Influence of recovery from acidification on the dynamics of dissolved organic carbon (DOC) in organic soils

在英国高地上占主导地位的泥炭土壤代表着大量的碳储量，约占全球陆地碳总量的三分之一，相当于大气中储存的碳总量。这些土壤缓慢地向河流和湖泊释放碳。正是这种溶解的有机碳赋予了高地水域棕色。在过去的15年里，随着泥炭地排放的溶解有机碳的数量平均增加了91%，这些水域的颜色变得更深了。泥炭地土壤碳流失的增加加剧了人们的担忧，即我们已经扰乱了全球碳循环的稳定。水色的增加也是自来水公司面临的一个问题，因为在水处理过程中，溶解的有机碳可能会与氯反应，产生潜在的致癌化学物质。一些科学家认为，全球变暖导致的气温上升或降雨量减少，正在导致泥炭地释放更多的碳，而另一些科学家则认为，大气中二氧化碳的增加本身就是原因。如果这些气候变化机制导致溶解有机碳的增加趋势，这表明泥炭地正在变得不稳定，对全球碳循环(对气候产生反馈影响)、水质和水处理产生重大影响。然而，我们认为，最近气温和二氧化碳的上升不足以引起所观察到的溶解有机碳的变化。我们认为，过去20年来酸雨的减少对溶解有机碳浓度产生了更重要的影响，因为有机碳的溶解度受pH控制：水越酸，溶解的越少。如果这是正确的，这将对全球碳循环和长期水质产生截然不同的后果，因为这些系统只是在恢复到工业化前的状态。因此，淡水中溶解有机碳的增加可能代表着环境恢复到更自然的条件，而不是对气候变化的环境退化。因此，这项研究项目的总体目标是，确定酸雨的减少是否可以解释自1988年以来观察到的英国淡水中DOC浓度增加的主要原因。这项研究将以两种方式进行。我们将通过实验室实验来测量土壤在不同程度污染下的变化。我们还将研究英国不同地区土壤中这些变化的证据。这项研究将耗时三年完成，利兹大学、生态与水文学中心和伦敦大学学院的科学家合作完成。最后，将试验结果与以有机土壤为主的旱地集水区长期监测数据分析相结合。

Peaty soils, which dominate the uplands of the UK, represent a significant store of carbon, containing around a third of the global terrestrial carbon, which is equivalent to the total amount of carbon stored in the atmosphere. These soils slowly release carbon into rivers and lakes. It is this dissolved organic carbon that gives upland waters their brown colour. Over the last 15 years, the colour of these waters has become darker as the amount of dissolved organic carbon draining from peatlands has increased, by on average 91%. This increase in the loss of carbon from peatlands soils has promoted fears that we have disturbed the stability of the global carbon cycle. The increase in water colour is also a problem for water companies as the dissolved organic carbon can react with the chlorine in water-treatment processes to produce potentially carcinogenic chemicals. Some scientists have suggested that increasing temperatures or decreasing rainfall due to global warming is resulting in more carbon being released from peatlands, while others have suggested that increasing atmospheric carbon dioxide is itself the cause. If these climate change mechanisms are responsible for the increasing trend in dissolved organic carbon, it suggests that peatlands are becoming unstable, with major implications for the global carbon cycle (with feedback effects on climate), water quality and water treatment. We argue, however, that recent rises in temperature and carbon dioxide have been insufficient to cause the observed changes in dissolved organic carbon. We believe that the decline in acid rain over the past 20 years has been a more important influence on dissolved organic carbon concentrations, as the solubility of organic carbon is controlled by pH: the more acid the water, the less is dissolved. If correct, this has very different consequences for the global carbon cycle and long-term water quality, as the systems are simply returning to their pre-industrial conditions. Therefore, increased dissolved organic carbon in freshwaters may represent an environmental recovery to more 'natural' conditions, and not an environmental degradation in response to climate change. The overall aim of this research project is therefore, to determine whether the decline in acid rain can account for the majority of the observed increase in DOC concentration in freshwaters across the UK since 1988. The research will be conducted in two ways. We will use laboratory experiments to measure the changes in soils subjected to different levels of pollution. We will also study evidence for these changes in soils from different locations across the UK. The research will take three years to complete and involves collaboration between scientists at the University of Leeds, Centre for Ecology and Hydrology and University College London. Finally we will integrate the experimental results with analysis of long-term monitoring data for upland catchments dominated by organic soils.