[Safe Utilization Effect of Passivator on Mild to Moderate Cadmium Contaminated Farmland].

In order to study the safe utilization of acid cadmium （Cd） contaminated soil， light and moderate Cd-contaminated farmland in Shangluo， Shaanxi Province was taken as the research object， and lime， biochar， and calcium magnesium phosphate fertilizer were applied. Through the wheat-maize rotation experiment， the safe utilization effect of different amounts of passivator on Cd-contaminated soil was explored， and the best ratio of passivator was selected. The results showed that： ① the soil quality could be improved to varying degrees by applying the passivator. ② After the application of amendments， the grain yield of wheat and maize increased to different degrees. ③ The lime 2 340 kg·hm-2 （C3） treatment had the best effect， which increased the soil pH of wheat and corn by 1.453 and 1.717 units， respectively， and reduced the available Cd content by 34.38% and 30.20%， respectively. ④ The application of biochar 1 800 kg·hm-2 （B2） treatment had the best effect on reducing the Cd contents in wheat roots， straws， and grains， which were significantly reduced by 53.60%， 38.86%， and 52.96%， respectively， compared with that in CK. The Cd content in wheat grains was reduced to 0.09 mg·kg-1， which was lower than the limit value of wheat Cd （0.1 mg·kg-1） specified in the "National food safety standard food pollutant limit" （GB 2762-2017）. The application of the biochar 1 260 kg·hm-2 （B1） treatment had the best comprehensive effect on reducing the Cd contents of maize roots， straws， and grains， which were significantly reduced by 43.74%， 53.20%， and 94.57%， respectively， compared with that in CK. The Cd content of maize grains was reduced to 0.001 9 mg·kg-1， which was far lower than the limit value of maize Cd （0.1 mg·kg-1） specified in the "National food safety standard food pollutant limit" （GB 2762-2017）. Therefore， under the conditions of the field experiment， considering the influence of various indexes， biochar had the best effect on farmland soil in the wheat-maize rotation area with mild to moderate Cd pollution.

The effect of erbium on the adsorption and photodegradation of orange I in aqueous Er3+-TiO2 suspension.

Pure TiO(2) and erbium ion-doped TiO(2) (Er(3+)-TiO(2)) catalysts prepared by the sol-gel method were characterized by means of XRD and diffusive reflectance spectra (DRS). The XRD results showed that erbium ion doping could enhance the thermal stability of TiO(2) and inhibit the increase of the crystallite size, and the DRS results showed that the optical absorption edge slightly shifted to red direction owing to erbium ion doping and the Er(3+)-TiO(2) catalysts had three typical absorption peaks located at 490, 523 and 654 nm owing to the transition of 4f electron from (4)I(15/2) to (4)F(7/2), (2)H(11/2) and (4)F(9/2). With a purpose of azo dyes degradation, orange I was used as a model chemical. And the adsorption isotherm, degradation and mineralization of orange I were investigated in aqueous suspension of pure TiO(2) or Er(3+)-TiO(2) catalysts. The results showed that Er(3+)-TiO(2) catalysts had higher adsorption equilibrium constants and better adsorption capacity than pure TiO(2). The adsorption equilibrium constants (K(a)) of Er(3+)-TiO(2) catalysts were about twice of that of pure TiO(2). The maximum adsorption capacity (Q(max)) of 2.0% Er(3+)-TiO(2) catalyst was 13.08x10(-5)mol/g, which was much higher than that of pure TiO(2) with 9.03x10(-5)mol/g. Among Er(3+)-TiO(2) catalysts, 2.0% Er(3+)-TiO(2) catalyst achieved the highest Q(max) and K(a) values. The kinetics of the orange I degradation using different Er(3+)-TiO(2) catalysts were also studied. The results demonstrated that the degradation and mineralization of orange I under both UV radiation and visible light were more efficient with Er(3+)-TiO(2) catalyst than with pure TiO(2), and an optimal dosage of erbium ion at 1.5% achieved the highest degradation rate. The higher photoactivity under visible light might be attributable to the transitions of 4f electrons of Er(3+) and red shifts of the optical absorption edge of TiO(2) by erbium ion doping.

Relationship between light and heavy fractions of organic matter for several agricultural soils in China.

Although numerous studies about the nature and turnover of soil organic matter(SOM) in light and heavy fractions(LFOM and HFOM, respectively) have been made, little information is available in relation to the relationship between LFOM and HFOM, and no attempts have been made to quantify a general relationship between LFOM and HFOM for agricultural soils under field condition. Our hypothesis is there may be an inherent relationship between LFOM and HFOM for agricultural soils under certain unaltered management practices for a long period, to this end, we therefore studied typically soils taken from different parts in China by using a simple density fractionation procedure. The results indicated that LFOM was positively correlated with LFOM/HFOM ratio for three typical soils. This information will be of particular use not only in deepening our understanding of the dynamics of SOM fractions but also in evaluating the potential of agricultural soils to sequestrate C under different management practices in a long term.

[Variations of soil fertility level in red soil region under long-term fertilization].

Based on the long-term (1982-2007) field experiment of "anthropogenic mellowing of raw soil" at the Qiyang red soil experimental station under Chinese Academy of Agricultural Sciences, and by using numerical theory, this paper studied the variations of the fertility level of granite red soil, quaternary red soil, and purple sandy shale soil under six fertilization patterns. The fertilization patterns included non-fertilization (CK), straw-returning without fertilizers (CKR), chemical fertilization (NPK), NPK plus straw-return (NPKR), rice straw application (M), and M plus straw-return (MR). The soil integrated fertility index (IFI) was significantly positively correlated with relative crop yield, and could better indicate soil fertility level. The IFI values of the three soils all were in the order of NPK, NPKR > M, MR > CK, CKR, with the highest value in treatment NPKR (0.77, 0.71, and 0.71 for granite red soil, quaternary red soil, and purple sandy shale soil, respectively). Comparing with that in the treatments of no straw-return, the IFI value in the treatments of straw return was increased by 6.72%-18.83%. A turning point of the IFI for all the three soils was observed at about 7 years of anthropogenic mellowing, and the annual increasing rate of the IFI was in the sequence of purple sandy shale soil (0.016 a(-1)) > quaternary red clay soil (0.011 a(-1)) > granite red soil (0.006 a(-1)). It was suggested that a combined application of organic and chemical fertilizers and/or straw return could be an effective and fast measure to enhance the soil fertility level in red soil region.

Sorption of pyrene by regular and nanoscaled metal oxide particles: influence of adsorbed organic matter.

Sorption of pyrene by regular and nanoscaled aluminum, zinc, and titanium oxides was examined. All oxides had low sorption for pyrene because of sorbed water molecules. Due to the larger surface area (SA) of nanoparticles, they had higher sorption for pyrene than the regular ones. Organic matter (OM) coating greatly enhanced pyrene sorption by all oxides, noting the importance of sorbed OM in sorption of hydrophobic organic compounds (HOCs). Due to higher sorption site density in the sorbed OM phase on the regular oxide surfaces, SA-normalized distribution coefficients (K(dSA)) of pyrene by OM-regular oxide complexes (6.0-40.6) were greater than the OM-coated oxide nanoparticles (0.7-12.5). Furthermore, the OM-regular oxide complexes had higher organic carbon content-normalized K(dSA) values of pyrene (48-17 300) than the OM-nanoscaled oxide complexes (15-1530). This variation may be due to different physical forms and fractionation of the loaded OM on regular and nanoscaled oxide particles.

Sorption of organic contaminants by carbon nanotubes: influence of adsorbed organic matter.

Sorption of three types of dissolved organic matter (DOM; i.e., humic acid, peptone and alpha-phenylalanine) by a mutiwalled carbon nanotube (MWNT40) and sorption of phenanthrene (Phen), naphthalene (Naph), and 1-naphthol (1-Naph) by the original and DOM-coated MWNT40 were examined. Sorption data of Phen, Naph, and 1-Naph by all sorbents were fitted with Freundlich and Polanyi models. MWNT40 had nonlinear isotherms for all DOMs examined. Sorption of DOMs by MWNT40 followed the order peptone > humic acid > alpha-phenylalanine. The humic acid used in this study had much lower sorption for Phen, Naph, and 1-Naph than MWNT40, but its coating did not make striking changes on sorption of these compounds by MWNT40, suggesting that humic acid coating dramatically altered the physical form and surface properties of MWNT40. Peptone coating made the strongest suppression on sorption of Phen, Naph, and 1-Naph by MWNT40 among the three DOMs used, due to its highest sorption on MWNT40, thus causing a great reduction in accessibility of sorption sites. Polanyi modeling results showed that reduction in the maximum volume sorption capacity (Q0) of MWNT40 induced by DOM coating followed the order Phen < Naph < 1-Naph. 1-Naph was less hydrophobic than Phen and Naph but it had much higher sorbed volume (V(m)) than Phen and Naph at individual RT In(S(w)/C(e))/V(s)points for all sorbents. The correlation curve for the Polanyi model was applicable for sorption of aromatic compounds of similar structure by the original and DOM-coated carbon nanotubes.

[Effects of long-term potassium fertilization on potassium fixation in soils under different ecological conditions: a mechanism study].

By using X-ray diffraction and laboratory simulation, this paper studied the effects of long-term potassium (K) fertilization on K fixation in black soil, loess soil, and grey desert soil under different ecological conditions and cropping systems. The results showed that long-term K fertilization had greater effects on the K fixation capacity of soils with lower hydromica content. When the K application rate was 400 to 4 000 mg x kg(-1), the K fixation capacity of black soil and loess soil, whose hydromica contents were low or relatively low, decreased by 75-747 mg x kg(-1) and 16-238 mg x kg(-1), respectively, compared with no K application, while no change was observed in grey desert soil whose hydromica content was high. Long-term K application could affect the changes of soil K-bearing minerals, i.e., slowing down or holding back the transformation of hydromica into mixed-layered mica-smectite, and consequently, decreased the K fixation capacity of soil. The increase of soil slow-available K content and K+ saturation owing to the long-term K application also induced the decrease of the K fixation capacity.

[Nutrient leaching and acidification of Southern China coniferous forest red soil under stimulated N deposition].

In an eight months interval leaching experiment with soil column (10 cm in diameter and 60 cm in height) at 20 degrees C, this paper studied the effects of N deposition on the leaching losses of soil NO -, NH4+ , H+, Ca2+, Mg2+ , K+, and Na+ , and on soil acidification. Soil columns were taken from the coniferous forest experimental plot at the Red Soil Ecological Experiment Station of Chinese Academy of Sciences in Southern China, and the N deposition loads were 0, 7.8, 26 and 52 mg N x month (-1) x column (-1) , respectively. The results indicated that the leaching losses of total exchangeable cations, Ca2+ , and Mg2+ increased with increasing N deposition loads, but K+ and Na+ were little affected. The proportion of net cations leaching loss (difference of cations in eluate and leachate) to total exchangeable cations was 13.9% , 18.6% , 31.8% and 57.9% under 0, 7.8, 26 and 52 mg N x month (-1) column (-1) deposition loads, respectively, and that for exchangeable Ca2+ and Mg2+ was 19. 6%, 25.8% , 45. 3% and 84.8% , and 4.4% , 6.1% , 10. 9% and 17.1% , respectively. The leaching losses of inorganic N, NO3- and H+ also increased with increasing N deposition loads. Topsoil pH decreased with increasing N deposition loads, being 3.85, 3.84, 3.80 and 3.75 under 0, 7.8, 26 and 52 mg N x month (-1) x column(-1) N deposition loads, respectively. N deposition could increase the apparent mineralization rate of soil organic nitrogen, and accelerate the nutrient losses and acidification of coniferous forest red soil.

[Influence of long-term fertilization on phosphorus fertility of calcareous soil II. Inorganic and organic phosphorus].

By the Jiang-Gu inorganic phosphorus fractionation method and the Bowman-Cole organic phosphorus fractionation method, this paper studied the forms and compositions of inorganic and organic phosphorus in 0-100 cm layer of calcareous soil after 23 years located experiment. The result showed that the content of inorganic phosphorus was in the order of treatment animal manure > fallow > chemical fertilizer > low rate straw > high rate straw > medium rate straw > no fertilizer. The IPi value of inorganic phosphorus forms in different fertilizer treatments had the following characteristics: a) it was relatively low for Ca2-P, Ca8-P and Al-P, but relatively high for Ca10-P, Fe-P and O-P; b) comparing with no fertilizer treatment, treatments animal manure and fallow had a notably high IPi value of Ca2-P, Ca8-P and Al-P and a low IPi value of Ca10-P, Fe-P and O-P; while treatment chemical fertilizer had a high IPi value of Ca2-P, Ca8-P, Al-P and O-P, but a low IPi value of Ca10-P and Fe-P; c) as for available phosphorus source (Ca2-P, Ca8-P and Al-P), their content was higher in treatment animal manure than in treatment chemical fertilizer, and higher in treatment chemical fertilizer than in treatments straws. A combined application of straw and chemical fertilizer could increase soil organic phosphorus content notably. Applying animal manure could increase the content of all organic phosphorus forms, while applying chemical fertilizer could promote the transformation of soil resistant organic phosphorus to labile and medium labile organic phosphorus. No fertilizer treatment had a relatively lower content of labile and medium labile organic phosphorus, but a relatively high content of resistant organic phosphorus. For treatment fallow, it had a relatively low content of soil organic matter and organic phosphorus, but a relatively high content of labile and medium resistant organic phosphorus.

[Influence of long-term fertilization on phosphorus fertility of calcareous soil I. Organic matter, total phosphorus and available phosphorus].

A 23 years-located experiment of wheat-corn rotation showed that long term application of animal manure combined with chemical fertilizer contributed greater to the contents of soil organic matter, total phosphorus, inorganic phosphorus and available phosphorus. Applying chemical fertilizer could increase soil organic matter, total phosphorus, inorganic phosphorus and available phosphorus contents, but the increment was lower than treatments animal manure and fallow. Compared with no fertilization, different fertilization treatment had its own distribution characteristics of soil organic matter, total phosphorus and available phosphorus in 0-100 cm soil layer.