On 13 December Maryna Strokal defended her PhD thesis “River export of nutrients to the coastal waters of China: The MARINA model to assess sources, effects and solutions”. She graduated cum laude.
Maryna was a PhD student in the Environmental Systems Analysis group, and now a postdoc in the Water Systems and Global Change group. Her promotors are Carolien Kroeze (WSG), Ma Lin (CAS, China) and Luan Shengji (Peking University, China).
Clean water is essential to support our daily needs and to maintain our and ecosystems’ health. However, today the availability of clean water is threatened by nutrient pollution. Nutrients like nitrogen (N) and phosphorus (P) are present at increasing levels in many rivers worldwide. Rivers transport these nutrients to coastal waters and this can cause eutrophication and consequent symptoms like blooms of harmful algae and oxygen depletion. These environmental problems can damage living organisms in anoxic conditions and threaten human health through toxic algae.
China has experienced such environmental problems over past several decades. This is a result of the rapidly developing economy and population growth. These drivers have intensified crop and animal production and expanded urbanization. However, the relative importance of these human activities to river export of nutrients to Chinese seas is not well studied. “There are two important issues that need further investigation,” Maryna Strokal says. “First, the relative importance of upstream pollution on downstream impacts is not well known. This is needed especially for rivers with large drainage areas as they supply large quantities of nutrients to Chinese coastal waters. Second, there are sources of nutrients in rivers that are typical for China, but are generally not well studied. These are point sources of N and P from animal production and uncollected human waste.” Maryna’s PhD thesis therefor aims to better understand trends in river export of nutrients to the coastal waters of China by source from sub-basins, and the associated coastal eutrophication. Maryna Strokal: “To this end, I developed a model to assess river inputs of nutrients to seas (MARINA), to analyse nutrient export from land to sea. The novelty of this work is in an elegant downscaling approach, and a better modeling of animal manure and sewage. It changed the way we think about coastal eutrophication in China. It shows how important point source emissions of manure are as a source of pollution in China. This is very different than in Europe. The MARINA model shows the need for improved manure management and waste water treatment in China.”