Bioremediation of aerobically treated distillery sludge mixed with cow dung by using an epigeic earthworm Eisenia fetida

The potential of the epigeic earthworm Eisenia fetida to stabilize sludge␣(generated from a distillation unit of the sugar industry) mixed with cow dung, in different proportions i.e. 20% (T₁), 40% (T₂), 60% (T₃) and 80% (T₄) has been studied under laboratory conditions for 90 days. The␣ready vermicompost was evaluated for its’ different physico-chemical parameters using standard methods. At the end of experiment, all vermibeds expressed a significant decrease in pH (7.8–19.2%) organic C (8.5–25.8%) content, and an increase in total N (130.4–170.7%), available P (22.2–120.8%), exchangeable K (104.9–159.5%), exchangeable Ca (49.1–118.1%), and exchangeable Mg (13.6–51.2%) content. Overall, earthworms could maximize decomposition and mineralization efficiency in bedding with lower proportions of distillery sludge. DTPA extractable metal reduction in substrate was recorded between the ranges of 12.5–38.8% for Zn, 5.9–30.4% for Fe, 4.7–38.2% for Mn and 4.5–42.1% for Cu. Maximum values for the mean individual live weight (809.69 ± 20.09 mg) and maximum individual growth rate (mg wt. worm⁻¹ day⁻¹) (5.81 ± 0.18) of earthworms was noted in T₁ treatment, whereas cocoon numbers (69.0 ± 7.94) and individual reproduction rate (cocoon worm⁻¹ day⁻¹) (0.046 ± 0.002) was highest in T₂ treatment. Earthworm mortality tended to increase with increasing proportion of distillery sludge, and maximum mortality in E. fetida was recorded for the T₄ (45.0 ± 5.0) treatment. Results indicate that vermicomposting might be useful for managing the energy and nutrient rich distillery sludge on a low-input basis. Products of this process can be used for sustainable land restoration practices. The feasibility of worms to mitigate the toxicity of metals also reduces the possibility of soil contamination, which has been reported in earlier studies during direct field application of industrial wastes.     

Growth and fecundity of earthworms: <Emphasis Type="Italic">Perionyx excavatus</Emphasis> and <Emphasis Type="Italic">Perionyx sansibaricus</Emphasis> in cattle waste solids

Epigeic earthworms (Oligochaeta) have been appeared as key organisms to convert organic waste resources into value-added products, i.e., vermicompost and worm biomass. The assessment of reproduction potential of composting earthworm may be beneficial for large-scale earthworm production. Although, the waste minimizing potential of Perionyx excavatus and Perionyx sansibaricus is well proved, but little information is available about their fecundity rate. In this study, the efforts have been made to explore the growth and reproduction biology of P. excavatus and P. sansibaricus, using cattle waste solid as culture substrate, under laboratory conditions. Earthworms were weighed weekly and number of cocoons produced per week assessed. Biomass productions, fecundity, maturation, natality all were significantly different between P. excavatus and P. sansibaricus. The highest mean individual biomass was 767.7 ± 18.4 mg and 612.6 ± 20.6 mg, respectively in P. sansibaricus and P. excavatus. However, the highest cocoon numbers occurred in P. excavatus (492.3 ± 13.6), significantly higher than P. sansibaricus (269.6 ± 17.1). Fecundity was slightly different in both species: 1.38 ± 0.77 cocoons adult worm⁻¹ week⁻¹ (P. excavatus) and 1.58 ± 0.74 cocoons adult worm⁻¹ week⁻¹ (P. sansibaricus). The hatchling success rate (%) was highest in P. excavatus. Overall natality (juveniles adult⁻¹ week⁻¹) was highest in P. sansibaricus (1.52) than P. excavatus (1.26), which suggests that P. sansibaricus may be a better candidate for rapid propagation of earthworms in cattle waste solid.     

Enrichment of vermicomposts prepared from cow dung spiked solid textile mill sludge using nitrogen fixing and phosphate solubilizing bacteria

Textile mill waste can be vermicomposted if it is mixed in the range of 20–30% with cow dung. This article reports the effect of inoculation, of nitrogen fixing Azotobacter chroococcum strain; Azospirillum brasilense strain and phosphate solubilizing Pseudomonas maltophila, on nitrogen and phosphorus content of vermicomposts prepared from cow dung (CD) and cow dung spiked textile mill sludge (CD + STMS). The CD vermicompost was more supportive to the growth and multiplication of all the three bacteria than CD + STMS vermicompost. In Azotobacter chroococcum treated vermicomposts maximum nitrogen content was recorded between 45 and 60 days [CD␣vermicompost (25.9 ± 0.45 g kg⁻¹) and CD + STMS vermicompost (20.6 ± 0.62 g kg⁻¹)] followed by Azospirillum brasilense inoculation [CD vermicompost (19.4 ± 0.60 g kg⁻¹) and CD + STMS vermicompost (18.6 ± 0.17 g kg⁻¹)]. Phosphorus content in Pseudomonas maltophila inoculated CD vermicompost was 20.8 ± 0.20 g kg⁻¹ and CD + STMS vermicompost was 13.4 ± 0.45 g kg⁻¹ after 75th day of inoculation.     

Effect of stocking density and food quality on the growth and fecundity of an epigeic earthworm (<Emphasis Type="Italic">Eisenia fetida</Emphasis>) during vermicomposting

Physico-chemical characteristics of the feed and optimum worm density are important parameters for the efficient working of a vermicomposting system. Overcrowding of worms can affect the efficiency of a vermicomposting system even if all other parameters have been optimized. This article reports the effect of stocking density and feed quality on the growth and fecundity of Eisenia fetida under laboratory conditions. The feed mixtures contained cow dung and textile mill wastewater sludge in different ratios. Three feed mixtures and five stocking rates (1, 2, 4, 8, and 12) were tested for 12 weeks. The results showed that E. fetida growth rate was faster at higher stocking densities; however, biomass gain per worm was faster at lower stocking densities. Sexual maturity was attained earlier at higher stocking densities. Growth rate was highest in 100% cow dung at all the stocking densities when compared to textile mill wastewater sludge containing feed mixtures. A worm population of 27–53 worms per kg of feed was found to be the most favorable stocking density.     

Investigating efficiency of <Emphasis Type="Italic">Lampito mauritii</Emphasis> (Kinberg) and <Emphasis Type="Italic">Perionyx ceylanensis</Emphasis> Michaelsen for vermicomposting of different types of organic substrates

The vermicomposting ability of Lampito mauritii (Kinberg) and Perionyx ceylanensis Michaelsen was evaluated by using three different types of organic substrates such as leaf litter of Polyalthia longifolia, Pennisetum typhoides cobs (pearl millet) and a weed, Rottboellia exaltata (whole plant except the roots) in combination with cowdung (1:1). Vermicomposting studies (120 days) conducted to optimize the number of worms required for efficient conversion based on the reduction of C/N ratio, percentage decomposition of organic substrates, total number and biomass of earthworms recovered from the vermibed substrates clearly showed that vermibeds with 4 kg of organic materials can hold about 60–80 L. mauritii and about 90–120 P. ceylanensis for efficient decomposition. The percentage decomposition of each organic substrate treated with different numbers of L. mauritii (20, 40, 60, 80 and 100 earthworms) and P. ceylanensis (30, 60, 90, 120 and 150) showed significant difference (P < 0.001) between numbers of worms introduced per vermibed but the difference between substrates was not significant within the treatments. Vermicomposting resulted in significant increase in electrical conductivity (28.54–49.82%), total nitrogen (43.96–90.83%), total phosphorus (27.42–68.10%) and total potassium (27.42–113.18%), whereas decrease in organic carbon (35.05–49.74%), C/N ratio (55.48–73.18%) and C/P ratio (50.46–66.90%) in different vermibeds introduced with L. mauritii and P. ceylanensis. Both the earthworm species can be used for vermicomposting different organic substrates; however, duration of vermicomposting with P. ceylanensis is not as much of L. mauritii. The use of L. mauritii for vermicomposting of other substrates has been well established by other workers also but standardization of P. ceylanensis, a locally available species, for vermicomposting of different organic substrates is a new finding and the species could be useful for vermiconversion of organic substrates under local conditions.     

Livestock excreta management through vermicomposting using an epigeic earthworm Eisenia foetida

In India, millions of tones of livestock excreta are produced. Our study explores the potential of an epigeic earthworm Eisenia foetida to compost different livestock excreta (cow, buffalo, horse, donkey, sheep, goat and camel) into value added product (vermicompost) at the laboratory scale. Vermicomposting resulted in lowering of pH, electrical conductivity, potassium and C:N ratio and increase in nitrogen and phosphorus contents. Total K was lower in the final cast than in the initial feed. C:N ratios of the vermicomposts ranged from 16.2 ± 2.17 to 75.4 ± 6.84. Microbial activity measured as dehydrogenase activity in buffalo, donkey and camel wastes increased with time up to day 90. But in sheep and goat wastes, maximum dehydrogenase activity was recorded on day 60 and decreased thereafter. The cocoons and hatchlings production by Eisenia foetida in different excreta were also investigated. The greatest number and biomass of hatchlings was recorded in horse excreta followed by cow, goat and sheep excreta. Thus, cow, horse, sheep and goat excreta show potential as good substrates in vermicomposting using Eisenia foetida, although further research is required to explore the feasibility of use of buffalo, donkey and camel excreta in combination with cow/sheep/goat excreta.     

Elemental contaminants in groundwater: A study of trace metals from residential area in the vicinity of an industrial area in Lagos, Nigeria

Groundwater (well water) from a residential area within the vicinity of an industrial estate in Lagos, Nigeria were sampled and analysed by Flame Atomic Absorption Spectroscopy for their heavy metals content. This was with a view of assessing the quality of the water, which was being used for domestic activities, especially, drinking usually without treatment. Total trace metal determination by mineral acid digestion of water samples was applied. This method proved to be better than an extractive concentration technique in the quality assurance protocols with the recovery range being 90.7 ± 0.006–97.6 ± 0.003%. Mean concentration of trace metals in water samples ranged from Fe: 0.05–0.47 mg l⁻¹; Al: 0.1–1.54 mg l⁻¹; Cu: 0.14–1.39 mg l⁻¹; Zn: 0.04–0.43 mg l⁻¹; Cd: trace–0.02 mg l⁻¹; Pb: trace–0.03 mg l⁻¹, Mn: 0.01–0.18 mg l⁻¹ and Ni: 0.02–0.11 mg l⁻¹. Physical parameters of water samples examined were within the drinking water safety limits except for conductivity. Results generally indicate the presence of heavy metal constituents in groundwater samples. Detection of metals such as cadmium and lead which have serious health implications above WHO and USEPA limits in drinking water gives cause for concern.     

Response of Soil Inorganic Nitrogen to Land Use and Topographic Position in the Cofre de Perote Volcano (Mexico)

This study addressed the effects of land use and slope position on soil inorganic nitrogen and was conducted in small watersheds. The study covered three land use types: tropical cloud forest, grassland, and coffee crop. To conduct this research, typical slope small watersheds were chosen in each land use type. Slopes were divided into three positions: shoulder, backslope, and footslope. At the center of each slope position, soil sampling was carried out. Soil inorganic nitrogen was measured monthly during a period of 14 months (July 2005–August 2006) with 11 observations. Significant differences in soil NH₄ ⁺–N and NO₃ ⁻–N content were detected for both land use and sampling date effects, as well as for interactions. A significant slope position-by-sampling date interaction was found only in coffee crop for NO₃ ⁻–N content. In tropical cloud forest and grassland, high soil NH₄ ⁺–N and low NO₃ ⁻–N content were recorded, while soil NO₃ ⁻–N content was high in coffee crop. Low NO₃ ⁻–N contents could mean a substantial microbial assimilation of NO₃ ⁻–N, constituting an important mechanism for nitrogen retention. Across the entire land use set, the relationship between soil temperature and soil inorganic N concentration was described by an exponential decay function (N = 33 + 2459exp^−0.23T, R ² = 0.44, P < 0.0001). This study also showed that together, soil temperature and gravimetric soil water content explained more variation in soil inorganic N concentration than gravimetric soil water content alone.     

Changing effluent chemistry affect survival,growth and physiological function of <Emphasis Type="Italic">Acacia nilotica</Emphasis> seedlings in northwestern region of India

Recycling and conservation efforts for water are the need of the day because of the lack of new water sources and the ever-increasing demand for drinking water. Seedlings of Acacia nilotica L. were irrigated with: canal water (T₁, control); municipal effluent (T₂); textile effluent (T₃); steel effluent (T₄); textile + municipal effluent in 1:1 ratio (T₅); steel + municipal effluent in 1:2 ratio (T₆); steel + textile in 1:2 ratio (T₈) and steel + municipal + textile in 1:2:2 ratio (T₇) with views to observe effluents effect on the seedlings and its adaptability and to recommend safe disposal of these effluents. Seedlings in T₆, T₇ and T₈ showed 50% lesser height and collar diameter than those in control. Seedlings in T₂ attained greatest height, collar diameter, numbers of branches and produced 140 g dry biomass seedling⁻¹. Highest concentration of manganese (Mn), iron (Fe), copper (Cu) and zinc (Zn) and lowest concentration of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg) in the seedlings of T₄, T₆, T₇ and T₈ resulted in nutritional imbalance, mineral toxicity and reduction in photosynthetic (Pn) and transpiration (E) rates and caused seedling mortality. Seedlings of T₃ had highest sodium concentration and low concentration of Ca, Mg and micronutrients resulting in nutritional imbalance, augmented chlorosis and reduced gas exchange and biomass by half as compared to control. Increased growth, Pn and E and biomass in seedlings of T₅ over T₃ and survival period in T₆, T₇ and T₈ seedlings suggested a beneficial effect of effluents mixing. Unscientific disposal should be avoided and toxic concentration of metal ions␣may be reduced for long-term application and harmless disposal of effluents in afforestation and urban development.     

Metal contamination of surface water,sediment and <Emphasis Type="Italic">Tympanotonus fuscatus</Emphasis> var. <Emphasis Type="Italic">radula</Emphasis> of Iko River and environmental impact due to Utapete gas flare station,Nigeria

Inter-seasonal studies on the trace metal load of surface water, sediment and Tympanotonus fuscatus var. radula of Iko River were conducted between 2003 and 2004. The impact of anthropogenic activities especially industrial effluent, petroleum related wastes, gas flare and episodic oil spills on the ecosystem are remarkable. Trace metals analyzed included cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), lead (Pb), manganese (Mn), nickel (Ni), vanadium (V) and zinc (Zn). Sediment particle size analysis revealed that they were characteristically psammitic and were predominantly of medium to fine grained sand (>73%), less of silt (<15%) and clay (<10%). These results correlated with low levels of trace elements such as Pb (0.03 ± 0.02 mg kg⁻¹), Cr (0.22 ± 0.12 mg kg⁻¹), Cd (0.05 ± 0.03 mg kg⁻¹), Cu (0.04 ± 0.02 mg kg⁻¹) and Mn (0.23 ± 0.22 mg kg⁻¹) in the sediment samples. This observation is consistent with the scarcity of clayey materials known to be good scavengers for metallic and organic contaminants. Sediments indicated enhanced concentration of Fe, Ni and V, while other metal levels were relatively low. The concentrations of all the metals except Pb in surface water were within the permissible levels, suggesting that the petroleum contaminants had minimal effect on the state of pollution by trace metals in Iko River. Notably, the pollutant concentrations in the sediments were markedly higher than the corresponding concentrations in surface water and T. fuscatus tissues, and decreased with distance from point sources of pollution.     

Heavy metal distribution in crab (<Emphasis Type="Italic">Callinectes amnicola</Emphasis>) living on the shores of Ojo Rivers,Lagos, Nigeria

Crab samples, both male and female specie, were purchased from fishermen at the Ojo Rivers, Lagos, Nigeria. The samples separated into abdomen, muscle tissue, and thorax were oven dried at 80°C for 3 days. The dried samples were then pulverized in a clean acid-washed mortar and pestle. Approximately 1.00 g each of the pulverized samples was weighed and Zn, Cr, Pb, and Cd were determined in the solution of the aqua regia digested samples by means of AAS (Buck Scientific 210 GVP model). The results obtained showed Zn metal to be consistently higher in all the female parts compared to the male with values of 12.92 ± 3.65 μg/g to 16.03 ± 1.08 μg/g and 9.33 ± 1.77 μg/g to 15.75 ± 1.02 μg/g, respectively. Mean values of 0.39 ± 0.09 μg/g and 0.22 ± 0.02 μg/g cadmium were found in the abdomen and tissue of the male crab as against 0.35 ± 0.07 μg/g and 0.17 ± 0.07 μg/g in the female crab. The tissues of both species have comparable value of chromium. Lead was below the detection limit of 0.05 μg/g in the tissues of male crab but the female tissue contained 0.83 ± 0.13 μg/g and in other parts identified, lead was consistently higher than the 2.00 μg/g permissible level of WHO in foods. A simple pair t-test did not demonstrate any significant difference in the distribution of metals between the male and female crabs. The coefficient of variation (CV) calculated for each metal with respect to the studied parts showed Pb to be widely distributed (56.23–89.54%) while Cr did not vary widely (4.17–8.20%).     

Efficacy of vermicomposting for recycling organic portion of hospital wastes using <Emphasis Type="Italic">Eisenia fetida</Emphasis>: standardization of cow manure proportion to increase enzymatic activities and fungal biomass

Hospital wastes are infectious wastes generated in hospitals and need to be disposed in such a way that they do not spread disease. In this experiment, 5, 10, 15 and 20% cow manure (CM) were mixed with hospital wastes (HW), and mixed wastes were subjected to vermicomposting. In control treatment, only HW was used for vermicomposting. Results suggested that significantly (P ≤ 0.05) higher total nitrogen content was recorded in vermicomposts when 10% or more CM was added to HW. Higher mineralization rate (decrease in C/N ratio) and cellulase activity is probably responsible for rapid organic matter decomposition (loss of total organic carbon). Ergosterol content i.e., total fungal biomass and cellulolytic fungal population were almost constant initially, but increased in the latter stage of vermicomposting. All the vermicompost samples, prepared in this experiment, showed the absence of coliform bacteria. Therefore, it could be concluded that 10% CM addition with HW was the most economical to obtain best quality vermicompost in terms of nutrient content and microbial status.     

The metabolic pathway of 4?Hz mechanical vibration-induced effect on snail heart muscle contractility

It was shown that the 4 Hz 30 dB mechanical vibration (MV) of physiological solution (PS) had modulation effect on snail heart contractility. However, the nature of metabolic pathway of MV-treated PS-induced effect is not clear yet. It was suggested that the MV-induced modulation of water molecules dissociation leads to the variation of reactive oxygen species’ level in cell bathing medium, which could serve as a messenger for switching on the metabolic pathway(s) responsible for modulation of muscle contractility. The aim of present work was to check this hypothesis and to elucidate the metabolic pathway through which the effect of MV-treated PS on heart contractility was realized. For this purpose, the effect of MV on heat fusion periods (HFP) and H₂O₂ content in PS, as well as on heart contractility, ⁴⁵Ca²⁺ efflux, intracellular levels of cGMP and cAMP, muscle hydration, and ouabain binding were studied. It was shown that MV treatment of PS increased the HFP-(21.33 ± 4%) and decreased the H₂O₂ content-(5 ± 0.9%). The intracardiac perfusion by MV-treated PS increased the amplitudes of heart contractility, which was accompanied by the increasing of ⁴⁵Ca²⁺ efflux (252.4 ± 16%), elevation of cGMP’s level (42.05 ± 7%), decreasing of cAMP’s level (82.67 ± 7%), increasing of the tissue hydration (18.64 ± 3%), and increasing of the number of ouabain binding sides (25 ± 4%). It was suggested that MV-induced increasing of heart muscle contraction amplitudes is due to the decreases of H₂O₂ content in the medium, which leads to the elevation of heart muscle contractility in result of activation of cGMP-dependent Na⁺/Ca²⁺ exchange in forward regime.     

Role of physiographic factors in distribution of <Emphasis Type="Italic">Abies pindrow</Emphasis> (<Emphasis Type="Italic">Silver Fir</Emphasis>) along an altitudinal gradient in Himalayan temperate forests

We have made an attempt to understand the significance of physiographic factors viz., altitude, aspect, slope and soil characteristics in determining the structure, composition, growth behavior and distribution of Himalayan Silver Fir (Abies pindrow Spach.) through a comparative analysis of two temperate forests. The occurrence of highest density (370 and 225 ind/ha), importance value index (213.10 and 190.60) and total basal cover (TBC; 95.72 and 51.15 m²/ha) values along with the availability of higher organic carbon (6.53 and 4.47%), nitrogen (N; 0.73 and 0.44%) and potassium (K; 621 and 319 ppm) contents in the soils just beneath the hilltops (2,650–2,800 and 2,550–2,650 m asl), on steeper slopes (45°–50° and 42°–45°) and North-East aspects have revealed better growth of A. pindrow on both the sites. Stem density positively correlated with TBC (0.771), Shannon–Wiener diversity index (H′; 0.879), OC (0.601), N (0.758) and K (0.752), whereas TBC has shown significant positive relationship with H′ (0.894), K (0.793) and N (0.716). Similarly, H′ has also shown significant positive correlation with slope (0.721), K (0.855) and N (0.791). Interestingly, positive correlation of altitude with stem density (0.557) and of slope with TBC (0.608) was noticed in the distribution of A. pindrow individuals.     

Nutrient chemistry of the Densu River in Ghana

The impact of anthropogenic activities on the fluctuation of nutrients along the Densu River and its tributaries was studied. High concentrations of nutrients were observed in the study area but the river was found to be circumneutral and fresh with pH ranging between 6.54 and 7.84. The levels of NH₄ ⁺–N ranged between 0.21 and 2.1 mg L⁻¹ with mean concentration of 1.19 ± 0.02 mg L⁻¹ while that of nitrate is between 0.13 and 5.21 mg L⁻¹ with a mean concentration of 2.07 ± 0.01 mg L⁻¹. The levels of PO₄ ³⁻–P fluctuated within the range 0.54 and 1.04 mg L⁻¹ with a mean of 0.84 ± 0.01 mg L⁻¹. The Densu River Basin was also found to be with organic matter with depleted dissolved oxygen. The river recorded high BOD values ranging from 6.91 to 18.8 mg L⁻¹. Concentration of nutrients and organic pollutants increased as a consequence of anthropogenic inputs particularly from domestic, agricultural and municipal sources. The highly impaired sites were those located close to the urbanized, agricultural and high-density residential areas. The relatively high concentration of nitrate and phosphate in the river indicated that it was quite eutrophic.     

Evaluation of tidal marsh restoration: Comparison of selected macroinvertebrate populations on a restored impounded valley marsh and an unimpounded valley marsh within the same salt marsh system in Connecticut,USA

Macroinvertebrates were examined on an impounded valley marsh in Stonington, Connecticut, that has changed from aTypha-dominated system to one with typical salt-marsh vegetation during 13 years following the reintroduction of tidal exchange. Animal populations on this restored impounded marsh were evaluated by comparing them with populations on a nearby unimpounded valley marsh of roughly the same size. Populations of the high marsh snail,Melampus bidentatus Say, were quantitatively sampled along transects that extended from the water-marsh edge to the upland; those of the ribbed mussel,Geukensia demissa Dillwyn, were sampled in low marsh areas on transects along the banks of creeks and mosquito ditches. The occurrence of other marsh invertebrates also was documented, but their abundance was not measured. The mean density ofMelampus was 332±39.6 SE/m² on the restored impounded marsh and 712±56.0 SE/m² on the unimpounded marsh. However, since snails were larger on the restored impounded marsh, the difference in snail biomass was less pronounced than the difference in snail density. MeanMelampus biomass was 4.96±0.52 SE g dry wt/m² on the restored impounded marsh and 6.96±0.52 SE g dry wt/m² on the unimpounded marsh. On the two marshes, snail density and biomass varied in relation to plant cover and other factors. The density and biomass ofGeukensia at the edge of the marsh were comparable on the restored impounded and unimpounded marshes. Mean mussel densities ranged from 80 to 240/m² and mean mussel biomass varied from 24.8–64.8 g dry wt/m² in different low marsh areas. In contrast, below the impoundment dike, meanGeukensia density was 1100±96.4 SE/m² and meanGeukensia biomass was 303.6±33.28 SE g dry wt/m². A consideration of all available evidence leads to the conclusion that the impounded marsh is in an advanced phase of restoration.     

Nitrous Oxide Emission from <Emphasis Type="Italic">Deyeuxia angustifolia</Emphasis> Freshwater Marsh in Northeast China

Here we report N₂O emission results for freshwater marshes isolated from human activities at the Sanjiang Experimental Station of Marsh Wetland Ecology in northeastern China. These results are important for us to understand N₂O emission in natural processes in undisturbed freshwater marsh. Two adjacent plots of Deyeuxia angustifolia freshwater marsh with different water regimes, i.e., seasonally waterlogged (SW) and not- waterlogged (NW), were chosen for gas sampling, and soil and biomass studies. Emissions of N₂O from NW plots were obviously higher than from the SW plots. Daily maximum N₂O flux was observed at 13 o′clock and the seasonal maximum occurred in end July to early August. The annual average N₂O emissions from the NW marsh were 4.45 μg m⁻² h⁻¹ in 2002 and 6.85 μg m⁻² h⁻¹ in 2003 during growing season. The SW marsh was overall a sink for N₂O with corresponding annual emissions of −1.00 μg m⁻² h⁻¹ for 2002 and −0.76 μg m⁻² h⁻¹ for 2003. There were significant correlations between N₂O fluxes and temperatures of both air and 5-cm-depth soil. The range of soil redox potential 200–400 mV appeared to be optimum for N₂O flux. Besides temperature and plant biomass, the freeze–thaw process is also an important factor for N₂O emission burst. Our results show that the freshwater marsh isolated from human activity in northeastern China is not a major source of N₂O.     

Perceived Conflicts Between Pastoralism and Conservation of the Kiang Equus kiang in the Ladakh Trans-Himalaya, India

An emerging conflict with Trans-Himalayan pastoral communities in Ladakh’s Changthang Plateau threatens the conservation prospects of the kiang (Equus kiang) in India. It is locally believed that Changthang’s rangelands are overstocked with kiang, resulting in forage competition with livestock. Here, we provide a review and preliminary data on the causes of this conflict. Erosion of people’s tolerance of the kiang can be attributed to factors such as the loss of traditional pastures during an Indo-Chinese war fought in 1962, immigration of refugees from Tibet, doubling of the livestock population in about 20 years, and increasing commercialization of cashmere (pashmina) production. The perception of kiang overstocking appears misplaced, because our range-wide density estimate of 0.24 kiang km⁻² (± 0.44, 95% CL) is comparable to kiang densities reported from Tibet. A catastrophic decline during the war and subsequent recovery of the kiang population apparently led to the overstocking perception in Ladakh. In the Hanle Valley, an important area for the kiang, its density was higher (0.56 km⁻²) although even here, we estimated the total forage consumed by kiang to be only 3–4% compared to 96–97% consumed by the large livestock population (78 km⁻²). Our analysis nevertheless suggests that at a localized scale, some herders do face serious forage competition from kiang in key areas such as moist sedge meadows, and thus management strategies also need to be devised at this scale. In-depth socioeconomic surveys are needed to understand the full extent of the conflicts, and herder-centered participatory resolution needs to be facilitated to ensure that a sustainable solution for livelihoods and kiang conservation is achieved.     

Arsenic uptake and phytotoxicity of T-aman rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.) grown in the As-amended soil of Bangladesh

A pot-culture experiment was conducted in open-field conditions with highly cultivated locally transplanted (T) aman rice (Oryza sativa L.) named BR-22 in arsenic (As)-amended soil (0, 1.0, 5.0, 10.0, 20.0, 30.0, 40.0 and 50.0 mg kg⁻¹ As) of Bangladesh to see the effect of As on the growth, yield and metal uptake of rice. Arsenic was applied to soil in the form of sodium arsenate (Na₂HAsO₄). Arsenic affected the plant height, tiller and panicle numbers, grain and straw yield of T-aman rice significantly (P ≤ 0.05). The grain As uptake of T-aman rice was found to increase with increase of As in soil and a high grain As uptake was observed in the treatments of 30–50 mg kg⁻¹ As-containing soil. These levels exceed the food hygiene concentration limit of 1.0 mg kg⁻¹ As. However, the straw As uptake varied significantly (P ≤ 0.05) from a low concentration of As in soil (5 mg kg⁻¹) and the highest uptake was noticed in 20 mg kg⁻¹ As treatment.     

Thermal modeling and analysis of novel twin-chamber community solar cooker as a replacement of biomass-based cooking

A novel design of twin-chamber community solar (TCCS) cooker is presented as a replacement of biomass-based cooking. The novelty of separating a single rectangular cooking chamber into separate twin chambers (of 1-m² aperture area each) improves the cooking performance as opening of one chamber for unloading of food cooked in lesser time (rice) does not disturb the stagnation temperature of the other chamber (pulses and meat) needing more time to cook besides resulting in reduction in side heat loss coefficient due to common wall. Aperture area and cooking volume of TCCS cooker are 9.54 and 35.33 times more as compared to single-chamber domestic solar (SCDS) cooker which makes it a community-scale large-capacity solar cooker. The developed solar radiation capture model and overall heat loss coefficient (U_l) computed for TCCS cooker have been used in a thermal model developed between various interactive components. First (F₁) and second figures of merit (F₂) values are 0.13 and 0.42, respectively, for TCCS cooker at par with ‘A’ grade category SCDS cooker. Techno-economic analysis shows that the net present value of TCCS cooker is Rs. 83,253 with break-even point occurring after cooking 43,461 meals with payback period of only 25, 50, and 72 months if used as a replacement for LPG, cow dung cakes, and wood-based cooking, respectively. Environmental impact analysis shows that the use of the proposed cooker can mitigate 2, 5.9, and 4.1 tonnes of CO₂ emissions every year by not burning LPG, cow dung cakes, and wood respectively.