INFLUENCE OFDRAINAGESYSTEMSONCONTAMINATIONWATERANDSOIL
Ivan Šimunić, Franjo Tomić, Lepomir Čoga
Faculty of agriculture University of Zagreb, Croatia, e-mail:
ABSTRACT
This study was aimed: at determining the concentration and leaching of nitrate, atrazine and heavy metals in drainage water and at determining the concentration of atrazine and heavy metals (Pb, Zn and Cd) in hydroameliorated soil.. The study was conduced on reclamation test field, during of four years. The crop corn was grown. The weed protection was primextra.Nitrogen fertilization rate was 145 kg.ha-1 to 175 kg.ha-1Based on the results, it may be concluded that concentrations of atrazine and NO3 –N in drainage waters exceeded the allowable values (0.1 μg.dm-3) and (10 μg.dm-3), while the concentrations of heavy metals were below from limited values,like and concentrations of atrazine and heavy metals in soil.
Since the concentrations of atrazine and NO3 –N in drainage water exceeded the allowable values they need to be monitored and the actions need to be taken for their reduction.
Key words: reclaimed soil, drainage water, nitrates, atrazine, heavy metals
INTRODUCTION
Different drainage systems with agricultural practices and applications of mineral fertilizers and herbicides may affect through different pollutants on contamination drainage water and hydroameliorated soil, this is, could influence on eutrophication of watercourses. In various soil plant systems pollutants may represent a potencial risk to the environment (Capriel et al. 1985, Mikanová et al. 2001) and uptake by plants and subsequent input into food chain (Borůvka et al.1996, 1997). The danger ensuing from their tendency to accumulate in vital organs of humans, animals and plants (bake et al. 1972, Pratt and Jury, 1984, Santa Maria et al. 1986)
Drainage systems and contamination have been the subject of many studies, among which are: Jani and Klaghofer (1975), Förster (1984), Bocken (1987), Gaynor et al (1989), Milburn and Richards (1994), Webster et al.(1999), Accinelli et al. (2002) Šimunić at al. (2002a, 2000b and 2002c).
In view of the above facts, this study was aimed
-at determining the concentration and leaching of nitrate, atrazine and heavy metals in drainage water;
-at determining the concentration of atrazine and heavy metals in hydroameliorated soil, since 161 530 ha of undergrounddrainage systems have been built in Croatia (Marušić, 1995).
2. MATERIALANDMETHODS
Trials were carried out on the experimental amelioration field “Jelenščak”-near Kutina (central Sava valley) on soil type defined as hydroameliorated Gleyic Podzoluvisol. Trial variants involved pipe drainage spacing of 15 m, 20 m, 25 m and 30 m, set up in four replications. All variants were combined with gravel as contact material (ø 5-25 mm) in the drainage ditch above the pipe. Drainpipe characteristics were: length 95 m, diameter 65 mm, average slope 3‰ and average depth 1 m. Drainpipes discharged directly into open channels. Variants covered areas of: 1425 m2, 1900 m2, 2375 m2 and 2850 m2. Pipes were plastic (PVC)- annular- ribbed and perforated.
The same crop was grown and the same agricultural practices were applied in all pipe drainage variants in each trial year (Table 1).
Drainage discharge was measured continually by means of automatic electronic gauges - limnimeters. Limnimeters were set up in each variant, at the drainpipe outlet into the open canal.
Sampling of drainage water were done three times each month during the discharge period and sampling of soil were donethree times each two months (to atrazine) and each year (to heavy metals).
Nitrates were determined by yellow coloring of phenol disulphonic acid, atrazine was determined by chromatographic analysis, while heavy metals (Pb, Zn and Cd) by AAS.
The total annual quantity leached of nitrogen, atrazine and heavy metals were estimated on the basis of average yearly concentration and yearly quantity of drainage discharge.
Data were statistically processed by means of the analysis of variance.
Table 1: Agricultural practices and application terms for maize grown during the period
Year / Sowing data / Fertilization / Protection / HarvestApplication date / Quantity
(kg N.ha-1) / Application date / Quantity
(l.ha-1)
1991 / April 30 / April 29
July 10 / 121
54
175 / May 2 / Primextra
(6 l. ha-1
=1200 g. ha-1
atrazine) / Oct 20
1993 / May 1 / April 30
June 18 / 94
51
145 / May 2 / Primextra
(6 l. ha-1) / Oct 14
1996 / May 22 / May 20
July 8 / 97
48
145 / May 23 / Primextra
(6 l. ha-1) / Nov. 16
1999 / May 25 / May 23
July 21 /
101
54155 / May 27 / Primextra
(6 l. ha-1) / Oct. 20
3. RESULTS
To facilitate interpretation of research results, the site factors - soil and precipitation - were taken into consideration.
3.1 Soil properties
Drained Gleyic Podzoluvisol is located in the Sava river valley, on level relief (slope<1‰), at an average altitude of 96.4 m a.s.l. Before the trial was set up, the area was utilised as a pasture, which was in association with swamp vegetation (Salix sp., Juncus sp. etc.).
Genetic texture of the soil profile with major hydropedological indicators is presented in Graph 1, while the major physical and chemical properties are given in Table 2.
1. Soil type: Gleyic Podzoluvisols, drained, medium deep
02. Main mode of soil moistening: surface and ground water
3. Vertical hydraulic conductivity:
Ap 35 35 - 75 cm = 0.011 m/day (very low)
75 - 115 cm = 0.011 m/ day (very low)
Bg 75 4. Layering of soil profile:
Ap - Bg - Gso/r - Gr,c
1155. Depth to impervious horizon, D in m:
Gso/r ca. 2 m
6. Mean rise of groundwater level, measured from
130soil surface: ca. 75 cm.
Gr,c
Figure 1. Genetic texture of Gleyic Podzoluvisol
Table 2: Major properties of drained Gleyic Podzoluvisol
Horizon / Depth(cm) / Content of particles
(%) / Porosity
(%) / Capacity
(%) / Permeability
(m/day) / Bulk density
(g.cm-3) / pH / Humus
(%)
Silt / Clay / % / Water / Air / H2O / 1M KCl
Ap / 0-35 / 47 / 46 / 48 / 44 / 4 / 0.011 / 1.35 / 6.7 / 5.3 / 3.0
Bt,g / 35-75 / 45 / 48 / 49 / 45 / 4 / 0.010 / 6.5 / 5.2
Gso / 75-115 / 55 / 39 / 46 / 42 / 4 / 0.011 / 7.9 / 7.1
Gr / 115-130 / 63 / 25 / 49 / 45 / 4
The soil has silty clayey texture to the depth of 0.75 m. The clay content of this soil section is in the range of 46-48 %, and the silt content is 45-47 %. The soil depth of 0.75-1.15 m is of lighter texture. The silt component preponderates in soil texture (55%), while the clay content decreases (39%). Soil texture at depths over 1.15 m is silty loamy. The soil is porous with the total pore volume of 48-49 %. Soil water capacity is 42-45 %. Air capacity is low - 4 %. Vertical hydraulic conductivity is very low (0.011 m/day).
3.2 Precipitation characteristics
For the needs of this work, fluctuations of precipitation and drainage discharge have been studied in terms and out of the growing season.
The four-year precipitation ranged from 897 mm (1996/97) to 1025 mm (1996/97). The primary precipitation maximum was recorded in the autumn period and the secondary maximum generally in late spring.
Results from Table 3 point to a relatively high precipitation, which had a substantial effect on the particular pollutants leaching dynamics.
Table 3: Total monthly and annual precipitation and its mean values(mm)
Year / V / VI / VII / VIII / IX / X / XI / XII / I / II / III / IV / Σ1991/92 / 156 / 20 / 160 / 52 / 50 / 152 / 108 / 21 / 15 / 45 / 78 / 59 / 916
1993/94 / 44 / 134 / 30 / 119 / 90 / 107 / 165 / 112 / 50 / 58 / 37 / 79 / 1025
1996/97 / 71 / 31 / 90 / 83 / 190 / 46 / 135 / 79 / 44 / 55 / 26 / 45 / 895
1999/00 / 107 / 89 / 86 / 66 / 95 / 72 / 92 / 104 / 29 / 37 / 63 / 77 / 917
3.3Hydrological relations
Drainage discharge and duration are important indicators of pipe drainage efficiency in draining excess water from soil. Systems with higher discharge and its shorter duration are more efficient. It would be impossible to estimate the quantity of leached pollutants in the tested pipe drainage variants without determining the quantity and dynamics of drainage discharge. Values of the said indicators for different drainpipe spacings are presented in Table 4
Table 4: Quantities of drainage discharge (mm) and total duration drainage discharge (days) per variants
Variant / Year / Precipitation (mm) / Drainage discharge / Duration of drainagedischarge
(days) / Quantity of drainage discharge
(l/sec)
mm / % of precipitation
R 15 / 1991/92 / 916 / 228 / 24.9 / 134 / 0.20
R 20 / 219 / 23.9 / 136 / 0.19
R 25 / 213 / 23.3 / 139 / 0.18
R 30 / 229 / 25.0 / 141 / 0.19
R 15 / 1993/94 / 1025 / 266 / 26.0 / 167 / 0.18
R 20 / 271 / 26.4 / 170 / 0.18
R 25 / 268 / 26.1 / 177 / 0.18
R 30 / 277 / 27.0 / 182 / 0.18
R 15 / 1996/97 / 895 / 198 / 22.1 / 140 / 0.16
R 20 / 198 / 22.1 / 146 / 0.16
R 25 / 203 / 22.7 / 153 / 0.15
R 30 / 199 / 22.2 / 157 / 0.15
R 15 / 1999/00 / 917 / 174 / 19.0 / 124 / 0.16
R 20 / 175 / 19.1 / 126 / 0.16
R 25 / 166 / 18.1 / 129 / 0.15
R 30 / 171 / 18.6 / 129 / 0.15
It can be seen from Table 4 that there are certain differences in the quantity of drainage discharge, both between the tested variants in each year and between the trial years. The largest quantities of discharge in all variants were recorded in the out of the growing season, when evaporation is the lowest, precipitation is the most abundant and there is no vegetable cover on soil, or plants are in their initial development stage. There are several reasons for these differences in drainage discharge, primarily the different total annual quantity and distribution of precipitation, as well as the different efficiency of each particular pipe drainage system. According to Klačić et al. (1998) an average drainage discharge was 246 mmor 22.5% of total precipitation (1094 mm).
Also there are yearly and seasons differences in the duration of drainage discharge between the tested pipe drainage systems. Duration of drainage discharge increases with the width of drainpipe spacing and with the quantity of precipitation and vice versa, narrower spacing and less precipitation cause shorter drainage discharge. We relate the duration of drainage discharge to the efficiency of each particular pipe drainage system and to all other factors mentioned for drainage discharge. The foregoing allows the conclusion that narrower drainpipe spacing is more efficient in these edaphic conditions, which is especially expressed in more humid years. Petošić et al. (1998) report that the variant involving drainpipe spacing of 10 m rendered the best results in terms of drainage discharge intensity.
3.4.Concentration nitrate nitrogen and leaching in drainage water
Results on the nitrate concentration in drainage water are presented per variants in Table 5.
Table 5: Average and maximum concentration NO3-N (mg.dm-3) in drainage water, per variants
Vari. / 1991/92 / 1993/94 / 1996/97 / 1999/00Aver / Max / Aver / Max. / Aver / Max. / Aver / Max
R 15 / 16.25 / 32.82 / 12.90 / 29.15 / 10.21 / 20.05 / 9.51 / 18.15
R 20 / 13.95 / 30.93 / 12.22 / 29.03 / 10.36 / 20.81 / 8.99 / 19.24
R 25 / 15.67 / 31.67 / 12.88 / 29.13 / 10.58 / 20.34 / 9.54 / 20.21
R 30 / 15.26 / 30.63 / 11.95 / 29.07 / 10.51 / 19.91 / 9.47 / 18.43
Maximum concentrations of NO3-Nin all variants during the four-year trial period exceeded the concentration of 10 mg.l-1 (Table 5), which is maximal admission concentration of nitrates in water. The highest maximum concentration for all variants was recorded in 1991/92 and the lowest maximum concentration in 1999/00 .
Average values of NO3-Nconcentrations (for all variants) only in 1999/00 were below 10 mg.dm-3, while the by far highest average concentrations was recorded in 1991/92.
It can be seen (Figure 2. pipe drainage spacing of 15 m) that the maximum NO3-Nconcentrations of all variants in all years were determined either in the spring or in the summer, soon after sowing and topdressing, which generally coincided with primary or secondary precipitation (that is, after higher drainage discharge) maxima. Higher fertilization and higher drainage discharge caused higher concentrations.
The foregoing points to the conclusion that drainage water is exceeded maximal admission concentration of nitrates in one part of the year (until six monds after second application of fertilization)- (Figure 2 to distance 15 m).
Similar results for drainage water were obtained in a three-year study done by Jani and Klaghofer (1975) in Petzenkirchen (Lower Austria). They determined an average NO3-Nconcentration of 14. 3 mg.l-1. Foerster (1984) estimated an average concentration of NO3-N in drainage water of 24.5 mg.l-1 – 38.3 mg.l-1 in northwestern Germany. Šimunić et al. (2002a) recorded an maximum NO3-N concentration of 28.79 mg/l -32.43 mg/l.
Figure 2. Fluctuation of NO3-N concentration in drainage water
The total quantity of leached nitrogen and its percentage relative to the total nitrogen added with fertilization are presented in Table 6.
Table6:. Quantity of nitrogen leached per pipe drainage variants (kg.ha-1) and percentage of nitrogen leached relative to the total N added with fertilization
Vari. / 1991/92 / 1993/94 / 1996/97 / 1999/00Kg.ha-1 / % / Kg.ha-1 / % / Kg.ha-1 / % / Kg.ha-1 / %
R 15 / 35.7 / 20.4 / 34.4 / 23.7 / 20.3 / 14.0 / 16.6 / 10.7
R 20 / 30.7 / 17.5 / 33.2 / 22.9 / 20.6 / 14.2 / 15.8 / 10.2
R 25 / 33.9 / 19.4 / 34.6 / 23.9 / 21.5 / 14.8 / 15.9 / 10.3
R 30 / 34.9 / 19.9 / 33.2 / 22.9 / 21.0 / 14.5 / 16.2 / 10.5
Since the nitrates bind poorly to colloid soil particles, it is important to determine the dynamics of their leaching It can be seen from Table 6 that the quantity of nitrogen leached varied per years and per trial variants. The lowest nitrogen leaching was recorded in all variants 1999/00 (the lowest quantity of drainage discharge and lower quantity of nitrogen added with fertilization). The highest leaching occurred in 1991/92 and 1993/94 (either the highest nitrogen added with fertilization or was the highest drainage discharge). According to Šoškić et al., (1987) quantity of nitrogen leached is in linear correlation with the quantity of drainage discharge. The results (Table 6) are in agreement with the results obtained by Skaggs and Gilliam (1985) and Klačić et al. (1998). Different quantities of leached nitrogen are conditioned by the climate, namely the quantity and distribution of precipitation (drainage discharge), crops grown, that is, their development stages, as well as by the agricultural practices and the time of their application. Hence, the largest quantities of leached nitrogen were recorded in years with the highest drainage discharge, this is, with highest precipitation and the highest nitrogen added with fertilization.
It was determined by the analysis of variance that there were no statistically significant differences between the tested variants of drainpipe spacing in drainage water concentrations of NO3-N and the quantity of nitrogen leached in a particular year, at P=0.05 and 0.01.
3.5.Atrazine concentration and leaching in drainage water
Results on atrazine concentration in drainage water and its leaching with drainage water are presented in Tables7 and 8.
Table 7: Average and maximum concentration atrazine (μg.dm-3) in drainage water, per variants
Vari. / 1991/92 / 1993/94 / 1996/97 / 1999/00Aver / Max / Aver / Max / Aver / Max / Aver / Max
R 15 / 1.75 / 7.23 / 1.55 / 6.87 / 0.94 / 2.88 / 1.15 / 5.05
R 20 / 1.79 / 7.46 / 1.71 / 6.20 / 0.86 / 2.32 / 1.31 / 5.70
R 25 / 1.84 / 7.58 / 1.89 / 6.31 / 0.84 / 2.95 / 1.29 / 5.84
R 30 / 1.73 / 7.15 / 1.57 / 6.16 / 0.93 / 2.99 / 1.34 / 5.80
It can be seen from Table 7 that different maximal and average values were determined for atrazine concentrations in drainage water, both between the trial years and between different drainpipe spacings. This was influenced by the date of atrazine application, quantity and distribution of rainfall, this is, the quantity of drainage discharge, efficiency of each particular pipe drainage system. Maximum atrazine concentrations in drainage water were recorded soon after application and beginninghigher drainage discharge (May 1991, Juni 1993, 1999 and Sep. 1996) and in all years decreased with later drainage discharges (Figure 3 to distance 15 m). Namely, atrazine is very water-soluble and is readily transported with waters (Albanis et al. 1988) and degraded in soil(Frank et al. 1991b). These results are in agreement with results, as reported by Ng et al (1995), as well as Accinelli at al. (2002).
In the case of the mentioned atrazine rate (1200 g/ha) applied to the hidroameliorated soil type (Table 2) and the recorded quantities of precipitation drainage discharge, atrazine concentration were in all years in 10 months higher from the tolerated limit..Albanis et al. (1988) reported that no atrazine residues were detected in water after 247 days.
Frank et al. (1991b) reported unequal duration of atrazine degradation in soil, from 149 to 684 days, depending on the temperature and microbiological activity of the soil.
Figure 3. Fluctuation of atrazine concentration in drainage water
Table 8: Quantity of atrazine leached per pipe drainage variants (g.ha-1) and percentage of leached relative to the total added with applicatin
Vari / 1991/92 / 1993/94 / 1996/97 / 1999/00g.ha-1 / % / g.ha-1 / % / g.ha-1 / % / g.ha-1 / %
R 15 / 3.99 / 0.33 / 4.12 / 0.34 / 1.86 / 0.16 / 2.00 / 0.17
R 20 / 3.92 / 0.33 / 4.63 / 0.39 / 1.98 / 0.17 / 2.29 / 0.19
R 25 / 3.92 / 0.33 / 5.07 / 0.42 / 1.71 / 0.14 / 2.14 / 0.18
R 30 / 3.96 / 0.33 / 4.35 / 0.36 / 1.85 / 0.15 / 2.29 / 0.19
Mostly atrazine was lost during the growing season.The larger quantity of total atrazine leached occurred in first two years(higher total drainage discharge andhigher concentrations) and vice verse. Atrazine losseswere ranging from 0.14 % to 0.42 %. Frank et al. (1991b) recorded higher values of leached atrazine in drainage water and soil of predominantly sandy texture (0.2% to 1.9% of 3200 active ingredients). Albanis et al. (1988) reported different quantities of leached atrazine with respect to soil texture (0.54% in clay, 0.66% in loam and 0.47% in silt-loam) and as Accinelli at al. (2002) reported about 0.61 % atrazine losses in silty loam.
3.6Atrazine concentration in soil
Atrazine concentration in soil is presented in Table 9, and the dynamics of its concentration in Figure4.
Table 9. Atrazine concentration in soil (μg.kg-1), per variants
Vari / μg.kg-11991/92 / 1993/94 / 1996/97 / 1999/00
J / A / O / D / F / A / J / A / O / D / F / J / A / O / D / F / A / J / A / O / D / F / A
R 15 / 76 / 37 / 15 / 7 / 4 / * / 59 / 22 / 14 / 4 / * / 95 / 39 / 25 / 16 / 6 / * / 105 / 56 / 37 / 17 / 6 / *
R 20 / 77 / 38 / 15 / 8 / 4 / * / 60 / 23 / 14 / 4 / * / 93 / 39 / 24 / 16 / 6 / * / 103 / 55 / 37 / 17 / 5 / *
R 25 / 78 / 37 / 16 / 9 / 4 / * / 59 / 24 / 15 / 5 / * / 93 / 40 / 25 / 16 / 7 / * / 102 / 55 / 38 / 18 / 6 / *
R 30 / 76 / 37 / 15 / 7 / 4 / * / 59 / 23 / 14 / 4 / * / 93 / 41 / 24 / 15 / 6 / * / 102 / 56 / 35 / 18 / 5 / *
* Not detected, limit of detection is 2 μg.kg-1
It can be seen from Table 9 that atrazine concentration in soil recorded in the highest values inmonth Juni, (first taken of sampling ) and after duration year values are decreased and not detected in April in all years and February 1993/94.Starting concentrations in first two years were recorded lowerthan in last two years. Maybe was reason earlier application active ingredient (Table 1), this is, later taken of sampling and earlierdrainage discharge (May) in 1991/92 and 1993/94(a part of atrazine leached and degradeted). According Frank et al. (1991b) soil content of atrazine is, in fact, the difference between atrazine input into and its output from the soil (losses of residues to water leaching, disappear by dispersion into air or by degradation) and there are unequal duration of atrazine degradation in soil, depending on the temperature and microbiological activity of the soil. Half-time dissipation of atrazine in soil (Figure 4 to distance 15 m) durated until Sept..
Figure 4. Contents of atrazine in soil and half-time of disspation
The same results are reported by Kozak and Vacek (1996). Frank et al. (1991b) reported half-time of atrazine in soil from 125 to 198 days. The tolerance limit for atrazine concentration in soil depends on the susceptibility of the next crop, as well as on the soil physical and chemical properties. Šilješ (1980) for heavy clay soils, gives the following tolerated atrazine concentrations in soil for the next crop in the crop rotation: oil rape 0.1 ppm (100 g. kg-1) and oats 0.25 ppm.
3.7 Heavy metals in drainagewater and their leaching
Results of average concentrations of heavy metals in drainage water and their leaching are presented per year and per variants in Table 10a, 10b and 10c.
Table 10a. Average yearly concentration of Pb in drainage water (μg.dm-3) and leaching (g.ha-1)
Vari. / 1991/92 / 1993/94 / 1996/97 / 1999/00μg.dm-3 / g.ha-1 / μg.dm-3 / g.ha-1 / μg.dm-3 / g.ha-1 / μg.dm-3 / g.ha-1
R 15 / 28.5 / 64.98 / 29.0 / 77.14 / 27.0 / 53.46 / 24.5 / 42.63
R 20 / 27.0 / 59.13 / 28.5 / 77.24 / 26.5 / 52.47 / 24.0 / 42.00
R 25 / 26.0 / 55.38 / 27.5 / 73.70 / 27.0 / 54.81 / 23.5 / 39.01
R 30 / 27.0 / 61.83 / 27.5 / 76.18 / 26.5 / 52.74 / 24.0 / 41.04
Table 10b. Average yearly concentration of Zn in drainage water (μg.dm-3) and leaching(g.ha-1)
Vari. / 1991/92 / 1993/94 / 1996/97 / 1999/00μg.dm-3 / g.ha-1 / μg.dm-3 / g.ha-1 / μg.dm-3 / g.ha-1 / μg.dm-3 / g.ha-1
R 15 / 14.9 / 33.97 / 17.5 / 46.55 / 15.4 / 30.42 / 13.9 / 24.19
R 20 / 14.3 / 31.32 / 16.7 / 45.26 / 15.0 / 29.70 / 14.1 / 24.68
R 25 / 15.1 / 32.16 / 16.5 / 44.22 / 15.1 / 30.65 / 13.7 / 22.74
R 30 / 14.5 / 33.21 / 16.9 / 46.81 / 14.8 / 29.45 / 13.8 / 23.60
Table 10c. Average yearly concentration of Cd in drainage water (μg.dm-3) and leaching(g.ha-1)
Vari. / 1991/92 / 1993/94 / 1996/97 / 1999/00μg.dm-3 / g.ha-1 / μg.dm-3 / g.ha-1 / μg.dm-3 / g.ha-1 / μg.dm-3 / g.ha-1
R 15 / 1.9 / 4.33 / 2.2 / 5.85 / 1.7 / 3.37 / 1.5 / 2.61
R 20 / 1.7 / 3.72 / 2.2 / 5.96 / 1.7 / 3.37 / 1.5 / 2.63
R 25 / 1.7 / 3.62 / 2.2 / 5.90 / 1.7 / 3.45 / 1.4 / 2.32
R 30 / 1.8 / 4.12 / 2.2 / 6.09 / 1.7 / 3.38 / 1.5 / 2.57
Concentrations of heavy metals in drainage water do not indicate pollution, which is in agreement with the results obtained by Moore et al. (1981a and 1981b), Đumija et al. (1989) and Čoga et al. (1998). Different average concentrations of heavy metals were recorded per years and per drainage system variants. The average the highest concentration of all heavy metals were recorded in 1993/94 when were the highest total drainage discharge. Maximal concentration duration of all years recorded in the period of higher drainage discharge(Figure 5 to distance 15 m). Maximal concentration of Pb was from 36.5 μg.dm-3(1996/97) to 50.5μg.dm-3(1991/92), Zn from 20.5μg.dm-3 (1999/00) to 28.2 μg.dm-3 (1991/92) and Cd
Figure 5. Fluctuation of heavy metals (Pb, Zn and Cd) in drainage water
The recorded concentration of heavy metals and the drainage discharge (Table 4) served to calculate the quantity of heavy metals leached. The highest leaching were also determined by all heavy metals at the time of its highest drainage discharge (1993/94), and vice verse. According to Bear and Verryjit (1987), variations in the quantity and percentage of leached Zn and Cd depend mostly on precipitation, as well as on the quantity and speed of drain water, which has an appreciable influence on the physical transport of heavy metals.The quantity of leached heavy metals was smaller than their overall input into soil (Table 11)
The available data point to the conclusion that there are no substantial differences between the tested variants in each year. Greater differences were recorded between the tested years, which was the effect of the hydrological conditions, agricultural management procedures applied and air cleanliness.
3.8. Heavy metals in hydroameliorated soil
Table 11. Contents of total heavy metals in soil (mg.kg-1), per variants
Vari / Contets of heavy metalsmg.kg-1 / Total introduced
g.ha-1 / Total leaching
g.ha-1 / Difference
(Introduced-leaching)
g.ha-1 / Contets of heavy metals
mg.kg-1
1991 / During four years / During four years / 2000
Pb / Zn / Cd / Pb / Zn / Cd / Pb / Zn / Cd / Pb / Zn / Cd / Pb / Zn / Cd
R 15 / 13.5 / 77.2 / 0.7 / 295.1 / 655.6 / 55.5 / 238.2 / 135.1 / 16.2 / 79.7 / 520.5 / 39. / 13.5 / 77.2 / 0.7
R 20 / 13.5 / 77.2 / 0.7 / 230.8 / 131.0 / 15.7 / 64.3 / 524.6 / 39.8 / 13.5 / 77.2 / 0.7
R 25 / 13.5 / 77.2 / 0.7 / 222.9 / 129.8 / 15.3 / 72.2 / 525.8 / 40.2 / 13.5 / 77.2 / 0.7
R 30 / 13.5 / 77.2 / 0.7 / 231.8 / 133.1 / 16.2 / 63.3 / 522.5 / 39.3 / 13.5 / 77.2 / 0.7
Weight of soil (0-0.3 m)= 4050 t.ha-1
It is need 405 g.ha-1 to increasing 0.1 mg.kg-1
The obtained results did not indicate contamination of hydroameliorated soil by heavy metals (Table 11). According to Mengel and Kirkby (1979), symptoms of toxicity at levels of about 400 mg.kg-1 Zn and higher, Cd levels in uncontaminated soils do not exceed 1 mg.kg-1.