Calculation methodology of marine environmental capacity for heavy metal: A case study in Jiaozhou Bay, China

Results from past pollution control practices show that environmental quality can be ensured by controlling the actual amount of pollutants formed in the environment. Therefore, the marine environmental capacity for heavy metals was introduced. Marine environmental capacity for heavy metals is defined as the maximum amount of heavy metals permitted in the marine environment system to preserve the benign cycle of materials in the oceansphere, and to limit the adverse effects of heavy metals on the biosphere, hydrosphere, atmosphere, and lithosphere. Based on the box or three-dimensional model in the target coastal region, including the self-purification and output of heavy metals, the marine environmental capacity for heavy metals can be calculated within a given criterion and time. In this study, a method was proposed to calculate the marine environmental capacity for heavy metals which includes four steps: (1) gathering the basis information of target coastal ecosystem, (2) selection of water control points and water quality criteria for these points, (3) development of numerical models for the biogeochemical cycling of heavy metals in target coastal region, and (4) calculation of environmental capacity using the developed model. According to the proposed method, the marine environmental capacity for lead is approximately 60 tons per year if Grade I seawater quality is set as the control criterion in Jiaozhou Bay. An effective seawater quality management plan can also be framed based on the environmental capacity for metals.