Nearly half of Shenzhen's coastal waters were found to be seriously contaminated last year, and nine sewage drainage lines were found to be discharging excessive pollutants, according to a maritime study. A professor of marine chemistry says the problem could worsen this year, as some temporary efforts to improve water quality last year for the World University Games are no longer in effect. The 2011 study, issued on Wednesday by Shenzhen's Urban Planning and Land Resources Commission, found a total of 565 square kilometres of seriously contaminated seawater. Of the remaining waters, 145 square kilometres were lightly or moderately polluted, and 435 square kilometres were clean. The contaminated waters were concentrated in Deep Bay and at the mouth of the Pearl River. Inorganic nitrogen and phosphates were the major pollutants.