Environmental Engineering Reference
In-Depth Information
in the intertidal zone with high organic matter will tend to retain more water at low tide when
exposed to aerial conditions than soils with less organic matter (Brady, 1974).
The average value of percentage of sand ranged from 6.73 to 17.47 with a minimum
value (6.13) found in winter and a maximum value (19.05) recorded in monsoon. The
findings of the present study agreed with the result of Ihm and Lee (1998) who found high
variations (8-76%) in sand content of salt marsh while they conducted their research on salt
marsh, swamp and sand dune dominated by 24 coastal vegetation communities in Korea. The
highest sand content in the present observations was found during monsoon since the wave
action and tidal currents are strong enough to produce the development of sandy sediment in
intertidal zones as stated by Friedman and Sanders (1978). The average value for silt content
was ranged from 50.05 to 51.24% with the lowest value (49.13%) recorded during
premonsoon and the highest value (52.01%) measured during winter. The findings of the
present study agreed with the result of Ihm and Lee (1998) who reported silt content of soil in
salt marsh communities as 11-62%.
Fluctuations in the percentage of clay were varied from 32.17 to 42.04% with a minimum
value (28.36%) found in monsoon and a maximum value (42.89%) recorded in winter in the
present study. Wide variations (8-31%) in clay content of soil in salt marsh communities were
found by Ihm and Lee (1998) that coincide with the present observations. Marchand et al.
(2008) stated that the association of organic carbon in sediment is crucially dependent upon
the grain size itself, whereby higher organic content will be represented in the finer particles
and vice versa. Thus, low organic carbon concentration in the study area recorded in monsoon
may be due to the sediment grain size which was dominated by moderately coarse sand.
Moisture level of soil was varied significantly between seasons that were ranged from
1.02 to 2.16% with the lowest value (0.75%) observed during monsoon and the highest value
(2.31%) recorded during winter. Seasonal differences in soil moisture values were noticed by
Tan Le (2008) as the results found in the present study. Soil moisture and soil bulk density in
the present study indicate that decreases in moisture lead to increases in soil bulk density. Soil
bulk density was also found to have a relationship with the organic matter. Correspondingly,
in monsoon and premonsoon when lower organic matter was found due to regular tidal
flushing of the study area had a higher soil bulk density which also agrees with data presented
by Mitsch and Gosselink (2000); Gambrell and Patrick (1978).
Field water capacity of soil recorded from the
Porteresia
bed of Fauzderhat region of
Chittagong coast was 45.75- 52.38% throughout the study period with lower values (44.59)
found during monsoon and higher values (54.50%) recorded during winter. As regards soil
texture, the higher content of loamy particles increases the soil capacity and thus it can hold
more water for plant growth (Gavande, 1972). Therefore the highest value for the field water
capacity in the present study was found during winter while the sediment bear more silt and
clay particle rather than sand. Mitsch and Gosselink (2000) suggested that soil bulk density
decreases as the water holding capacity of the soil and the organic matter in the soil increase.
Similar results were found in this study.
Bulk density of soil showed a distinct seasonal variation that was ranged from 1.22 to
1.67gcm
-3
with the lowest value (1.19gcm
-3
) found in winter and the highest value
(1.74gcm
-3
) recorded in monsoon. Similarly, particle density of soil varied significantly from
2.80 to 3.67gcm
-3
with a minimum value (2.65gcm
-3
) found in winter and a maximum value
(3.73gcm
-3
) recorded in monsoon. Soil particle density is assumed to range between 2.60 and
