RESULTS AND DISCUSSION

Transcription

1 CHAPTER 4 RESULTS AND DISCUSSION

2 4. RESULTS AND DISCUSSION Results and discussion related to seasonal (summer, monsoon, winter) and spatial (BCF, CRRF, SCRF, AWS, TFF) variation in forest soil properties in the National Capital Region of Delhi are presented here. Present investigation has included the analyses of soil physico-chemical. parameters viz. ph, electrical conductivity (EC), organic carbon, total-n, C:N ratio, total-s and total trace element contents like lead (Pb),. chromium (Cr), nickel (Nil. iron (Fe), manganese (Mn), zinc (Zn) and copper (Cu) and presehted in Tables 5-16: Soil properties running along the study transect according to down wind gradient of five different forest locations from Bawana City Forest, New Delhi to Tilpat Forest, Faridabad has been analyzed in seven depths viz. 0-10, 10-20,20-30,30-40,40-50, and cm in three seasons namely summer, monsoon and winter. Some soil physical parameters viz. mechanical composition of soil or soil texture (Table 3), bulk density and soil moisture content (Table 4) has been analyzed. Soil moisture retention capacity at 33 k Pa (field capacity) has also been analyzed. To compare the soil characteristics (Tables 5-16) with atmospheric deposition of pollutants; SOx and NOx gases in ambient air (Table 18) and dust fall deposition due to gravity (Table 19) has also been studied. Trace element contents, S04 and N03 concentration have been studied in dustfall (Tables 20-21). Along with the above parameters, the present short term investigation has included 63

3 the results of atmospheric deposition and their possible effects on comparatively undisturbed forest soil profile on regional basis. Surface soil characteristics have been shown in Figures The variation in mean monthly rainfall based onwaas unit at Indian Agricultural Research Institute, New Delhi is shown in Table 2. About 75% of the annual rainfall is received during monsoon. Table 2 Monthly average weather data in Delhi Months Temperature Relative Rainfall Wind speed (OC) humidity (mm) (km h- 1 ) (%) January February March April May June July Au,gust September October November December January February March April Inherent Soil Properties Inherent soil properties represent the influences of parent material, topography, climate and vegetation integrated over time through the processes of soil formation. These properties are supposed to change only 64

4 gradually in a long span of time i.e. centuries or millennia. Though sites were selected to be as similar as possible in a gradient study manner, they differed in various inherent soil properties. Results showed that soil properties are not much affected by pollutant deposition Properties susceptible to pollutant deposition Properties susceptible to pollutant deposition involve those soil properties that are subject to change over relatively short time periods Le. years to decades as a result of both natural processes and pollutant deposition. These properties include total-n, total-s and other elements in forest soil. These properties could be directly affected by pollutant deposition or could change indirectly as a result of pollutant effects on overstory nutrient cycling (Johnson et at, 1982). Interpretation of pollutant-deposition effect on soil properties by direct site-to-site comparisons is difficult because of unavoidable soil differences related to climate and parent material (MacDonald et at, 1991). However an attempt have been made in present investigation to find out the possibilities of pollutant deposition impact on the soil profile characteristics in such a manner that involved in a gradient study and site-to-site variation., 4.3. Soil physical parameters Mechanical composition of soil Mechanical composition of soil has been analysed in summer season of the year 2007 for all the seven soil depths. 1. BCF: At Bawana City Forest site, clay content was 15.6% in

5 cm soil depth while 0-20 cm depth witnessed higher clay content of 18.6% (Table 3). Clay contents decreased with increasing soil depth. Silt contents also decreased with increasing soil depth except cm depth where silt was at par with cm depth. There was no definite trend observed in case of sand content ranging from to 56.46%. The textural class was loam in case of 0-10 and cm soil depth while the rest of the depth was sandy loam. 2. CRRF: At Central Ridge Reserved Forest site, all the seven soil depths (0-70 cm) were sandy loam soil (Table 3). Clay contents were at par (14.6%) in 0-10 and cm soil depths. However, in and cm soil depth clay contents increased to 15.6% and 15.1 %, respectively. Higher silt content was observed in cm depth (33.06%) while sand content was higher in 0-10 cm soil depth (71.34%). 3. SCRF: At South Central Ridge Forest Site, higher clay was observed (14.6%) in cm depth as compared to cm depth (14.2%) followed by 0-10 cm (12.6%) (Table 3). Results indicated that all the seven soil depths (0-70 cm) may be texturally classified as sandy loam soil cm soil depth contained higher silt (26.46%) and cm depth contained higher sand (64.56%). 66

6 Table 3 Mechanical composition of soil samples at various sites in different seasons Site Depth Clay (%) Silt Sand (%) Textural (em) (%) class Bawana City Loam Forest (BCF) Loam Sandy loam Sandy loam ~ Sandy loam Sandy loam Sandy loam Central Ridge Sandy loam Reserved Forest Sandy loam (CRRF) Sandy loam Sandy loam Sandy loam Sandy loam Sandy loam South Central Sandy loam Ridge Forest Sandy loam (SCRF) Sandy loam Sandy loam Sandy loam Sandy loam Sandy loam Asola Wildlife Sandy loam Sanctuary (AWS) Sandy loam Sandy loam Sandy loam Sandy loam Sandy loam Sandy loam Tilpat Forest Loam Faridabad (TFF) Sandy loam Sandy loam Sandy loam Sandy loam Sandy loam Sandy loam 67

7 4. AWS: At Asola Wildlife Sanctuary site, results showed that higher clay was present in upper most soil (l6.6%). silt in cm depth (19.6%) and sand in cm depth (72.34%). Lower clay content was observed to be 11.6%in 20..,30 cm soil depth (Table 3). 5. TFF: At Tilpat Forest Faridabad site, higher clay content was observed to be 16.6% in 0-10 cm soil depth and textural class of this soil was loam (Table 3). Rest of the six lower depths belonged to textural class sandy loam. In the soil depth cm lower clay content was observed to be as 14%. In three soil depths (10-40 cm), silt content was at par (32.06%). Variation in clay and sand percentage were observed due to depth. Higher sand per cent was found to be 58.06% in cm soil depth. Clay contents in cm soil depth running along the transect were either similar or higher than 0-10 cm depth in the vicinity of highly urbanized sites i.e. BCF and SCRF. But the gradient is differing at AWS and TFF sites where surface soil showed higher clay contents. Soils of Bawana are clay loam to sandy loam in texture as sampling was done at ten locations in Bawana, New Delhi for the physico-chemical characteristics of soil. (NTPC, 2002) Bulk density and moisture retention capacity Seasonal variations in bulk density of surface soil are presented in Table 4. AWS site witnessed comparatively higher bulk density of 1.66 Mg m- 3 (or g cm- 3 ) in winter and monsoon seasons however, SCRF site witnessed 68

8 lower bulk density of 1.14 Mg m- 3 in summer season. No appreciable change in bulk density of soil was noticeable among all the three seasons and five sites. But per cent soil moisture content on weight basis (determined along with bulk density) of AWS site in monsoon season showed an increase of about 1 per cent than in winter while bulk densities were similar 0.66 Mg m- 3 ) in both the seasons. Higher soil moisture content of 39.43% was observed at SCRF site with a lower bulk density of 1.14Mg m- 3 in summer season. Per cent moisture retention capacity of soil at 33 k Pa (field capacity) was determined of surface soil in summer season of 2007 only. 34.2% soil moisture retention capacity was observed at SCRF site followed by TFF site (33.8%), AWS site (33.5%), BCF site (32.4%) and CRRF site (32%). Modifications associated with urban infrastructure directly impact soil properties (Scharenbroch et al., 2005). In particular, soil bulk density, microbial activity, and organic matter are impacted by anthropogenic activities. They proposed that urban soil properties are not only distinguishable from other systems, but also variable within types of landscapes in urban environments. They found soils from older urban landscapes (mean landscape age of 64 years) to be distinct from newer urban landscapes (mean landscape age of 9 years). Soil bulk densities were significantly greater in newer 0.73 g cm- 3 ) compared to older urban soils (1.41 g cm- 3 ). 69

9 Table 4 Seasonal variation in physical parameters of surface soil samples (0-15 cm) at various sites Season/ site Soil moisture Bulk content (0/0) density Weight Volume (Mg m- 3 ) basis basis Summer BCF CRRF SCRF AWS TFF Monsoon BCF CRRF SCRF AWS TFF Winter BCF CRRF SCRF AWS TFF Herrmann et al. (2005) reported that as both the amount and the proportion of the two nitrogen compounds vary among sites, the leaching of N03- and NH4+ obviously does not only depend on bulk deposition rates, but also on vegetation and on site conditions such as soil moisture. 70

10 4.4. Physico-chemical characteristics of forest soil at different experimental locations ph 1. BCF: During summer season no significant changes in ph values.. were observed among the different depths and the range was 7.94 to This trend was continued during monsoon and winter seasons also. In monsoon the ph range was 7.68 to 7.88 and in winter season it was 7.38 to This indicated no significant role of depth variations at BCF site regarding ph values (Table 5). Seasonal variations were observed in surface soil (0-10 cm depth) at this site (Fig. 2). 2. CRRF: The ph values at different depths during summer season were not stgnificantly varied and the range was 7.74 to Whereas during monsoon season a significant(p ::0.05) change in ph values were observed. It was 4.15 in cm depth and 6.66 in cm depth. Increasing trend (6.11 in 0-10 and 6.85 in cm depth) of ph was observed in winter season (Table 5). 3. SCRF: At this experimental location, no significant changes in ph values were observed. However, in winter season at the depth of cm a Significant (p ::0.05) decrease in ph was found. In all the depths in winter season ph varied from 7.49 in 0-10 cm to 8.07 in cm depth (Table 5). 71

11 Table 5 ph (1:2.5) of soil samples at various sites in different seasons Site BCF ph Depth (em) Summer Monsoon Winter S S S 7.S6 40-S0 7.9S SO CRRF S S SO S S 6.8S SCRF S SO~ S S ~ AWS S S S6 SO S S S S TFF S 40-S SO S S:64 8.1S CD(p=O.05} Season x Site 0.2 Site x Depth 0.3 Season x Site x Depth

12 4. AWS: Results indicated that during summer season, there was significant (p~.05) increase in ph observed to be 7.75 in cm depth when compared with 0-10 cm (6.64) and cm (7.13) depth. In monsoon season, lower ph was found to be 6.15 in 0-10 em, 6.48 in cm and 5.66 in cm soil depth. In winter season ph was found to be increasing from 6.82 in 0-10 cm to 7.61 in cm depth. Other values were not significantly influenced due to depth and seasons (Table 5). Seasonal variation was observed in surface soil ph (Fig. 2). 5. TFF: Throughout the experiment no significant changes in ph values were observed in summer and winter seasons. While, at the depth of 40-50, and cm decreasing trend in ph values was observed as 7.79, 6;97 and 5.64 respectively during monsoon season (Table 5). The soils of the five sites were neutral to slightly alkaline in nature. Soils of Bawana site was reported grey and brown in colour, alkaline in nature and ph varies from 7.6 to 11.2 (NTPC, 2002) Electrical conductivity (EC) 1. BCF: The observations made it clear that changes in EC values were not significant when compared statistically for season x site x depth. However, EC values in all the seasons indicated salt deposition up to the lower soil depth (Table 6). At this site highest EC was observed to be 5.62 ds m- 1 in cm depth in winter 73

13 season and lowest 3.67 ds m- I in 0-10 cm depth in monsoon season. At this site EC values are much higher than rest of the sites in all the three seasons and in all the soil depths. However, soil depth 0-10 cm showed variations in summer, monsoon and winter as 4.35, 3.67 and 5.31 ds m- I respectively (Fig. 3). 2. CRRF: At this site mixed trend in changes of EC values were observed in all the three seasons and in all the depths. In summer season, comparatively high values 0.40 to 0.60 ds m- I were observed among all the depth. (Table 6). 3. SCRF: The similar trend was observed as in case of CRRF site in all the seasons and depths except in winter season where comparatively higher EC 0.29, 0.25, 0.22 and 0.21 ds m- I were observed in decreasing trend in first four soil depths (0-40 cm), respectively (Table 6). 4. AWS: The 0-10 cm soil layer indicated higher EC values 0.14 ds m I in summer, 0.09 ds m- I in winter and 0.07 ds m- I in monsoon season as compared to lower soil depths in all the three seasons and soil depths (Table 6). At this site EC values were lower among rest of the sites in all the seasons and depths ranging from 0.04 ds m- I in monsoon in cm to 0.85 ds m- I in summer in cm depth. In monsoon season EC was found to be 0.04 ds m- I in cm soil depth which was lowest among all the five forest sites. 74

14 ~. -.-Summer Monsoon -:-*-Winter I BCF CRRF SCRF Sites Fig. 2 Seasonal and spatial variation in ph of surface soil AWS TFF ~Summer 1.4 ~ 1.2 E 1 if) LJ w ~Monsoon ~VVinter BCF CRRF serf AWS TFF Sites Fig. 3 Seasonal and spatial variation in electrical conductivity of surface soil 75

15 Table 6 Electrical conductivity of soil samples at various sites in different seasons Site BCF EC (ds mot) Depth (cm) Summer Monsoon Winter CRRF : SCRF AWS TFF C D(p=O. 05) Season x Site 0.3 Site x Depth Season x Site x Depth NS NS 76

16 5. TFF: In summer and monsoon season leaching of salts were observed from upper soil layer (0-10 cm) to lower horizons however in winter season decreasing trend (0.41 ds m- I in 0-10 cm and 0.26 ds m- I in cm depth) was found towards lower soil horizons (Table 6). Higher EC were observed in all the three seasons at Bawana site. Soils of Bawana have high electrical conductivity observed in the range of 44 to mhos cm- l (NTPC, 2002) Organic carbon 1. BCF: At this location higher organic carbon contents were observed to be 1.01% in 0-10 cm and 0.94% in cm soil depth in winter season. In the upper two soil depths (0-20 cm) summer and monsoon seasons witnessed the values as 0.90%, 0.23% and 0.47%, 0.40% respectively. A significant build up of organic carbon was found in winter season (1.01%) followed by summer season (0.90%) and monsoon season (0.47%)in 0-10 cm soil depth. But in all the three seasons, organic carbon contents were in decreasing trend towards lower soil depths (Table 7). In winter season organic carbon was on higher side (1.01%) as compared to summer (0.9%) and monsoon (0.47%) in surface soil (Fig. 4). 2. CRRF: At this site higher organic carbon contents were observed to be 1.81, 1.70 and 1.05% in winter season in soil depths of 0-10 cm, cm and cm respectively followed by summer as 77

17 Table 7 Organic carbon content of soil samples at various sites in different seasons Site Organic carbon (%) Depth (cm) Summer Monsoon Winter BCF CRRF SCRF AWS TFF C D(p=O. 05) Season x Site 0.1 Site x Depth 0.1 Season x Site x Depth

18 1.17, 1.07, 0.74% and monsoon season as 0.88, 0.94, 0.59%. Significantly higher content of organic carbon was observed in winter season as 1.81 % as compared to summer (1.17%) and monsoon (0.88%) in 0-10 cm soil depth (Fig. 4). Decreasing trend of organic carbon was observed in lower soil depths in all the three seasons (Table 7). 3. serf: Higher organic carbon was found in upper soil layer (0-10 cm) in winter season (1.07%) followed by summer (1.01%) and monsoon (0.87%, Fig. 4). A decreasing trend of organic carbon was observed as increasing soil depths (Table 7). 4. AWS: Organic carbon content at this site followed the order winter>monsoon>summer in 0-10, and cm depths as 0.66, 0.62, 0.55%; 0.55, 0.35, 0.34% and 0.51, 0.27, 0.16% respectively. The trends were in decreasing pattern in lower soil depths in all the three seasons (Table 7). In winter season organic carbon was on higher side (0.66%) as compared to summer (0.51 %) and monsoon (0.55%) in surface soil (Fig. 4). 5. TFF: In summer season, organic carbon content was higher (1.51 %) followed by winter (1.44%) and monsoon (0.94%) in upper 0-10 cm soil layer. A Significant decrease in organic carbon content was observed in cm soil depth as compared to upper soil layer in summer (0.44%) and in winter season (1.07%). But in monsoon season, a constant non-significant decrease of organic carbon was observed towards lower soil depths (Table 7). In summer season organic carbon Was on higher side (1.51%) as 79

19 compared to monsoon (0.94%) and Winter (1.44%) in surface soil (Fig. 4). The reason behind higher organic carbon contents in upper soil layers (0-10 cm) at all the sites was appeared to be well decomposition of litters falling from trees. In monsoon season, comparatively lower organic carbon was observed and this may be the result of water logging conditions and leaching behavior of soils. The organic matter is of great importance not only in the lead adsorption, but also in influencing its natural distribution (Sipos et al., 2004). Dustfall rates were found to be higher in the Winter season at all the sites excepting TFF. Higher concentration of atmospheric particulate-bound OC is generally observed in the Winter season due to greater degree of emissions and stagnant atmospheric conditions (Gray et ai., 1986). Dry deposition of this particulate-bound OC in the form of dustfall may be the reason behind higher OC content in surface soils of the first four sites Total nitrogen (Total-N) 1. BCF: In upper three soil depths namely 0-10, and cm, N content was highest in Winter (1330, 1190 and 910mg kg- l soil). In monsoon, the contents were ( and 700 mg kg- 1 soil) and summer season (1190, 770 and 490 mg kg- 1 soil), respectively. But in lower depths mixed trends were found. The results were statistically not significant when compared as season x site x depth (Table 8). 80

20 Table 8 Total Nitrogen content of soil samples at various sites in different seasons Site Total N (mg kg- 1 ) Depth (cm) Summer Monsoon Winter BCF CRRF SCRF 30~ AWS TFF CD(p=O.05j Season x Site Site x Depth Season x Site x Depth NS 81

21 2. CRRF: In upper soil layer highest N content of 1470 mg kg-l soil was observed in both winter and summer seasons, but in monsoon season it was 1330 mg kg- 1 soil. The overall pattern of N distribution followed a mixed trend (Table 8). 3. SCRF: The total-n contents in upper soil layer at this site were 1190, 1120 and 1090 mg kg- 1 soil and was in order of winter>summer>monsoon. The overall pattern of N distribution at this site also followed a mixed trend (Table 8). 4. AWS: At this site total-n content of 980 mg kg- 1 soil was observed in upper soil layer in winter and summer followed by 630 mg kg- 1 soil in monsoon season. Decreasing trend was observed in lower depths in all the three seasons. The minimum N content was found to be 415 mg kg- 1 soil in cm soil depth in summer season when compared among all the sites (Table 8). 5. TFF: Iri winter, total-n content was 1610 mg kg- I soil which is comparatively highest among all the sites followed by 1470 mg kg- 1 soil in summer and 1190 mg kg:l soil in monsoon season in upper soil layer (Table 8). Total-N of 630 mg kg-i soil was observed in monsoon season at AWS site while 1610 mg kg- 1 soil total-n was observed in winter at TFF site in surface soil (Fig. 5). 82

22 ;R ~ Summer 1..:..e-:- Monsoon 0.9 ~Winter BCF CRRF SCRF AWs.TFF Sites Fig. 4 Seasonal and spatial variation in organic carbon content of surface soil bj ~ 0> 1400 E1300 Z I co +-' o I ~~~~... j... ~Sumfner ~MonsObn -.-Winter 900 _ ~~--~~~~~ rl ~----~.-~--~--, BCF CRRF serf AWS TFF Sites Fig. 5 Seasonal and spatial variation in total Nitrogen content of surface soil 83

23 Crowe et al. (2004) reported while working in Great Britain that, the soils exhibited similar soil profile nitrogen values, because changes in bulk density and organic matter composition offset increases in N concentrations in highly organic soils. In their data on Scottish Podzol soils they showed that soil profile nitrogen declined with increasing precipitation, but increased with the amount of pollutant N deposited from the atmosphere. Total N content of surface soils in this study was found to be the lowest in monsoon season at all the sites. A probable reason for this may be enhanced leaching of nitrate from the soil Total sulphur (Total-S) 1. BCF: A decreasing trend of total-s was observed towards lower soil depth. Total-S in soil depth 30-40, 40-50, and cm in summer season were significantly higher (192.5, 221.2, and mg kg- 1 soil, respectively) than those of monsoon by their corresponding values. However, higher sulphur (251.7 mg kg- 1 soil) was observed in winter followed by summer (238.8 mg kg- 1 soil) and monsoon season (214.4 mg kg- 1 soil) in 0-10 cm depth (Fig. 6). Changes in total-s content in lower soil depths were observed in all the three seasons (Table 9). 2. CRRF: Total-S contents in all the six lower soil depths except 0-10 cm in summer season were significantly higher (256.3, 198.8, 149.9, 245, and 198 mg kg- 1 soil) than those of monsoon (125;1,46.5,38.8, 16.1, 13.5 and 11.5 mg kg- 1 soil). InO-IO cm 84

24 depth in summer, S content was mg kg- 1 soil while in monsoon season it was 232 mg kg- l soil (Fig 6). Higher sulphur contents were found in summer followed by winter and monsoon season in upper soil layer. However the trend was in decreasing order towards lower depths (Table 9). 3. SeRF: Total-S values in soil depth 10-20,20-30,40-50, and cm in summer season (306.3, 205, 211.3, and mg kg- 1 soil) were significantly higher than those of monsoon season values (186.8, 117.9, 67.7,54 and 18.2 mg kg- l soil), respectively. In winter season the values were 214.8, 185.1, 144.7, and 65.9 mg kg- 1 soil. The highest S among all the sites was found to be mg kg- 1 soil depth cm in summer season (Table 9, Fig. 6). 4. AWS: Total-S contents in summer were significantly higher (170, 203.7, 227, and 174 mg kg- 1 soil) than their counterparts in monsoon season (93.7, 43.5, 24, 17.4 and 11.2 mg kg- 1 soil) in five soil depths from to cm, respectively. However, in winter season total-s contents were higher than monsoon season in all the depths except upper soil layer, where S content (282.0 mg kg- 1 soil) is significantly higher than their counterparts in summer (183.3 mg kg- l soil) and monsoon (158.6 mg kg- 1 soil). The lowest S among all the sites was found to be 11.2 mg kg- l soil in cm depth in monsoon season (Table 9). 85

25 Table 9 Total Sulphur content of soil samples at various sites in different seasons Site Total S (mg kg- 1 ) Depth (cm) Summer Monsoon Winter BCF CRRF SCRF AWS TFF CD(p=O.05) Season x Site 23.5 Site x Depth 36.0 Season x Site x Depth

26 5. TFF: At this site total-s content in monsoon and winter were decreasing with increasing soil depth. It decreased from to 30.6 mg kg- 1 soil in monsoon and to 19.7 mg kg- 1 in winter season. In summer season higher S were observed to be mg kg- 1 soil in 0-10 cm depth. Seasonal variations may not be significant at this site (Table 9). The season x site x depth interactions were significant (p=o.05). The upper two soil depths at all the sites accumulated the. highest total sulphur content all the depths in soil profile. The similar results were obtained by Kopstic and Alewell (2007). They stated that spatial distribution of total-s in soils seems to be depended both on pollution and natural factors but total-s is weakly correlated with S deposition in organic soil horizons. Sulphate content in dustfall is found to be higher in the winter season at all the sites excepting SeRF (where the dustfall rate in summer was found to be marginally higher than that in winter). Thus there may be a relationship between increased sulphate content of dustfall and higher total S content observed in soils in the winter season Trace elements Lead (Ph) 1. BCF: Total lead contents were higher in winter season (30.5, 30 and 1.4, 15.6, 18.6, 16.7 and 17.2 mg kg- 1 soil) followed by summer (14.4, 12.5, 12.2, 9.5, 15.5,8.9 and 9 mg kg- 1 soil) and monsoon (13.6, 16.3, 10, 14.6, 8.8, loa, 10.3 mg kg- 1 soil) for all 87

27 the seven depths (Table 10). For season x site, site x depth and season x site x depth, variations in lead contents were significant (p=o.05). Sipos et al. (2005) stated that different soil horizons have different lead adsorption capacity due to their variable composition. 2. CRRF: In sumnier and winter seasons lead contents were observed to be more in cm soil depth (45.4 and 51.1 mg kg- 1 soil) than 0-10 cm depth (38 and 46.5 mg kg- 1 soil), respectively whereas in monsoon, 0-10cm soil depth evidenced higher value (31.1 mg kg- 1 soil) than lower six soil depths (10-70 cm). For each soil depth, significant variations in lead contents were observed among all the three seasons (Table 10). The sandy loam soil under study thus constitutes a natural control for Pb contamination (Patricia et al., 2007). 3. SCRF: Lead contents for the soil depth 0-10 cm were observed to be 36.2, 30.6 and 17.7 mg kg- I soil in order of winter>summer>monsoon. In and cm depth, the contents were 32.4, 32.2; 22.5, 28.5 and 12.5, 12.5 mg kg- 1 soil, respectively following the order of summer>monsoon>winter. For the last four depths (30-70 cm), mixed trends were observed. Significant seasonal variations were observed from 0-50 cm depth (Table 10). 4. AWS: At this site lead contents were increased significantly in order of winter>monsoon>summer for the first two depths (from 0-20 cm). In 88

28 Table 10 Lead content of soil samples at various sites in different seasons Site Total Pb (mg kg- 1 ) Depth (cm) Summer Monsoon Winter _ BCF CRRF SCRF ~ AWS TFF CD(p=O.05) Season x Site 2.4 Site x Depth 3.7 Season x Site x Depth

29 winter, monsoon and summer seasons the contents were 17.3, 16.1, 10.4 and 15, 13.6, 7 mg kg- 1 soil, respectively. Variations due to seasons were significant in summer and monsoon but in winter, higher lead content were observed to be 17.3 mg kg- 1 soil in 0-10 cm soil depth (Table 10). 5. TFF: In summer and winter seasons significant variations were observed in lead content due to soil depth and it decreased as soil depth increased. The contents decreased in summer from 47.2 mg kg- 1 soil in 0-10 cm depth to 14.6 mg kg- 1 soil in cm depth and in winter season from 46.4 mg kg- 1 soil in 0-10 cm depth to 12.8 mg kg- 1 soil in cm depth. But in monsoon, higher lead content was found to be 28 mg kg- 1 soil in cm soil layer. The highest lead content at this site was observed to be 47.2 mg kg- 1 soil in 0-10 cm soil depth in summer whereas, 12.8 mg kg-l soil were observed in cm soil depth in winter season which was minimum at this site. Variations due to depth were significant in summer while in monsoon and winter seasons no definite trends were recorded (Table 10). The most extensively used measures of urbanization. are trace metals, especially Pb (Gulson etal., 1981). Several studies have reported that trace metal concentrations in surface soil of woodlands located within urban areas are elevated in comparison to 90

30 rural areas (Pouyat and McDonnell, 1991; Pouyat et al., 1995). Several studies have found thatpb concentrations in soils declined sharply. with increasing distance from the road (Kardell and Larsson, 1978; Baesand Ragsdale, 1981). Higher surface soil lead contents were observed in winter season in all the four sites namely BCF, CRRF, SCRF and AWS except TFF site (Fig. 7). Different soil horizons have different lead adsorption capacity due to their variable composition. The most important lead adsorbentsin the natural brown forest soil profile in the order of importance are the organic matter, clay minerals and iron oxides (Peter Sipos, 2004). The distribution of lead within the soil profile is mostly determined by the organic matter and carbonate content of the soil, as well as the amount and mineralogical characteristics of the soil clays. The varying amounts of these phases within the profile affect the chemical properties of the soils resulting in differences in the distribution 91

31 i::n -"'" 0> -S ~ -'= a.. "S (/) Monsoon -Winter BCF CRRF SCRF AWS TF,F Sites' Fig. 6 Seasonal and spatial variation in total Sulphur content of surface soil ,0Summer ~" ~, 0>.:::L. tn " E "'-"".....0' lib MO(1soon 151 Winter 10 0 BCF SCRF TFF Sites' Fig. 7 Seasonal and spatial variation in total Lead content of surface soil samples 92

32 of the lead among the soil components and within the soil profile. The adsorption of lead varies in the different soil horizons because of their different composition Chromium (Cr) 1. BCF: Significant changes were observed due to season x site x depth but no definite trend was observed within the seasons and within the soil depths. In upper soil layer (0-10 cm) at this site, winter witnessed highest total-cr content (24.6 mg kg- 1 soil) followed by summer (21 mg kg- 1 soil) and monsoon (20.9 mg kg- 1 soil). At this site, highest value of Cr was observed to be 24.6 mg kg- 1 soil in 0-10 cm soil depth in winter and lowest to be 7.1 mg kg- 1 soil in cm depth in monsoon season {Table II}. 2. CRRF: At this forest location highest Cr content (29.5 mg kg- 1 soil) among all the five sites were observed in winter season in cm soil depth. ~n summer and monsoon season, variations due to soil depth took place. In summer and monsoon seasons, 0-10 cm soil depth witnessed 18.8 and 23 mg kg- 1 soil Cr whereas; cm depth values were 7.4 and 9.7 mg kg- 1 soil, respectively (Table II). 3. SCRF: In monsoon Cr contents were significantly higher and the range was mg kg- 1 soil than in winter season ranged mg kg- l soil (Table II) in all the depths but no variations were observed due to soil depth in these seasons. In cm soil layer 93

33 summer witnessed higher Cr content (18.6 mg kg- 1 soil) followed by monsoon (16.1 mg kg- 1 soil) and winter (7.9 mg kg- 1 soil). 4. AWS: In summer season variations were observed due to soil depth ranged from 10 mg kg- 1 soil (60-70 em depth) to 16.8 mg kg- 1 soil (0-10 cm depth) and values were decreased as soil depth increased. For the first three soil depths (0-30 em) Cr contents were in order of summer (16.8, 15.9, 15.3 mgkg- 1 soil»monsoon (13.9, 13.5, 14.9 mg kg- 1 soil»winter (8.7,12.4,13.6 mgkg- 1 soil) (Table 11). 94

34 Table 11 Chromium content of soil samples at various sites in different seasons Site Total Cr (mg kg-1l Depth (cm) Summer Monsoon Winter 0..; BCF S S SO S.4 1S.6 29.S S CRRF S S SO S SCRF S S.7 40-S S.2 SO S S.O S.9 13.S S AWS S SO S S 1S S S.1 TFF S SO C D(p=O. 05) Season x Site 1.3 Site x Depth 2.1 Season x Site x Depth

35 5. TFF: In monsoon season Cr contents were significantly higher than winter season. In monsoon values ranged from mg kg- 1 soil and in winter from mg kg- 1 soil. Decreasing trends were observed due to increasing soil depth in summer and winter seasons. The lowest Chromium content among all the five sites was observed to be 2.1 mg kg- 1 soil in winter season in both and cm soil depth (Table 11). It is likely that Cr concentrations are naturally derived. The results indicated lack of definite trend of Cr content as observed in surface soils when compared with season x sites (Fig. 8) Nickel (Nil 1. BCF: In winter season, 0-10, and cm soil depth witnessed significantly higher total-ni content (30.1, 24 and 30.6 mg kg- 1 soil) as compared to summer (2l.6, 19.3 and 16.7 mg kg- 1 soil) and monsoon season (2l.2, 18.7 and 13.5 mg kg- 1 soil), respectively. In summer, cm soil depth witnessed significantly more Ni content (24.2 mg kg- 1 soil) than in monsoon (18.3 mg kg- 1 soil). No definite trend was found due to depth in all the three seasons (Table 12). 2. CRRF: In winter season, all the seven soil depths (0-70 cm) showed a significant increase in total-ni content as compared to monsoon season. The increase was 8.6 mg kg- 1 soil in 0-10 cm depth and 7 mg kg- 1 soil in cm depth. In winter season Ni contents were decreased constantly but not significantly as 96

36 increasing soil depth. Overall decrease in total-ni contents were observed as soil depth increased in all the seasons (Table 12). 3. SeRF: total-ni contents in winter, summer and monsoon seasons in upper two soil depths (0-20 cm) were 28.4,22.7,20.1 and 23.9, 23.4, 16.7 mg kg- 1 soil, respectively. The contents were in order of winter>summer>monsobn. In winter season it was significantly higher (28.4 mg kg- 1 soil) than that of summer (22.7 mg kg- 1 soil) and monsoon (20.1 mg kg- 1 soil) in 0-10 cm soil depth (Fig. 9). In monsoon; in 30-40, and cm soil depths, total-ni contents were significantly higher (I5.4, 14.6 and 12.9 mg kg- 1 soil) than those of summer season (9.5, 6.6 and 6.1 mg kg- 1 soil), respectively (Table 12). 4. AWS: total-ni content in winter season (25. 7 mg kg- 1 soil) in upper most soil depth was significantly higher than that of monsoon season (19.7 mg kg- 1 soil) and in this depth it was in order of winter>summer>monsoon (Fig. 9). In summer season in cm soil depth total-ni content (21 mg kg- 1 soil) was significantly higher than that of monsoon season (I4.9 mg kg- 1 soil, table 12). 5. TFF: In soil depths and cm, in monsoon season totai Ni contents were 23.7 and 23 mg kg- 1 soil and values were significantly higher than summer (16 and 13.4 mg kg- 1 soil). Total Ni contents were decreased from 26.3 to 14.2 mg kg~l soil as depth increased in winter where in summer and monsoon seasons mixed trends were observed (Table 12). 97

37 Table 12 Nickel content of soil samples at various sites in different seasons Site Total Ni (mg kg- 1 ) Depth (cm) Summer Monsoon Winter BCF CRRF SCRF AWS TFF C D(p=O. 05) Season x Site 1.8 Site x Depth 2.8 Season x Site x Depth

38 122 Summer IllIMonsoon!5IWinter. CRRF serf AWS TFF Sites Fig. 8 Seasonal and spatial variation in total Chromium content of surface soil EI Summer 1m Monsoon I2IVVinter 25 b> 20 ~.0> E,,---,15. z 10 5 o +-J.LL.t._ BCF CRRF serf Sites AWS TFF Fig. 9 Seasonal and spatial variation in total Nickel content of surface soil 99

39 In recent past at AWS site, mining activity has taken place and this may be the reason affecting normal distribution of trace elements. Ni content seems to be of natural origin at AWS site, since no industrial activity is taking place now. Ni was observed to be higher in upper soil depth at all the sites as compared to lower depths and leaching of Ni from upper soil horizons will take place in more than 200 years as reported by Barcan (2002) Iron (Fe) 1. BCF: Winter season witnessed comparatively higher total iron contents (24175 mg kg- 1 soil) in 0-10 cm soil depth (Fig. 10) followed by summer (24050 mg kg- 1 soil) and monsoon (19130 mg kg- 1 soil). Summer and winter values were significantly higher than monsoon season. In summer and monsoon seasons cm soil depth witnessed higher Fe content (26220 and mg kg- 1 soil) than 0-10 cm soil depth (24050 and mg kg- 1 soil), respectively (Table 13). 2. CRRF: In upper most soil depth (0-10 cm), significant variations in Fe contents were observed.(fig 10). It was in order of summer (29950 mg kg- 1 soil»monsoon (16795 mg kg- 1 soil»winter (13336 mg kg- l soil). In cm soil depth, contents were higher than that of 0-10 cm soil depth in summer, monsoon and winter seasons as 31230, and mg kg-l soil, respectively (Table 13). Mixed trend of results showed inherent soil properties. 100

40 Table 13 Iron content of soil samples at various sites in different seasons Site Total Fe (mg kg- 1 ) Depth (cm) Summer Monsoon Winter BCF CRRF SCRF AWS TFF CD(p=O.05) Season x Site Site x Depth Season x Site x Depth

41 3. serf: In upper five soil depths (0-50 cm) Fe contents were in order of winter>summer>monsoon (Table 13). The winter season values in all the seven depths (0-70 cm) were significantly higher (ranging mg kg- 1 soil) than monsoon season (ranging mg kg- 1 soil). In monsoon season, Fe contents decreased to mg kg- l soil as depth increased to cm where, in summer and winter mixed trends took place. 4. AWS: In 0-10 cm soil depth, Fe content in summer season was significantly higher (18224 mg kg- 1 soil) than monsoon (11930 mg kg- 1 soil) and winter (13016 mg kg- 1 soil); however in winter Fe content of mg kg- 1 soil was higher but not significant than monsoon value of mg kg- l soil (Fig. 10). In upper five soil depths (0-50 cm) iron contents were in order of summer>winter>monsoon. In monsoon season in cm soil depth Fe content was lowest (10718 mg kg- l soil) among all the five forest soil locations (Table 13). 5. TFF: In 0-10 cm soil, Fe content was in order of winter>summer>monsoon (Fig. 10). In winter season in cm soil depth Fe content was mg kg- l soil (highest among all the five forest soil locations), which was significantly higher than summer (26640 mg kg- 1 soil) and monsoon (28215 mg kg- 1 soil). Season x site x depth interaction was significant (p=o.05, Table 13). The findings show a close relationship between soil processes and Fe 102

42 movement in profiles. The dominant process is eluviations from surface and illuviation in the sub-surface horizons. Compared to the total Fe in the parent materials, surface soils have 80% of total Fe. Total contents of Fe ranged from 1.5% to 4.5% in Indo-Gangetic plains (Sharma et at, 2000) Manganese (Mn) 1. BCF: The season x site x depth interaction was not significant. However, in all the seven soil depths summer season values of Mn were on higher side (ranging mg kg- 1 soil) followed by winter (ranging mg kg- 1 soil) and monsoon (ranging mg kg- 1 soil, Table 14). 2. CRRF: At this location interaction among variables were also not significant. But in 0-10 cm soil depth, Mn content was higher (357 mg kg- 1 soil) in summer season than winter (285.2 mg kg- 1 soil) followed by monsoon (223.2 mg kg- 1 soil, Fig. II). The overall distribution of Mn followed a mixed trend (Table 14). 3. SCRF: In 0-10 cm soil depth total Mn content was in order of winter>summer>monsoon (Fig. II). In lower depth (60-70 cm) Mn content was lowest in winter season (192.9 mg kg- 1 soil) followed by monsoon (207.Img kg- 1 soil) and summer (351 mg kg- 1 soil). The season x site x depth interactions were not significant (Table 14). 103

43 Table 14 Manganese content of soil samples at various sites in different seasons Site BCF Total Mn (mg kg-i) Depth (cm) Summer Monsoon Winter ~ CRRF SCRF AWS TFF CD(p=O_05j Season x Site 29.3 Site x Depth Season x Site x Depth NS NS 104

44 35000 f21summer IIlIMonsoon Winter (\) LL 10000, 5000 o BCF CRRF SCRF AWS TFF" Sites Fig. 10 Seasonal and spatial variation in total Iron content of surface soil b>.::.::. 0> g c: ~ 500 " ~ '150 " BCF.CRRF SCRF: ~Suminer mlmonsoon 151 Winter AWS TFF 'Sites Fig. 11 Seasonal and spatial variation in total Manganese content of surface soil 105

45 4. AWS: The overall distribution of Mn followed a mixed trend however; in monsoon season cm soil depth contained higher Mn (183 mg kg- l soil) than 0-10 cm soil layer (164.4 mg kg- l soil). The season x site x depth interactions were not significant (Table 14). 5. TFF: The season x site x depth interaction was not significant. Among all the three seasons, in 0-10 cm soil depth Mn content in winter was higher (326.2 mg kg- l soil) than that of summer (304 mg kg- 1 soil) followed by monsoon (297.6 mg kg- 1 soil, Fig. 11). In monsoon season, Mn contents decreased as soil depth increased. This trend was not followed in summer and winter seasons (Table 14). Irregular distribution of Mn was observed in soil profiles ( mg kg- 1 soil). The clay content is important factor determining tota1-ni distribution in soils as evidenced from significant positive correlation between them (Sharma et at, 2000) Zinc (Zn) 1. BCF: The season x site x depth.interaction was not significant in case if zinc also. In winter and summer seasons the Zn contents decreased from 52.7 and 61.3 mg kg- l soil in 0-10 cm depth (Fig. 12) to 21.8 and 16.5 mg kg- 1 soil, respectively as soil depth increased to cm. But in monsoon mixed trend was observed (Table 15). Decrease in total Zn content in sub-surface horizons in Alfisols, Inceptisols and Entisols of Indo-Gangetic plains was observed by Sharma et al., (2000). 106