Adsorption–desorption behavior of atrazine on agricultural soils in China

Adsorption and desorption are important processes that affect atrazine transport,transformation,and bioavailability in soils.In this study,the adsorption–desorption characteristics of atrazine in three soils(laterite,paddy soil and alluvial soil) were evaluated using the batch equilibrium method.The results showed that the kinetics of atrazine in soils was completed in two steps:a"fast" adsorption and a "slow" adsorption and could be well described by pseudo-second-order model.In addition,the adsorption equilibrium isotherms were nonlinear and were well fitted by Freundlich and Langmuir models.It was found that the adsorption data on laterite,and paddy soil were better fitted by the Freundlich model;as for alluvial soil,the Langmuir model described it better.The maximum atrazine sorption capacities ranked as follows:paddy soil alluvial soil laterite.Results of thermodynamic calculations indicated that atrazine adsorption on three tested soils was spontaneous and endothermic.The desorption data showed that negative hysteresis occurred.Furthermore,lower solution pH value was conducive to the adsorption of atrazine in soils.The atrazine adsorption in these three tested soils was controlled by physical adsorption,including partition and surface adsorption.At lower equilibrium concentration,the atrazine adsorption process in soils was dominated by surface adsorption;while with the increase of equilibrium concentration,partition was predominant.     

Influences of greenhouse effect on agricultural production in China

An obvious warming in China induced by doubled carbon, dioxide as simulated by the climatic models have been found. It is also noticed that there might be drying or wetting in some parts of China induced by doubled CO2 as simulated by the general circulation models(GCMs). Agricultural productivity mainly depends on the temperature, rainfall and soil moisture in China. The changes of agricultural productivity in the different parts of China induced by doubled CO2 have been estimated in this paper. It is shown that the greenhouse effect might cause increasing production in some parts of China and decreasing production in other parts of China.     

Adsorption and desorption of Cu(Ⅱ) and Pb(Ⅱ) in paddy soils cultivated for various years in the subtropical China

The adsorption and desorption of Cu(Ⅱ) and Pb(Ⅱ) on upland red soil,and paddy soils which were originated from the upland soil and cultivated for 8,15,35 and 85 years,were investigated using the batch method.The study showed that the organic matter content and cation exchange capacity (CEC) of the soils are important factors controlling the adsorption and desorption of Cu(Ⅱ) and Pb(Ⅱ).The 15-Year paddy soil had the highest adsorption capacity for Pb(Ⅱ),followed by the 35-Year paddy soil.Both the 35-Year paddy soil and 15-Year paddy soil adsorbed more Cu(Ⅱ) than the upland soil and other paddy soils.The 15-Year paddy soils exhibited the highest desorption percentage for both Cu(Ⅱ) and Pb(Ⅱ).These results are consistent with the trend for the CEC of the soils tested.The high soil CEC contributes not only to the adsorption of Cu(Ⅱ) and Pb(Ⅱ) but also to the electrostatic adsorption of the two heavy metals by the soils.Lower desorption percentages for Cu(Ⅱ) (36.7% to 42.2%) and Pb(Ⅱ) (50.4% to 57.9%) were observed for the 85-Year paddy soil.The highest content of organic matter in the soil was responsible for the low desorption percentages for the two metals because the formation of the complexes between the organic matter and the metals could increase the stability of the heavy metals in the soils.     

Effects of aging process on adsorption–desorption and bioavailability of fomesafen in an agricultural soil amended with rice hull biochar

Biochar has been introduced as an acceptable soil amendment due to its environmental benefits such as sequestering soil contaminants. However, the aging process in biochar amended soil probably decreases the adsorption capacity of biochar through changing its physico-chemical properties. Adsorption, leaching and bioavailability of fomesafen to corn in a Chinese soil amended by rice hull biochar after 0, 30, 90 and 180 days were investigated.Results showed that the addition of 0.5%–2% fresh biochar significantly increases the adsorption of fomesafen 4–26 times compare to unamended soil due to higher SSA of biochar. Biochar amendment also decreases fomesafen concentration in soil pore water by5%–23% resulting lower risk of the herbicide for cultivated plants. However, the aging process decreased the adsorption capacity of biochar since the adsorption coefficient values which was 1.9–12.4 in 0.5%–2% fresh biochar amended soil, declined to 1.36–4.16, 1.13–2.78 and 0.95–2.31 in 1, 3 and 6-month aged treatments, respectively. Consequently, higher desorption, leaching and bioavailable fraction of fomesafen belonged to 6-month aged treatment. Nevertheless, rice hull biochar was effective for sequestering fomesafen as the adsorption capacity of biochar amended soil after 6 months of aging was still 2.5–5 times higher compared to that of unamended soil.     

Occurrence and congeners specific of poiychlorinated biphenyls in agricultural soils from Southern Jiangsu, China

A total of 198 agricultural soil samples were collected from Zhangjiagang and Changshu in Southern Jiangsu for analysis of 13 polychlorinated biphenyls (PCBs) in order to assess the levels of pollution, sources, area distribution, and potential risk for the environment. All methods were rigorously tested and an adequate quality control was ensured. Only one site had no PCBs residues, and the highest total PCBs concentration in the surface soils was 32.83 ng/g. The average concentration in all the soil samples was 4.13 ng/g, signaling low-level pollution. Tetra-, penta-, and hexa-chlorinated biphenyls were dominant species in soil samples, accounting for more than 75% ofΣPCBs in the soil samples. PCB118 was the most abundant congener in all the samples. The PCB118 was about 20% ofΣPCBs. The soil organic matter content showed only a weak correlation with the levels of all PCB congeners, in which a better correlation was noted for the more volatile lighter PCB congeners than for the heavier homologues. To a certain extent, the sources and land use seemed to influence the levels of PCBs.     

Lead content of urban soils in China

ＬｅａｄｃｏｎｔｅｎｔｏｆｕｒｂａｎｓｏｉｌｓｉｎＣｈｉｎａＺｈａｎｇＸｕｅｌｉｎ（ＣｈａｎｇｃｈｕｎＩｎｓｔｉｔｕｔｅｏｆＧｅｏｇｒａｐｈｙ，ＣｈｉｎｅｓｅＡｃａｄｅｍｙｏｆＳｃｉｅｎｃｅｓ，Ｃｈａｎｇｃｈｕｎ１３００２１，Ｃｈｉｎａ）ＭｅｎｇＫｅ...     

Effects of simulated acid rain on cation releasing in soils of South China

ＥｆｅｃｔｓｏｆｓｉｍｕｌａｔｅｄａｃｉｄｒａｉｎｏｎｃａｔｉｏｎｒｅｌｅａｓｉｎｇｉｎｓｏｉｌｓｏｆＳｏｕｔｈＣｈｉｎａＷｕＱｉｎｇ，ＱｉｕＲｏｎｇｌｉａｎｇ，ＬｕＹｕｅｎａＤｅｐａｒｔｍｅｎｔｏｆＥｎｖｉｒｏｎｍｅｎｔａｌＳｃｉｅｎｃｅ，Ｚ...     

Effects of simulated acid rain on cation release in soils of South China

This paper deals with the release of base cations and Al3+ at the treatment with simulated acid rain (SAR) in main soil types collected from South China. Results showed that the amounts of base cations increased obviously when the pH value of simulated acid rain was lower than 3.0 or 3.5. Compared with the leaching of K+ and Na+, the leaching of Ca2+ and Mg2+ was affected by the pH value of SAR. Only when the amounts of base cations leached from soils exceeded the cation exchange capacity, the pH value of leaching solutions decreased sharply and the amounts of released Al3+ increased. The H+ buffering mechanisms, which were affected notonly by the pH values of SAR, but also by the types and solid components of soils, were proposed for the main soils studied.     

Simulation study on vertical transport of atrazine in soil column

ＩｎｔｒｏｄｕｃｔｉｏｎＡｔｒａｚｉｎｅ (2 ｃｈｌｏｒｏ 4 ｅｔｈｙｌａｍｉｎｏ 6 ｉｓｏｐｒｏｐｙｌａｍｉｎｏ ｓ ｔｒｉａｚｉｎｅ)ｉｓｏｎｅｏｆｔｈｅｍｏｓｔｗｉｄｅｌｙｕｓｅｄｈｅｒｂｉｃｉｄｅａｎｄｍａｉｎｌｙｕｓｅｄｆｏｒｃｏｎｔｒｏｌｏｆｃｅｒｔａｉｎａｎｎｕａｌｂｒｏａｄｌｅａｆａｎｄｇｒａｓｓｗｅｅｄｓａｎｄｐｒｉｍａｒｉｌｙｈａｓｂｅｅｎｃｏｍｍｏｎｌｙｕｓｅｄｉｎｃｏｒｎｏｒｉｎｃｏｒｎ ｗｈｅａｔｄｏｕｂｌｅｃｒｏｐｐｉｎｇｓｙｓｔｅｍｉｎＮｏｒｔｈｅａｓｔａｎｄＮｏｒｔｈｏ…     

Sensitivity of soils to acid rain in South China

This paper deals with the sensitivity of soils to acid rain in 5 provinces, South China. Based on field work and literature, and taking soil pH, CEC, and the types of residua into account, the authors classified the sensitivity into 4 categories: highly sensitive, sensitive, slightly sensitive, and non-sensitive. By overlapping the maps of soil pH, CEC, and types of residua, the map of soil sensitivity in South China has finally resulted.The authors try to summarize the regularity of soil sensitivity to acid rain in this area. The sensitivity of different soil types in the studied area has also discussed.The seriousness and its prospects of acid rain in this area have been pointed out in order to draw the attention of relevant authorities.     

Adsorption and desorption of lanthanum at sulfide mineral surface

Batch adsorption experiment with four sulfide minerals - Chalcocite galena, pyrite and sphalerite - were used to study for the adsorption and desorp-tion behavior of La (III) in the presence of EDTA, a model humic matter. Linear adsorption was found in all cases.The presence of soluble organic complexing ligand should reduce the mobility of La (III) in porous media and its transport to groundwater in the percolating soil solution. Binding mechanism is proposed to account for this preferential binding behavior.     

Adsorption behavior of phosphate on Lanthanum（III） doped mesoporous silicates material

A series of lanthanum doped meosoporous MCM-41 (LaxM41, x is Si/La molar ratio) was prepared by sol-gel method. The surface structure of the materials was investigated with X-ray diffraction and N2 adsorption/desorption technique. The content of La in the materials was determined by ICP. It was found that the La content of La25M41, La50M41 and La100M41 was 7.53%, 3.89% and 2.32%, respectively. The phosphate adsorption capacities increased with increasing amount of La incorporation. With 0.40 g La25M41 99.7% phosphate could be removed. The effects of Si/La molar ratio, LaxM41 dose, pH, initial concentration of phosphate solution, co-ions on phosphate adsorption were also evaluated. The phosphate adsorption kinetics of LaxM41 could be well-described by the pseudo second-order model, and Langmuir isotherm fit equilibrium data much better than the Freundlich isotherm.     

Adsorption characteristic of bensulfuron-methyl at variable added Pb^2＋ concentrations on paddy soils

The combined pollution of heavy metal Pb²⁺ and bensulfuron-methyl (BSM), originating from chemical herbicides, in agroecological environments has become commonplace in southern China. The adsorption of BSM on three paddy soils in the presence of Pb²⁺ was examined using high-performance liquid chromatograph (HPLC). Results indicated that adsorption of BSM could accurately be described by a Freundlich isotherm equation with correlation constant (R) > 0.98, irrespective of the presence of spiked Pb²⁺. Of the various factors influencing BSM sorption, soil pH appeared to be the most influential. The constant K_f of Freundlich isotherm equation tended to increase with increasing Pb²⁺ concentration in soil which indicated that the spiked of Pb²⁺ in paddy soils would promote the sorption of BSM. ΔG^θ of BSM in three paddy soils was less than 40 kJ/mol in all treatments, indicating the adsorption of BSM is mainly physical in nature. The elution of soil dissolved organic matter (DOM) enhanced the adsorption of BSM in paddy soils. The mechanisms involved in the promotion effects of the spiked Pb²⁺ on BSM adsorption might be the modified surface characteristics of paddy soil solids due to the soil acidification and the increase of soil organic matter concentration because of DOM binding.     

Adsorption behavior of phosphate on Lanthanum(Ⅲ) doped mesoporous silicates material

A series of lanthanum doped meosoporous MCM-41 (La_xM41, x is Si/La molar ratio) was prepared by sol-gel method. The surface structure of the materials was investigated with X-ray diffraction and N_2 adsorption/desorption technique. The content of La in the materials was determined by ICP. It was found that the La content of La_(25)M41, La_(50)M41 and La_(100)M41 was 7.53%, 3.89% and 2.32%, respectively. The phosphate adsorption capacities increased with increasing amount of La incorporation. With 0.40 g La_(25)M41 99.7% phosphate could be removed. The effects of Si/La molar ratio, La_xM41 dose, pH, initial concentration of phosphate solution, co-ions on phosphate adsorption were also evaluated. The phosphate adsorption kinetics of La_xM41 could be well-described by the pseudo second-order model, and Langmuir isotherm fit equilibrium data much better than the Freundlich isotherm.     

Effect of petroleum on decomposition of shrub–grass litters in soil in Northern Shaanxi of China

The impacts of petroleum contamination on the litter decomposition of shrub–grass land would directly influence nutrient cycling, and the stability and function of ecosystem. Ten common shrub and grass species from Yujiaping oil deposits were studied. Litters from these species were placed into litterbags and buried in petroleum-contaminated soil with 3 levels of contamination (slight, moderate and serious pollution with petroleum concentrations of 15, 30 and 45 g/kg, respectively). A decomposition experiment was then conducted in the lab to investigate the impacts of petroleum contamination on litter decomposition rates. Slight pollution did not inhibit the decomposition of any litters and significantly promoted the litter decomposition of Hippophae rhamnoides, Caragana korshinskii, Amorpha fruticosa, Ziziphus jujuba var. spinosa, Periploca sepium, Medicago sativa and Bothriochloa ischaemum. Moderate pollution significantly inhibited litter decomposition of M. sativa, Coronilla varia, Artemisia vestita and Trrifolium repens and significantly promoted the litter decomposition of C. korshinskii, Z. jujuba var. spinosa and P. sepium. Serious pollution significantly inhibited the litter decomposition of H. rhamnoides, A. fruticosa, B. ischaemum and A. vestita and significantly promoted the litter decomposition of Z. jujuba var. spinosa, P. sepium and M. sativa. In addition, the impacts of petroleum contamination did not exhibit a uniform increase or decrease as petroleum concentration increased. Inhibitory effects of petroleum on litter decomposition may hinder the substance cycling and result in the degradation of plant communities in contaminated areas.     

Stipulation of the criteria for the construction of eco agricultural county in China

ＩｎｔｒｏｄｕｃｔｉｏｎＮｏｗｗｅａｌｌｃｏｎｃｅｒｎｏｕｒｓｅｌｖｅｓｗｉｔｈｔｈｅｃｏｎｔｅｍｐｏｒａｒｙｐｒｏｂｌｅｍｓｏｆｏｖｅｒｐｏｐｕｌａｔｉｏｎ,ｒｅｓｏｕｒｃｅｅｘｐｌｏｉｔａｔｉｏｎ,ｅｎｖｉｒｏｎｍｅｎｔａｌｐｏｌｌｕｔｉｏｎａｎｄ...     

Solid components and acid buffering capacity of soils in South China

ＳｏｌｉｄｃｏｍｐｏｎｅｎｔｓａｎｄａｃｉｄｂｕｆｅｒｉｎｇｃａｐａｃｉｔｙｏｆｓｏｉｌｓｉｎＳｏｕｔｈＣｈｉｎａＱｉｕＲｏｎｇｌｉａｎｇ，ＷｕＱｉｎｇ，ＺｈａｎｇＹｕｎｎｉＤｅｐａｒｔｍｅｎｔｏｆＥｎｖｉｒｏｎｍｅｎｔａｌＳｃｉｅｎｃｅ，Ｚｈｏ...     

Study on the toxicity of acid rain to microbiota in soils

With simulated acid rain and acidification, the soils from both Nanning and Liuzhou municipalities, Guangxi Zhuang Nationality Autonomous Region have been studied to determine the counts of azotobacter, bacteria, actinomyces and the activity of urease in soils, and the changes in respiratory intensity of soil so as to identify the toxicity of acidic substances to microbiota and enzyme in such soils. The concept of the critical pH of toxicity has been developed and used to discuss the representation of the concept, the basis on which the soil treated with simulated acid rain can be taken as an object of study, and the criteria for the identification of toxicity. Based on that as mentioned above, it was found that acid rain behaved to have toxicity to the microbiota in soils from Liuzhou other than from Nanning. The findings may be regarded as an objective basis to study the toxicity of acidic substances to microbiota and enzyme in soils in this region.     

Advances of studies on biomonitoring of water pollution in China

The progress of biomonitoring on water pollution in recent years in China has been summarized in this paper.     

Adsorption of herbicide triclopyr on homoionic clays

ＡｄｓｏｒｐｔｉｏｎｏｆｈｅｒｂｉｃｉｄｅｔｒｉｃｌｏｐｙｒｏｎｈｏｍｏｉｏｎｉｃｃｌａｙｓＬｉｕＷｅｉｐｉｎｇ（ＤｅｐａｒｔｍｅｎｔｏｆＣｈｅｍｉｓｔｒｙ，ＺｈｅｊｉａｎｇＵｎｉｖｅｒｓｉｔｙ，Ｈａｎｇｚｈｏｕ３１００２７，Ｃｈｉｎａ）ＡｌｂａＰｕ...