Chunye Lin

Properties comparison of biochars from corn straw with different pretreatment and sorption behaviour of atrazine

Biochar has been recognised as an efficient pollution control material. In this study, biochars (CS450 and ADPCS450) were produced using corn straw with different pretreatment techniques (without and with ammonium dihydrogen phosphate (ADP)). The character of the two biochars was compared using elemental analysis, specific surface area (SSA) and Fourier transform infrared spectra (FTIR). ADPCS450 had a higher residue yield and a much larger specific surface area than CS450. The Freundlich, Langmuir and Redlich-Peterson models were used to interpret the sorption behaviour of atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine), and the results fit the Redlich-Peterson equation best. The isothermal sorption parameters indicated that the sorption capacity of atrazine on ADPCS450 was much larger than the sorption capacity of atrazine on CS450. Atrazine sorption was also favoured in acidic solution and under higher temperature conditions.

Anthropogenic Chromium Emissions in China from 1990 to 2009

An inventory of chromium emission into the atmosphere and water from anthropogenic activities in China was compiled for 1990 through to 2009. We estimate that the total emission of chromium to the atmosphere is about 1.92×105t. Coal and oil combustion were the two leading sources of chromium emission to the atmosphere in China, while the contribution of them showed opposite annual growth trend. In total, nearly 1.34×104t of chromium was discharged to water, mainly from six industrial categories in 20 years. Among them, the metal fabrication industry and the leather tanning sector were the dominant sources of chromium emissions, accounting for approximately 68.0% and 20.0% of the total emissions and representing increases of15.6% and 10.3% annually, respectively. The spatial trends of Cr emissions show significant variation based on emissions from 2005 to 2009. The emission to the atmosphere was heaviest in Hebei, Shandong, Guangdong, Zhejiang and Shanxi, whose annual emissions reached more than 1000t for the high level of coal and oil consumption. In terms of emission to water, the largest contributors were Guangdong, Jiangsu, Shandong and Zhejiang, where most of the leather production and metal manufacturing occur and these four regions accounted for nearly 47.4% of the total emission to water.

In situ remediation of cadmium-polluted soil reusing four by-products individually and in combination

PurposeThe aim of this study was to evaluate the effectiveness of mining, industrial and agricultural solid by-products in the in situ immobilisation of soil cadmium (Cd) based on soybean plant Cd content, soil pH, Cd extractability, bioavailability, leachability and Cd distribution in soils.Materials and methodsThe experiment was conducted as a field experiment in Cd-polluted-soil, wherein four by-products, including fly ash, spent mushroom substrate, silkworm excrement and limestone, were tested individually and in combination. The total Cd in soybean and the soil/by-products samples were determined. The Cd contents in the contaminated soil were analysed by the diffusive gradients in thin-film technique, the toxicity characteristic leaching procedure and four chemical methods. Changes in the fractions of Cd were determined following the Tessier method.Results and discussionThe results showed that all the additions of the by-products increased the soil pH significantly and simultaneously decreased Cd mobility, bioavailability and leachability, particularly weakened the rate of Cd2+ ion transport from soil to solution. The by-products caused 23.5–76.4% of the exchangeable (EX) fraction of Cd to immobilised Cd fractions which include carbonates bound (CA), Fe-Mn oxides bound (OX), organic matter bound and residual fractions. The mobile faction of Cd was reduced from 33.7 to 16.8–27.8% for the amendments addition, respectively. Limestone was the most effective in immobilising the soil Cd among all the treatments, followed by fly ash. Soil pH observed significantly negative correlations with the Cd concentration in extractability, bioavailability and leachability. Soil pH had positive correlations with the percentages of CA-Cd and OX-Cd, but negatively correlated with the percentages of EX-Cd and the sum of EX-Cd and CA-Cd.ConclusionsBy-products addition increased the soil pH and decreased Cd mobility, bioavailability and leachability. The addition of limestone and fly ash exhibited higher efficiency than the other five additions. The combined additions had better performance on Cd extractability and soil pH than the corresponding single treatment, which decreased more concentrations of mobile, bioavailable and leachable Cd. This study offered four potentially cost-effective amendments singly or jointly for Cd immobilisation, reducing the potential hazards associated with excess Cd and the waste-disposal pressure and promoting a resource-saving development strategy.

Anthropogenic impact on diffuse trace metal accumulation in river sediments from agricultural reclamation areas with geochemical and isotopic approaches.

A better understanding of anthropogenic impact can help assess the diffuse trace metal accumulation in the agricultural environment. In this study, both river sediments and background soils were collected from a case study area in Northeast China and analyzed for total concentrations of six trace metals, four major elements and three lead isotopes. Results showed that Pb, Cd, Cu, Zn, Cr and Ni have accumulated in the river sediments after about 40 years of agricultural development, with average concentrations 1.23-1.71 times higher than local soil background values. Among them Ni, Cr and Cu were of special concern and they may pose adverse biological effects. By calculating enrichment factor (EF), it was found that the trace metal accumulation was still mainly ascribed to natural weathering processes, but anthropogenic contribution could represent up to 40.09% of total sediment content. For Pb, geochemical and isotopic approaches gave very similar anthropogenic contributions. Principal component analysis (PCA) further suggested that the anthropogenic Pb, Cu, Cr and Ni inputs were mostly related to the regional atmospheric deposition of industrial emissions and gasoline combustion, which had a strong affinity for iron oxides in the sediments. Concerning Cd, however, it mainly originated from local fertilizer applications and was controlled by sediment carbonates.

Soil respiration and carbon loss relationship with temperature and land use conversion in freeze-thaw agricultural area.

Soil respiration (Rs) was hypothesized to have a special response pattern to soil temperature and land use conversion in the freeze-thaw area. The Rs differences of eight types of land use conversions during agricultural development were observed and the impacts of Rs on soil organic carbon (SOC) loss were assessed. The land use conversions during last three decades were categorized into eight types, and the 141 SOC sampling sites were grouped by conversion type. The typical soil sampling sites were subsequently selected for monitoring of soil temperature and Rs of each land use conversion types. The Rs correlations with temperature at difference depths and different conversion types were identified with statistical analysis. The empirical mean error model and the biophysical theoretical model with Arrhenius equation about the Rs sensitivity to temperature were both analyzed and shared the similar patterns. The temperature dependence of soil respiration (Q10) analysis further demonstrated that the averaged value of eight types of land use in this freeze-thaw agricultural area ranged from 1.15 to 1.73, which was lower than the other cold areas. The temperature dependence analysis demonstrated that the Rs in the top layer of natural land covers was more sensitive to temperature and experienced a large vertical difference. The natural land covers exhibited smaller Rs and the farmlands had the bigger value due to tillage practices. The positive relationships between SOC loss and Rs were identified, which demonstrated that Rs was the key chain for SOC loss during land use conversion. The spatial-vertical distributions of SOC concentration with the 1.5-km grid sampling showed that the more SOC loss in the farmland, which was coincided with the higher Rs in farmlands. The analysis of Rs dynamics provided an innovative explanation for SOC loss in the freeze-thaw agricultural area. The analysis of Rs dynamics provided an innovative explanation for SOC loss in the freeze-thaw agricultural area.

Multivariate interactions of natural and anthropogenic factors on Cd behavior in arable soil

Multivariate interactions are far more complex between natural factors and pollutants resulting from anthropogenic practices than between pollutants themselves. But little attention has been focused on the complex interpretation of multivariate interactions. To bridge this research gap, this study aimed to identify the interactive effect of multiple affecting factors including freeze–thaw cycles (FT), soil water (SW) content, and chlorpyrifos (CP) on soil Cd behavior in arable soil, based on the analysis of changes in Cd fractionations and Cd availability. Moreover, the significant effect was computed via design of experiments. The content of Cd fractions and the evaluated index of Cd availability were obtained by employing the modified six-step sequential extraction method. The results showed that the main effect of FT, SW and CP on Cd fractionation and availability was significant. The binary interactions weakened the main effect of FT or SW, but enhanced the main effect of CP on Cd fractionation. The ternary interactions further weakened the binary interactions, whereas CP enhanced the interaction between SW and FT. The interaction between SW and CP had a negative effect on residual Cd, but positively affected water-soluble and organic matter-bound Cd. The binary interaction between CP and FT had a positive effect on residual Cd (21.0%), but negatively affected water-soluble and Fe–Mn-oxide-associated Cd (25.9% and 21.1%). These results covered more innovative information on the multivariate interactions between natural and anthropogenic factors on Cd behavior in arable soil. A possible new way to quantify the significant impact of multivariate factors also was provided.

Using river sediments to analyze the driving force difference for non-point source pollution dynamics between two scales of watersheds

The formation and transportation processes of non-point source (NPS) pollution varied among the studied watersheds in the Northeastern China, so we hypothesized that the driving force behind NPS pollution followed the spatial scale effect. With a watershed outlet sedimentary flux analysis and a distributed NPS pollution loading model, we investigated the temporal dynamics of NPS and the differences in driving forces. Sediment core samples were collected from two adjacent watersheds, the smaller Abujiao watershed and the larger Naoli watershed. The natural climatic conditions, long-term variations in the distribution of land use, soil properties and tillage practices were the same in the two watersheds. The vertical distributions of total nitrogen, total phosphorus, Zn and As at 1-cm intervals in the section showed clear differences between the watersheds. There were higher concentrations of total nitrogen and total phosphorus in the larger watershed, but the heavy metals were more concentrated in the smaller watershed. Lead-210 (210Pb) analyses and the constant rate of supply model provided a dated sedimentary flux, which was correlated with the corresponding yearly loading of NPS total nitrogen and total phosphorus in the two watersheds. The total phosphorus showed a stable relationship in both watersheds with an R2 value that ranged from 0.503 to 0.682. A rose figure comparison also demonstrated that the pollutant flux in the sediment was very different in the two watersheds, which had similar territorial conditions and different hydrological patterns. Redundancy analysis further indicated that expanding paddy areas had a large impact on the sedimentary flux of nitrogen and phosphorus in the smaller watershed, but precipitation had a direct impact on NPS loading in the larger watershed. We concluded that the spatial scale effect affected the NPS pollution via the transport processes in the waterway, which was mainly influenced by branch length and drainage density.

Novel approach for quantitatively estimating element retention and material balances in soil profiles of recharge basins used for wastewater reclamation

We investigated changes in element content and distribution in soil profiles in a study designed to monitor the geochemical changes accruing in soil due to long-term secondary effluent recharge, and its impact on the sustainability of the Soil Aquifer Treatment (SAT) system. Since the initial elemental contents of the soils at the studied site were not available, we reconstructed them using scandium (Sc) as a conservative tracer. By using this approach, we were able to produce a mass-balance for 18 elements and evaluate the geochemical changes resulting from 19 years of effluent recharge. This approach also provides a better understanding of the role of soils as an adsorption filter for the heavy metals contained in the effluent. The soil mass balance suggests 19 years of effluent recharge cause for a significant enrichment in Cu, Cr, Ni, Zn, Mg, K, Na, S and P contents in the upper 4m of the soil profile. Combining the elements lode record during the 19 years suggest that Cr, Ni, and P inputs may not reach the groundwater (20 m deep), whereas the other elements may. Conversely, we found that 58, 60, and 30% of the initial content of Mn, Ca and Co respectively leached from the upper 2-m of the soil profile. These high percentages of Mn and Ca depletion from the basin soils may reduce the soils ability to buffer decreases in redox potential pe and pH, respectively, which could initiate a reduction in the soils holding capacity for heavy metals.