Formation Mechanism And The Outbreak Of The Track Of The Delayed Geochemical Hazards-a Case Study Of The Mercury Anomaly Area In Fujian Dehua

Delayed geochemical hazard of heavy metals in the soil occurred due to its long-term forming, delayed harmful effects and suddenness of outbreaks. A mercury anomaly area near an abandoned gold mine in Fujian Dehua was chosen as the research object, and we researched the formation mechanism of delayed geochemical hazard by the accumulation mechanism and influence factors of mercury in the study area, the outbreak mechanism of DGH by the release mechanism and influence factors of mercury in the soil, and the characteristics of DGH of mercury in the area based on them.The total mercury concentration in the case area was between0.117mg·kg-1and69.1mg·kg-1, and the highest concentration nearly reached617times than the soil background value. The formation distribution of mercury was mainly bound with the organic combined state, followed by residual state, exchangeable ions, Fe/Mn oxide fraction and carbonate combination fractions, which was in line with the outbreak delayed geochemical hazard of mercury element. Formation process of delayed geochemical hazards of mercury included rapid reaction and slow reaction, and its shape distribution changed from the activity state to the stable state, which was relative to the physical and chemical properties of the soil. Besides, under the condition of weakly acidic or neutral pH value and high organic matter content of the soil, the accumulation of mercury was constructive. Thus, the process was contributing to the formation of delayed geochemical hazard of mercury elemental in the case area.Outbreak process of delayed geochemical hazard of mercury included rapid reaction and slow reaction, and its shape distribution changed from the stable state to the activity state, which was relative to the physical and chemical properties of the soil. Under the condition of high environmental temperature, acidic pH environment, the right amount of soil-liquid ratio (rainfall), high ionic strength and low organic matter of the soil, the release of mercury in the soil was beneficial, which was promoting the occurrence of the delayed geochemical hazard of mercury elemental.The DGH research showed that the TRCPHg content exceeded the critical point of DGH, with a value of1.5%～3.5%in the study area, so it was greatly possible to outbreak DGH.