Prediction And Early-Warning For Soil Environmental Safety In A Mixed Contaminated Area

Soil is one of the basic elements of ecosystems,and it is also one of the primary natural resources for mankind's survival and development.Soil pollution and degradation in China is very serious,especially in the region of rapidly economic development such as Yangtze River Delta and Pearl River Delta.According to preliminary estimation,about 1/10 of the total cultivated land was polluted or/and degradated.Soil pollution and degradation have become one of the main environmental problems.Soil environment is an important part of the environmental systems,and it is closely connected to water environment,atmospheric environment and biological environment.Therefore,soil environment security is one key component of the entire environment safety,and it is an important material foundation of the entire ecological and environmental safety and protection.In recent years,soil environment for mankind survival has faced more and more serious threaten as soil environmental issues have become increasingly prominent,and the consciousness of soil environment safety needs to be gradually enhanced.It has become an important measure for soil environmental safety protection that establishing a forecast and early-warning information system for soil environmental safety and using it to forecast and early warning some contaminated site soil environmental safety.Our government attaches importance to the study on the forecast and early warning for soil environmental safety,and putted forward that China will establish a forecast and early-warning information system for soil environmental safety step by step in 2004.In this study,we analyzed the characteristics of soil pollution hazards and the needs of domestic and abroad environmental risk management for polluted soil,investigated and studied the existing forecast and early-warning information systems and early-warning methods for environmental safety of water and atmosphere.We also carried out the key research on soil contaminants concentrations prediction,the scope of soil pollution identification,source analysis of soil contaminant,soil environmental quality assessment and environmental risk assessment for Fuyang study area,closely together with the establishment of forecast and early-warning system for soil environmental safety and the design and development of soil environment information system. With respect to research on soil contaminants concentrations prediction,(1)we used the conventional statistical analysis methods to study the distribution characters of soil contaminants concentrations data sets,studied the methods of normal transformation and spatial prediction to high skewed data with a few high peak values,and compared the merits and shortcomings of normal score kriging,rank order kriging and the combined the method of lognormal kriging and triangulated irregular network(TIN)interpolation in spatial prediction for these types of data sets;(2)we tried to spatially predict the heavy metals concentrations in soil taking into account soil map units and studied the roles of soil map units in soil heavy metals concentrations spatial prediction;and(3)we also studied the temporal prediction methods of soil contaminants concentrations with single phase data set and predicted the concentrations of heavy metals in soil in 2020 by the method of scenario analysis.With respect to research on the scope of soil pollution identification and source analysis of soil contaminants,(1)we studied how to integrated identify the scope of soil pollution by using the spatial distribution map of soil contaminant and the probability map of soil pollution, and discussed how to take supplementary sampling;and(2)we used principal component analysis,Pearson correlation analysis and scene investigation to analyze the main source of soil contaminants.With respect to research on soil environmental quality assessment and environmental risk assessment,(1)we studied the scopes of application and shortcomings of existing methods and existing criteria of soil environmental quality assessment,modified the norm grey relation and used it to soil environmental quality assessment,assessed the soil environmental quality of Fuyang study area from the aspect of soil heavy metals pollution,and integratively assessed the soil environmental quality;(2)we assessed and classified the ecological risk of study area in different periods by methods of ecological risk index,potential ecological risk index and ecological risk quotient and synthesized the three results;(3)we assessed and classified the human health risk of children,adult and lifetime arose from soil pollution exposure,and analyzed the impact of the spatial variability of soil contaminants on the results of human health risk assessment.Prediction and early warning for soil environmental safety could let us realize the risks of soil pollution and take action to avoid or alleviate the harm to human health and ecology as soon as possible.There is not an existing prediction and early-warning system for soil environmental safety in present.In this study,we want to establish a new prediction and early-warning system for soil environmental safety,and design and develop a soil environmental information system taking into account the aim and demands of prediction and early-warning for soil environmental safety,status quo on soil environment and the prediction and early-warning systems for other type of environment.The new system was based on soil environmental quality assessment,ecological risk assessment and human health risk assessment,and made status warning for the single aspect and comprehensive status of soil environmental safety by using the three kinds of results as early-warning index.We also made a prediction and early-warning for soil environmental security in Fuyang study area by using the new prediction and early-warning systems and new soil environmental information system.The main results and findings in this study were summarized as following:(1)The data analysis results of soil contaminants concentrations showed that the soil contaminants concentrations in the studied area had moderate-strong spatial variability, particularly a few "hot spots" had extremely strong local variability;normal transformation and kriging interpolation could not meet the need of the spatial prediction for heavy metal concentrations in soil because almost all data sets of heavy metal concentrations had a high skew and a few high peak values.However,the combined interpolation method of lognormal kriging and triangulated irregular network could well satisfy the requirement of spatial prediction for soil contaminants in the studied area after their concentration data were splitted into two parts.In addition,we try to predict soil heavy metals concentrations taking into account the soil map units,and the results showed that the method could improve prediction accuracy.(2)The scope indeification results of the soil pollution showed that the current soil sampling scheme could not meet the demand for scope indeification of soil pollution in the studied area,and needed supplementary sampling in the uncertain region.A large proportion of study area in 2003 was polluted by soil heavy metals,and the combined pollution that polluted by more than one contaminant was very popular.The results of source analysis of soil contaminants showed that the majority of Cu,Zn,Pb and Cd in soil were possiblly from the emissions of small furnaces of local smelting factories,the majority of soil As,Ni and Hg were from soil parent material and partly from the emissions of small furnaces in some high concentration regions.(3)The temporal prediction results of heavy metals concentrations in soil showed that the heavy metals concentrations in soil would slightly decrease in optimistic scene in 2020; however,it would significantly increase in unmutation scene in 2020.(4)The results of soil environmental quality assessment showed that the soil environmental quality of study area was very bad,about 40%of study area was in degree of moderate to heavy pollution in 2003;it would has a slight improvement in optimistic scene in 2020,and about 50%of study area was polluted;whereas,about 90%of study area was polluted in unmutation scene in 2020.(5)The results of ecological risk assessment showed that there had a relatively high ecological risk in the majority of study area in 2003,about 68%of study area was in degree of moderate to heavy ecological harm;the proportion would decrease to 54%in optimistic scene in 2020,and it would sharply increase to 84%in unmutation scene in 2020.(6)The results of human health risk assessment showed that the human health risk of study area was in degree of especially high harm in 2003,it would be in degree of high harm in optimistic scene and still in degree of especially high harm in unmutation scene in 2020.The results of uncertainty analysis of human health risk assessment showed that the spatial variability of soil contaminants produced larger uncertainty to the results of human health risk assessment,and directly affected the decision of human health risk management.(7)The result of integrated early warning for soil environmental safety showed that there had about 14.5%of study area was in huge warning level in 2003,the remains was in high warning level;and there had 53.5%study area in middle warning level and 43.1%in high warning level in optimistic scene,and about 77.6%in high warning level and 22.4%in huge warning level in unmutation scene in 2020.(8)The results of the soil environmental information systems testing and application showed that the new information system almost could meet the demand of prediction and early-warning for soil environmental safety of the contaminated site,but it still need improvement.The innovations or new developments in this study were made as follows:(1)We splitted the dataset of soil contaminants concentrations into two parts,one described the spatial variability as a whole and the other described the huge local variability nearby the hot spots,then used the lognormal kriging and triangulated irregular network interpolation to predicted them,respectively.The results showed that the new method could solve the problem of spatial prediction for high skew data with a few high peak values.(2)We predicted the spatial distribution of heavy metals in soil by taking into account soil map units,and the results showed that it could better describe the local spatial variability and the spatial distribution in high concentrations area.(3)We identified the pollution scope of soil contaminants by integratively using their spatial prediction maps and probability maps of soil pollution for the first time in China,and further discussed the scheme of supplementary sampling. (4)We established a new prediction and early warning system for soil environmental safety of contaminated site for the first time in China and developed a relavent soil environmental information system,and used the information system to make a prediction and early warning for soil environmental safety to the contaminated site-Fuyang study area.