and temperature of the soil. Data from the sensors were collected via the connection of GS3 sensors to a data logger.

Figure 1

Schematic set-up of the columns (Shahrivar et al. 2019).

Figure 1

Schematic set-up of the columns (Shahrivar et al. 2019).

The columns were equipped with three water extractors adjacent to their respective GS3 sensors in 100, 300 and 500 mm of the columns (Figure 1). Water samples were extracted from different soil depths using these samplers in conjunction with the suction pumps. Finally, kikuyu grass from a nursery was laid on top of the columns and irrigated with the respective irrigation waters to ensure the grass survived and established.

Irrigation waters

Treated wastewaters used for this study were collected from Pennant Hills Golf Club's wastewater treatment plant and Richmond Sewage Treatment Plant, both located in Sydney where the former uses an MBR system and the latter one implements an IDAL system system for wastewater treatment. MBR is a secondary treatment of the wastewater process that combines a membrane process with a biological process (Judd 2010); an IDAL system is an advanced treatment of wastewater for removing nutrients, particularly nitrogen. In this system, all processes including sedimentation, biological treatment and clarification take place in one reactor (Ngo et al. 2007). Tap water (TW), which was provided by the Sydney Water Corporation to the Sydney Metropolitan area, was used at the control water in the study.

Both treated wastewaters used in the study provide disinfection stages at the end of their treatment processes to remove microorganisms, including bacteria, viruses and parasites like Giardia and Cryptosporidium, which are harmful to public health. Chlorine is a powerful disinfectant used in both wastewater treatment plants for this purpose.

Irrigation scheduling

Data from GS3 sensors in conjunction with collected data from the weather station installed at the study area were used to identify the interval of irrigation and the amount of water to be applied to the columns. Due to the loamy sand having a field capacity of 19% and an available water content of 9%, the soil moisture content was maintained at over 15% to avoid any water stress for the grass. Figure 2 illustrates the irrigation scheduling and climatic conditions during the study. Daily evapotranspiration (ET) for kikuyu grass was calculated as (Allen et al. 1998): 
formula
(1)
where ET is daily evapotranspiration for kikuyu grass (mm/day), KC is kikuyu grass monthly crop coefficient (Connellan 2013) and ET0 is reference crop evapotranspiration (mm/day) from weather station.
Figure 2

Irrigation scheduling and climatic conditions.

Figure 2

Irrigation scheduling and climatic conditions.

Soil and water analysis

EC and pH of irrigation waters were analysed using respective meters. Total nitrogen (TN) and total phosphorus (TP) were analysed using the persulfate digestion method. Persulfate digestion method is a very effective and practical way for simultaneous analysis of TN and TP in water samples. Samples after digestion were analysed using the discrete analyser (Gallery, Thermoscientific) in the form of NOX–N (NO2 and NO3) and PO43−, respectively (Apha 1995). Main cations (Ca, K, Mg and Na) were measured by inductively coupled plasma–optical emission spectrometry (ICP–OES, Agilent Technology 700 series). Pore waters extracted monthly from three different depths of the columns and were analysed for pH, EC and other parameters similar to irrigation waters. At the end of the study period, the columns were dismantled and soil samples from different depths were collected. After removing all the roots from these samples, they were analysed for different parameters, including pH (pH1:5) and EC (EC1:5), using soil analysis methods proposed by Rayment & Lyons (2011).

RESULTS AND DISCUSSIONS

Characteristics of irrigation waters

Table 2 summarises the mean values of irrigation water quality parameters. It can be seen that irrigation waters have different characteristics based on the treatments they have gone through. MBR-treated wastewater has high concentrations of nitrogen and phosphorus compared to other irrigation waters. By comparison, both treated wastewaters have considerably higher values of sodium than TW and that causes higher levels of sodium adsorption ratio (SAR) in treated wastewaters. The SAR is considered a monitoring factor for determining the sodium hazard associated with an irrigation water application (Lesch & Suarez 2009). It is defined as the ratio between sodium and two other cations in the irrigation water (calcium and magnesium) and is calculated as: 
formula
(2)
Table 2

Mean values of selected parameters of irrigation waters

ParametersMBRIDALTW
pH 7.25 ± 0.41 7.52 ± 0.35 7.25 ± 0.46 
EC25̊C (dS/m) 0.99 ± 0.18 0.93 ± 0.073 0.26 ± 0.026 
TN (mg/L) 15.33 ± 3.28 0.90 ± 0.32 0.58 ± 0.33 
TP (mg/L) 5.55 ± 2.10 1.31 ± 0.75 0.48 ± 0.44 
Ca2+ (mg/L) 29.59 ± 5.51 16.10 ± 1.70 20.33 ± 4.61 
K+ (mg/L) 25.69 ± 7.28 28.58 ± 8.14 7.74 ± 5.42 
Mg2+ (mg/L) 11.57 ± 3.39 26.04 ± 4.62 7.30 ± 2.57 
Na+ (mg/L) 143.37 ± 31.23 113.68 ± 25.57 18.87 ± 5.51 
SAR 5.67 ± 0.21 4.08 ± 0.62 0.91 ± 0.15 
ParametersMBRIDALTW
pH 7.25 ± 0.41 7.52 ± 0.35 7.25 ± 0.46 
EC25̊C (dS/m) 0.99 ± 0.18 0.93 ± 0.073 0.26 ± 0.026 
TN (mg/L) 15.33 ± 3.28 0.90 ± 0.32 0.58 ± 0.33 
TP (mg/L) 5.55 ± 2.10 1.31 ± 0.75 0.48 ± 0.44 
Ca2+ (mg/L) 29.59 ± 5.51 16.10 ± 1.70 20.33 ± 4.61 
K+ (mg/L) 25.69 ± 7.28 28.58 ± 8.14 7.74 ± 5.42 
Mg2+ (mg/L) 11.57 ± 3.39 26.04 ± 4.62 7.30 ± 2.57 
Na+ (mg/L) 143.37 ± 31.23 113.68 ± 25.57 18.87 ± 5.51 
SAR 5.67 ± 0.21 4.08 ± 0.62 0.91 ± 0.15 

The concentrations of Na+, Ca+ and Mg+ in Equation (2) are expressed in milliequivalent per litre (mEq/L). Irrigation waters with high SAR levels can cause high levels of sodium accumulation in the soil over time, which can adversely affect soil infiltration and also lead to soil crusting, poor aeration and poor plant production (Lesch & Suarez 2009).

Comparison of the EC and SAR values listed for the irrigation waters in Table 2 with irrigation water quality categorised by Ayers & Westcot (1985) indicates that the soil sodification risk for all three types of irrigation waters in the current study is considered as slight to moderate.

Soil-water pH

Extracted water pH from different depths of the soil varied seasonally from column to column. Figure 3 shows seasonal pH values from 10 (Figure 3(a)), 30 (Figure 3(b)) and 50 cm (Figure 3(c)) depths of the soils irrigated with different types of irrigation waters. As it can be seen from the graphs, the pH in soil irrigated with treated wastewater produced by IDAL remained higher than the two other irrigation waters with values over pH 7 in 10 cm depth of the soil throughout the study.

Figure 3

Seasonal variation in soil-water pH extracted from (a) 10 cm, (b) 30 cm and (c) 50 cm depth of the columns.

Figure 3

Seasonal variation in soil-water pH extracted from (a) 10 cm, (b) 30 cm and (c) 50 cm depth of the columns.

Considering that the highest concentration of grass root is in the top soil, variation in soil characteristics in this area can important in relation to the impact on grass growth and production. As mentioned before, kikuyu grass is known to grow well at the optimum pH 5–7 (Dickenson et al. 2004; Clark 2007).

Soil-water EC

Similar to pH, extracted water EC varied seasonally from depth to depth among the treatments. The seasonal EC values from 10, 30 and 50 cm depth of the soils irrigated with different types of irrigation waters are illustrated in Figure 4. It is obvious that soils irrigated with two types of treated wastewaters have high levels of EC throughout the study time in different depths of the columns compared to the soil irrigated with TW.

Figure 4

Seasonal variation in soil-water EC extracted from (a) 10 cm, (b) 30 cm and (c) 50 cm depth of the columns.

Figure 4

Seasonal variation in soil-water EC extracted from (a) 10 cm, (b) 30 cm and (c) 50 cm depth of the columns.

Soil pH and EC (pH1:5 and EC1:5)

At the end of the study, soil samples were collected from various depths of the columns. Analysis of soil samples showed similar results compared to soil-water analysis during the study in terms of pH and EC. Figure 5 shows the change of soil pH and EC from different depths of the columns.

Figure 5

(a) Soil pH (pH1:5) and (b) EC (EC1:5) in different depths of soil irrigated with different irrigation waters.

Figure 5

(a) Soil pH (pH1:5) and (b) EC (EC1:5) in different depths of soil irrigated with different irrigation waters.

These parameters of soil and their effect on kikuyu grass production have been comprehensively discussed in Shahrivar et al. (2019). In brief, a high concentration of cations in conjunction with a low level of nitrogen may have led to higher pH values of soil irrigated with IDAL treated wastewater. This high value of pH can limit the kikuyu grass growth, which is known to grow optimally at pH 5–7. The results were short term in duration; however, they can adversely affect the plant growth during a period when these undesirable conditions are present.

CONCLUSIONS

Soils irrigated with treated wastewaters resulted in higher values of EC compared to the control, particularly due to their high concentration of sodium. Although these increases can be short term in duration, high levels of EC can affect the plant growth under deficient nutrient conditions.

Irrigation with treated wastewater produced by the IDAL system resulted in higher values of soil pH at different depths. The value of pH increased over a relatively short time period suggesting that the plant growth may be affected if the system is used over a longer period. The results of the current study have shown that the wastewater produced by the IDAL system costs more and, due to the lack of valuable nutrients and higher values of EC, was not ideal for irrigation of kikuyu grass.

Results of this study indicated that treated wastewater obtained from the MBR system can be a more suitable source of irrigation water for urban areas because it supplied the grass with a constant and low dosage of valuable nutrients. This has several benefits, such as savings in the cost of treatment, recovery of nutrients from wastewater and prevention of pollutants being discharged into urban waterways. However, disinfection of wastewater to remove the harmful bacteria, viruses and parasites in wastewater treatment plants is crucial to ensure that there is no risk to public health. Furthermore, by regular monitoring of soil parameters and proper management of irrigation it would be possible to use the treated wastewaters for irrigation in a safe and successful way.

ACKNOWLEDGEMENTS

The authors wish to acknowledge the Pennant Hills Golf Club operators, in particular Kurt Dahl and Richard Kirkby of Permeate Partners Pty for providing access to collect MBR treated wastewater. The authors are also grateful to Roger Attwater and Lyn Anderson for their assistance in collecting IDAL treated wastewater. Contributions from environmental engineering lab staff at the Penrith campus of Western Sydney University and Louise Prouteau, an internship student of ENSCR, France, are gratefully acknowledged.

REFERENCES

REFERENCES
Allen
R. G.
,
Pereira
L. S.
,
Raes
D.
&
Smith
M.
1998
Guidelines for computing crop water requirements
.
Irrigation and Drainage Paper
56
,
300
.
Angelakis
A. N.
&
Bontoux
L.
2001
Wastewater reclamation and reuse in Eureau countries
.
Water Policy
3
,
47
59
.
Apha
A.
1995
WPCF, Standard Methods for the Examination of Water and Wastewater
.
American Public Health Association
,
Washington, DC
.
Ayers
R. S.
&
Westcot
D. W.
1985
Water Quality for Agriculture
.
Food and Agriculture Organization of the United Nations
,
Rome
.
Bernstein
L.
1975
Effects of salinity and sodicity on plant growth
.
Annual Review of Phytopathology
13
,
295
312
.
Botha
P. R.
,
Meeske
R.
&
Snyman
H. A.
2008
Kikuyu over-sown with ryegrass and clover: grazing capacity, milk production and milk composition
.
African Journal of Range & Forage Science
25
,
103
110
.
Brede
D.
2000
Turfgrass Maintenance Reduction Handbook: Sports, Lawns, and Golf
.
John Wiley & Sons
,
Hoboken, NJ, USA
.
Connellan
G.
2013
Water use Efficiency for Irrigated Turf and Landscape
.
CSIRO Publishing
,
Clayton, VIC, Australia
.
Costa
M.
,
Beltrao
J.
,
De Brito
J. C.
&
Guerrero
C.
2011
Turfgrass plant quality response to different water regimes
.
WSEAS Transactions on Environment and Development
7
,
167
176
.
Dickenson
E. B.
,
Hyam
G. F. S.
,
Breytenbach
W. A. S.
,
Metcalf
H. D.
,
Basson
W. D.
,
Williams
F. R.
,
Scheepers
L. J.
,
Plint
A. P.
,
Smith
H. R. H.
&
Smith
P. J.
2004
Kynoch Pasture Handbook 1st English Edition
.
Paarl Print. Cape town
,
South Africa
.
Fulkerson
B.
2007
Kikuyu grass. Available from: http://futuredairy.com.au/wp content/uploads/2016/02/TechNoteKikuyu.pdf. Future Dairy, Brownlow Hill, NSW, Australia
.
Fulkerson
W. J.
,
Slack
K.
&
Havilah
E.
1999
The effect of defoliation interval and height on growth and herbage quality of kikuyu grass (Pennisetum clandestinum)
.
Tropical Grasslands
33
,
138
145
.
Gherbin
P.
,
De Franchi
A. S.
,
Monteleone
M.
&
Rivelli
A. R.
2007
Adaptability and productivity of some warm-season pasture species in a Mediterranean environment
.
Grass and Forage Science
62
,
78
86
.
Gori
R.
,
Ferrini
F.
,
Nicese
F. P.
&
Lubello
C.
2000
Effect of reclaimed wastewater on the growth and nutrient content of three landscape shrubs
.
Journal of Environmental Horticulture
18
,
108
114
.
Havilah
E.
,
Warren
H.
,
Lawrie
R.
,
Senn
A.
&
Milham
P.
2005
Fertilisers for Pastures
.
New South Wales Department of Primary Industries
,
Sydney
.
Judd
S.
2010
The MBR Book: Principles and Applications of Membrane Bioreactors for Water and Wastewater Treatment
.
Elsevier
,
Oxford, UK
.
Khan
S.
,
Cao
Q.
,
Zheng
Y. M.
,
Huang
Y. Z.
&
Zhu
Y. G.
2008
Health risks of heavy metals in contaminated soils and food crops irrigated with wastewater in Beijing, China
.
Environmental Pollution
152
,
686
692
.
Lesch
S. M.
&
Suarez
D. L.
2009
A Short Note on Calculating the Adjusted SAR Index
.
Manios
T.
,
Papagrigoriou
I.
,
Daskalakis
G.
,
Sabathianakis
I.
,
Terzakis
S.
,
Maniadakis
K.
&
Markakis
G.
2006
Evaluation of primary and secondary treated and disinfected wastewater irrigation of tomato and cucumber plants under greenhouse conditions, regarding growth and safety considerations
.
Water Environment Research
78
,
797
804
.
Mohammad
M. J.
&
Mazahreh
N.
2003
Changes in soil fertility parameters in response to irrigation of forage crops with secondary treated wastewater
.
Communications in Soil Science and Plant Analysis
34
,
1281
1294
.
Muyen
Z.
,
Moore
G. A.
&
Wrigley
R. J.
2011
Soil salinity and sodicity effects of wastewater irrigation in South East Australia
.
Agricultural Water Management
99
,
33
41
.
Ngo
H.
,
Vigneswaran
S.
&
Sundaravadivel
M.
2007
Advanced treatment technologies for recycle/reuse of domestic wastewater
.
Wastewater Recycle Reuse and Reclamation
1
,
77
98
.
Pedrero
F.
,
Kalavrouziotis
I.
,
Alarcón
J. J.
,
Koukoulakis
P.
&
Asano
T.
2010
Use of treated municipal wastewater in irrigated agriculture – review of some practices in Spain and Greece
.
Agricultural Water Management
97
,
1233
1241
.
Pettygrove
G. S.
&
Asano
T.
1984
Irrigation with Reclaimed Municipal Wastewater. A Guidance Manual
.
California State Water Resources Control Board
,
Davis, CA, USA
.
Rahman
M. M.
,
Hagare
D.
,
Maheshwari
B.
&
Dillon
P.
2015
Impacts of prolonged drought on salt accumulation in the root zone due to recycled water irrigation
.
Water Air & Soil Pollution
226
,
90
.
Rahman
M. M.
,
Hagare
D.
&
Maheshwari
B.
2016
Use of recycled water for irrigation of open spaces: benefits and risks
. In:
Balanced Urban Development: Options and Strategies for Liveable Cities
. (B. Maheshwari, V. P. Singh & B. Thoradeniya, eds), Springer International, New York, USA, pp.
261
288
.
Rattan
R. K.
,
Datta
S. P.
,
Chhonkar
P. K.
,
Suribabu
K.
&
Singh
A. K.
2005
Long-term impact of irrigation with sewage effluents on heavy metal content in soils, crops and groundwater – a case study
.
Agriculture, Ecosystems & Environment
109
,
310
322
.
Rayment
G. E.
&
Lyons
D. J.
2011
Soil Chemical Methods: Australasia
.
CSIRO Publishing
,
Clayton, VIC, Australia
.
Schipper
L. A.
,
Williamson
J. C.
,
Kettles
H. A.
&
Speir
T. W.
1996
Impact of land-applied tertiary-treated effluent on soil biochemical properties
.
Journal of Environmental Quality
25
,
1073
1077
.
Seelig
B.
2000
Salinity and Sodicity in North Dakota Soils
.
North Dakota State University of Agriculture and Applied Science, and US Department of Agriculture
,
Fargo, ND, USA
.
Shahrivar
A. A.
,
Rahman
M. M.
,
Hagare
D.
&
Maheshwari
B.
2019
Variation in kikuyu grass yield in response to irrigation with secondary and advanced treated wastewaters
.
Agricultural Water Management
222
,
375
385
.
Sparling
G. P.
,
Barton
L.
,
Duncan
L.
,
McGill
A.
,
Speir
T. W.
,
Schipper
L. A.
,
Arnold
G.
&
Van Schaik
A.
2006
Nutrient leaching and changes in soil characteristics of four contrasting soils irrigated with secondary-treated municipal wastewater for four years
.
Soil Research
44
,
107
116
.
Tabatabai
M. A.
&
Olson
R. A.
1985
Effect of acid rain on soils
.
Critical Reviews in Environmental Science and Technology
15
,
65
110
.
Xu
J.
,
Wu
L.
,
Chang
A. C.
&
Zhang
Y.
2010
Impact of long-term reclaimed wastewater irrigation on agricultural soils: a preliminary assessment
.
Journal of Hazardous Materials
183
,
780
786
.