Environmental Engineering Reference
In-Depth Information
Variations in the concentrations of total P observed in soil among monsoon, postmonsoon,
winter and premonsoon were significant at 5% level of significance (Table 1). Significantly
(p<0.05) higher value in postmonsoon and lower value in winter was recorded in this study.
Available P showed a positive correlation with dissolved oxygen, tidal height, inundation
period, bulk density, exchangeable Ca, Mg & K and total N of soil and a negative correlation
with water transparency, water table depth, soil salinity, soil organic carbon, organic matter,
field water capacity and porosity of soil at a significant level of p<0.01. It also positively
correlated with total suspended solids, percentage of sand, particle density and negatively
influenced by water salinity, percentage of clay at the level of p<0.05 (Appendix B).
Associations of different hydropedological factors recorded in the present study were
shown in Figure 24. Highly correlated factors were clustered together with a minimum
distance. Figure 24 indicated that water temperature and soil temperature remained in the
same group than the others. Similarly soil nutrients like exchangeable Ca, Mg & K, total N
and available P grouped together with minimum difference in their nature. Soil organic
carbon and soil organic matter was highly correlated factors so that they were grouped
together.
Other factors like water salinity, soil salinity and water transparency showed similar
distribution pattern in the study area and thus they were clustered together with minimum
euclidean distance level.
D
ISCUSSION
All the hydropedological factors studied except water and soil pH showed noticeable
seasonal variations, which may be attributed to the local climatic conditions as well as the
exchange mechanism between salt marsh bed and the surrounding water bodies affected by
the tidal flushing of the Bay of Bengal.
Seasonal variations of the sub-surface water temperature in the vicinity of
P. coarctata
bed of Fauzderhat coast, Chittagong were significantly varied among seasons which was
ranged from 20.60ºC to 34.44ºC throughout the sampling period. Similarly seasonal
variations of soil temperature were significantly varied among seasons that were ranged from
22.18ºC to 31.09ºC. The physico-chemical parameters of the estuarine environment of
Bangladesh show regular seasonal patterns of variation and the average annual surface water
temperature of the estuarine system in the country was recorded at 30ºC in different studies
(Mahmood et al.
,
1976, 1978; Rashid, 1999). The findings of the present study also agreed
with earlier reported works in Bangladesh coastal waters conducted by Zafar (1992) who
reported temperature ranges of between 21°C-32°C and Das(2002) who reported temperature
varies of between 25°C-30°C with a marked seasonal fluctuations. Jagtap et al. (2006) studied
on the characteristics of
P. coarctata
bed along the Goa coast of India and they reported that
the surface water temperature varied from 21.5 °C to 32.5°C. Temperature showed significant
seasonal variation (p<0.05) in the present study. The temperature values were significantly
higher in the monsoon months and lower in winter months due to the local climatic condition
which is mainly influenced by the south eastern and north western wind pattern prevailing in
the Bay of Bengal coast (Holmgren, 1994). A similar trend was reported in the study
conducted by Abu Hena and Khan (2009), Chowdhury et al. (2010) and Paulo and Claudia
