Scientists say 80% of the phenol and cyanide in the sea water will decompose in three months, but it will take at least 50 years for the marine ecosystem in the four coastal provinces of Ha Tinh, Quang Binh, Quang Tri and Thua Thien-Hue to fully recover after being devastated by Formosa’s discharge of toxic waste.

Dead coral on the seabed in Vietnam's central provinces

According to surveys conducted by experts in the panel responsible for investigating the mass fish deaths in Vietnam’s central coast, Formosa’s discharge of toxic waste has caused serious damage to marine life.

The surveys were conducted at a number of sites including Mui Ron Ma and Hon Son Duong (Ha Tinh province), Hon La port and Hon Nom Island, Vung Chua (Quang Binh province), Cua Tung and Con Co (Quang Tri province), and Hon Son Cha, Bai Chuoi and Bac Hai Van (Thua Thien-Hue province).

It is estimated that half of the 800 hectares of coral in the above-mentioned provinces were destroyed.

At Con Co, scientists discovered no abnormal deaths of coral, fish and other creatures living on reefs and found many fish with high economic value.

Meanwhile, at other survey sites the ecosystem was rather poor and no fish with high economic value were found. Only some species of the Pomacentridae family, which has little economic value, were spotted.

At Cua Tung, scientists found no trace of young lobsters in rock holes although, according to fishermen, this is the best time of the year to harvest young lobsters.

In Thua Thien-Hue province, the toxic waste has not only reduced biodiversity and destroyed the undersea habitats of marine creatures, but has also ruined nesting areas of valuable fish, leading to an imbalance in the ecosystem, undermining the ability to add young creatures to the existing populations.

At the Bai Chuoi coral reef, algae will have the opportunity to grow and cover the entire sea bottom surface, killing coral colonies and destroying beds for coral larvae to hold on to in their initial phase of growth.

This means it will take a great deal of time for coral colonies to recover, even when the quality of the environment becomes normal again.

Dr Vu Duc Loi from the Institute of Chemistry, Vietnam Academy of Science of Technology (VAST) estimates that it will take at least 50 years for the marine ecosystem in these four provinces to recover to their state before the discharge of toxic waste.

Dr Loi says in theory 80% of the phenol and cyanide will decompose after three months. For now, scientists are conducting surveys at 13 cross sections from Vung Ang (Ha Tinh province) to Thua Thien-Hue province, analysing forms of sediment and determining the remaining amounts of phenol and cyanide.

“I cannot give any recommendations to the people until specific scientific data are available”, Dr Loi emphasised.

Dr Trinh Van Tuyen from the Institute of Environmental Sciences, VAST says over time the sea can clean itself as toxic substances will gradually diffuse into the water and have their concentration decrease.

Toxins can also be broken down by some kinds of microbes in the sea water. But Dr Tuyen stresses that this can only happen when there is no more discharge of waste into the sea.

He explains that the marine environment consists of three elements, namely seawater, sea sediments and coral. Analysis of seawater samples shows that the concentration of pollutants is quite low and only the concentration of iron in Son Duong is a little higher than the standard for surface seawater.

For sediments, scientists are working with the Ministry of Natural Resources and Environment to survey 13 cross sections at different times to assess the variation in the concentration of toxic substances.

The result of this survey will be the foundation for plans to address marine pollution in the four central coastal provinces.

According to Dr Loi, if the sea water contains high amounts of phenol and cyanide as well as heavy metals, sediments must be sucked up because heavy metals cannot decompose themselves.

This method requires the use of dredging vessels. Large deep pits would need to be dug to contain sediments for safe processing.

As an expert who directly assessed Formosa’s discharge, Dr Tuyen says the majority of the company’s steelmaking processes are fine, but the waste treatment process needs improvement and must be controlled in a stricter manner. One of the main sources of pollution is Formosa’s coke-making process. The company should replace wet quenching with dry quenching.

In addition to requesting Formosa to improve its waste treatment process and environmental quality control, Dr Tuyen notes that Vietnamese authorities should step up supervision over the company’s waste discharge.

He also recommends building tanks to test the impact of post-treatment waste on plants and animals to ensure the quality of discharge is safe for marine life and to help the marine ecosystem quickly recover.

Nhan Dan