Sediment Testing

1. Introduction to Sediment Testing

Sediment refers to clay, silt, organic matter, and various minerals that have settled at the bottom of water bodies through prolonged physical, chemical, and biological processes under the influence of water transport. The top 0 to 15 cm of sediment is referred to as surface sediment, while sediment exceeding 15 cm in depth is classified as deep sediment.

Sediment testing involves sampling and analyzing sediment to determine the types and concentrations of pollutants present.

2. Testing Scope

Sediment/silt from rivers, streams, lakes, black and odorous water bodies, and other watersheds, including:

(1) Testing for sediment pollution status;

(2) Investigation and testing of internal pollution sources, among others.

3. Hazards

Sediment is the deposit in rivers and lakes and an essential component of natural water bodies. When water bodies become polluted, some pollutants can accumulate in the sediment through precipitation or adsorption onto particles. Under certain conditions, these pollutants can be released back into the water, becoming a secondary pollution source. This type of pollution is known as sediment pollution. In the process of river and lake pollution control, sediment pollution remediation is one of the major challenges and a common environmental issue. There is a dynamic balance of absorption and release between water and sediment. When water pollution is severe, some pollutants enter the sediment through precipitation and adsorption. After external pollution sources are controlled, accumulated organic and inorganic pollutants in the sediment can re-enter the overlying water through physical, chemical, and biological exchanges, becoming a secondary pollution source that affects water quality.

Sediment contains nutrient pollution, which can alter the survival and growth of farmed fish. In mild cases, it can lead to slow growth and various diseases in aquatic organisms; in severe cases, it can cause fish poisoning and death, resulting in water eutrophication. Organic pollution in sediment undergoes biological oxidation and decomposition, consuming dissolved oxygen in the water and leading to hypoxia. Simultaneously, fermentation occurs, promoting bacterial growth, deteriorating water quality, and damaging the water ecosystem. Organic pollution in industrial water can also reduce product quality.

Additionally, sediment contains numerous heavy metal pollutants. These heavy metals not only harm aquatic ecosystems and adversely affect aquatic organisms but also impact human health directly or indirectly through drinking water and the food chain. Particularly in industrial wastewater discharge, a significant amount of heavy metal elements settle into natural water bodies. Therefore, many factories and enterprises conduct wastewater or sediment testing to ensure that substance levels meet standards.

4. Testing Items

Total cadmium, total mercury, total lead, total chromium, hexavalent chromium, total arsenic, total nickel, total zinc, total copper, total boron, mineral oil, fluorides (as F), cyanide (as CN), total phosphorus, total nitrogen, particle size, organic matter, 27 volatile organic compounds (including: chloroform, chloromethane, 1,1-dichloroethane, 1,2-dichloroethane, 1,1-dichloroethylene, cis-1,2-dichloroethylene, trans-1,2-dichloroethylene, dichloromethane, 1,2-dichloropropane, 1,1,1,2-tetrachloroethane, 1,1,2,2-tetrachloroethane, tetrachloroethylene, 1,1,1-trichloroethane, 1,1,2-trichloroethane, trichloroethylene, 1,2,3-trichloropropane, vinyl chloride, benzene, chlorobenzene, 1,2-dichlorobenzene, 1,4-dichlorobenzene, ethylbenzene, styrene, toluene, m-xylene + p-xylene, o-xylene), 11 semi-volatile organic compounds (nitrobenzene, aniline, 2-chlorophenol, benzo[a]anthracene, benzo[a]pyrene, benzo[b]fluoranthene, benzo[k]fluoranthene, chrysene, dibenzo[a,h]anthracene, indeno[1,2,3-cd]pyrene, naphthalene), pH, moisture content, fecal coliform value, etc.

5. Relevant Standards

"Technical Specification for Soil Environmental Monitoring" HJ/T 166-2004

"Soil Environmental Quality—Risk Control Standard for Soil Contamination of Development Land" GB36600-2018

"Technical Guidelines for Environmental Dredging Engineering of Lakes and Rivers"