No abstract

The impact of the nutrient level on the water quality in the Hooghly and Matla estuarine complex in Indian Sundarbans was assessed for three decades (1984-2014). Nitrate, phosphate and silicate were used as indicators of nutrient related water quality in the estuarine water. Our first order analysis reflects significant spatio-temporal variations of selected nutrients with relatively higher values in the Hooghly estuary (in the western Indian Sundarbans) compared to the Matla estuary (in the central Indian Sundarbans). Significant variations were observed in dissolved nitrate, phosphate and silicate concentrations between stations and years (p < 0.01). Such pronounced variations may be attributed to the location of highly industrialized and urbanized city of Kolkata, Howrah and Haldia port-cum-industrial complex adjacent to the Hooghly estuary. The sudden rise of selected nutrients during premonsoon, 2009 (irrespective of sampling stations) is directly related to AILA, a super-cyclone that occurred in the lower Gangetic delta during 22nd-25th May, 2009.

Methane (CH4) is 21 times more powerful as a greenhouse gas than carbon dioxide. Wetlands including flooded paddy fields are one of the major sources for this gas. Paddy fields are responsible for producing 25 to 54 Tg of CH4 annually. Methane emission rate could be affected by several factors such as irrigation pattern, fertilizer type, soil organic matter and soil temperature. Among them, soil temperature is a determining factor which deserves to be investigated. This study performed with the aim of understanding the effect of soil temperature on the methane emission rate from paddy soil in a short period of time (hourly) and long term (during rice growing season). The results of this study suggest that soil temperature could control the amount of methane emission and there is a positive and strong correlation in both soil temperature and methane emission pattern in short period of time. However, in case of long term trend, other factors such as water management and plant age decreased this correlation from 0.768 to 0.528.