Evaluating the biotoxicity of surface water in a grassy lake in North China

The biological toxicity of aquatic ecosystems should be considered when assessing the effects of toxicity on the water environment.The aim of this study was to identify the main pollutants in the Baiyangdian(BYD)and the factors that contribute to biological toxicity.We determined various physical and chemical indicators in the surface water of the BYD,including nutrients and heavy metals,and the biological toxicity.We also explored the sources of the main pollutants and how the pollutants contributed to toxicity in the lake,using correlation analysis and an index of the biological toxicity.The results showed that total nitrogen(TN),ammoniacal nitrogen(NH4^(+)-N),chromium(Cr),and zinc(Zn)were the main pollutants in the BYD surface water.The average concentration of Cr was 2.3 times greater than the Class V threshold,and the concentrations at about 65%of the sampling points,mainly those in the southern part of the BYD,exceeded the threshold standard.The average concentration of Zn was 1.25 times higher than the Class V threshold,with the concentrations of about 35%of the samples greater than the threshold concentration.The integrated toxicity of the surface water to luminescent bacteria ranged from 0.51%to 58%,and averaged 24.07%,which was within the range of moderate toxicity.The inhibition rates were high near Diantou(59%)and Duan(51.6%).The pollutant levels in the BYD tend to be related to the population density,with pollution mainly caused by sewage and domestic garbage,with little influence from local industries.Cr and TN were strongly correlated,but the biological toxicity was not correlated with any of the individual environmental indicators,which suggests that the toxicity in the surface water of the BYD reflected the combined effects of the environmental factors,rather than a single factor.The information from this study,about the main pollutants and the relationships between the physical and chemical properties of the surface water in the BYD,can be used to support plans for restoring the BYD.

Elucidating dominant factors of PO43–, Cd2+ and nitrobenzene removal by biochar: A comparative investigation based on distinguishable biochars

Biochars produced from crab shell(CSB),oak sawdust(OB),Jeru salem artichoke tuber(JAB) and sorghum grain(SB) displayed distinguishable adsorption-related characteristics,such as specific surface area(SSA),ash content and acidic oxygen-containing functional groups(AFGs),which linked to the biochar adsorption mechanisms of most pollutants.Herein,PO4^3-,Cd^2+,and nitrobenzene(NB) were employed for adsorption by these biochars to elucidate the dominant factors for the adsorption.Adsorption performance of the three pollutants onto these four biochars varied considerably,as exemplified by the excellent adsorption of PO4^3- and Cd^2+ onto CSB(225.3 and 116.0 mg/g,respectively) as compared with onto the other three biochars(4.2-37.1 mg/g for P043-and 9.7-41.0 mg/g for Cd^2+).OB displayed the best adsorption of NB(72.0 mg/g),followed by SB(39.5 mg/g),JAB(31.1 mg/g),and CSB(23.6 mg/g).The kinetics and isotherm adsorption assessments couple with material characterization suggested that the sorption of selected pollutants on biochars was attributed to the multiple mechanisms involved,including coprecipitation,chemical bonds,cation exchange,physical absorption,and complexation.Further path analysis suggested that AFGs and ash content in biochars were more important than SSA with regards to pollutant removal,especially,with ash playing a crucial role in the removal of Cd2+ and PO43-,and AFGs being mainly re s ponsible for NB adsorption.These findings might offer guidance on the preparation or modification of biochar with a targeted function for pollutant removal through an understanding the dominant factors.