Water pollution little changed, team finds(2)

The Xiaoqiandengpu sluice on Dianshan Lake in Kunshan City, Jiangsu Province

China uses a water quality ranking system of 1 to 5. Level 1 is excellent quality requiring only simple treatment; Level 2 means slightly polluted but drinkable with treatment; Level 3 is for swimming pools and fish farming; Level 4 is undrinkable and can be used for industrial purposes and artificial scenery without human contact; while Level 5 water is for agriculture and landscape.

From the result, the PH value was 7 in all samples, the DO was 7 in all locations except one 6 at Qiandun Bridge in north of Dianshan Lake in Qingpu District, and nitrogen trioxide was 10 in all locations.

These three indicators were acceptable and better than Level 3 water quality. But the level of permanganate index (8 on average), phosphorus (>0.1 in six locations) and ammonia nitrogen (>0.02) was worse than 3, meaning the water has high levels of eutrophication and excessive organic matter that's typically the result of farming.

In some samples, the heavy metal level was slightly higher as different regions have diverse functions and produce different pollution levels.

The results showed that water quality is best at the port of Dianshan Lake among the eight locations, while the northernmost part of the lake (in Jiangsu Province) is the worst. It has extremely high nitrogen levels (5 when Level 3 requires 0.02) and phosphorus (0.3 when Level 3 requires 0.1).

The Dianshan Lake water area covers Shanghai as well as Jiangsu Province, and the water quality differs. The findings showed that the water quality in Shanghai is better than those in Jiangsu, mainly because the Jiangsu area is an industrial zone with leather factories and electronics companies.

"It's worrying to see these companies and entertainment facilities by Dianshan Lake, and (you wonder) if the water flowing into Shanghai is in the safe state," Zhang says.

One basic approach to alleviating the problem is for Shanghai to initiate eco-compensation for water source areas, asking officials to stop economic expansion and shut down factories, he says.

"People in the conservation areas should be paid for stopping their works and ensure the safety of water," he says. "It can be carried out in the region surrounding Dianshan Lake, and the perimeter can be expanded as the economy develops."

During the trip, Zhang also explained that even though the water quality is not at its best, children — especially infants — should not be drinking purified water or distilled water with very low TDS value (total dissolved solids) because they lack minerals and can cause malabsorption.