Sorption-Desorption, Degradation and Leaching of Napropamide in Selected Malaysian Soils

Sorption, degradation and leaching are the important processes affecting fates of pesticides in the soil environment. Sorption influences the magnitude of the other processes and is considered to be one of the major processes affecting the interactions occurring between pesticides and the solid phase in the soil environment. Dissipation of pesticides can occur by degradation and leaching. There is no reported study on napropamide fates in Malaysian soils or even in tropical soils. Napropamide is one of the pre-emergence herbicides used to control several grasses and broadleaf weeds in tobacco and kenaf fields in Malaysia. Sorption-desorption, degradation and leaching of napropamide were studied in selected Malaysian soils and Baging soil amended with chicken dung (CD) and palm oil mill effluent (POME). The ability of a UV-spectrophotometry to determine napropamide concentration in soil sorption study was studied as well. Results showed that UV-spectrophotometry method was as reliable as the HPLC in determining napropamide concentration in the supernatant of batch equilibrium sorption study. Interference by dissolved organic carbon in the napropamide determination by the spectrophotometer method could be easily corrected using a dual beam spectrophotometer. Baging soil has very low affinity for napropamide. The sorption capacity (Kf) of Baging soil and Baging soil amended with 80 Mg ha-1 CD and POME were 0.22, 41.6 and 3.96, respectively. Dissolved organic carbon (DOC) derived from CD or POME did not affect sorption capacity of amended Baging soil. The sorption capacities of the selected Malaysian soils for napropamide were in the following order: Linau (Kf = 66.2) > Teringkap (Kf = 56) > Gunung Berinchang (Kf = 43) > Jambu (Kf = 26) > Rudua (Kf = 8) > Baging soil (Kf = 0.22). The results indicated that sorption increased with increasing clay and organic carbon content (OC) of the soils. Among the BRIS soils studied, the Baging which has the lowest organic matter and clay content, also has the lowest Kf. Napropamide half-life was lowest in the Baging soil (43 d) and its half-life was increased to 69 (d) and 49.5 (d) with the addition of 20 Mg ha-1 CD and POME, respectively. Degradation of napropamide decreased in Baging soil receiving DOC derived from CD and POME. The shortest and longest half-lives among the selected Malaysian soils were observed in Baging (43 d) and Linau soil (100 d), respectively. The results indicated that napropamide degradation decreased with the increasing soil sorption capacity. Napropamide was leached out earlier in the Baging soil as compared to the other soils. The results showed that soils which have low sorption capacities for napropamide leached napropamide earlier from the soil column. On the other hand, for Linau soil which had the highest sorption capacity for napropamide (Kf = 66.2), no napropamide was detected in the leachate even after seven pore volumes of effluent water. The results also suggested that DOC did not affect the leaching of napropamide. Overall, application of napropamide in the selected Malaysian soils would not pose a threat to the environment especially the groundwater except in soil with low organic matter and clay content, and high hydraulic conductivity such as the Baging soil

Characterization of biochars produced from oil palm and rice husks and their adsorption capacities for heavy metals

The objectives of this study were to determine the selected physicochemical properties of two biochars, one commercially produced from rice husks and the other from oil palm empty fruit bunches, and to evaluate their adsorption capacities for Zn, Cu, and Pb using a batch equilibrium method. The results showed that there was no significant difference between the carbon content of biochars formed from empty fruit bunches (EFBB) and rice husks (RHB). However, the EFBB did present higher quantities of O, H, S, N, and K, compared to the RHB. Although the EFBB had a much lower surface area than the RHB, the former adsorbed much more Zn, Cu, and Pb than the RHB. The higher adsorption capacity of the EFBB over the RHB was a result of the EFBB having higher amounts of oxygen-containing functional groups, a higher molar ratio of O/C, and a higher polarity index [(O + N)/C]. This suggests that the biochar’s chemical properties were more important than its surface area in the adsorption of Zn, Cu, and Pb

Sorption and desorption of napropamide in sandy soil amended with chicken dung and palm oil mill effluent

Beach Ridges Interspersed with Swales (BRIS) is a sandy soil and in Malaysia it is found exclusively in the east coast of Peninsular Malaysia. It is a marginal soil because of its low nutrient and water-holding capacity. However, with proper management and organic matter amendments some areas with BRIS soil are cultivated. Napropamide is a selective herbicide widely used to control weeds in BRIS soil. No previous studies have been reported on the effects of organic matter amendments on napropamide sorption in BRIS soil. This study was conducted to determine sorption and desorption of napropamide in BRIS soil amended with chicken dung (CD) and palm oil mill effluent (POME) at 0, 20, 40, and 80 Mg ha−1. Potential interaction of dissolved organic carbon (DOC) with napropamide and their competition for sorption sites were also determined. Sorption isotherm data were fitted to the log-transformed Freundlich's equation. Sorption of napropamide was higher in soils amended with CD and POME as compared to non-amended soil. At the same rates of application, sorption was higher in soil amended with CD than POME. The Freundlich's coefficient (Kf) values were 0.22, 3.96, and 41.6 for nonamended soil, soil amended with 80 Mg ha−1 POME, and soil amended with 80 Mg ha−1 CD, respectively. Desorption of napropamide showed positive hysteresis and the hysteresis were greater with higher rates of CD and POME. There was no association between napropamide and DOC extracted from BRIS soil amended with either CD or POME and also there were no competitions between napropamide and DOC extracted from either CD or POME for sorption sites of the soil samples

Degradation and leaching of Napropamide in BRIS soil amended with chicken dung and palm oil mill effluent.

The degradation and leaching of napropamide were compared between Beach Ridges Interspersed with Swales (BRIS) soil samples, and the same soil samples amended with 20mgha-1 of either chicken dung (CD) or palm oil mill effluent (POME). The effects of removing dissolved organic carbon (DOC) from the soil samples on napropamide degradation and leaching were also studied. The addition of CD and POME to BRIS soil increased the napropamide half-life values to 69 and 49.5 days, respectively. Sterilization of the soil samples resulted in partial inhibition of napropamide degradation in all soil samples. The half-lives of napropamide in BRIS soils receiving 0, 20, 100, and 200mgkg-1 of DOC derived from CD were 43, 46.2, 53.4, and 63 days, respectively. The napropamide half-lives in soil samples treated with 0, 20, 100, and 200mgkg-1 of DOC derived from POME were 43, 49.2, 57.7, and 69 days, respectively. However, in the sterilized soil samples, there were no significant effects of adding DOC derived from either CD or POME on napropamide half-lives. Incorporating either CD or POME decreased napropamide leaching and total amounts of napropamide remained in the soil columns after two pore volumes of water has been leached were higher in the amended than the non-amended soil. The CD was more effective in decreasing napropamide leaching than the POME. There were no effects of DOC on napropamide leaching in all soil treatments

Adsorption of As(III) and As(V) by Fe coated biochars and biochars produced from empty fruit bunch and rice husk

The study was conducted to determine the adsorption capacity of commercially produced empty fruit bunch biochar (EFBB) and a rice husk biochar (RHB) for As(III) and As(V). The effects of coating the biochars with Fe(III) on adsorption of As(III) and As(V) were also studied. Batch equilibrium adsorption was employed to determine the adsorption capacity of the biochars for As(III) and (V). The adsorption data were fitted to the Langmuir adsorption model. The maximum adsorption capacity (Qmax) of both EFBB and RHB for As(III) was higher than for As(V). The Qmax of EFBB and RHB for As(III) was 18.9 mg g−1 and 19.3 mg g−1, respectively. In contrast, the Qmax of EFBB and RHB for As(V) was only 5.5 mg g−1 and 7.1 mg g−1, respectively. Coating the EFBB and RHB with Fe(III) increased their Qmax values for both As(III) and As(V). The Qmax of Fe-coated EFBB (FC-EFBB) and Fe-coated RHB (FC-RHB) for As(III) was 31.4 mg g−1 and 30.7 mg g−1, respectively. The Qmax of FC-EFBB and FC-RHB for As(V) was 15.2 mg g−1 and 16.0 mg g−1, respectively. Although the surface area of the EFBB (1.890 m2 g−1) was much lower than the RHB's (25.161 m2 g−1), its adsorption capacity for the As was not much different than the RHB, suggesting that oxygen-containing functional groups, zeta potentials, the amounts of functional groups, O/C ratios, (O + N)/C ratios and polarity indices [(O + N)/C] were important in determining As adsorption by these biochars. The biochar surfaces were smooth before As adsorption and became coarser after As was adsorbed. The adsorption of As was confirmed by the EDS data. EFBB and RHB have potentials to be used as low cost adsorbents for removal of As(III) from waste water while FC-EFBB and FC-RH could be used for removal of both As(III) and As(V)

The effects of acidic functional groups and particle size of biochar on Cd adsorption from aqueous solutions

The removal of Cd from the wastewater is necessary because of its harmful health effects. The practice of using biochar as a low-cost adsorbent for heavy metals removal from water bodies is common. However, the effects of total acidic functional groups and particle size class on heavy metals removal by biochar are not studied well. Therefore, this study was undertaken with the objective of determining the effects of total acidic functional groups and particle size class on Cd adsorption from aqueous solution by an empty fruit bunch biochar (EFBB) and a rice husk biochar (RHB). The results showed that there was no significant difference in the carbon content between the EFBB and RHB. However, higher quantity of total acidic functional groups was found in the EFBB compared to the RHB. The total acidic functional groups of EFBB were higher than of the RHB for the same particle size class. In contrast, the surface area of RHB was higher than the EFBB for the same size class. The Langmuir’s maximum adsorption capacity (Qmax) of EFBB was higher than RHB when compared at each particle size class. Significant correlations were observed between Qmax and the total acidic functional groups of both biochars. There were significant correlations between Qmax and the cation exchange capacity (CEC) as well. However, the correlations were non-significant between Qmax and particle size, surface area and pore volume of both biochars. It can be concluded that only the total acidic functional groups and the CEC were influential in determining the adsorption capacities of both EFBB and RHB for Cd adsorption

Fate of napropamide herbicide in selected Malaysian soils.

This study was carried out to determine the sorption-desorption, degradation and leaching of napropamide in selected Malaysian soils. The sorption capacities of the selected Malaysian soils for napropamide were the following in descending order: Linau > Teringkap > Gunung Berinchang > Jambu > Rudua > Baging soil. The results indicate that napropamide degradation decreased with increasing soil sorption capacity. Napropamide was leached out earlier in the Baging soil than the other soils. Overall, the application of napropamide in the selected Malaysian soils would not pose a threat to the environment except in soil with low organic matter and clay content and high hydraulic conductivity, such as the Baging soil

Effects of electric-arc furnace dust application on soil properties, sorghum growth, and heavy-metal accumulation

This study investigated the possibility of using electric-arc furnace dust (EAFD) as an acidic soil amendment. The experiments were conducted using incubation and pot experiments. In the incubation experiment, various rates of EAFD were added to an acidic soil and properties such as pH; electrical conductivity of the saturation extract (ECse); and available phosphorus (P), potassium (K), iron (Fe), zinc (Zn), copper (Cu), manganese (Mn), lead (Pb), and cadmium (Cd) were determined. In the pot experiment rates of EAFD incorporated with soil were 0.25%, 0.5%, 1%, and 2%. The results showed that with increasing the rate of EAFD application, soil pH, EC, and available P and K were enhanced. However, addition of EAFD more than 2% caused high salinity and alkalinity; hence, it is not recommended for reclamation of this acidic soil. A pot experiment was carried out to determine its effects on sorghum (Sorghum bicolor L.) dry matter and heavy-metal accumulation. Plant dry matter was enhanced with increase the EAFD rates. The concentrations of Fe, Zn, Cu, Cd, and Pb were enhanced with the increasing rate of applied EAFD in root and shoot. However, content of these elements in plant shoot were in the normal range

Saline soil reclamation by means of layered mulch

Water conservation and prevention of salt accumulation are important issues in arid and semi-arid regions. Mulching is the most frequently used method for water conservation and prevention of salt accumulation. A mulch with various layers, hence named layered mulch (LM), was applied for reclamation of saline soil. The LM comprises of a light-colored mineral, farmyard manure, and common reed (Arundo donax L.). Two treatments, one with LM and the other without LM (NLM), were carried out on saline soil for 2 years. Soil temperature, water content, and electrical conductivity (EC) were measured during March and September at the depths of 1 to 120 in 4 cm intervals. The results showed that LM soil had a lower temperature and EC than NLM soils. The LM soil recorded higher soil water content than the NLM soil. The LM soil had a lower temperature possibly because it reflected the sunlight, had high heat capacity, and was less permeable to heat conduction. Consequently, the lower temperature in LM soil resulted in higher soil water content and this can be a soil condition, that enables enhanced salt leaching by subsequent rains