Anthropogenic activities have deeply altered the state of levels and accumulation of heavy metals in the earth surface. Geochemical background, the state that excludes any potential anthropogenic factors, is a unique tool in assessing the extent of human impact. However, with the intensive and widespread social and economic development of humans on the earth, the “pure” natural background has become rarely existent.

Fortunately, a new alternative tool called “geochemical baseline” has been developed to resolve such a problem. The baseline, the commonly abbreviation of the geochemical baseline, can be defined as the upper limit of geochemical background, or lower limit of the human impact.

Series key research plans on baselines were launched in Europe in the late two decades in the 20th century. Before the 2012 London Olympic Games, a research plan called “London Earth” was established. The plan, via obtaining baselines for various heavy metals in soils, had intended to assess the impact of urbanization and industrialization on Greater London area.

Given the fact that no large research plan in baseline being established in China, Dr. WEI Chaoyang and his colleagues from the Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences (IGSNRR, CAS), have tried to focus their interests in setting up the baselines for heavy metals in the sediments in two large shallow freshwater lakes (Taihu and Dianchi) in China (Wei & Wen,Environmental Geochemistry and Health, 2012, DOI: 10.1007/s10653-012-9492-9).

The two lakes, located in the most developed areas in China, have become serious concerns of the governments, publics and researchers due to their hyper-eutrophication since 1990s. The researchers sampled and analyzed concentrations of various heavy metals including arsenic, antimony, mercury, cobalt, chromium, copper, nickel, lead and zinc in the surface sediments of the two lakes, they also collected relevant qualified data in Chinese literature to expand their database.

The baselines, obtained via two approaches as cumulative frequency curves and normalization using the data from the database, were generally comparable with the sediment records before 1990s in the two lakes. Such phenomenon indicates the enrichment of various heavy metals during the last 30 years around the two lake areas.

Inflexions in the cumulative frequency curves represent human disturbance. The researchers found that only copper and lead in Taihu, antimony, lead and zinc in Dianchi appeared with two inflexions. They pointed out that those were consistent with the industrial structures around the two lakes. Animal husbandry and aquaculture are populous around Taihu, in which copper is a routine feed additive; while around Dianchi area the mining and smelting of nonferrous metal ores have been prevailing, usually in presence with high antimony concentrations.

The research was financially supported by the National Program on Key Basic Research Project of China(973 program) “Water Environmental Quality Evolution and Water Quality Criteria in Lakes” (2008CB418200)