Chunyan Du

Cadmium removal from simulated wastewater to biomass byproduct of Lentinus edodes

A kind of agricultural waste, the byproduct of brown-rot fungus Lentinus edodes, was used as an efficient biosorbent for the removal of cadmium from water in this paper. The sorption conditions, such as pH, the dose of biomass and the initial concentration of cadmium were examined. Three kinds of adsorption models were applied to simulate the biosorption data. Uptake of cadmium was higher in weak acid condition than in strong acid condition. Nearly no sorption of cadmium occurred when the pH value was lower than 2.5. Biosorption isothermal data could be well simulated by Freundlich model, and then Langmuir and Temkin model. Langmuir simulation of the biosorption showed that the maximum uptake of cadmium was 5.58mmol/g in weak acid condition, which was much higher than many other biosorbents. The exchanged proton was highly related to the uptake of cadmium in weak acid condition. Fourier transform infrared spectrums and energy-dispersive X-ray microanalyzer were used to reveal ion-exchange mechanism between cadmium and the functional groups or participated inorganic metal ions during biosorption.

Spatial analysis of human health risk associated with ingesting manganese in Huangxing Town, Middle China

This paper spatially analyzed human health risk associated with ingesting manganese (Mn) contents in groundwater and vegetables irrigated with contaminated pond water in Huangxing Town, Middle China. The combination of monitoring data and sequential indicator simulation (SIS) was used to determine Mn exposure distributions in pond water and groundwater. Hazard quotient (HQ) associated with ingesting Mn was calculated to evaluate the risk to human health. Many HQs determined from risks exceed 1 in the region, indicating that the use of groundwater and pond water poses potential risk to human health. Lower risk areas are located in the northwest and partly southeast of the region. The probabilistic risk assessment formulated suitable references for pollution remedy and control in Huangxing Town. Safe areas in 75th percentile of HQ map are suggested to be safe for use and, the manganese residues in the unsafe areas of the 25th percentile of HQ map is to be treated firstly.

Transfer of heavy metals from compost to red soil and groundwater under simulated rainfall conditions

It is well known that compost can be polluted with heavy metals. A self-designed soil column system was used to clarify the leaching or residue of heavy metals when compost was added to red soil. Less than 4% of Cu and more than 58.3% of Zn were transferred to groundwater. Maximum concentrations of Cu and Zn in leachate were 22 and 246 microg/L, respectively. pH in leachate decreased during 6.75-11.25 h, comparing with the control. Electrical conductivity was higher in the treatment of compost polluted by both Cu and Zn than that polluted only by Cu. Over 75.3% of Cu and 78.2% of Zn remained in the residual formation. Maximum bioavailability parameters in soil were 0.099 for Cu and 0.160 for Zn. Long-term field experiments with cycling application are needed to study the cycling effect on heavy metal residue in soil or leaching to the groundwater in the future.

Modeling research on the sorption kinetics of pentachlorophenol (PCP) to sediments based on neural networks and neuro-fuzzy systems

The sorption kinetics of pentachlorophenol (PCP) to sediments (from 8 different lakes, south of China) was studied in batch experiments. The comparison of a radial basis function neural network (RBFN) and an adaptive neuro-fuzzy inference system (ANFIS) applied for modeling the sorption behaviors was presented. Although the physical and chemical characteristics were different, the modeling results showed that the sorption behaviors of 8 different sediments were similar. Both RBFN and ANFIS could model the sorption behaviors and make predictions in high accuracy, which illustrated that the two models reflected the internal principle of the sorption better than the traditional model Ficks second law (FSL). Especially, RBFN held the promise of being able to work under noisy conditions to obtain high accuracy. In conclusion, RBFN was the valid options for modeling the sorption kinetics of PCP to the lake sediments. The individual changes of the three different inputs (the concentration of PCP in the aqueous phase, the reversible fraction and the irreversible fraction) affected the modeling results to the similar extent, from which we could infer that the sorption kinetics of PCP to these sediments were affected by all the three factors rather than only by the concentration of PCP in the aqueous phase.

Deposition pattern of precipitation and throughfall in a subtropical evergreen forest in south-central China

The effects of dry deposition, canopy leaching, precipitation ion concentration, and precipitation H+ concentration on net throughfall flux (NTF, throughfall minus bulk precipitation) were evaluated on a seasonal basis by using a multiple regression analysis approach based on an observation period of 4 years in Shaoshan subtropical mixed evergreen forest, south-central China. Regression analysis results indicated that the estimated canopy exchange flux was the dominant factor regulating the NTF and the calculated dry deposition was a minor term. The seasonal dry deposition of base cations accounted for 15%–43% of the NTF. The NTF analysis showed that K+, Ca2+, Mg2+, Na+, and weak acids in throughfall were derived from foliar leaching and the canopy uptakes of H+, NH4+, and NO3− were from precipitation. The retention rate of proton (H+ and NH4+) in the canopy was close to the canopy leaching rate of base cations when corrected for weak acids because weak acid-induced canopy leaching did not exchange with protons, which suggested that the canopy leaching processes neutralized acid precipitation in Shaoshan forest.

Optimal solute transport in heterogeneous aquifer: coupled inverse modelling

Characterisation of transmissivity heterogeneity is critical for groundwater flow and solute transport. The heterogeneity of transmissivity is studied through variogram-based techniques. Conventionally, the parameters in variogram are obtained by fitting measurements to a theoretical variogram. However, conditioning to the sampled geological variables neglects the effects of observed concentration data. This paper presents a coupled inverse modelling system conditioning to both types of measurement. The results of a hypothetical two-dimensional steady flow indicated that the description of transmissivity and solute concentration field was improved when both measured transmissivity data and solute concentration data were combined in the coupled inverse modelling system.

Deposition, Canopy and Soil Retention of Inorganic Nitrogen in a Subtropical Mixed Forest in Central-South China

Nitrogen deposition, leaching and retention were monitored in a subtropical mixed forest in central-south China. Bulk precipitation, throughfall, and stream water were monitored from January, 2001 to December, 2004. The research results showed that mean flux of inorganic nitrogen input was 3.136 g m-2 a-1, net retention of nitrogen by forest canopy was 1.2516 g m-2 a-1, and by soil profile of Shaoshan forest reached 1.6644 g m-2 a-1, which indicated that most of nitrogen input (92.98%) was reserved in Shaoshan forest and Shaoshan forest is still a finer buffering system to nitrogen deposition.