The oxygen isotope composition of phosphate: a potential tool in UK freshwater studies?

该提案是一个小型的“试点”研究项目，旨在研究河流系统中磷酸盐中氧原子的同位素组成。河流和湖泊中高浓度的磷酸盐是“富营养化”的主要原因：营养物质的过度富集导致严重的环境破坏（生物多样性减少，缺氧，鱼类死亡），健康问题（有毒藻类）和经济问题（昂贵的水处理）。英国和世界其他地区的许多河流都存在这个问题，因为污水处理厂或农业活动产生的富含磷酸盐的沃茨被泵入或泄漏到河流中。解决这个问题需要知道磷酸盐来自哪里，以及当它进入河流时会发生什么。磷酸根离子由一个磷原子和四个氧原子组成，氧原子可以是不同的同位素类型：原子质量18的氧和原子质量16的氧（两者都是天然存在的非放射性同位素）。初步研究表明，这两种同位素的比例取决于磷酸盐的来源（例如，污水与农业肥料），这两种同位素比例的变化表明了磷酸盐在水中的使用方式。然而，这一初步工作非常有限，主要是在其他国家的河口和沿海地区的盐水沃茨进行的。我们想看看它是否能在英国的淡水环境中工作。因此，该计划有两个方面：1）分析来自少量污水和农业废水的磷酸盐中氧-18和氧-16的比例，看看它们是否不同。如果他们这样做了，我们就可以通过测量河水来确定磷酸盐污染的来源。2)以观察来自特定来源（例如污水厂排入河流的排污口）的磷酸盐中氧-18和氧-16的比例是否随着磷酸盐被带到下游而变化。如果是这样的话，我们也许能够使用这样的测量来确定磷的需求或系统的“限制”-控制富营养化的一个重要因素。

The proposal is for a small, 'pilot' research project to look at the isotopic composition of oxygen atoms in phosphate in river systems. High concentrations of phosphate in rivers and lakes are a primary cause of 'eutrophication': an over-enrichment in nutrients leading to conditions which can result in severe environmental damage (reduced biodiversity, oxygen starvation, fish deaths), health issues (toxic algae), and economic problems (expensive water treatment). Many rivers in the UK, and other parts of the world suffer from this problem because phosphate-rich waters from sewage works or from farming activities are pumped or leak into the rivers. Dealing with this problem involves knowing where the phosphate comes from, and understanding what happens to it when it gets into the river. The phosphate ion consists of a phosphorus atom and four oxygen atoms, and the oxygen atoms can be of different isotope types: oxygen of atomic mass 18 and oxygen of atomic mass 16 (both are naturally-occurring, non-radioactive isotopes). Preliminary studies have shown that the proportions of these two isotopes differ depending on where the phosphate came from (e.g. sewage compared with agricultural fertilizer), and that changes in the proportion of the two isotopes indicates the way in which the phosphate is being used in the water. However, this preliminary work is very limited, and has been mainly done in saline waters in estuaries and coastal areas in other countries. We want to see if it might work in fresh water environments in the UK. The plan is therefore two-fold: 1) to analyse the proportions of oxygen-18 and oxygen-16 in phosphate from a small number of sewage and agricultural effluents, to see if they differ. If they do, we may be able to use measurements of river water to determine where phosphate pollution is coming from. 2) to see if the proportion of oxygen-18 and oxygen-16 in phosphate coming from a particular source (e.g. the outfall of a sewage works into a river) changes as the phosphate is carried downstream. If it does, we may be able to use such measurements to determine the phosphorus demand or 'limitation' of the system - an important factor in controlling eutrophication.