| Objective:Heavy metal pollution in the soil means that the toxic trace elementsexceeded the background value and deposited in the soil due to thehuman activity. Heavy metal can cause the great harm to the surroundingenvironment because they are more enrichment and difficult to degrade inthe environment. By far now, the few investigations and the risk assessmentof the heavy metal pollution on the region in Shijiazhuang city were reported,and the risk assessment of potential ecological risk of8heavy metals inShijiazhuang is rarer. In this study, the sewage-irrigated area was selected asthe main object and the groundwater-irrigated area as control. The soilsamples from the two areas were collected and the content of Cd, Cr, Hg, As,Pb measured. The difference between the content of5heavy metals from twoareas were compared in order to understand the status and its ecological risk ofthe heavy metal pollution on the region in Shijiazhuang. The results willprovide a scientific focus for the further development of pollution controlprograms, and offer a scientific basis for improving the living environmentand for preventing environmental pollution-related disease.Methods：1Sample collectionTo sample in the farmland surround villages along the direction of EastOpen Channel-Xiao River, collecting several soil samples of the sewageirrigation area. Collecting several soil samples in farmland which irrigated bywell water as the control area. In the collected processing, positioning by theGPS.2Sample pretreatmentBy air-dried and sample fine grinding, the samples packed in the bags with the labels.3Determination of the sample①Determination of soil moisture：weighing method②Determination of pH:pH electrode method③Pre-digestion processing and determination of soil：Pb, Cd, Cr take the Wet digestion of HF-HNO3-HCLO4-HCL, As, Hgemploy the Wet digestion of aqua regia(1+1). The detection method of Pb、Cdis graphite furnace atomic absorption spectrometry(GB/T17141-1997); Thedetection method of Cr is Inductively Coupled Plasma-Atomic EmissionSpectrometer(Icp-aes); The detection method of As、 Hg is AtomicFluorescence Spectrometry (AFS)(GB/T22105.1-2008).④The quality control in the determination of the samplesBy The monitoring technical specification of the soil environmental, thestudy takes the standard soil (GBW-07427) as a standard substance todetermine the recoveries between90%and105%. Each batch of digestionsamples with two blank samples and20%parallel samples. The RSD is lessthan25%in the relative within batch. The RSD is less than30%in the controlsamples between the batches.Results：1The impact between the pH of the study areas and the content of theheavy metalsThe pH value of research regional soil ranges among6.89～8.79, theaverage is7.76, and the soil is generally alkalescent. There were deeplysignificant negative correlation between Soil pH value and Cd content, and thecorrelation coefficient is-0.489. Soil pH value and As content is a significantpositive correlation, correlation coefficient is0.243.2Correlation analysis of heavy metals in soilThe As-Cr content in Soil has significant positive correlation, correlationcoefficient is0.234; there is extremely significant positive correlation in Pb-Cr,correlation coefficient is0.324.3The content of heavy metals in the sewage irrigation and the control areaThe content of Cr and As in sewage irrigation higher than controlled area;the content of Pb, Hg, Cd showed no significant differences between sewagearea and controlled area. Evaluating by the soil environmental qualitystandards, the first grade proportion soil of Cr, Pb, Hg, As in sewage irrigationlower than controlled area. The exceed rate of Cd in sewage irrigation higherthan controlled area. Evaluating by the local background standards，the exceedrate of Cr, As in sewage irrigation higher than controlled area. The quality ofthe soil in controlled area is better than sewage irrigation.4The quality of pollution assessment in sewage irrigation and controlareaEvaluating by the local background standards, the index of Nemero in thesewage area and controlled area is4.7643and4.3117. They all have beenpolluted heavily. Pollution index of five heavy metals in the sewage area andcontrolled area are followed by the order of Cd>Hg>Pb>Cr>As. Pollutionindex of Cd is the highest in any conditions.Evaluating by the soil environmental quality standards, the index ofNemero is0.7339in the sewage area which belongs to the clean state, theindex of Nemero is0.6468in the controlled area which belongs to the cleanstate. The sewage area and controlled area have not been polluted Pollutionindex of five heavy metals in the sewage area and controlled area are followedby the order of Cd>As>Cr>Hg>Pb. The other villages belongs to the cleanstate except NO.7, NO.9and NO.20villages which reached the small polluted.5The quality of pollution assessment in silt of the sewage irrigationEvaluating by the local background standards, Cr, Cd, Hg, Pb in silt hadbeen contaminated except As. The index of Nemero in slit is19.0094，the silthad been polluted heavily.Evaluating by the soil environmental quality standards, Cr, Cd, Hg, As insilt had been contaminated except Pb. The index of Nemero in slit is1.2058，the silt had been polluted lightly.6Assessment of Potential ecological risk of heavy metals in sewage irrigation and control areaThe RI in the sewage irrigation area and controlled area is381.4351and391.1641. It all belongs to the strong ecological hazard level. The potentialecological hazard index of the five heavy metals in the sewaged irrigation andcontrolled area are followed by the order of Hg>Cd>Pb>As>Cr. Mostimportantly, Hg, Cd achieved very strong ecological hazard level and Cr, As,Pb are not achieved small ecological hazard level. Heavy metals which resultsin the potential ecological hazard are mainly Hg and Cd. The NO.5samplingpoint that the RI is495.0992is the highest ecological hazard.Conclusions：1The quality of the soil gets worse by sewage irrigation and the contentof Cr, As in the sewage irrigation area increased more significantly.2The content of Hg, Cd, Pb, Cr in sewage irrigation area which ispolluted heavily exceeds the local background standards. The content of Cd inindividual villages exceeds the national standard. The villages are no longersuitable for crop cultivation.3The pollution of heavy metal in the sewage irrigation area is relativelyserious which belongs to the strong ecological hazard level. Heavy metalelements resulting in strong ecological hazard of heavy metals are mainly Hgand Cd. |
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