Assessment of private economic benefits and positive environmental externalities of tea plantation in China

Tea plantations are rapidly expanding in China and other countries in the tropical and subtropical zones, driven by relatively high private economic benefit. However, the impact of tea plantations on the regional environment, including ecosystem services and disservices are unclear. In this study, we developed an assessment framework for determining the private economic benefits and environmental externalities (the algebraic sum of the regulating services and disservices) of tea plantations in China. Our results showed that tea plantations provided private economic benefits of 5,652 yuan ha^?1 year^?1 (7.6 yuan?=?1 USD in 2007) for tea farmers, plus positive environmental externalities of 6,054 yuan ha^?1 year^?1 for the society. The environmental externalities were calculated as the sum of the value of four regulating services, including carbon sequestration (392 yuan ha^?1 year^?1); soil retention (72 yuan ha^?1 year^?1); soil fertility protection (3,189 yuan ha^?1 year^?1) and water conservation (2,685 yuan ha^?1 year^?1), and three disservices, including CO₂ emission (?39 yuan ha^?1 year^?1), N₂O emission (?137 yuan ha^?1 year^?1) and nonpoint source pollution (?108 yuan ha^?1 year^?1). Before the private optimal level, the positive environmental externalities can be maintained by private economic benefits; if a social optimal level is required, subsidies from government are necessary.     

Spatial and temporal estimation of soil loss for the sustainable management of a wet semi-arid watershed cluster

The ungauged wet semi-arid watershed cluster, Seethagondi, lies in the Adilabad district of Telangana in India and is prone to severe erosion and water scarcity. The runoff and soil loss data at watershed, catchment, and field level are necessary for planning soil and water conservation interventions. In this study, an attempt was made to develop a spatial soil loss estimation model for Seethagondi cluster using RUSLE coupled with ARCGIS and was used to estimate the soil loss spatially and temporally. The daily rainfall data of Aphrodite for the period from 1951 to 2007 was used, and the annual rainfall varied from 508 to 1351 mm with a mean annual rainfall of 950 mm and a mean erosivity of 6789 MJ mm ha^?1 h^?1 year^?1. Considerable variation in land use land cover especially in crop land and fallow land was observed during normal and drought years, and corresponding variation in the erosivity, C factor, and soil loss was also noted. The mean value of C factor derived from NDVI for crop land was 0.42 and 0.22 in normal year and drought years, respectively. The topography is undulating and major portion of the cluster has slope less than 10°, and 85.3 % of the cluster has soil loss below 20 t ha^?1 year^?1. The soil loss from crop land varied from 2.9 to 3.6 t ha^?1 year^?1 in low rainfall years to 31.8 to 34.7 t ha^?1 year^?1 in high rainfall years with a mean annual soil loss of 12.2 t ha^?1 year^?1. The soil loss from crop land was higher in the month of August with an annual soil loss of 13.1 and 2.9 t ha^?1 year^?1 in normal and drought year, respectively. Based on the soil loss in a normal year, the interventions recommended for 85.3 % of area of the watershed includes agronomic measures such as contour cultivation, graded bunds, strip cropping, mixed cropping, crop rotations, mulching, summer plowing, vegetative bunds, agri-horticultural system, and management practices such as broad bed furrow, raised sunken beds, and harvesting available water using farm ponds and percolation tanks. This methodology can be adopted for estimating the soil loss from similar ungauged watersheds with deficient data and for planning suitable soil and water conservation interventions for the sustainable management of the watersheds.     

Separate estimation of N export into baseline N leakage without disturbance and N loss due to insect defoliation in a pine forest watershed in central Japan

Pine wilt disease (PWD) is caused by a non-native pest that has spread extensively throughout Japan. Previous research has indicated that most infected trees have died and the litter deposited has resulted in changes to stream-water chemistry, particularly increased nitrate (NO ₃ ^? ) concentrations. In this study, we divided stream nitrogen (N) export into N loss due to PWD and baseline N leakage without disturbance based on long-term monitoring. The annual N export was 110.0 mol N ha^?1 year^?1 in 1990 and 749.8 mol N ha^?1 year^?1 in 1997, and had decreased to 37.0 mol N ha^?1 year^?1 in 2005. N export under PWD influence was estimated to be 3697 mol N ha^?1, and N loss due to PWD was 2810 mol N ha^?1. N loss due to PWD was three times larger than baseline N leakage for the disturbed period. These changes in plant–herbivore relationships could affect N status in a forest ecosystem. So-called “semi-natural” disturbances related to non-native species invasion and increases of atmospheric N deposition caused by human activity will increase. Long-term monitoring studies of various aspects are necessary to offer insight into this ecosystem.     

Vegetation ecology and carbon sequestration potential of shrubs in tropics of Chhattisgarh,India

Tropical forests are well known to have great species diversity and contribute substantial share in terrestrial carbon (C) stocks worldwide. Shrubs are long-neglected life form in the forest ecosystem, playing many roles in the forest and human life. Shrub has great impact on vegetation attributes which in turn modify the C storage and capture. In the present investigation, an attempt has been made to explore the dynamics of shrub species in four fire regimes, viz. high, medium, low, and no fire zones of Bhoramdeo Wildlife Sanctuary of Kawardha forest division (Chhattisgarh), India. The variations in structure, diversity, biomass, productivity, and C sequestration potential in all the sites were quantified. The density and basal area of shrub varied from 1250 to 3750 individuals ha^?1 and 2.79 to 4.92 m² ha^?1, respectively. The diversity indices showed that the value of Shannon index was highest in medium fire zone (3.77) followed by high, low, and no fire zones as 3.25, 3.12, and 2.32, respectively. The value of Simpson’s index or concentration of dominance (Cd) ranged from 0.08 to 0.20, species richness from 0.56 to 1.58, equitability from 1.41 to 1.44, and beta diversity from 1.50 to 4.20, respectively. The total biomass and C storage ranged from 6.82 to 15.71 and from 2.93 to 6.76 t ha^?1, respectively. The shrub density, importance value index (IVI), and abundance to frequency ratio (A/F) significantly correlated between high fire and medium fire zone. The basal area was found to be significantly positively correlated between high fire and medium fire, and low and no fire zones, respectively. Two-way cluster analysis reflected various patterns of clustering due to influence of the forest fire which showed that some species have distant clustering while some have smaller cluster. Principal component analysis (PCA) reflects variable scenario with respect to shrub layer. Ventilago calyculata and Zizyphus rotundifolia showed higher correlation between themselves in terms of basal area (BA). The total shrub production was 1.59–3.53 t ha^?1 year^?1 while the C sequestration potential of 0.71–1.57 t ha^?1 year^?1 under different fire regimes. Shrub community in the medium fire zone reflected higher productivity and higher C sequestration in comparison to other fire zone. Among the different plant parts, the biomass accumulation ratio was highest in the root of shrub community among various fire regimes. Screening of species for restoration and different land-use pattern on the basis of biomass accumulation and carbon sequestering potential would be an effective strategy for decision-making in sustainable forest management.     

Erosivity, surface runoff, and soil erosion estimation using GIS-coupled runoff–erosion model in the Mamuaba catchment, Brazil

This study evaluates erosivity, surface runoff generation, and soil erosion rates for Mamuaba catchment, sub-catchment of Gramame River basin (Brazil) by using the ArcView Soil and Water Assessment Tool (AvSWAT) model. Calibration and validation of the model was performed on monthly basis, and it could simulate surface runoff and soil erosion to a good level of accuracy. Daily rainfall data between 1969 and 1989 from six rain gauges were used, and the monthly rainfall erosivity of each station was computed for all the studied years. In order to evaluate the calibration and validation of the model, monthly runoff data between January 1978 and April 1982 from one runoff gauge were used as well. The estimated soil loss rates were also realistic when compared to what can be observed in the field and to results from previous studies around of catchment. The long-term average soil loss was estimated at 9.4 t ha^?1 year^?1; most of the area of the catchment (60 %) was predicted to suffer from a low- to moderate-erosion risk (<6 t ha^?1 year^?1) and, in 20 % of the catchment, the soil erosion was estimated to exceed >?12 t ha^?1 year^?1. Expectedly, estimated soil loss was significantly correlated with measured rainfall and simulated surface runoff. Based on the estimated soil loss rates, the catchment was divided into four priority categories (low, moderate, high and very high) for conservation intervention. The study demonstrates that the AvSWAT model provides a useful tool for soil erosion assessment from catchments and facilitates the planning for a sustainable land management in northeastern Brazil.     

Biogeochemical indicators of elevated nitrogen deposition in semiarid Mediterranean ecosystems

Nitrogen (N) deposition has doubled the natural N inputs received by ecosystems through biological N fixation and is currently a global problem that is affecting the Mediterranean regions. We evaluated the existing relationships between increased atmospheric N deposition and biogeochemical indicators related to soil chemical factors and cryptogam species across semiarid central, southern, and eastern Spain. The cryptogam species studied were the biocrust-forming species Pleurochaete squarrosa (moss) and Cladonia foliacea (lichen). Sampling sites were chosen in Quercus coccifera (kermes oak) shrublands and Pinus halepensis (Aleppo pine) forests to cover a range of inorganic N deposition representative of the levels found in the Iberian Peninsula (between 4.4 and 8.1 kg N ha^?1 year^?1). We extended the ambient N deposition gradient by including experimental plots to which N had been added for 3 years at rates of 10, 20, and 50 kg N ha^?1 year^?1. Overall, N deposition (extant plus simulated) increased soil inorganic N availability and caused soil acidification. Nitrogen deposition increased phosphomonoesterase (PME) enzyme activity and PME/nitrate reductase (NR) ratio in both species, whereas the NR activity was reduced only in the moss. Responses of PME and NR activities were attributed to an induced N to phosphorus imbalance and to N saturation, respectively. When only considering the ambient N deposition, soil organic C and N contents were positively related to N deposition, a response driven by pine forests. The PME/NR ratios of the moss were better predictors of N deposition rates than PME or NR activities alone in shrublands, whereas no correlation between N deposition and the lichen physiology was observed. We conclude that integrative physiological measurements, such as PME/NR ratios, measured on sensitive species such as P. squarrosa, can provide useful data for national-scale biomonitoring programs, whereas soil acidification and soil C and N storage could be useful as additional corroborating ecosystem indicators of chronic N pollution.     

Quantification of forest fragmentation in pre- and post-establishment periods,inside and around Apuseni Natural Park,Romania

Protected areas (PAs) represent real cornerstones in the conservation of biodiversity and natural habitats. Their protection must be a priority today for each society. The enhanced socio-economic requirements increase the pressure upon protected areas, and the effect can result in a reduction of biodiversity. The aim of this study is to quantify forest fragmentation in the pre- (1986–2002) and post-establishment (2002–2016) periods, inside and around (buffer 1, buffer 2 and buffer 3) Apuseni Natural Park (ANP), Romania, using a series of classified Landsat satellite images and six landscape metrics. The results show that forest fragmentation occurred both in the pre- and post-establishment periods, inside and around ANP. Inside the park, the deforestation rate increased four times, from 0.03% year^?1 in the pre-establishment period to 0.14% year^?1 in the post-establishment period. Around the park, the deforestation rate decreased from 0.31% year^?1 in the pre-establishment period (buffer 1) to 0.10% year^?1 in the post-establishment period (buffer 1). Forest fragmentation resulted in an increase in the patch density and edge density, and a decrease in the total core area and mean patch size leading to isolation of patches and fragmentation of landscape, especially in ANP in the post-establishment period. Several measures can be taken in order to stop forest fragmentation inside and around ANP, including the education of buffer-zone communities, reforestation, enforcement of park regulations, and forest legislation.     

Native plant restoration combats environmental change: development of carbon and nitrogen sequestration capacity using small cordgrass in European salt marshes

Restoration of salt marshes is critical in the context of climate change and eutrophication of coastal waters because their vegetation and sediments may act as carbon and nitrogen sinks. Our primary objectives were to quantify carbon (C) and nitrogen (N) stocks and sequestration rates in restored marshes dominated by Spartina maritima to provide support for restoration and management strategies that may offset negative aspects of eutrophication and climate change in estuarine ecosystems. Sediment C content was between ca. 13 mg C g^?1and sediment N content was ca. 1.8 mg N g^?1. The highest C content for S. maritima was recorded in leaves and stems (ca. 420 mg C g^?1) and the lowest in roots (361?±?4 mg C g^?1). S. maritima also concentrated more N in its leaves (31?±?1 mg N g^?1) than in other organs. C stock in the restored marshes was 29.6 t C ha^?1; ca. 16 % was stored in S. maritima tissues. N stock was 3.6 t N ha^?1, with 8.3 % stored in S. maritima. Our results showed that the S. maritima restored marshes, 2.5 years after planting, were sequestering atmospheric C and, therefore, provide some mitigation for global warming. Stands are also capturing nitrogen and reducing eutrophication. The concentrations of C and N contents in sediments, and cordgrass relative cover of 62 %, and low below-ground biomass (BGB) suggest restored marshes can sequester more C and N. S. maritima plantations in low marshes replace bare sediments and invasive populations of exotic Spartina densiflora and increase the C and N sequestration capacity of the marsh by increasing biomass production and accumulation.     

Aerial and terrestrial-based monitoring of channel erosion,headcutting, and sinuosity

Headcuts are points of accelerated channel erosion that frequently have ecological consequences. A particularly large and dynamic headcut in southwest Wyoming has affected natural and anthropogenic resources for decades. To better understand and address this issue, we undertook a review of the headcut’s upstream retreat, followed by photogrammetric monitoring of the present condition for erosion monitoring. Aerial photography shows the Bitter Creek headcut retreated >?200 m upstream in 68 years (1948–2016) at ~?1.4 m year^?1. Following installation of a concrete slab structure in the mid-1970s, headcut retreat slowed to ~?0.5 m year^?1. Channel sinuosity downstream of the headcut is greater than upstream, which we attribute to the presence of the headcut, given that there are no major changes in valley geometry, geology, or soils through this reach. Both aerial and terrestrial-based image platforms were used to collect stereo imagery and create 3D photogrammetric models of the headcut in 2016. From these two models, we measured soil loss downstream of the headcut at ~?126 m³ m^?1 valley length. Since 1954, soil loss within the channel has been ~?98 m³ year^?1 or ~871 t ha^?1 year^?1since then. Models created from aerial- and terrestrial-based images differed in volumetric estimates by 2%, indicating that either method could be used for this type of monitoring. The ground-based imagery model showed more detail, especially on vertical and overhanging surfaces, while the aerial imagery model produced a more realistic orthomosaic and efficiently covered a larger area. Ground-based image acquisition took longer and was more costly per unit area, but is an efficient method for small project areas, or areas where aerial imagery cannot be safely or practically acquired. Historical imagery and photogrammetric modeling proved very useful in elucidating stream dynamics associated with this large, dynamic headcut.     

Seasonal perspective of dietary arsenic consumption and urine arsenic in an endemic population

Exposure to arsenic in arsenic endemic areas is most remarkable environmental health challenges. Although effects of arsenic contamination are well established, reports are unavailable on probable seasonal variation due to changes of food habit depending on winter and summer seasons, especially for endemic regions of Nadia district, West Bengal. Complete 24-h diets, drinking–cooking water, first morning voided urine samples, and diet history were analyzed on 25 volunteers in arsenic endemic Chakdah block of Nadia district, once in summer followed by once in winter from the same participants. Results depicted no seasonal variation of body weight and body mass index. Arsenic concentration of source drinking and cooking water decreased (p?=?0.04) from 26 μg L^?1 in summer to 6 μg L^?1 in winter season. We recorded a seasonal decrease of water intake in male (3.8 and 2.5 L day ^?1) and female (2.6 and 1.2 L day^?1) participants from summer to winter. Arsenic intake through drinking water decreased (p?=?0.04) in winter (29 μg day^?1) than in summer (100 μg day^?1), and urinary arsenic concentration decreased (p?=?0.018) in winter (41 μg L^?1) than in summer (69 μg L^?1). Dietary arsenic intake remained unchanged (p?=?0.24) over the seasons. Hence, we can infer that human health risk assessment from arsenic needs an insight over temporal scale.     

Affects of mining activities on Cd pollution to the paddy soils and rice grain in Hunan province, Central South China

Located in Central South China, Hunan province is rich in mineral resources. To study the influence of mining on Cd pollution to local agricultural eco-system, the paddy soils and rice grain of Y county in northern Hunan province were intensively monitored. The results were as follows: (1) Total Cd (T-Cd) content in the soils of the county ranges from 0.13 to 6.02 mg kg^?1, with a mean of 0.64 mg kg^?1, of which 57.5 % exceed the allowable limit specified by the China Soil Environmental Quality Standards. T-Cd in the soils varies largely, with the coefficient of variation reaching 146.4 %. The spatial distribution of T-Cd in the soils quite matches with that of mining and industries. The content of HCl-extractable Cd (HCl-Cd) in the soils ranges from 0.02 to 2.17 mg kg^?1, with a mean of 0.24 mg kg^?1. A significant positive correlation exists between T-Cd and HCl-Cd in the soils (r?=?0.770, ρ?<?0.01). (2) Cd content in the rice produced in Y county ranges from 0.01 to 2.77 mg kg^?1, with a mean of 0.46 mg kg^?1. The rate of rice with Cd exceeding the allowable limit specified by the Chinese Grain Security Standards reaches 59.6 %; that with Cd exceeding 1 mg kg^?1, called as “Cd rice,” reaches 11.1 %. (3) Cd content in the rice of Y county is positively significantly correlated with HCl-Cd (r?=?0.177, ρ?<?0.05) but not significantly with T-Cd in the soils (r?=?0.091, ρ?>?0.05), which suggests that the amount of Cd accumulating in the rice is more affected by its availability in the soils, rather than the total content. (4) The dietary intake of Cd via rice consumption in Y county is estimated to be 179.9 μg day^?1 person^?1 on average, which is far beyond the allowable limit specified by FAO/WHO and the target hazard quotients of Cd much higher than 1, suggesting the high risk on human health from Cd exposure.     

Biological endpoints, enzyme activities, and blood cell parameters in two anuran tadpole species in rice agroecosystems of mid-eastern Argentina

Different biological variables of tadpoles, including survival, development and growth rates, and biomarkers [cholinesterases, glutathione-S-transferases (GST), and blood cell morphology] were evaluated in two anuran species, Scinax squalirostris (Hylidae) and Leptodactylus mystacinus (Leptodactylidae), using in situ experimental chambers in a rice field (RF) sprayed with insecticide Lambda-cyhalothrin (LTC) by aircraft in Santa Fe Province, Argentina. We found a significant decrease in body weight (0.62?±?0.04 g) of L. mystacinus and an increased development rate of S. squalirostris in individuals from RF (41?±?1; Gosner) with respect to individuals from the reference site (RS: 0.93?±?0.04 g and 37?±?0; respectively). In S. squalirostris, individuals from RF mean values of butyrylcholinesterase activities decreased at 48 (4.09?±?0.32 nmol min^-1 mg^-1 of TP) and 96 h (3.74?±?0.20 nmol min^-1 mg^-1 of TP), whereas inhibition of acetylcholinesterase was observed at 96 h (47.44?±?2.78 nmol min^-1 mg^-1 of TP). In L. mystacinus from RF, an induction of acetylcholinesterase activity was observed at 96 h (36.01?±?1.09 nmol min^-1 mg^-1 of TP). Glutathione-S-transferase levels varied between species, being higher in L. mystacinus individuals but lower in S. squalirostris from RF at 48 (272.29 ±11.78 and 71.87?±?1.70 nmol min^-1 mg^-1 of TP; respectively) and 96 h (279.25?±?13.06 and 57.62?±?4.58 nmol min^-1 mg^-1 of TP, respectively). Blood cell parameters revealed a lower number of mitotic cells (MC: 0.36?±?0.31%o for S. squalirostris and 0.08?±?0.05 %o for L. mystacinus) and higher number of eosinophils (E: 3.45?±?1.75 %o for S. squalirostris and 7.64?±?0.98 %o for L. mystacinus) in individuals from the RF than in individuals from the RS (MC: 2.55?±?0.74 %o for S. squalirostris and 1.87?±?0.72%o for L. mystacinus; and E: 0.13?±?0.09 for S. squalirostris and 3.20?±?0.80 for L. mystacinus). Overall, our results demonstrate the existence of apparent differences in sensitivity between species in a series of sublethal responses to short-term exposure in RF after the application of Lambda-cyhalothrin. We suggest that the integral use of biological endpoints (development and growth) together with biomarkers (cholinesterase, GST, and blood cell parameters) may be a promising integral procedure for investigating pesticide exposure in wild frog populations.     

Mapping aboveground woody biomass using forest inventory,remote sensing and geostatistical techniques

Mapping forest biomass is fundamental for estimating CO₂ emissions, and planning and monitoring of forests and ecosystem productivity. The present study attempted to map aboveground woody biomass (AGWB) integrating forest inventory, remote sensing and geostatistical techniques, viz., direct radiometric relationships (DRR), k-nearest neighbours (k-NN) and cokriging (CoK) and to evaluate their accuracy. A part of the Timli Forest Range of Kalsi Soil and Water Conservation Division, Uttarakhand, India was selected for the present study. Stratified random sampling was used to collect biophysical data from 36 sample plots of 0.1 ha (31.62 m?×?31.62 m) size. Species-specific volumetric equations were used for calculating volume and multiplied by specific gravity to get biomass. Three forest-type density classes, viz. 10–40, 40–70 and >70 % of Shorea robusta forest and four non-forest classes were delineated using on-screen visual interpretation of IRS P6 LISS-III data of December 2012. The volume in different strata of forest-type density ranged from 189.84 to 484.36 m³ ha^?1. The total growing stock of the forest was found to be 2,024,652.88 m³. The AGWB ranged from 143 to 421 Mgha^?1. Spectral bands and vegetation indices were used as independent variables and biomass as dependent variable for DRR, k-NN and CoK. After validation and comparison, k-NN method of Mahalanobis distance (root mean square error (RMSE)?=?42.25 Mgha^?1) was found to be the best method followed by fuzzy distance and Euclidean distance with RMSE of 44.23 and 45.13 Mgha^?1 respectively. DRR was found to be the least accurate method with RMSE of 67.17 Mgha^?1. The study highlighted the potential of integrating of forest inventory, remote sensing and geostatistical techniques for forest biomass mapping.     

Effect of land use land cover change on soil erosion potential in an agricultural watershed

Universal soil loss equation (USLE) was used in conjunction with a geographic information system to determine the influence of land use and land cover change (LUCC) on soil erosion potential of a reservoir catchment during the period 1989 to 2004. Results showed that the mean soil erosion potential of the watershed was increased slightly from 12.11 t ha^???1 year^???1 in the year 1989 to 13.21 t ha^???1 year^???1 in the year 2004. Spatial analysis revealed that the disappearance of forest patches from relatively flat areas, increased in wasteland in steep slope, and intensification of cultivation practice in relatively more erosion-prone soil were the main factors contributing toward the increased soil erosion potential of the watershed during the study period. Results indicated that transition of other land use land cover (LUC) categories to cropland was the most detrimental to watershed in terms of soil loss while forest acted as the most effective barrier to soil loss. A p value of 0.5503 obtained for two-tailed paired t test between the mean erosion potential of microwatersheds in 1989 and 2004 also indicated towards a moderate change in soil erosion potential of the watershed over the studied period. This study revealed that the spatial location of LUC parcels with respect to terrain and associated soil properties should be an important consideration in soil erosion assessment process.     

Temporal variability in water quality parameters—a case study of drinking water reservoir in Florida, USA

Our objective was to evaluate changes in water quality parameters during 1983–2007 in a subtropical drinking water reservoir (area: 7 km²) located in Lake Manatee Watershed (area: 338 km²) in Florida, USA. Most water quality parameters (color, turbidity, Secchi depth, pH, EC, dissolved oxygen, total alkalinity, cations, anions, and lead) were below the Florida potable water standards. Concentrations of copper exceeded the potable water standard of <30 μg?l^?1 in about half of the samples. About 75 % of total N in lake was organic N (0.93 mg?l^?1) with the remainder (25 %) as inorganic N (NH₃-N: 0.19, NO₃-N: 0.17 mg?l^?1), while 86 % of total P was orthophosphate. Mean total N/P was <6:1 indicating N limitation in the lake. Mean monthly concentration of chlorophyll-a was much lower than the EPA water quality threshold of 20 μg?l^?1. Concentrations of total N showed significant increase from 1983 to 1994 and a decrease from 1997 to 2007. Total P showed significant increase during 1983–2007. Mean concentrations of total N (n?=?215; 1.24 mg?l^?1) were lower, and total P (n?=?286; 0.26 mg?l^?1) was much higher than the EPA numeric criteria of 1.27 mg total N l^?1 and 0.05 mg total P l^?1 for Florida’s colored lakes, respectively. Seasonal trends were observed for many water quality parameters where concentrations were typically elevated during wet months (June–September). Results suggest that reducing transport of organic N may be one potential option to protect water quality in this drinking water reservoir.     

Persistence behaviour of imidacloprid and its metabolites in soil under sugarcane

The persistence and metabolism of imidacloprid in soil under sugarcane were studied following application of imidacloprid at 20 and 80 g active ingredient (a.i.) ha^?1. Soil samples were collected at different time intervals (7, 15, 30, 45, 60 and 90 days after application), and the residues of imidacloprid and its metabolites (6-chloronicotinic acid, nitrosimine, imidacloprid-NTG, olefin, urea and 5-hydroxy) were quantified by high-performance liquid chromatography. In soil, the total imidacloprid residues were mainly constituted by the parent compound followed by 6-chloronicotinic acid, nitrosimine and imidacloprid-NTG metabolites. Maximum residues of imidacloprid and its metabolites were 4.29 and 7.81 mg kg^?1 in soil samples collected 7 days after the application of imidacloprid at 20 and 80 g a.i. ha^?1, respectively. At both doses, these residues declined to below the detectable limit in soil after 90 days of application. Olefin, urea and 5-hydroxy metabolites were not detected in soil. Dissipation of total imidacloprid residues did not follow the first-order kinetics with a coefficient of determination value of 0.883 and 0.838 for the recommended dose and four times the recommended dose, respectively. The half-life (T _1/2) value of total imidacloprid was observed to be 10.64 and 10.10 days for the recommended dose and four times the recommended dose, respectively.     

Dissipation and residue behavior of mepiquat on wheat and potato field application

A modified LC-MS method for the analysis of mepiquat residue in wheat, potato, and soil was developed and validated. A hydrophilic interaction liquid chromatographic column has been successfully used to retain and separate the mepiquat. Mepiquat residue dynamics and final residues in supervised field trials at Good Agricultural Practice (GAP) conditions in wheat, potato, and soil were studied. The limits of quantification for mepiquat in all samples were all 0.007 mg kg^?1, which were lower than their maximum residue limits. At fortification levels of 0.04, 0.2, and 2 mg kg^?1 in all samples, recoveries ranged from 77.5 to 116.4 % with relative standard deviations of 0.4–7.9 % (n?=?5). The dissipation half-lives (T _1/2) of mepiquat in soil (wheat), wheat plants, soil (potato), and potato plants were 4.5–6.3, 3.0–5.6, 2.2–4.6, and 2.4–3.2 days, respectively. The final residues of mepiquat were below 0.153 mg kg^?1 in soil (wheat), 0.052–1.900 mg kg^?1 in wheat, below 0.072 mg kg^?1 in soil (potato), and below 1.173 mg kg^?1 in potato at harvest time. Moreover, pesticide risk assessment for all the detected residues was conducted. A maximum 0.0012 % of acceptable daily intake (150 mg kg^?1) for national estimated daily intake indicated low dietary risk of these products.     

Influence of the insecticides acetamiprid and carbofuran on arylamidase and myrosinase activities in the tropical black and red clay soils

The objective of this study was to determine the effects of two insecticides, namely, acetamiprid and carbofuran on the enzymatic activities of arylamidase (as glucose formed from sinigrin) and myrosinase (as β-naphthylamine formed from l-leucine β-naphthylamide) in the black and red clay soils collected from a fallow groundnut (Arachis hypogaea L.) fields in the Anantapur District, Andhra Pradesh, India. The study was realized within the framework of the laboratory experiments in which the acetamiprid and carbofuran were applied to the soils at different doses (1.0, 2.5, 5.0, 7.5, 10.0 kg ha^?1). Initially, the physicochechemical properties of the soil samples were analyzed. After 10 days of pesticide application, the soil samples were analyzed for the enzyme activities. Acetamiprid and carbofuran stimulated the arylamidase and myrosinase activities at lower concentrations after 10 days incubation. Striking stimulation in soil enzyme activities was noticed at 2.5 kg ha^?1, persists for 20 days in both the soils. Overall, higher concentrations (5.0–10.0 kg ha^?1) of acetamiprid and carbofuran were toxic or innocuous to the arylamidase and myrosinase activities. Nevertheless, the outcomes of the present study clearly indicate that the use of these insecticides (at field application rates) in the groundnut fields (black and red clay soils) stimulated the enzyme (arylamidase and myrosinase) activities.     

Determination of trace amounts of zirconium in real samples after microwave digestion and ternary complex dispersive liquid–liquid microextraction

In this study, a ternary Zr(IV) system with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) and fluoride was chosen on the basis of dispersive liquid–liquid microextraction method. Zirconium was extracted into the fine droplets of dichlorobenzene as extracting solvent. These drops dispersed as a cloud in the aqueous sample with the help of ultrasonic waves, and the procedure was done. Finally, atomic absorption spectrometry was applied for the determination of zirconium. The effects of different factors that influence complex formation and extraction, such as pH, amounts of complexing agents, type and volume of the extracting solvent, as well as sonication and centrifuging time, were optimized. Under optimum conditions, the calibration curve was linear in the range of 150.0–800.0 ng mL^?1 with a limit of detection of 44.0 ng mL^?1. Relative standard deviation was calculated to be 4.1 % (n?=?7, c?=?400.0 ng mL^?1). The enrichment factor was 80. The proposed method was successfully used to determine the zirconium in several water, wastewater, and soil samples.     

Environmental fate of chlorantraniliprole residues on cauliflower using QuEChERS technique

Chlorantraniliprole, an anthranilic diamide insecticide with novel mode of action is found effective against several lepidopteran as well as coleopteran, dipteran, and hemipteran pests. The present studies were carried out to study the dissipation pattern of chlorantraniliprole on cauliflower and to suggest suitable waiting period for the safety of consumers. Quick, easy, cheap, effective, rugged, and safe method was used for the extraction and cleanup of samples and the residues of chlorantraniliprole were estimated using high-performance liquid chromatograph (HPLC) and confirmed by liquid chromatograph–mass spectrometer and high-performance thin layer chromatograph. Following three applications of chlorantraniliprole (Coragen 18.5 SC) at recommended dose (9.25 g a.i.?ha^?1) and double the recommended dose (18.50 g a.i.?ha^?1), the average initial deposits of chlorantraniliprole were observed to be 0.18 and 0.29 mg kg^?1, respectively. These deposits were found to be less than the maximum residue limit of 2.0 mg kg^?1 prescribed by the Codex Alimentarius Commission. These residues dissipated below the limit of quantification of 0.10 mg kg^?1 after 3 and 5 days at recommended and double the recommended dosages, respectively. The half-life value (T _1/2) of chlorantraniliprole was worked out to be 1.36 days following its application at recommended dosages. Hence, the use of this pesticide at recommended dosages does not seem to pose any risk, and a waiting period of 1 day is suggested for safe consumption of cauliflower curds.