The Dongguan section of Dongjiang River water quality testing and analysis

Abstract

Objective To have a knowledge of water pollution situation and reasons in Dongguan section of Dongjiang River.Methods 7 sampling sections were set up in Dongguan section and the northsouth main stream of Dongjiang River.Detected and analyzed water quality in Dongguan section from 3 aspects according to The Surface Water Environment Quality Standard (GB3838-2002),including organoleptic parameters (transparency,chroma,water temperature,pH),chemical indexes (dissolved oxygen,potassium permanganate index,BOD,3-nitrogen,chromium,cadmium,lead and other 8 kinds of metal ions) and bacteriological indexes,covering a total of 26 items.Results The water quaility was neutral,the change of water temperature was obvious,and the chroma in water aggravated gradually from upstream to downstream.In the wet season,the level of dissolved oxygen was 0.04-2.26 mg/L,COD 1.49-2.83 mg/L,BOD 4.50-22.00 mg/L,ammonia nitrogen 2.40-29.84 mg/L,nitrate nitrogen 8.43-23.46 mg/L,nitrite nitrogen 0.008-0.449 mg/L,hexavalent chromium 0.500-12.714 mg/L.In the dry season,the level of dissolved oxygen was 0.62-2.30 mg/L,COD 3.75-4.86 mg/L,BOD 4.40-19.00 mg/L,ammonia nitrogen 3.98-27.99 mg/L,nitrate nitrogen 0.57-0.99 mg/L,nitrite nitrogen 42.70-83.28 mg/L,hexavalent chromium 0.336-8.609 mg/L.14 kinds of metal ions detected at 7 monitoring sites didn' t exceed standards in wet season or dry season,including cadmium,lead,arsenic,mercury,manganese,nickel,potassium,sodium,calcium,magnesium,iron,selenium,zinc and copper.The results overall showed that the upstream water quality standard went to level Ⅱ-Ⅲ,while the downstream' s went to level Ⅳ-Ⅴ,and water of the marine outfall was severely polluted.Conclusions The water in Dongguan section of Dongjiang River is mainly polluted by organics,by heavy metals at a slight degree.It is necessary to strengthen the supervision of domestic sewage,industrial wastewater emissions and protect the environment. Key words: Dongjiang River; Water quality test; Reason analysis