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Objectives: This study was conducted to a) find out and compare the period prevalence of HBsAg in children attending outdoor and indoor of an urban and a rural hospital b) determine the risk factors for Hepatitis B surface antigen positivity. Materials and Methods: Three hundred and twenty three children were included in this study. Among them 162 attended an urban hospital and 161 attended a rural hospital. Collected sera were examined for HBsAg by ELISA method in a standard laboratory. Results: Among the 162 urban children 17 (10.5%) were found to be HBsAg positive and among the 161 rural children 6 (3.7%) were found to be HBsAg positive. This difference is statistically significant (P value < 0.05). In urban area, 12 (16.2%) school aged, 3 (6%) pre-school children and 2 (5.5%) infants were found to be HBsAg positive. In rural area, more pre-school (6%) than school children (2.8%) were found to be HBsAg positive. In urban area, 11.5% male children and 9.5% female children were found to be HBsAg positive and in rural area, 5.2% male and 2.8% female children were to be HBsAg positive. Among 17 HBsAg positive cases who attended urban hospital, 11 (19.6%) had past history of jaundice and 6 (5.6%) had no past history of Jaundice (P value < 0.05). Among those 17 HBsAg positive cases, 13 (14.6%) had past history of inoculation within last 6 months and 4 (5.5%) had no such history. This difference is also statistically significant (P value < 0.005). Conclusion: Prevalence of positive HBsAg marker is fairly high in urban children (10.5%). Prevalence of HBsAg has no age and sex prediction. More sero-positive children in urban area have previous history of jaundice and history of inoculation in last 6 months, but no one in rural area had history of jaundice or inoculation within last 6 months. Key word: Serosurvilance; Hepatitis B virus. N.B. This publication is based on a dissertation DOI: 10.3329/bjch.v30i1.6178 Bangladesh J Child Health 2006; VOL 30 (1/2/3): 17-21

This study deals with the nature and state of geomorphic environmental changes of a coastal river basin at southwestern Bangladesh over a period of three decades (1973-2009). The study concentrates on the Kholpetua river basin, which receive fresh water flow from Betna in the upstream and tidal flow in the middle from Morichapa and finally drains to the Bay of Bengal through Kapotakshi River. The whole Kholpetua basin may be divided into three distinct parts: fresh water upstream, brackish water middle part and saline lower part. Large-scale population increase, both in the upper and middle basin; infrastructure development, in the form of road network and introduction of HYV rice in the floodplain of Betna and shrimp farming on the brackish water have lead to the loss of both quality and extent of wetland resources in the basin area, endangering the geomorphological balance in terms of input and output between upstream and downstream. A large section of Betna has dried-up, and most of the tributaries and distributaries of the Morichapa have been silted up, partly because of extensive polders of the sub-basin. As a result, energy exchange (through tide) between basin plains and channels ways has lost vitality. Multi-spectral remote sensing data, in conjunction with topographical maps and ancillary data analysis reveals that throughout the basin, a wide range of anthropogenic interference have physically altered the characteristic ecosystem of the basin. The agricultural land is about 79,395 ha. in 1973, which is reduced at about 53,328 ha in 2009. With 1779 to 2001, a strip of about 20 km wide mangrove forest has been disappeared. Such physical alteration has been initiated with the poldering of middle brackish water part of the basin and later with the introduction of extensive shrimp cultivation. Attempt has been made to explore the linkage of upstream landuse activities and drainage alteration to the hydrological and geomorphological behavior of the downstream basin areas, extrapolate ecological sensitivity of the basin.

Soil acts as a large reservoir of Organic Carbon (OC) but the amount varies significantly with space and time. Thus, soil analysis and interpretation of spatial variability of Soil Organic Carbon (SOC) are keys to site-specific management. The study aimed to characterize the spatial variability of SOC in an active floodplain. Soil samples were collected in three major landform categories (natural levee, back slope, marsh land) from the lower Brahmaputra River floodplain and then analyzed for SOC measurement in the laboratory. The measured data were then analyzed for spatial variability interpretation using descriptive statistics and geo-statistical analysis. The study found that the amount of SOC varies with landform variation, soil texture and distance between sample points. The topsoil of marsh land has the highest (1.41%), back slope holds a moderate amount (1.15%) and the natural levee has the lowest (0.75%) amount of SOC. The amount of clay particles at the top layer was found to be positively correlated to the SOC whereas in the same layer of sand and silt showed a negative correlation. The geo-statistical analysis illustrated the nugget effect. Low (<1%) SOC is commonly found in the agricultural soils of Bangladesh which was corroborated in this study; moderate (1.1%) SOC was found in the floodplain. This study aimed to provide an insight into spatial variability to assist in predicting SOC in the active floodplain; consequently, the interpretation of spatial variability analysis can be implemented for site specific management strategies and to calculate carbon stock in floodplain soils. The Dhaka University Journal of Earth and Environmental Sciences, Vol. 8(2), 2019, P 33-40

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