Natural attenuation of nitrogen in groundwater discharging through a sandy beach

作者：Loveless Alicia M^*; Oldham Carolyn E

来源：Biogeochemistry, 2010, 98(1-3): 75-87.

DOI：10.1007/s10533-009-9377-x

• Groundwater nitrogen
• Permeable sand
• Coastal aquifer
• Submarine groundwater discharge

This paper presents an uncomplicated approach to improve estimates of groundwater nutrient load to a marine embayment. A two-dimensional chemical profile of shallow groundwater was analysed in a sandy beach in three seasons (early summer, late summer and mid winter) and an adjusted estimate of groundwater nutrient discharge was derived that accounts for a complex biogeochemical environment and non-conservative behaviour of nutrients in the pre-discharge beach groundwater. The study was conducted at Cockburn Sound, Western Australia, where there has been significant groundwater contamination and associated marine ecological degradation. Losses in nitrogen and increases in phosphorus were observed along the discharge pathway beyond that expected from mixing with marine water, and the changes were attributed to chemically and biologically mediated reactions. A slow groundwater velocity (0.14-0.18 m day(-1)), high organic carbon (TOC = 0.35-4.9 mmol l(-1), DOC = 0.28-4.6 mmol l(-1)) and low to sub-oxic conditions (DO = 0.4-24% saturation) were deemed suitable for chemically and biologically mediated reactions to occur and subsequently alter regional estimates of groundwater nutrient concentration. Accounting for this environment, groundwater loads were calculated that were 1-2 orders of magnitude less than previous regional-based estimates: 0.4-13 kg NO (x) (-) day(-1), 0.2-24 kg NH(4) (+) day(-1) and 0.004-0.8 kg FRP day(-1). This paper applies knowledge of recent research and presents scope to marine managers or modellers to account for groundwater inputs to the marine environment.

• 出版日期2010-4