Study On Spatial Pattern Of Soil Heavy Metals In Ganzhou City Base On The Relationship Between Source And Sink

The risk of soil pollution in China is becoming a topic of concern.Because heavy metals may migrate into agricultural crops and lead to excessive content in food,the management of heavy metal risk has become a key point of soil environmental management.With the change of the strategy of national soil environment management from pollution remediation to risk control,there is an urgent need to grasp the regional situation and sources of soil environmental risks when making the soil environmental risk control plans.At present,the spatial distribution of soil heavy metals in a region can be mastered through soil pollution investigation,but the information about the transport process of soil heavy metals from pollution sources to surrounding areas is lost.In this study,the transport process of heavy metals in soil under different scales has been considered from the very beginning.The distribution plan of soil pollution survey points and the method of multivariate statistical analysis have been improved in the perspective of the relationship between the source and sink of heavy metals in soil.Taking Ganzhou city as the research area,this study delimited the pattern of soil heavy metal source apportionment in Ganzhou city,and analyze the relationship between source and sink of soil heavy metal at the regional scale.Meanwhile,the transport modes and characteristics of heavy metals around the sources were analyzed in,and the reason for spatial differences in soil heavy metal contents from the perspective of the source sink relationship was discussed in this paper.The main conclusions are as follows:(1)The level of soil heavy metal contamination risk in Ganzhou city was low,but there was potential soil heavy metal pollution risk in some areas,which required pollution remedy or make risk control plan.Ganzhou city’s soil is generally acidic,the median and average values of the five heavy metal in the survey data were all lower than the acid soil risk screening values of agricultural land in soil environmental quality risk control standard for soil contamination of agricultural land(GB15618-2018),the overall risk of heavy metal pollution in the region was low.However,the maximum value,data kurtosis and data skewness of the survey data were all high,implying that the survey data had high outliers.The outliers exceed the intervention values for soil contamination of agricultural land,the areas where outliers lay have a great environmental risk of heavy metals contamination in the soil.(2)There were six main soil heavy metal sources in Ganzhou city,including rare earth mining,industrial sulfuric acid leakage,tungsten mining,ore-dressing agent leakage,lead-zinc mining,rock weathering.The mining of rare earth minerals was the main source of cadmium and lead content in soil.Industrial sulfuric acid leakage mainly causes the increase of mercury content in soil.The tungsten mining mainly causes the increase of lead content in soil.The concentration of arsenic and cadmium in soil was increased by the leakage of the ore-dressing agent.lead-zinc mining mainly causes the increase of arsenic,cadmium and lead content in soil.The soil background value in Ganzhou city was generally lower than the acid soil risk screening values of agricultural land,so there was a rare environmental risk of heavy metals in soil caused by rock weathering.(3)There are two main soil heavy metal transport processes in Ganzhou city—by the atmosphere and by water.The water transport characteristic was obvious,and the atmosphere transport characteristic was not comparatively.The distance of water transport was about 2-3km,and the heavy metals from the mining activities of lead-zinc ores,copper ores and tungsten ores were the most obvious with the transport and diffusion by water.The heavy metals released by the pollution source in the catchment without upstream showed more obvious water transport characteristics than the downstream catchment.(4)There were five pollution source influence zones and 25 heavy metal transmission characteristic zones in Ganzhou city,including two heavy metal atmospheric transmission characteristic zones,23 heavy metal water transmission characteristic zones,rare earth mining influence zone,tungsten mining influence zone,lead-zinc mining influence zone,soil heavy metal pollution high risk zone and rock weathering influence zone.(5)There were three kinds of soil heavy metal transport processes in Ganzhou city at the regional scale and the scale of 10 km around the pollution source.The areas which play important roles in the processes are the key points in the risk management of regional soil contamination.In the scale of the city,there were two processes,including the process that heavy metal transport from the rock to surface soil,and the process that heavy metal transport from high content soil to low content soil.In the risk management,the key points were the “source”,including bare rock,tailing pond and the soil affected by human but heavy metal content was lower than the screening values.In the scale of 10 km around pollution sources,there was one process in which heavy metals transport from the pollution source to the surrounding soil.Evaluating the blocking ability of the “sink”,and analyzing the relationship between the blocking ability and the structure of “sink” are the key points in the risk management.