Characteristics and Risk Assessment of Soil Heavy Metal Contents in Facility Agriculture of Guangxi

[Objectives]To study the characteristics of soil heavy metal contents in facility agriculture of Guangxi and analyze its risks.[Methods]The heavy metal content of 30 surface soil samples taken from facility agriculture in Guangxi was analyzed.The status of soil heavy metal pollution in facility agriculture of Guangxi was evaluated by the single factor index method,geo-accumulation index method and Hakanson potential ecological risk index method with reference to the soil background value in Guangxi.[Results]Compared with the soil background value in Guangxi,the over-limit rates of heavy metals cadmium,lead,arsenic,chromium,mercury,copper and zinc in soil samples were 56.67%,56.67%,16.67%,30.00%,50.00%,60.00%and 80.00%,respectively.Compared with the screening values of the Soil Environmental Quality-Risk Control Standard for Soil Contamination of Agricultural Land(for trial implementation)(GB15618-2018),the overlimit rates of the heavy metals cadmium,arsenic,copper and zinc in the surface soil of agricultural facilities in Guangxi were 56.67%,10.00%,16.67%and 23.33%,respectively.Except for the average content of soil cadmium exceeding the screening value,the evaluation content of the other six soil heavy metals did not exceed the screening value.According to the evaluation results of the single factor pollution index method,the surface soil arsenic and chromium of the agricultural facilities in Guangxi belonged to the clean level,lead,mercury,and copper belonged to mild pollution,and cadmium and zinc belonged to moderate pollution.According to the evaluation results of the geo-accumulation index,the lead,arsenic,chromium and mercury in the surface soil of the agricultural facilities in Guangxi belonged to the pollution-free level,while the cadmium,copper and zinc belonged to the mild-moderate pollution.According to the evaluation results of the potential ecological risk index method,the potential ecological risks of the heavy metals of lead,arsenic,chromium,copper and zinc in the soil of agricultural facilities in Guangxi belonged to low potential ecological risk level,and the potential ecological risks of cadmium and mercury belonged to moderate risk level.The potential ecological risk index(RI)of the seven heavy metals in the soil was 132.46,which belonged to moderate potential ecological risk.The largest contribution of soil heavy metals to the potential ecological risk index was cadmium and mercury.[Conclusions]Taking the soil of facility agriculture in Guangxi as the object,this paper studied the characteristics of heavy metal content in facility agricultural soil and its risk assessment,in order to provide a scientific basis for facility soil heavy metal risk prevention and control and provide safe technology for facility agriculture.

Physicochemical and elemental studies of Hydrocotyle javanica Thunb. for standardization as herbal drug

Objective: To explore the leaves of Hydrocotyle javanica Thunb. as a source of safe and effective antibacterial herbal medicine.Methods: The standardization was validated by stepwise physicochemical studies,element analysis, determination of ash values, fluorescence analysis, assessment of moisture content, extractive values in different solvent systems and extraction methods.Heavy metal contents, mineral and element contents were analysed by atomic absorption spectrophotometry, inductively coupled plasma-mass spectrometer and CHNS/O analyser, respectively.Results: The methanol extract of the folklore medicinal plant having antibacterial efficacy contained flavonoids and phenolic OH groups. The ICP multi standard indicated the presence of three major compounds with molecular mass of 161 190 and 221 Da. Heavy metals viz. lead, mercury and copper content were 4.38 ppm, < 0.05 ppm and 24.70 ppm,respectively. Minerals content of calcium, phosphorus, potassium and iron were 1 190.94 mg/100 g, 375.57 mg/100 g, 2 820 mg/100 g and 340.20 mg/100 g of plant sample, respectively. Elements like carbon, hydrogen, nitrogen and sulphur contents were38.18%, 5.67%, 2.23% and 0.51%, respectively. Heavy metal profile of the tested plant was within the permissible limits of the regulatory authorities.Conclusions: Hence the present physicochemical and elements studies reveals that the plant Hydrocotyle javanica Thunb. could be a potent source of herbal preparation as well as a safe and novel synthetic antibacterial drug.