聯合國環境署年報：磷肥、塑膠污染海洋

Enormous amounts of the fertilizer phosphorus are discharged into oceans due to inefficiencies in farming and a failure to recycle wastewater, the United Nations Environment Programme warns in its 2011 Year Book released today.

An emerging concern over plastics pollution of the oceans is identified in the Year Book as "persistent, bio-accumulating and toxic substances" associated with plastic marine waste.

Research indicates that tiny pieces of plastic are adsorbing and concentrating from the seawater and sediments chemicals from polychlorinated biphenols, PCBs, to the pesticide DDT.

"Many of these pollutants, including PCBs, cause chronic effects such as endocrine disruption, mutagenicity and carcinogenicity," states the 2011 Year Book.

Experts cited in the book say that both phosphorus discharge and new concerns over plastics underline the need for better management of the world's wastes and improved patterns of consumption and production.

"The phosphorus and marine plastics stories bring into sharp focus the urgent need to bridge scientific gaps but also to catalyze a global transition to a resource-efficient Green Economy in order to realize sustainable development and address poverty," said UNEP Executive Director Achim Steiner.

"Whether it is phosphorus, plastics or any one of the myriad of challenges facing the modern world, there are clearly inordinate opportunities to generate new kinds of employment and new kinds of more efficient industries," Steiner said.

Demand for phosphorus has soared during the 20th century, and the Year Book 2011 highlighted the nutrient in part because of the heated debate over whether or not finite reserves of phosphate rock will soon run out.

An estimated 35 countries produce phosphate rock. The top 10 countries with the highest reserves are: Algeria, China, Israel, Jordan, Russia, South Africa, Syria and the United States.

New phosphate mines have been commissioned in countries such as Australia, Peru and Saudi Arabia and countries and companies are looking further afield, even to the seabed off the coast of Namibia.

The Year Book recommends a global phosphorus assessment to more precisely map phosphorus flows in the environment and predict levels of economically viable reserves.

"While there are commercially exploitable amounts of phosphate rock in several countries, those with no domestic reserves could be particularly vulnerable in the case of global shortfalls," the Year Book notes.

There is an enormous opportunity to recover phosphorus by recyling wastewater, the Year Book advises. Up to 70 percent of this water is laden with nutrients and fertilizers such as phosphorus, which currently is discharged untreated into rivers and coastal areas.

Heavy doses of nutrients such as phosphorus and nitrogen increase the risk of harmful algal blooms, which can prompt the closure of fisheries and swimming areas.

Other measures to reduce discharges include cutting erosion and the loss of topsoil where large quantities of phosphorus are associated with soil particles and excess fertilizers are stored after application.

The Year Book advises that further research is needed on the way phosphorus travels through the environment to maximize its use in agriculture and livestock production and cut waste, while reducing environmental impacts on rivers and oceans.