Methane emission from fields with differences in nitrogen fertilizers and rice varieties in Taiwan paddy soils

Flooded rice fields are one of the major biogenic methane sources. In this study, methane emission rates were measured after transplanting in paddy fields with application of two kinds of nitrogen fertilizers (ammonium sulfate, NH4+-N and potassium nitrate, NO3(-)-N) and with two kinds of rice varieties (Japonica and Indica). The experiment was conducted in fields located at Tainan District Agricultural Improvement Station in Chia-Yi county (23 degrees 25'08"N, 120 degrees 16'26"E) of southern Taiwan throughout the first and the second crop seasons in 1999. The seasonal methane flux in the first crop season with NH4+-N and NO3(-)-N ranged from 2.48 to 2.78 and from 8.65 to 9.22 g CH4 m(-2); and the values ranged 24.6-34.2 and 36.4-52.6 g CH4 m(-2) in the second crop season, respectively. In the first crop season, there were significantly increased 3.1-3.7-fold in methane emission fluxes due to plantation of Indica rice. In comparison of two rice varieties, the Indica rice variety showed a tendency for larger methane emission than the Japonica rice variety in the second crop season. Moreover, ammonium sulfate treatment significantly reduced CH4 emissions by 37-85% emissions compared to potassium nitrate plots. It was concluded that the CH4 emission was markedly dependent on the type of nitrogen fertilizer and rice variety in Taiwan paddy soils.     

Estimation of methane and nitrous oxide emission from paddy fields and uplands during 1990-2000 in Taiwan

To investigate the greenhouse gases emissions from paddy fields and uplands, methane and nitrous oxide emissions were estimated from local measurement and the IPCC guidelines during 1990-2000 in Taiwan. Annual methane emission from 182,807 to 242,298 ha of paddy field in the first crop season ranged from 8,062 to 12,066 ton, and it was between 16,261 and 25,007 ton for 144,178-211,968 ha in the second crop season with local measurement. The value ranged from 12,132 to 17,465 ton, and from 16,046 to 24,762 ton of methane in the first and second crop season with the IPCC guidelines for multiple aeration treatments, respectively. Annual nitrous oxide emission was between 472 and 670 ton and between 236 and 359 ton in the first and second crop season, respectively. Methane and nitrous oxide emissions from uplands depend on crop, growth season, fertilizer application and environmental conditions. Annual methane emission from upland crops, vegetable, fruit, ornamental plants, forage crops and green manure crops was 138-252, 412-460, 97-100, 3-5, 4-5 and 3-51 ton, respectively. Annual nitrous oxide emission was 1,080-1,976, 1,784-1,994, 2,540-2,622, 31-54, 43-53 and 38-582 ton, respectively. Annual nitrous oxide emission ranged from 91 to 132 ton for 77,593-11,2095 ton of nitrogen-fixing crops, from 991 to 1,859 ton for 3,259,731-6,183,441 ton of non-nitrogen-fixing crops, and from 1.77 to 2.22 Gg for 921,169-1,172,594 ton of chemical fertilizer application. In addition, rice hull burning emitted 19.3-24.2 ton of methane and 17.2-21.5 ton of nitrous oxide, and corn stalk burning emitted 2.1-4.2 ton of methane and 1.9-3.8 ton of nitrous oxide. Methane emission from the agriculture sector was 26421-37914 ton, and nitrous oxide emission was 9810-11,649 ton during 1990-2000 in Taiwan. Intermittent irrigation in paddy fields reduces significantly methane emission; appropriate application of nitrogen fertilization and irrigation in uplands and paddy fields also decreases nitrous oxide emission.     

Model development for nutrient loading estimates from paddy rice fields in Korea

A field experiment was performed to evaluate water and nutrient balances in paddy rice culture operations during 2001-2002. The water balance analysis indicated that about half (50-60%) of the total outflow was lost by surface drainage, with the remainder occurring by evapotranspiration (490-530 mm). The surface drainage from paddy fields was mainly caused by rainfall and forced-drainage, and in particular, the runoff during early rice culture periods depends more on the forced-drainage due to fertilization practices. Most of the total phosphorus (T-P) inflow was supplied by fertilization at transplanting, while the total nitrogen (T-N) inflow was supplied by the three fertilizations, precipitation. and from the upper paddy field, which comprised 13-33% of the total inflow. Although most of the nutrient outflow was attributed to plant uptake. nutrient loss by surface drainage was substantial, comprising 20% for T-N and 10% for T-P. Water and nutrient balances indicate that reduction of surface drainage from paddy rice fields is imperative for nonpoint source pollution control. The simplified computer model, PADDIMOD, was developed to simulate water and nutrient (T-N and T-P) behavior in the paddy rice field. The model predicts daily ponded water depth, surface drainage, and nutrient concentrations. It was formulated with a few equations and simplified assumptions, but its application and a model fitness test indicated that the simulation results reasonably matched the observed data. It is a simple and convenient planning model that could be used to evaluate BMPs of paddy rice fields alone or in combination with other complex watershed models. Application of the PADDIMOD to other paddy rice fields with different agricultural environments might require further calibration and validation.     

Effects of copper concentration on methane emission from rice soils

Outdoor pot experiments with various paddy soils representing five soil types were conducted at Nanjing Agricultural University during the 2000 and 2001 rice-growing seasons. Eighteen soils and ten out of the eighteen soils were involved in the 2000 and the 2001 experiment, respectively. Two treatments were designed as mineral fertilization (MF) and mineral fertilizer + wheat straw incorporation (MF + WS) for the 2001 experiment. Seasonal average rate of CH4 emission from different soils ranged from 1.96 to 11.06 mg m(-2) h(-1) in the 2000 experiment, and from 0.89 to 5.92 mg m(-2) h(-1) for the MF treatment in the 2001 experiment, respectively. Incorporation of wheat straw enhanced considerably CH4 emission with an average increment of 7.09 mg m(-2) h(-1). CH4 emissions from the two-year experiment were negatively correlated to soil available and total copper concentration. A further investigation showed that CH4 emission from the MF treatment was positively related to the dissolved organic carbon (DOC) in the soil (r = 0.904, p < 0.001), and that the DOC was negatively correlated to the concentrations of available copper (r = -0.844, p < 0.01) and total copper (r = -0.833, p < 0.01), respectively. Nevertheless, the incorporation of wheat straw did not enhance the soil DOC, and the relationship between CH4 emission and soil DOC was not statistically significant (r = 0.470, p < 0.20). It was concluded that higher concentration of copper in the soils resulted in lower soil DOC and thus reduced CH4 emission when there was no additional organic matter input. Incorporation of wheat straw did not affect soil DOC and available copper concentration but enhanced CH4 emission.     

Greenhouse gas emission from rice fields: a review from Indian context

Environmental Science and Pollution Research - Agricultural soil acts as a source and sink of important greenhouse gases (GHGs) like methane (CH4), nitrous oxide (N2O), and carbon dioxide (CO2)....     

Partitioning of arsenic in soil-crop systems irrigated using groundwater: a case study of rice paddy soils in southwestern Taiwan

The accumulation of As in rice due to groundwater irrigation in paddy fields represents a serious health hazard in South and Southeast Asia. In Taiwan, the fate of As in long-term irrigated paddy fields is poorly understood. Groundwater, surface soil, and rice samples were collected from a paddy field that was irrigated with As-containing groundwater in southwestern Taiwan. The purpose of this study is to elucidate the source and sink of As in the paddy field by comparing the As fractions in the soils that were obtained by a sequential extraction procedure (SEP) with the As uptake of rice. The risks associated with eating rice from the field can thus be better understood. The concentration of As in groundwater varied with time throughout the growing seasons of rice, but always exceeded the permitted maximum (10 μg L⁻¹) for drinking water by the WHO. The As concentration increased with the concentration of Fe in the groundwater, supporting the claim that a large amount of As was concentrated in the Fe flocs collected from the internal wall of the groundwater pump. The results of the SEP revealed that As bound with amorphous and crystalline hydrous oxides exhibited high availability in the soils. The root of rice accumulated the largest amount of As, followed by the straw, husk, and grain. Although the As concentration in the rice grain was less than 1.0 mg kg⁻¹, the estimated intake level was close to the maximum tolerable daily intake of As, as specified by the WHO.     

Anaerobic biodegradation of biphenyl in various paddy soils and river sediment

The anaerobic degradation of biphenyl was investigated in four uncontaminated Japanese paddy soils and one river sediment sample contaminated with benzene and chlorinated aliphatics. Two of the paddy soils and the sediment were capable of degrading biphenyl anaerobically without any additional medium or electron acceptors. The half-lives of biphenyl biodegradation in the three samples were 212 d in the Kuridashi soil, 327 d in the Kamajima soil, and 429 d in the river sediment. The Kuridashi soil metabolized 1+/-0.3% of [U-14C]-biphenyl into CO2 and 5+/-2% into water-soluble metabolites after 45 d of incubation. Submerged conditions, which result in lower nitrate and iron oxide contents, and neutral pH, appeared to be the common properties among the samples that influenced their degradation capacities. The addition of 10mM sulfate and 20mM Fe(III) as electron acceptors did not enhance the biphenyl degradation rate, whereas 10mM nitrate completely inhibited biphenyl degradation. The addition of different electron donors (lactate, acetate, or pyruvate) slightly slowed the degradation. Molybdate (an inhibitor of sulfate-reducing bacteria) had an inhibitory effect on biphenyl biodegradation, but bromoethanesulfonic acid (an inhibitor of methanogens) did not. Most biphenyl degradation was observed when only water was added, with no other electron acceptors or donors. These results suggest that sulfate-reducing bacteria and fermentative microbial populations play important roles in anaerobic biphenyl biodegradation in paddy soil.     

Concentration of global fallout 99Tc in rice paddy soils collected in Japan

Analysis of global fallout 99Tc in environmental samples should provide useful information for predicting the nuclide behaviour under natural conditions which is important from the viewpoint of radioecology. Concentrations of 99Tc in rice paddy soils collected in Japan have been studied. After chemical separation, 99Tc in the final solution was measured by ICP-MS. The activity ratio of 99Tc/137Cs was used to understand the 99Tc behaviour in the environment because the fission yields of 99Tc and 137Cs from 235U or 239Pu are almost the same. The theoretical activity ratio from fission which is calculated now is about 3.0 x 10(-4). Our results showed that the range of activity ratios of 99Tc/137Cs in the soil samples was (2.0-5.2) x 10(-3); these ratios were one order of magnitude higher than the theoretical one. 99Tc has been accumulating in rice paddy soil like 137Cs has, although their mechanisms might differ. One of the reasons for the high ratio in the surface soil might be the ratios in the atmospheric samples, which have increased from the order of 10(-3) to 10(-2) (García-León et al., 1993).     

Phytoremediation of arsenic contaminated paddy soils with Pteris vittata markedly reduces arsenic uptake by rice

Arsenic (As) accumulation in food crops such as rice is of major concern. To investigate whether phytoremediation can reduce As uptake by rice, the As hyperaccumulator Pteris vittata was grown in five contaminated paddy soils in a pot experiment. Over a 9-month period P. vittata removed 3.5-11.4% of the total soil As, and decreased phosphate-extractable As and soil pore water As by 11-38% and 18-77%, respectively. Rice grown following P. vittata had significantly lower As concentrations in straw and grain, being 17-82% and 22-58% of those in the control, respectively. Phytoremediation also resulted in significant changes in As speciation in rice grain by greatly decreasing the concentration of dimethylarsinic acid (DMA). In two soils the concentration of inorganic As in rice grain was decreased by 50-58%. The results demonstrate an effective stripping of bioavailable As from contaminated paddy soils thus reducing As uptake by rice.     

Copper contamination in paddy soils irrigated with wastewater

Copper (Cu) contamination was investigated in paddy soils where Cu-rich wastewater (12 mg Cu/l) was used for irrigation. The results showed that Cu contamination increased the soil Cu content from 17.0 mg Cu/kg in the non-wastewater irrigated soils (NWIS) to 101.2 mg Cu/kg in the wastewater irrigated soils (WIS), and Cu accumulated mostly in the surface layer (0-10 cm) of the paddy soil. The average Cu contents in brown rice, rice hull and rice straw from NWIS were 1.4, 7.3 and 14.5 mg Cu/kg, while those from WIS were 15.5, 133.2, and 101.4 mg Cu/kg, respectively. Correlation analysis revealed that the relationship between the Cu content in the rice straw and the rice hull with the total Cu content of the soil could be described by an exponential function (R2 = 0.921 and 0.831, respectively; P <0.01). Rice plants grown in the WIS showed symptoms of black roots, less effective tiller, etc. Subsequently, the rice yield decreased by 18-25%, compared with that grown in NWIS.     

成都东郊稻田土中汞的分布特征研究

选取成都东郊唯一的火力发电厂周围的稻田土为研究对象,对稻田土中各种形态汞的分布特征进行了调查与研究,探讨稻田土中汞的分布规律,为分析和判断稻田土中汞的迁移和转化行为及该区汞污染土壤的修复提供重要依据。结果表明,处于火力发电厂烟尘排污口下风向的1#、2#、3#、4#采样点土样受到了严重的汞污染,呈现出高含汞特征,总汞平均质量浓度在9～41mg/kg,平均值为24.546mg/kg,远远超出《土壤环境质量标准》(GB 15618—1995)二级标准所规定的限值(0.5mg/kg),而处于排污口上风向的5#、6#、7#、8#土样没有受到明显的汞污染,大部分土样的总汞含量与成都市土壤汞平均含量接近;1#、2#、3#、4#土样中5种形态汞的垂直分布均呈现出随着土壤深度增加而减少的特征;1#、2#、3#、4#土样中的各形态汞平均百分比为有机结合态汞>硝酸溶汞>残渣态汞>铁锰氧化态汞>水溶和可交换态汞,土壤中含有的大部分汞化学性质比较稳定,难以被植物吸收利用,而易被植物吸收利用的水溶和可交换态汞虽然仅占极小一部分,但含量还是高于成都市土壤中水溶和可交换态汞的背景值。     

重庆市郊稻米Cd风险的原位钝化削减

为筛选适合应用于重庆市郊区稻田土壤及农作物Cd污染的修复技术,采用田间小区原位钝化实验和重金属来源加密监测相结合的方法,比较了石灰、腐殖酸、硅酸钾3种常见修复剂对Cd污染稻田的土壤基本理化性质、水稻各部位Cd富集量、稻米产量和稻米品质的影响。结果表明,该区域土壤Cd污染的主要原因为该区域土壤Cd本底值含量高且土壤酸化严重。在土壤全Cd为0.66 mg·kg-1,有效Cd为0.39 mg·kg-1的污染程度下,施用3种修复剂均可显著降低土壤有效Cd和稻米中Cd含量。其中,施用腐殖酸可显著提高土壤有机质含量,收获期种植2种水稻的土壤中有效Cd含量比CK处理分别减少了32.1%和34.8%,稻米中Cd含量比CK处理分别较少了53.3%和48.2%,同时低于国家食品污染物限量标准 0.2 mg·kg -1,其作用机理主要通过提高土壤有机质含量,降低水稻根系对土壤中Cd的富集量及向茎叶部Cd的运输量。同时,相比于其他修复剂,施加腐殖酸可降低稻米直链淀粉含量,提升稻米品质,但会降低稻米产量。施用石灰可显著提高土壤pH和稻米产量,但水稻收割后稻米中Cd含量高于腐殖酸处理,低于硅酸钾处理。     

Methane and carbon dioxide emissions from closed landfill in Taiwan

The atmospheric concentrations and emission rates of CH(4) and CO(2) were studied at three sites of the Fu-Der-Kan closed landfill and after as the multi-use recreational park in northern Taiwan. Atmospheric CH(4) and CO(2) concentrations of closed landfill were 1.7-4.6 and 324-409ppm, respectively. CH(4) and CO(2) emission rates ranged from 8.8 to 163mg m(-2)h(-1) and from 495 to 1531mg m(-2)h(-1), respectively. Diurnal variation was noted with higher values at night than those in daytime. After creation of the park, atmospheric CH(4) and CO(2) concentrations were 1.8-3.1 and 332-441ppm, respectively. CH(4) and CO(2) emission rates ranged from -1.1 to 2.3mg m(-2)h(-1) and from -135 to 301mg m(-2)h(-1), respectively. There were no notable diurnal variations in either atmospheric concentrations or emission rates.     

The abundances of rarer trace elements in paddy (rice) soils of Sri Lanka

Concentrations of Ti, Ga, As, Sc, Zr, Sn, Hf, Th, U and Y have been determined for 70 paddy soils from 14 villages, selected throughout Sri Lanka by means of ICP-MS. The mean elemental contents of all paddy soil samples were 6120 Ti, 14.1 Ga, 0.84 As, 7.26 Sc, 129 Zr, 2.27 Sn, 3.64 Hf, 12.71 Th, 1.53 U, and 13.35 Y (all data in microg/g). Paddy soils were classified into groups based on morphology and climate. Higher contents of Th and U were found in the wet zone lowland soils whereas the higher Ti contents were observed in dry zone soils. Arsenic, Zr and Hf contents were comparatively similar in all regions. Factor analysis was used to identify the relationships between the contents of elements.     

Bioaccumulation and human health risk assessment of chromium and nickel in paddy rice grown in serpentine soils

The natural abundance of Cr and Ni in serpentine soils is well-known, but the food safety of rice grown in these hazardous paddy soils is poorly understood. The study evaluated the bioaccumulation of chromium (Cr) and nickel (Ni) in rice (Oryza sativa) grown in serpentine-derived paddy soils in the Philippines. Surface soil (0–20 cm) samples were collected and characterized across three (i.e., Masinloc, Candelaria, and Sta. Cruz) paddy areas in Luzon Island, Philippines. At least 3 to 4 whole rice plants at mature stage were uprooted manually in each sampling point where the soil samples were collected. The total Cr and Ni concentrations in rice (i.e., roots, shoots, and grains) and soil, soil physicochemical properties, bioaccumulation factor (BAF), translocation factor (TF), and the hazard quotients (HQ) were determined. Results revealed that Cr and Ni in rice were accumulated mostly in the roots. Although paddy soils had elevated total Cr and Ni concentrations, the BAF and soil-to-root TF values for Cr and Ni were < 1. In terms of human health risks, results further revealed low risk for both male and female Filipino adults as HQ values for Cr and Ni were < 1. While it is safe to consume rice grown in the area in terms of Cr and Ni dietary intake, more studies are necessary to understand the dynamics and bioavailability of these heavy metals in other crops and drinking water from tube wells in these areas in order to provide a more holistic human health-based assessments and to ensure consumer safety in serpentine areas. In addition, a more reliable data on Cr and Ni speciation in serpentine soils and crops is critically important. Further studies are also needed to understand the contribution of bioavailable heavy metals in improving the soil health to achieve food safety.

     

Methane fluxes from tundra soils and snowpack in the maritime Antarctic

Methane fluxes were measured from three exposed tundra sites and four snowpack sites on the Fildes Peninsula in the maritime Antarctic in the summertime of 2002. The average fluxes at two normal tundra sites were −15.3 μg m⁻² h⁻¹ and −14.3 μg m⁻² h⁻¹, respectively. The fluxes from tundra site with fresh penguin dropping addition showed positive values with the average of 36.1 μg m⁻² h⁻¹, suggesting that the deposition of fresh droppings greatly enhanced CH₄ emissions from the poor Antarctic tundra during penguin breeding periods. The summertime variation in CH₄ flux was correlated with surface ground temperature and the precipitation. The correlation between the flux and PT₀, which is the product of the precipitation and surface ground temperature, was quite strong. The diurnal cycle of CH₄ flux from the tundra soils was not obtained due to local fluky weather conditions. The fluxes through four snowpack sites were also obtained by the vertical CH₄ concentration gradient and their average fluxes were −46.5 μg m⁻² h⁻¹, −28.2 μg m⁻² h⁻¹, −46.4 μg m⁻² h⁻¹ and −17.9 μg m⁻² h⁻¹, respectively, indicating that tundra soils under snowpack also consume atmospheric CH₄ in the maritime Antarctic; therefore these fluxes could constitute an important part of the annual CH₄ budget for Antarctic tundra ecosystem.     

Methane emission characteristics and its relations with plant and soil parameters under irrigated rice ecosystem of northeast India

Methane flux from rice varieties grown under two identical soils of Assam were monitored. In the first experiment, variety Jaya and GRT was grown in sandy loam soil of Lower Brahmaputra Valley Zone of Assam and the second experiment was conducted with variety Jyotiprasad and Bishnuprasad in sandy to sandy loam soils of Upper Brahmaputra Valley Zones of Assam. Methane flux recorded from variety Jyotiprasad and GRT was higher compared to variety Bishnuprasad and Jaya. The seasonal integrated flux recorded was 10.76 g m⁻², 9.98 g m⁻², 9.74 g m⁻² and 11.31 g m⁻² for variety GRT, Jaya, Bishnuprasad and Jyotiprasad, respectively. All the varieties exhibited two methane peaks one at maximum tillering stage and other at panicle initiation stage of the crop. Crop growth parameters such as leaf number, number of tillers and leaf area index (LAI) showed strong positive relationship with total methane flux. In both the experiments it was calculated that CH₄ emission was substantially influenced by crop phenology and growth. This study emphasise the relationship of different growth parameters with methane emission.     

Effects of open burning of rice straw on concentrations of atmospheric polycyclic aromatic hydrocarbons in central Taiwan

The sizes and concentrations of 21 atmospheric polycyclic aromatic hydrocarbons (PAHs) were measured at Jhu-Shan (a rural site) and Sin-Gang (a town site) in central Taiwan in October and December 2005. Air samples were collected using semi-volatile sampling trains (PS-1 sampler) over 16 days for rice-straw burning and nonburning periods. These samples were then analyzed using a gas chromatograph with a flame-ionization detector (GC/FID). Particle-size distributions in the particulate phase show a bimode, peaking at 0.32-0.56 microm and 3.2-5.6 microm at the two sites during the nonburning period. During the burning period, peaks also appeared at 0.32-0.56 microm and 3.2-5.6 microm at Jhu-Shan, with the accumulation mode (particle size between 0.1 and 3.2 microm) accounting for approximately 74.1% of total particle mass. The peaks at 0.18-0.32 microm and 1.8-3.2 microm at Shin-Gang had an accumulation mode accounting for approximately 70.1% of total particle mass. The mass median diameter (MMD) of 3.99-4.35 microm in the particulate phase suggested that rice-straw burning generated increased numbers of coarse particles. The concentrations of total PAHs (sum of 21 gases + particles) at the Jhu-Shan site (Sin-Gang site) were 522.9 +/- 111.4 ng/ml (572.0 +/- 91.0 ng/ml) and 330.1 +/- 17.0 ng/ml (or 427.5 +/- 108.0 ng/ml) during burning and nonburning periods, respectively, accounting for a roughly 58% (or 34%) increase in the concentrations of total PAHs due to rice-straw burning. On average, low-weight PAHs (about 87.0%) represent the largest proportion of total PAHs, followed by medium-weight PAHs (7.1%), and high-weight PAHs (5.9%). Combustion-related PAHs during burning periods were 1.54-2.57 times higher than those during nonburning periods. The results of principal component analysis (PCA)/absolute principal component scores (APCS) suggest that the primary pollution sources at the two sites are similar and include vehicle exhaust, coal/wood combustion, incense burning, and incineration emissions. Open burning of rice straw was estimated to contribute approximately 5.0-33.5% to the total atmospheric PAHs at the two sites.     

Methane and carbon dioxide emissions from Shan-Chu-Ku landfill site in northern Taiwan

To investigate the methane and carbon dioxide emissions from landfill, samples were taken of material up to 5 years old from Shan-Chu-Ku landfill located in the northern part of Taiwan. Atmospheric concentrations of carbon dioxide, methane and nitrous oxide ranged from 310 to 530, 2.64 to 20.16 and 0.358 to 1.516 ppmv with the measurement of gas-type open-path Fourier transform infra-red (FTIR) spectroscopy during February 1998 to March 2000, respectively. Average methane emission rate was 13.17, 65.27 and 0.99 mgm(-2)h(-1) measured by the gas chromatography chamber method in 1-2, 2-3 and 5 year-old landfill, respectively. Similarly, average carbon dioxide emission rate was 93.70, 314.60 and 48.46 mgm(-2)h(-1), respectively. About 2-3 year-old landfill had the highest methane and carbon dioxide emission rates among the tested areas, while 5 year-old landfill was the least. Methane emission rate at night in most tested locations was higher than that in the daytime. Total amount of methane and carbon dioxide emission from this landfill was around 171 and 828 ton in 1999, respectively.