| The Guangdong Dabaoshan Mine, near the Hengshi River, is a typical multimetallic sulfide mines which discharged with waste water and waste. The mine exits a lot of heavy metal pollution to the Hengshi River, natural and ecological environment also get deteriorated, and residents’ s health get damaged. It’s necessary to investigate and distribute the heavy metals pollution of the river basin, and evaluate the risk assessment of heavy metals.Take the Hengshi River which from Dabaoshan Mine Dam to Weng Jiang as the research object.Set the sample points and prepared sampling and preserving procedure by the environment monitorning standard required, and taked the representative samples of surfacewater and sediment of the river basin. Determinate nine heavy metals: As, Cd, Cr, Pb, Cu, Mn, Zn, Hg and Tl’s total contents in water, their sediments’ total content and four forms. Set up the preliminary treatment with HNO3-HF microwave digestion procedure to prepare nine heavy metals’ total and residue content in sediment, and improved BCR(Improved Community Bureau of Reference) extract procedure to prepare heavy metals’ forms in sediment.Use the ICP-MS(Inductively Coupled Plasma Mass Spectrometry) for the heavy metals instrument analyse method. The experiments runed with quality control procedures to ensure the results’ effective. Elucidate the Hengshi River’s nine heavy metals’ distribution, migration and transformation, at the same time use Geoaccumulation Index(Igeo), potential Ecological Risk Index(Eri) and Risk Assessment Code(RAC) to evaluate the risk assement of the Hengshi River’s heavy metal pollution. The research results show that:Firstly, take the control and improvement of improved BCR by temperature, p H and time of reducible and oxidation form, reagent`s metal content, the CRM with similar matrix, to enhance and guarantee the efficiency of the extraction. Use ICP-MS with instrument tunning, pulse/analog signal calibration, internal standard, calibrations with different matrix. the ICP-MS analysis can be more accurate and rapid in determination acid mine composite metal samples with quality control procedures, to ensure the accuracy and precision of the results.Secondly, the Hengshi River is heavily contaminated by the various metal compounds. The basin water’s nine heavy metals’ maximum value were more than the surface water quality standard of classⅢ(except Cr had not stated), where the Mn exceed 147 times, Cd exceed 82 times, Tl exceed 78 times, Hg exceed 53 times, Pb and Zn exceed 10 times, As and Cu were 1 and 4 times. The nine heavy metals and SO42- were significantly correlated, negatively correlated with p H. The nine total heavy metals in sediment compare with the soil background value of Guangdong: Cd exceed 222 times, As and Cu exceed 125 times, Pb and Hg exceed 66 times, Zn and Tl exceed 38 and 12 times, Mn and Cr exceed 2 times. As, Pb, Cu, Cr, Zn and Tl were significantly correlated, negatively correlated with p H. Mn and other metals had low correlation. Only Hg and Cd were significantly correlated. The correlation between Cd with Hg, Tl was significant, with Pb, Zn and As were less correlated.Thirdly, sediments’ nine heavy metals exists in different forms: As, Cr, Hg and Tl were mainly in the residual form, respectively to 43.22~664.0 mg/kg, 21.23~48.93 mg/kg, 0.14~2.49 mg/kg and 0.21~5.12 mg/kg(respectively 67.54%~77.67%, 61.78%~79.74%, 43.75%~87.37% and 41.18%~78.41%). Cd was mainly in weak acid extraction form(0.88~2.62 mg/kg), and with high bioavailability form(67.49% rise to 94.04%). Pb was mainly in the reduction form(81.83~771.6 mg/kg), and bioavailability from was from 90.90% dropped to 78.68%, which remained at a high level. Mn was mainly in weak acid extraction form(244.4~292.5 mg/kg) and residual form(282.2~292.5 mg/kg). The residual form of Cu(400.1~595.2 mg/kg) and Zn(88.5~555.9 mg/kg) was more than others but not obviously. The total and form contents of Cu were very high, and the change trend to flat, bioavailability from was from 58.29% dropped slightly to 45.88%. The total and form contents of Zn were very high, bioavailability from maintained in 61.98% to 71.24%, which presented as the medium or high level.Forthly, through the study of Hengshi River sediment’s nine heavy metals’ Igeo, it showed that: Cu and Cd were severe polluted, As and Pb were heavy polluted, Zn and Hg showed moderate pollution, Mn and Tl were lightly polluted, Cr was no polluted. The study of Eri show that: Tl represented extreme strong potential ecological risks. Pb and As represented very strong potential ecological risks. Cu and Cd represented stronger potential ecological risks. Though Zn and Mn content were a lot, the potential ecological risks represented in light level. Hg’s potential ecological risks showed middle or stronger level. Cr’s low migration made its potential ecological risk level very low. The potential ecological risk index RI show that bioavailability from and residual from of Hengshi River sediment’s nine kinds of heavy metals showed very strong potential ecological pollution. The study of RAC showed that: Cr was in no risk level; As was in low degree of risk; Hg’s risk level rose from free to medium, then decreased and remained at low level; Tl’s risk level was mainly medium, but Mine Tailings and Shengli Bridge were in low risk; Cu’s risk level decreased from medium to low; Pb and Zn were in the medium risk level, Pb decreased gradually, and Zn rose gradually; Mn’s risk level rose from moderate to high; Cd remained at high risk level. |
PDF Full Text Request