This study evaluated the sorption of atrazine [6‐chloro‐N‐ethyl‐N′‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine] to biochars and thereby explored their potential use as an efficient and low‐cost soil amendment for mitigating and removing agricultural contaminants. Biochars derived from corncobs (Zea mays L.) produced at incremental pyrolysis temperatures (350–650°C in 100°C intervals) were characterized using elemental analysis, specific surface area, scanning electron microscopy, x‐ray diffractometry, and Fourier‐transform infrared spectra to estimate the relationship between the physical and chemical properties of biochars and the treatment temperature. Generally, carbonization, aromatization, and specific surface area increased with the elevation of temperatures, whereas the occurrence of polar functional groups and crystallinity decreased. The sorption isotherms fit the Freundlich equation well. A negative correlation between the logarithm of the concentration‐dependent distribution coefficient Koc and H/C and (O + N)/C ratios suggested that the presence of aromatic C and hydrophobic structures are advantageous for biochars to sorb atrazine in aqueous solutions. Biochar prepared at 650°C has a relatively developed void space structure and therefore a much larger surface area than when prepared at lower pyrolysis temperatures, indicating that pore filling has occurred. These results may provide a reference for biochar design and application in agricultural pollution control.

Intensive agricultural development can change land use, which can further affect regional ecosystem services and functions. With the rapid growth of the population and the national demand for food, the northeast of China, which is located in the high latitudes, has experienced four agricultural developments since the 1950s. The original wetlands of this area were developed for farmland. The evaluation of ecosystem services is conducted to reveal the ecosystem status and variable trends caused by land reclamation. The aim of this study is to provide scientific basis for environmental management and for the sustainable development of agriculture in Northeast China. With GIS-RS technology, a typical farm was chosen to analyze variations in the ecosystem service value in response to land use changes during the study period. The total ecosystem service value of the farm decreased from 7523.10 million Yuan in 1979 to 4023.59 million Yuan in 2009 with an annual rate of -1.6 % due to the decreasing areas of woodland and wetland. The increased areas of cropland, water area and grassland partly offset the loss of the total value, but the loss was still greater than the compensation. Waste treatment and climate regulation were the top two service functions with high service values, contributing to approximately 50 % of the total service value. The spatial difference of the ecosystem service value also was analyzed. The wetlands located in the central and northeastern sections of the farm changed significantly. From the aspect of ecosystem service value, the wetland and water area should be conserved, as they have the highest value coefficients. The accuracy of the value coefficient, however, needs to be studied further in future research.

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Four types of biochars were prepared by using sawdust, corn straw, peanut hull and fallen leaves as materials, respectively. The characteristics of four types of biochars were analyzed by SEM, FTIR and BET, the SBET of SDC, PHC, CSC and FLC were 1168.45, 846.95, 825.51 and 401.26m2·g−1. The adsorption conformed to the pseudo-second-order model and the Langmuir isotherm.

The impact of tillage systems is obvious in the nitrogen mineralization. Few studies have focused on the relationship between labile fraction of soil organic nitrogen (SON) and crop nitrogen absorption under different tillage systems in freeze-thaw agricultural area. In this study, the effects of conventional tillage (CT) and no-tillage (NT) on the labile fractions of soil organic nitrogen and the relationships with the potentially mineralizable nitrogen (N0) at different soil depths in seeding, jointing, filling and maturity seasons over four years (2010, 2011, 2015 and 2016) were explored. It has been demonstrated that the labile fractions of SON and N0 in NT were higher than in CT at 0-5, 0-10 and 0-20cm. N0 was positively and highly related to the medium particulate organic carbon (mPOM-C) (P<0.01) under CT and NT, whereas highly significant and negative correlations (P<0.01) between N0 and medium particulate organic nitrogen (mPOM-N) were detected under both tillage systems at 0-5 and 0-10cm. The difference in these correlations between tillage systems had been found to be the most notable at the 0-5cm depth. The higher SON fractions content would contribute to the nitrogen mineralization potential because of freeze-thaw conditions during the crop growing season.