Journal of Environmental Science and Health, Part B (2015) 50, 463–472 Copyright © Taylor & Francis Group, LLC ISSN: 0360-1234 (Print); 1532-4109 (Online) DOI: 10.1080/03601234.2015.1018757

Effect of wheat and rice straw biochars on pyrazosulfuronethyl sorption and persistence in a sandy loam soil SUMAN MANNA and NEERA SINGH Division of Agricultural Chemicals, Indian Agricultural Research Institute, New Delhi, India

The objective of this research was to investigate the effect of wheat and rice biochars on pyrazosulfuron-ethyl sorption in a sandy loam soil. Pyrazosulfuron-ethyl was poorly sorbed in the soil (3.5–8.6%) but biochar amendment increased the herbicide adsorption, and the effect varied with the nature of the feedstock and pyrolysis temperature. Biochars prepared at 600 C were more effective in adsorbing pyrazosulfuron-ethyl than biochars prepared at 400 C. Rice biochars were better than wheat biochars, and higher herbicide adsorption was attributed to the biochar surface area/porosity. The Freundlich constant 1/n suggested nonlinear isotherms, and nonlinearlity increased with increase in the level of biochar amendment. Desorption results suggested sorption of pyrazosulfuron-ethyl was partially irreversible, and the irreversibility increased with increase in the level of biochar. Both sorption and desorption of pyrazosulfuron-ethyl correlated well with the content of biochars. The free energy change (DG) indicated that the pyrazosulfuron-ethyl sorption process was exothermic, spontaneous and physical in nature. Persistence studies indicated that biochar (0.5%) amendment did not have significant effect on herbicide degradation, and its half-life values in the control, 0.5% WBC600- and RBC600-amended rice planted soils were 7, 8.6, and 10.4 days, respectively. Keywords: Pyrazosulfuron-ethyl, wheat and rice straw biochars, adsorption, desorption, persistence.

Introduction A threshold level of organic matter in the soil is crucial for maintaining physical, chemical and biological integrity of the soil and to perform its agricultural production and environmental functions.[1,2] Direct incorporation of crop residues or composted crop residues is generally practiced to maintain the soil organic carbon pool and conserving soil nutrients. Although this management practice helps to improve soil fertility, the process creates significant increase in greenhouse emissions due to labile nature of carbon. Hence, conversion of biowaste to biochars using the pyrolysis process is one viable option that can enhance natural rates of carbon sequestration in the soil, reduce farm wastes and improve the soil quality.[3–5] Converting waste biomass into biochar would transfer very significant amounts of carbon from active to inactive carbon pool, since the biomass is protected from further oxidation from the material that would otherwise have degraded to release CO2 into the atmosphere. Biochars act as an important Address correspondence to Neera Singh, Division of Agricultural Chemicals, Indian Agricultural Research Institute, New Delhi 110012, India; E-mail: [email protected] Received October 7, 2014. Color versions of one or more figures in this article can be found online at www.tandfonline.com/lesa.

long-term carbon sink because their microbial decomposition and chemical transformations are slow. They have additional soil conditioning benefits such as reducing soil bulk density, enhancing water holding capacity, and managing soil acidity.[6] Depending upon the feedstock used, these can manage soil nutrients due to high cation exchange capacity, and high surface area and acidic surface group.[7–9] Few reports suggest increased crop yields in biochar-amended soils.[10,11] Rice–wheat cropping system is an important cropping system in India as these two cereal crops accounts for nearly 70% of the total cereal production. According to an estimate, about 500 million tonnes of field crop residues were produced in India in 1997, and rice and wheat residues constituted approximately 43% and 23%, respectively.[12] Out of nearly 120–150 million tonnes of surplus crop residues available in India, about 93 million tonnes are openly burned for land clearing. Thus, converting crop residues obtained during rice–wheat cultivation into biochars and incorporating them back in the same field will address the issue of land clearing, waste utilization, and nutrient conservation. Any amendment to soil changes its physicochemical properties, thus affecting the fate of herbicides applied to soil for weed management. Biochars, which have high organic carbon content, specific surface area and microporosity, have shown high herbicide retention capacity.[13,14]

464 Therefore, due to enhanced herbicide adsorption in biochar-amended soils, offsite migration and downward mobility of contaminants is restricted.[15–17] However, Cabrera et al.[18] reported that in spite of increase in fluometuron and 4-chloro-2-methylphenoxyacetic acid (MCPA) sorption in soil following amendment of six biochars, herbicide leaching increased. Enhanced leaching of herbicides was attributed to dissolved organic carbon content of these biochars, which compete/associate with herbicide molecules. Greater retention of herbicides on soil particles might reduce their bioefficacy for weed control. Further, higher retention of soil particles will affect the availability to these xenobiotics to soil microbes for degradation and there are chances that soil-applied pesticide may persist for longer period in biochar-amended soils.[19–21] Pyrazosulfuron-ethyl (ethyl-5-(4,6-dimethoxypyrimidin2-ylcarbamoylsulfamoyl)-1-methylpyrazole-4-carboxylate) (Fig. 1), a sulfonylurea herbicide, is recommended for selective pre- and early post-emergence control of grassy and broad-leaved weeds in direct seeded and transplanted paddy cultivation. Herbicide has very high efficacy at low application dose (10–25 g ha¡1) and has high mammalian toxicity (>5,000 mg kg¡1). It is weakly acidic in nature (dissociation constant, pKa 3.7), low aqueous solubility (14.5 mg L¡1) and high octanol–water partition coefficient (Log P – 3.16). Chu et al.[22] studied the fate of pyrazosulfuron-ethyl in flooded soil, water and rice in a semi-open model ecosystem under local conditions. The results showed that the half-life values of pyrazosulfuron-ethyl in soil and field water were 16–27 and 9–16 days, respectively. Generally, sulfonylurea herbicides have high aqueous solubility, low octanol water partition coefficient and are poorly sorbed, especially in alkaline soils.[22–24] Therefore, these are more prone to leaching and runoff losses and have been detected in surface water and groundwater. However, pyrazosulfuron-ethyl, which has low aqueous solubility and high KOW constant, should be moderately sorbed in soil than its other counterparts having high solubility. Absolutely no information is available about pyrazosulfuron-ethyl sorption behavior in soils. The greatest concern of using biochars in agriculture is decrease in herbicide bioefficacy due to greater sorption and desorption hysteresis. Pyrazosulfuron-ethyl was selected as the test

Fig. 1. Structure of pyrazosulfuron-ethyl.

Manna and Singh herbicide because among the sulfonylurea herbicides recommended for rice crop, it is the most hydrophobic herbicide and theoretically should be sorbed to maximum level among its counterparts. Sorption is directly linked with herbicide bioavailability, and the main concern regarding use of biochars in agricultural soils is their effect on weed controlling efficiency. Therefore, the present study reports the effect of wheat and rice biochars on pyrazosulfuronethyl adsorption–desorption behavior and persistence in rice-planted soil. Doses of biochars used ranged between 0.1% and 0.5%, and were calculated based on the wheat/ rice straw biomass obtained per hectare and straw-biochar conversion ratio.

Materials and methods Chemicals A reference standard of pyrazosulfuron-ethyl (purity 98%) was supplied by the United Phosphorus Ltd (UPL), Mumbai, India. Chemicals and solvents used in the study were of analytical grade and were purchased locally. Soil A sandy loam soil used in the study was collected from the experimental farm of the Indian Agricultural Research Institute, New Delhi, India. Soil was collected from the surface of 0–15-cm depth, dried in shade, ground to pass through 2-mm sieve and stored in polythene bags at room temperature. The physicochemical characteristics of the soil (Table 1) were determined using standard analytical procedures, including pH at 1:2 soil to water ratio; organic carbon (OC) content by the Walkley and Black method;[25] soil mechanical fractions employing the Bouyoucos hydrometer method; electrical conductivity and cation exchange capacity by the normal ammonium acetate (pH D 7.0) method.[25] Biochars Biochars (BC) prepared from rice straw (Oryza sativa) and wheat straw (Triticum aestivum) at 400 C and 600 C were used in the study. The straw was dried at 60 C for 24 h to 0.1 mg mL¡1. Otherwise, sample (10 mL) was made acidic (pH 2) using 6N HCl and was extracted using

466 dichloromethane (4 mL) for 1 min. After shaking, the samples were allowed to stand for 1 min and 1 g of anhydrous sodium sulfate was added to each tube to remove any trace of moisture from dichloromethane. The dichloromethane fraction (2 mL) was evaporated and the residue was dissolved in 1-mL acetonitrile, and residues were analyzed by HPLC. Soil samples (50 g) were transferred to 150-mL stoppered conical flasks, CH3OH:H2O, 1:1 (50 mL) was added and the contents were shaken in a horizontal shaker for 30 min. The mixture was centrifuged at 4,000 rpm for 5 min, and the supernatant was filtered using Whatman No. 1 filter paper. The soil was again extracted twice with CH3OH:H2O, 1:1 (30 mLC20 mL), centrifuged and finally filtered. The extracts were pooled and diluted with water (25 mL), and pH was adjusted to be acidic (pH 2) with 6N HCl. The aqueous phase was partitioned twice with dichloromethane (25 mLC25 mL). The dichloromethane layer was passed through anhydrous sodium sulfate. The solvent was evaporated to dryness at room temperature, and the residue was dissolved in 1-mL acetonitrile for further analysis by HPLC. A reverse phase HPLC was used to quantify pyrazosulfuron-ethyl residues. A Varian Prostar instrument equipped with degasser, quaternary pump, UV detector connected to a Rheodyne injection system (20 mL loop) was used for analysis. The stationary phase comprised of Lichrospher on C-18packed stainless steel column (250£4-mm i.d.). HPLC analysis was performed at wavelength of 234 nm using mobile phase of acetonitrile:0.1% aqueous o-phosphoric acid (75:25) at a flow rate of 0.5 mL min¡1. Under these conditions the retention time of pyrazosulfuron-ethyl was 7.5 min. The recovery of pyrazosulfuron-ethyl from water and soil samples was studied at the fortification levels of 0.01, 0.5 and 1 mg mL¡1 by fortifying the 10-mL water or 10 g soil with required amount of herbicide in 0.1-mL of methanol. The pyrazosulfuron-ethyl recovery ranged from 92.8 § 1.1%–93.4 § 1.0% from water and 75.7§2.1%–90.8§1.5% from soil.

Results and discussion The kinetics of pyrazosulfuron-methyl sorption was studied in the control and 0.5% WBC600 and RBC600 biochar-amended soils. The results (not shown here) suggested that sorption of pyrazosulfuron-methyl in soil was a quick process and the equilibrium was attained after 2 h of shaking. However, pyrazosulfuron-ethyl sorption in 0.5% BC-amended soils continued till 6 h; however, more than 95% sorption was attained after 2 h and no significant change in herbicide adsorption was observed after 6 h. However, for sorption–desorption studies of pyrazosulfuron-ethyl in soil/soilCBC mixtures, an equilibration period of 24 h was chosen. Pyrazosulfuron-ethyl was poorly sorbed in the sandy loam soil as only 5.3 to 8.6% sorption was observed in the

Manna and Singh Table 2. Freundlich parameters for pyrazosulfuron-ethyl adsorption in soil. Treatment Soil WBC400-0.1% WBC400-0.2% WBC400-0.5% WBC600-0.1% WBC600-0.2% WBC600-0.5% RBC400-0.1% RBC400-0.2% RBC400-0.5% RBC600-0.1% RBC600-0.2% RBC600-0.5%

Kf

1/n

R

Sorption (%)

KOC

KBC

0.22 0.24 0.51 0.85 0.27 3.02 7.02 0.33 0.92 1.25 2.54 6.79 11.12

1.37 1.20 0.95 0.88 1.27 0.88 0.83 1.36 0.86 0.79 0.97 0.93 0.80

0.996 0.995 0.974 0.997 0.990 0.995 0.991 0.995 0.997 0.998 0.996 0.995 0.998

5.3–8.6 5.5–10.0 17.1–28.0 21.6–35.5 6.9–11.2 51.9–59.8 80.9–86.0 7.5–14.0 32.5–37.5 41.7–50.4 55.9–59.9 78.6–81.1 90.5–91.8

47.8 48.2 95.1 130.8 53.9 557.2 1055.6 132.5 171.0 190.8 506.0 1248.2 1659.7

— 240 255 170 270 1510 1404 330 460 250 2540 3395 2224

control soil (Table 2). Amendment of wheat (WBC) and rice (RBC) biochars increased herbicide sorption, and in 0.1–0.5% BC-amended soils, adsorption increased to 5.5– 35.5% in WBC400-, 6.9–86% in WBC600-, 7.5–50.4% in RBC400- and 55.9–91.8% in RBC600-amended soils. Thus, biochars prepared at higher temperature were more effective in enhancing the pyrazosulfuron-ethyl adsorption. Earlier workers have shown that biochars prepared at higher pyrolysis temperature offer higher pesticide adsorption due to high specific surface area and higher microporosity.[26,27] Although surface area of RBC400 and RBC600 was nearly the same (Table 1), porosity of RBC600 was higher (0.034 cc g¡1) than the porosity of RBC400 (0.024 cc g¡1). Thus, the order of pyrazosulfuron-ethyl sorption in wheat and rice biochar-amended soils correlated well with biochar porosity. Rice strawbased biochars (RBC400 and RBC600) were more effective in enhancing pyrazosulfuron-ethyl sorption than wheat straw biochars (WBC400 and WBC600). Earlier reports suggest that nature of feed stock affects the physiochemical properties of biochars.[28] Cagnon et al.[29] showed that lignin was the major contributor of biochars; however, each component within the raw precursor (the hemicellulose, the cellulose and the lignin) contributed to the porosity of chars. Variation in char properties was due to the fact that during carbonization the lignocellulosic precursors, hemicellulose, cellulose and lignin decomposed at different rates and within distinct temperature ranges. The data of pyrazosulfuron-ethyl sorption (Table 2, Fig. 2) in soil and biochar-amended soils were subjected to the Freundlich adsorption isotherm: log Cs D log KfC1/n log Ce, where Cs is the amount of herbicide adsorbed at equilibrium (mg g¡1), Ce is the equilibrium concentration of herbicide (mg mL¡1) and Kf and 1/n are the constants. The Freundlich constant K-f (intercept) represents the amount of contaminant adsorbed at an equilibrium concentration of 1 mg mL¡1. The constant 1/n (slope) is the measure of the intensity of sorption and reflects the degree

Wheat and rice biochars’ effect on pyrazosulfuron-ethyl sorption in sandy loam to which sorption is the function of contaminant concentration. The values of correlation coefficient for all the cases were very high (R > 0.97), indicating that the Freundlich adsorption equation satisfactorily explained the results of pyrazosulfuron-ethyl sorption in biocharamended soils and the results were significant at 99% levels. The slope (1/n) values for pyrazosulfuron-ethyl adsorption in soil alone were >1, suggesting nonlinear adsorption isotherms. The slope value of >1 indicated S-type isotherm, which is characterized by a strong competition between the water molecule and the pesticide for adsorption sites at low pesticide concentration and/or molecular interaction between the sorbed species.[30] These types of isotherms are commonly found in the literature and involve the interaction of organic compounds having polar groups with soil/its components. However, biochar amendment to soil resulted in decrease in the slope and they become RBC400 > WBC400. Further, effect of biochar amendment on pyrazosulfuron-ethyl persistence was evaluated in a pot culture experiment. Table 6 represents the pyrazosulfuron-ethyl residues recovered from the water and soil samples of control (no biochars), and 0.5% WBC600- and RBC600amended rice-planted pots. Results indicated that in biochar-amended soils, higher amount of pyrazosulfuronethyl was recovered from the soil than the soil of control pots where no biochars was added. On day 2, pyrazosulfuron-ethyl recovered from soil samples of 0.5% biocharamended pots was nearly 5–6 times higher than that recovered from the soil of control pot. However, this difference was reduced following incubation and on 25th day it was less than three times, suggesting that as pyrazosulfuronethyl in water component dissipated, pyrazosulfuron-ethyl from soil component was desorbed and was available for dissipation. On the other hand, the amount of pyrazosulfuron-ethyl recovered from water samples of different treatments was nearly the same. Dissipation data of pyrazosulfuron-ethyl persistence in the soils followed the firstorder kinetics (Fig. 5), and dissipation constants k (mg g¡1 day¡1) in control, WBC600, and RBC600 treatments were 0.043, 0.035, and 0.029. Half-life (t1/2) of pyrazosulfuronethyl in the control field soil was 7 days. Biochar amendment slightly increased pyrazosulfuron-ethyl half-life in soils, and t1/2 values in WBC600- and RBC600-amended pots were 8.5 and 10.4 days, respectively. These results suggested that although 0.5% biochar amendment to soil resulted in 32 (WBC600) to 50 (RBC600) times increase in the pyrazosulfuron-ethyl sorption, t1/2 values showed only 1.2 to 1.4 times increase over control. Thus, wheat/rice

Fig. 5. Dissipation of pyrazosulfuron-ethyl in soil/water system in control, 0.5% WBC600- and RBC600-amended rice pots.

biochar amendment at ergonomically feasible rate may not have any significant effect on pyrazosulfuron-ethyl bioavailability. Earlier, most of the studies on the effect of biochars on bioavailabilty of pesticides were performed at higher levels (1%) of amendment where biochar amendment significantly reduced pesticide bioavailability. However, few reports suggested that application of lowtemperature biochars up to 0.5% levels did not have any significant effect on pesticide bioavailability. Yang et al.[33] showed that BC450 up to 0.5% levels did not have any significant effect on the half-life of chlorpyriphos and fipronil. Nag et al.[34] showed that percentage dissipation of trifluralin was nearly the same in control and 0.5% biochar-amended soils. The study suggested that pyrazosulfuron is a weakly sorbed herbicide in the sandy loam soil. Wheat and rice straw biochars affected herbicide sorption in soil, but the effect varied with the pyrolysis temperature and the type of feedstock, as they governed the physicochemical properties of the biochars. Rice biochars were more effective in retaining herbicide than the wheat biochars. Biochars prepared at 400 C marginally increased herbicide sorption but significant effects were observed in WBC600- and RBC600-amended soils. Sorption hysteresis was more in soil amended with biochars prepared at higher temperature. However, no significant difference was observed in the percentage dissipation of pyrazosulfuron-ethyl in the control and in 0.5% WBC600- and RBC600-amended soil.

References [1] Izaurralde, R.C.; McGill, W.B.; Robertson, J.A.; Juma, N.G.; Thurston, J.J. Carbon balance of the Breton classical plots over half a century. Soil Sci. Soc. Am. J. 2001, 65, 431–441. [2] Srinivasarao, Ch.; Venkateswarlu, B.; Lal, R.; Singh, A.K.; Kundu S. Sustainable management of soils of dryland ecosystems for enhancing agronomic productivity and sequestering carbon. Adv. Agro. 2013, 121, 253–329. [3] Verheijen, F.G.A.; Jeffery, S.; Bastos, A.C.; van der Velde, M.; Diafas, I. Biochar Application to Soils: A Critical Scientific Review of Effects on Soil Properties, Processes and Functions, EUR 24099

472

[4]

[5]

[6]

[7]

[8]

[9]

[10]

[11]

[12]

[13]

[14]

[15]

[16]

[17]

[18]

Manna and Singh EN; Office for the Official Publications of the European Communities: Luxembourg, 2009, 149 p. Lehmann, J.; Joseph, S. Biochar for environmental management: an introduction. In Biochar for Environmental Management: Science and Technology; Lehmann, J., Joseph, S., Eds.; Earthscan: London, 2009, 1–12. Kookana R.S.; Sarmah, A.K.; Van Zwieten, L,; Krull, E.; Singh, B. Biochar application to soil: agronomic and environmental benefits and unintended consequences. Adv. Agro. 2011, 112, 103–143. Yuan, J.H.; Xu, R.K. The amelioration effects of low-temperature biochars generated from nine crop residues on an acidic Ultisol. Soil Use Manag. 2011, 27, 110–115. Lehmann, J.; da Silva Jr., J.P.; Steiner, C.; Nehls, T.; Zech, W.; Glaser, B. Nutrient availability and leaching in an archaeological anthrosol and a ferralsol of the central Amazon basin: fertilizer, manure and charcoal amendments. Plant Soil 2003, 249, 343–357. Spokas, K.A.; Novak, J.M.; Venterea, R.T. Biochar’s role as an alternative N-fertilizer ammonia capture. Plant Soil 2012, 350, 35– 42 Mukherjee, A.; Zimmerman, A.R. Organic carbon and nutrient release from a range of laboratory-produced biochars and biochar– soil mixtures. Geoderma 2013, 193–194, 122–130. Graber, E.R.; Harel, Y.M.; Kolton, M.; Cytryn, E.; Silber, A.; David, D.R.; Tsechansky, L.; Borenshtein, M.; Elad, Y. Biochar impact on development and productivity of pepper and tomato grown in fertigated soilless media. Plant Soil 2010, 337, 481–496. Jones, D.L.; Rousk, J.; Edwards-Jones, G.; DeLuca, T.H.; Murphy, D.V. Biochar-mediated changes in soil quality and plant growth in a three-year field trial. Soil Biol. Biochem. 2012, 45, 113–124. NAAS. 2012. Management of Crop Residues in the Context of Conservation Agriculture. Policy Paper No. 58, National Academy of Agricultural Sciences, New Delhi. 12 p. http://naasindia.org/ Policy%20Papers/policy%2058.pdf Zhanga, P.; Suna, H.; Yua, L.; Sunb, T. Adsorption and catalytic hydrolysis of carbaryl and atrazine on pig manure-derived biochars: impact of structural properties of biochars. J. Hazard. Mat. 2013, 244–245, 217–224. Cabrera, A.; Cox, L.; Spokas, K.A.; Hermosín, M.C.; Cornejo, J.; Koskinen, W.C. Influence of biochar amendments on the sorption–desorption of aminocyclopyrachlor, bentazone and pyraclostrobin pesticides to an agricultural soil. Sci. Total Environ. 2014, 470–471, 438–443. Li, J.; Li, Y.; Wu M.; Zhang Z.; L€ u J. Effectiveness of low-temperature biochar in controlling the release and leaching of herbicides in soil. Plant Soil 2013, 370, 333–344. L€ u, J.; Li, J.; Li, Y.; Chen, B.; Bao, Z. Use of rice straw biochars simultaneously as the sustained release carrier of herbicides and soil amendment for their reduced leaching. J. Agric. Food Chem. 2012, 60, 6463–6470. Giori, F.G.; Tornisielo, V.L.; Regitano, J.B. The role of sugarcane residues in the sorption and leaching of herbicides in two tropical soils. Water Air Soil Pollut. 2014, 225, 1935–1938. Cabrera, A.; Cox, L.; Spokas, K.A.; Celis, R.; Hermosín, M.C.; Cornejo, J.; Koskinen, W.C. Comparative sorption and leaching study of the herbicides fluometuron and 4-chloro-2-

[19]

[20]

[21]

[22]

[23]

[24] [25]

[26] [27]

[28]

[29]

[30]

[31]

[32]

[33]

[34]

methylphenoxyacetic acid (MCPA) in a soil amended with biochars and other sorbents. J. Agric. Food Chem. 2011, 59, 12550– 12560. Nag, S.K.; Kookana, R.; Smith, L.; Krull, E.; Macdonald, L.M.; Gill, G. Poor efficacy of herbicides in biochar-amended soils as affected by their chemistry and mode of action. Chemosphere 2011, 84, 1572–1577. Kookana, R.S. The role of biochar in modifying the environmental fate, bioavailability, and efficacy of pesticides in soils: a review. Aust. J. Soil Res. 2010, 48, 627–637. Yang, Y.; Sheng, G.Y.; Huang, M.S. Bioavailability of diuron in soil containing wheat-straw-derived char. Sci. Total Environ. 2006, 354, 170–178. Chu, C.; Lin, H.T.; Wong, S.S.; Li, G.C. Distribution and degradation of pyrazosulfuron ethyl in paddy field. Plant Prot. Bull. 2002, 44, 147–156. Sarmah, A.K.; Kookana, R.S.; Alston, A.M. Leaching and degradation of triasulfuron, metsulfuron-methyl, and chlorsulfuron in alkaline soil profiles under field conditions. Aust. J. Soil Res. 2000, 38, 617–631. Sondhia, S. Leaching behaviour of metsulfuron in two texturally different soils. Environ. Monit. Assess. 2009, 154, 111–115. Singh N., Raunaq, Singh S.B. Effect of fly ash on metsulfuronmethyl sorption and leaching in soils. J. Environ. Sci. Health 2014, B49, 366–373. Jackson, M.L. Soil Chemical Analysis. Prentice Hall: New Delhi, India, 1967. Sun, K.; Keiluweit, M.; Kleber, M.; Pan, Z.; Xing, B. Sorption of fluorinated herbicides to plant biomass-derived biochars as a function of molecular structure. Biores. Technol. 2011, 102, 9897–9903. Yu, X.Y.; Ying, G,G.; Kookana, R.S. Sorption and desorption behavior of diuron in soil amended with Biochar. J. Agric. Food Chem. 2006, 54, 8545–8550. Cagnon, B.; Py, X.; Guillot, A.; Stoeckli, F.; Chambat, G. Contributions of hemicellulose, cellulose and lignin to the mass and the porous properties of chars and steam activated carbons from various lignocellulosic precursors. Biores. Technol. 2009, 100, 292–298. Giles, C.H.; McEvans, T.H.; Nakhwa, S.N.; Smith, D. Studies in adsorption. Part XI: a system of classification of adsorption isotherms and its use in diagnosis of desorption mechanism and measurement of specific surface areas of solids. J. Chem. Soc. 1960, 3, 3973–3993. Lattao, C; Cao, X.; Mao, J.; Dchmidt-Rohr, K.; Pignetello, J.J. Influence of molecular structure and adsorbent properties on sorption of organic compounds to a temperature series of wood chars. Environ. Sci. Technol. 2014, 48, 4790–4798. Wu, W.; Yang, M.; Feng, O.; McGrouther, K.; Wang, H.; Lu, H.; Chen, Y. Chemical characterization of rice straw-derived biochar for soil amendment. Biomass Bioenergy 2012, 47, 268–276. Yang, X.B.; Ying, G.G.; Peng, P.A.; Wang, L.; Zhao, J.L.; Zhang, L.J.; Yuan, P.; He, H.P. Influence of biochars on plant uptake and dissipation of two pesticides in an agricultural soil. J. Agric. Food Chem. 2010, 58, 7915–7921. Nag, S.K.; Kookana, R.; Smith, L.; Krull, E.; Macdonald, L.M.; Gill, G. Poor efficacy of herbicides in biochar-amended soils as affected by their chemistry and mode of action. Chemosphere 2011, 84, 1572–1577.

Copyright of Journal of Environmental Science & Health, Part B -- Pesticides, Food Contaminants, & Agricultural Wastes is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use.