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River rescue T he science behind nutrient pollution in rivers is still poorly understood despite the fact that nitrate and phos- phate concentrations in the UK's rivers are mostly unaccept- able, although an element of uncertainty exists about what an acceptable level actually is. Key to improving our under- standing of the sources and impacts of nutrient pollution is high-resolution monitoring across a broad spectrum of river types. Phosphates and nitrates occur naturally in the environ- ment and are essential nutrients that support the growth of aquatic organisms. However, water resources are under con- stant pressure from both point and di• use sources of nutrients. Under certain conditions, such as warm, sunny weather and slow-moving water, elevated nutrient concentrations can pro- mote the growth of nuisance phytoplankton causing algal blooms in a process known as eutrophication. These blooms can dramati- cally a• ect aquatic ecology in a number of ways. High densities of algal biomass within the water column – or, in extreme cases, blankets of algae on the water surface – prevent light from reaching submerged plants. Also, some algae, and the bacteria that feed on decay- ing algae, produce toxins. In combination, these two e• ects can lower dissolved oxygen lev- els and potentially kill - sh and other organisms. In conse- quence, aquatic ecology is dam- aged and the water becomes HydroCycle Phosphate Monitor € OTT Hydrometry's Nigel Grimsley discusses the technologies that have overcome traditional barriers to the continuous monitoring of phosphate and nitrate and can help provide the protection that UK rivers need unsuitable for human recreation and more expensive to treat for drinking purposes. In its State of the Environ- ment report, published in Feb- ruary, the Environment Agency said: "Unacceptable levels of phosphorus in over half of Eng- lish rivers, usually due to sew- age e‡ uent and pollution from farm land, chokes wildlife as algal blooms use up their oxy- gen. Groundwater quality is cur- rently deteriorating. This vital source of drinking water is o‰ en heavily polluted with nitrates, mainly from agriculture." Ecological status The EU Water Framework Direc- tive (WFD) requires the UK to achieve 'good status' of all water bodies (including rivers, streams, lakes, estuaries, coastal waters and groundwa- ter) by 2015. However, only 36 per cent of water bodies were classi- ed as 'good' or better in 2012. In the UK, nutrient water quality standards are set by Defra so, for example, phospho- rus water quality standards have been set, and vary accord- ing to the alkalinity and height above mean sea level of the river. Interestingly, the stand- ards were initially set in 2009, but in 75 per cent of rivers with clear ecological impacts of nutrient enrichment, the exist- ing standards produced phos- phorus classi- cations of good or even high status, so the phos- phorus standards were lowered. Highlighting the need for better understanding of the rela- tionships between nutrients and ecological status, Dr Mike 12 WET NEWS AUGUST 2018 | wwtonline.co.uk INSIGHT MONITORING Bowes from the Centre for Ecol- ogy & Hydrology has published research, with others, in which the e• ects of varying soluble reactive phosphate (SRP) con- centrations on periphyton growth rate (mixture of algae and microbes that typically cover submerged surfaces) were determined in nine di• erent riv- ers from around the UK. In all of these experiments, significantly increasing SRP concentrations in the river water for sustained periods (usually around nine days) did not increase periphy- ton growth rate or biomass. This indicates that in most UK rivers, phosphorus concentrations are in excess, and therefore the pro- cess of eutrophication (typified by excessive algal blooms and loss of aquatic plants, known as macrophytes) is not necessarily caused by intermittent increases in SRP. Clearly, more research is nec- essary to more fully understand the e• ects of nutrient enrich- ment, and the causes of algal blooms. Headwater streams represent more than 70 per cent of the streams and rivers in Britain but, because of their number, location and the lack of regula- tory requirement for continuous monitoring, headwater streams are rarely monitored for nutrient status. Traditional monitoring of upland streams has relied on either manual sampling or the collection of samples from auto- matic samplers. Nevertheless, research has shown that upland streams are less impaired by nutrient pollu- tion than lowland rivers, but is therefore generally preferred, but in the past this has been dif- - cult to achieve with the tech- nology available because of its requirement for frequent recali- bration and mains power. High resolution SRP monitor- ing has been made possible in almost any location with the launch by OTT Hydromet of the 'HydroCycle PO4', which is a battery-powered wet chemistry analyser for the continuous analysis of SRP. Typically, the HydroCycle PO4 is deployed into the river for monitoring purposes, but recent work by the Environment Agency has deployed it in a ¦ ow-through chamber for measuring extracted water. The HydroCycle PO4 meth- odology is based on US EPA standard methods, employing pre-mixed, colour-coded car- tridges for simple reagent replacement in the - eld. Weigh- ing less than 8kg fully loaded with reagents, it is quick and easy to deploy, even in remote locations. The instrument has an internal data logger with 1GB capacity and, in combination with telemetry, it provides oper- ators with near real-time access to monitoring data for SRP. Environment Agency application The National Laboratory Service Instrumentation team (NLSI) provides support to all high-res- olution water quality monitor- ing activities undertaken across the Agency, underpinning the EA's statutory responsibilities such as the WFD, the Urban Waste Water Directive and because of their size and limited dilution capacity they are more susceptible to nutrient impairment. Monitoring technology Sampling for laboratory analy- sis can be a costly and time-con- suming activity, particularly at upland streams in remote loca- tions with diª cult access. In addition, spot sampling reveals nutrient levels at a speci- c moment in time, and therefore risks missing concentration spikes. Continuous monitoring River rescue OTT Hydrometry's Nigel Grimsley discusses the technologies that have overcome traditional barriers to the continuous monitoring of phosphate and nitrate and can help provide the protection that UK rivers need The SUNA V2

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