Adsorption kinetics and mechanism of atrazine on iron-modified algal residue biochar in the presence of soil.

Atrazine has been widely used as an herbicide, and its harm has attracted more and more attention. In this study, magnetic algal residue biochar (MARB) was prepared from algae residue, a by-product of aquaculture, by ball milling it with ferric oxide to study the adsorption and removal of the triazine herbicide atrazine in a soil medium. The adsorption kinetics and isotherm results showed that atrazine removal by MARB reached 95.5% within 8 h at a concentration of 10 mg·L-1, but the removal rate dropped to 78.4% in the soil medium. The pseudo-first- and pseudo-second-order kinetics and Langmuir isotherms best described atrazine adsorption on MARB. It is estimated that the maximum adsorption capacity of MARB can reach 10.63 mg·g-1. The effects of pH, humic acids, and cations on the adsorption performance of MARB for atrazine were also studied. When pH was 3, the adsorption capacity of MARB was twice that of other pHs. Only in the presence of 50 mg·L-1 HA and 0.1 mol·L-1 NH4+, Na, and K, the adsorption capacity of MARB to AT decreased by 8% and 13%, respectively. The results showed that MARB had a stable removal profile over a wide range of conditions. The adsorption mechanisms involved multiple interaction forms, among which the introduction of iron oxide promoted hydrogen bonding formation and π-π interactions by enriching -OH and -COO on the surface of MARB. Overall, the magnetic biochar prepared in this study can be used as an effective adsorbent to remove atrazine in complex environments and is ideal for algal biomass waste treatment and environmental governance.+.

Metal-responsive elements confer cadmium response in Arabidopsis.

MAIN CONCLUSION: Molecular, biochemical, and genetic experiments demonstrate that metal-responsive elements (MREs), initially identified in animals, confer the cadmium transcriptional response in Arabidopsis, thus providing deep functional insights of MREs in plants. Cadmium (Cd) is highly toxic to all organisms including plants. Cd-responsive gene transcription is a fundamental aspect of the Cd response, in which Cd stress regulatory cis-acting elements are essential. However, little is known regarding such elements in plants. Metal-responsive elements (MREs, 5'-TGCRCNC-3', R: A or G, N: any base) are essential for transcriptional induction of Cd in animals. MREs are also contained in the promoters of some Cd-regulated plant genes, but whether MREs confer Cd responses in plants is poorly defined. Herein, we used a previously identified MRE of the tobacco feedback-insensitive anthranilate synthase α-2 chain gene as a representative MRE (named as MREa, 5'-TGCACAC-3') to explore the roles of MREs in the transcriptional response to Cd stress in Arabidopsis thaliana. First, we showed that MREa conferred Cd stress responsiveness on a minimal promoter in both concentration- and time-dependent manners, whereas the mutated MREa did not. Second, MREa specifically bound nuclear extracts, displaying a biochemical characteristic of cis-acting elements. We screened and identified four MREa-binding transcription factors, including ethylene response factor 13 (AtERF13). At last, MREa could mediate AtERF13 to activate the ß-glucuronidase (GUS) reporter expression. Overall, these molecular, biochemical, and genetic data suggest that MREa is instrumental in the Cd response in Arabidopsis, thus providing deep functional insights of MREs in plants.

Distribution Characteristics and Influencing Factors of Organochlorine Pesticides in Agricultural Soil from Xiamen City.

The concentration and distribution of 15 organochlorine pesticides in the soil of Xiamen City were determined. Overall, among the 15 selected target pesticides, 14 organochlorine pesticides (OCPs) were detected (hexachlorobenzene was not). The range of detected pesticides was undetected-10.04 ng/g, the total detection rate was 35.2%, and the three pollutants with the highest detection rate in all samples were Heptachlor (66.7%), δ-Hexachlorocyclohexane (60.0%), and p, p'-Dichlorodiphenyldichloroethane (58.3%). The degree of pollution in descending order was Tong'an > Xiang'an > Jimei > Haicang. Linear regression analysis of soil properties and OCP concentration distribution revealed that OCPs were positively correlated with water content, dissolved organic carbon, and pH and negatively correlated with cation exchange capacity. The origin of OCPs was evaluated using the relationship between the parent compound and its metabolites, with possible new hexachlorocyclohexane and isomer (HCHs) input. By comparing the risk screening values of ΣHCHs and ΣDDTs in "Soil Environmental Quality Standards", the concentrations in all soil samples were lower than the standard values, which indicated that the OCP residues in Xiamen were very low.

[Evaluating the utility of MODIS vegetation index for monitoring agricultural drought].

The exclusive shortwave bands provided by MODIS sensors offer new opportunities for agricultural drought monitoring, since they are very sensitive to vegetation moisture. In the present work, we selected Songnen Plain in Northeast China as study area aiming at monitoring agricultural drought of dry farmland here. Four types of vegetation water indices and vegetation greenness indices were calculated from the 8-day composite MODIS product (MODO9A1) in vegetation growing season between 2001 and 2010, respectively. Multi-scale standardized precipitation index (SPI) derived from precipitation data of weather stations was used as reference data to estimate drought sensitivity of various vegetation indices, and a pixel-to-weather station paired correlation approach was used to calculate the Pearson correlation coefficient between vegetation index and SPIs. The result indicated that vegetation water indices established by near infrared and shortwave infrared bands outperformed vegetation greenness indices based on visible and near infrared bands. Of these indices, NDII7 performs the best with highest correlation coefficients across all SPIs. The authors' results demonstrated the potential of MODIS shortwave spectral bands in monitoring agricultural drought, and this provides new insights to future research.