Howland R J, Tappin A D, Uncles R J, Plummer D H, Bloomer N J
NERC Centre for Coastal and Marine Sciences, Plymouth Marine Laboratory, UK.
Sci Total Environ. 2000 May 5;251-252:125-38. doi: 10.1016/s0048-9697(00)00406-x.
Monthly axial profiles of the Tweed Estuary were carried out between July 1996 and August 1997 as part of the UK Natural Environment Research Council Land Ocean Interaction Study. During these surveys, master variables and a range of chemical constituents, including pH and total alkalinity, were measured between the mouth of the estuary, at Berwick-upon-Tweed, and the freshwater tidal reach, at Union Bridge, approximately 10 km up-estuary. Alkalinity and pH showed clear seasonal variations in values within the lower salinity region of the estuary, and these could be related largely to changes in river flows, and hence to variations in the ratios of the source waters. River waters at high flows were dominated by poorly buffered surficial runoff, and pH and alkalinity values were low; conversely at low flows, groundwaters rich in weathered bedrock ions dominated the river water, and pH and alkalinity values were significantly higher. Biological production and respiration also had an effect on this seasonal variability, although this was secondary. The behaviour of pH and alkalinity within the estuary appeared generally conservative, although apparent non-conservative distributions were observed in the freshwater tidal reach. In a number of cases this behaviour could be attributed to biological activity. Estimated values of the excess partial pressures of CO2 within the fresh-water tidal reach were low (< 4), reflecting the relatively pristine character of the Tweed. During the spring and summer, CO2 was significantly undersaturated with respect to the atmosphere; extensive production by bed-anchored macroalgae was probably the reason for this, although the effects of water column algae cannot be discounted. In winter, production was minimal and respiration more important. As a result, partial pressures within the water column increased to a maximum of approximately four times atmospheric. Only infrequently was the CO2 in equilibrium between the river and atmosphere, suggesting that the tidal reach of the Tweed is a dynamic environment with respect to carbon cycling processes.
作为英国自然环境研究委员会陆地海洋相互作用研究的一部分，于1996年7月至1997年8月期间对特威德河口进行了月度轴向剖面测量。在这些调查中，在河口口（特威德河畔贝里克）以及河口上游约10公里处的联合桥的淡水潮汐段之间，测量了主要变量和一系列化学成分，包括pH值和总碱度。碱度和pH值在河口低盐度区域内呈现出明显的季节性变化，这在很大程度上可能与河流流量的变化有关，进而与源水比例的变化有关。高流量时的河水以缓冲性差的地表径流为主，pH值和碱度值较低；相反，在低流量时，富含风化基岩离子的地下水主导河水，pH值和碱度值显著更高。生物生产和呼吸作用也对这种季节性变化有影响，尽管是次要的。河口内pH值和碱度的行为总体上似乎是保守的，尽管在淡水潮汐段观察到明显的非保守分布。在许多情况下，这种行为可归因于生物活动。淡水潮汐段内二氧化碳过剩分压的估计值较低（<4），这反映了特威德河相对原始的特征。在春季和夏季，二氧化碳相对于大气明显不饱和；附着在河床的大型藻类大量繁殖可能是原因，尽管水柱藻类的影响也不能忽视。在冬季，生产活动最少，呼吸作用更为重要。结果，水柱内的分压增加到最高约为大气的四倍。只有在很少的情况下，河水与大气中的二氧化碳才处于平衡状态，这表明特威德河的潮汐段在碳循环过程方面是一个动态环境。
