IB ESS SL 4.4.5 Eutrophication Questions

Explain causes and consequences of eutrophication.

Exam points

define eutrophication and identify nutrient sources such as untreated sewage, fertilizer runoff and organic waste, together with algal blooms and hypoxia
explain the eutrophication sequence from nitrate or phosphate enrichment to algal growth, shading, decomposition, increased BOD, oxygen depletion, anaerobic conditions, hydrogen sulfide and possible pathogen impacts
apply and evaluate eutrophication evidence in aquatic and terrestrial contexts, comparing nutrient benefits in soil with pollution risks in water and considering prevention, monitoring and stakeholder trade-offs

[Maximum number: 1]

Pollutant	Unit	2011	2012	2013	2014	2015
Nitrate	kt	32.80	32.60	31.30	37.10	32.90
Phosphate	kt	4.50	4.40	4.00	4.80	4.40
Lead	kg	186.18	215.91	201.00	41.21	3.57
Arsenic	kg	28.09	21.34	15.11	8.00	11.04
Mercury	kg	1.72	0.49	0.64	0.10	0.33
Cadmium	kg	12.44	17.90	17.45	0.58	0.70
Chromium	kg	508.68	460.10	438.05	266.65	93.59

Figure 9(d): Pollutants in wastewater discharged into Beijing rivers, 2011-2015

With reference to Figure 9(d), identify the year in which eutrophication was most likely to have occurred.

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