Biogeochemical responses to nutrient inputs in a Cuban coastal lagoon: runoff, anthropogenic, and groundwater sources

Laguna Larga, a coastal lagoon in central Cuba, has been heavily altered by tourism infrastructure construction and sewage disposal. We hypothesize that this has decreased the circulation and caused eutrophication of the lagoon. To assess this, 12 bimonthly samplings were carried out in 2007–2008. Temperature, salinity, oxygen, nutrients and nitrogen, and phosphorous fractions (inorganic, organic, and total) were determined. Water and salt budgets, as well as biogeochemical fluxes of nitrogen and phosphorus were calculated using the LOICZ budget model for the three sections of the lagoon identified by morphological constrains and salinity patterns. Laguna Larga is a choked lagoon with restricted water circulation, low exchange, and high residence times that vary significantly along its sections. Residence time was estimated to be 0.1–0.7 years for the inner section and 1–9 days for the outer one. High levels of total nitrogen (annual means 126–137 μM, peaks up to 475 μM) and phosphorus (2.5–4.4 μM, peaks up to 14.5 μM) are evidence of eutrophication of Laguna Larga. During 2007, an average precipitation year, Laguna Larga exported water (703 m³ d^?1) and was a source of nitrogen (9.026 mmol m^?2 d^?1) and phosphorus (0.112 mmol m^?2 d^?1) to the adjacent sea. δ¹⁵N determinations in the seagrass Thalassia testudinum (?1.83 to +3.02?‰) differed significantly between sites in the lagoon and offshore reference sites located W of the inlet, but were similar to those located E of the inlet. δ¹⁵N determinations in the seaweed Penicillus dumetosus (+1.02 to +4.2) did not show significant differences.     

Biological response to physical processes in the Indian Ocean sector of the Southern Ocean: a case study in the coastal and oceanic waters

The spatial variation of chlorophyll a (Chl a) and factors influencing the high Chl a were studied during austral summer based on the physical and biogeochemical parameters collected near the coastal waters of Antarctica in 2010 and a zonal section along 60°S in 2011. In the coastal waters, high Chl a (>3 mg m^?3) was observed near the upper layers (～15 m) between 53°30′E and 54°30′E. A comparatively higher mesozooplankton biomass (53.33 ml 100 m^?3) was also observed concordant with the elevated Chl a. Low saline water formed by melting of glacial ice and snow, as well as deep mixed-layer depth (60 m) due to strong wind (>11 ms^?1) could be the dominant factors for this biological response. In the open ocean, moderately high surface Chl a was observed (>0.6 mg m^?3) between 47°E and 50°E along with a Deep Chlorophyll Maximum of ～1 mg m^?3 present at 30–40 m depth. Melt water advected from the Antarctic continent could be the prime reason for this high Chl a. The mesozooplankton biomass (22.76 ml 100 m^?3) observed in the open ocean was comparatively lower than that in the coastal waters. Physical factors such as melting, advection of melt water from Antarctic continent, water masses and wind-induced vertical mixing may be the possible reasons that led to the increase in phytoplankton biomass (Chl a).     

Assessment of physico-chemical qualities and heavy metal concentrations of Umgeni and Umdloti Rivers in Durban,South Africa

We assessed the effects of seasonal dynamics on the physico-chemical qualities and heavy metals concentrations of the Umgeni and Umdloti Rivers in Durban, South Africa. Water samples were taken from nine different sampling points and analysed for the following parameters; temperature, pH, turbidity, electrical conductivity (EC), biological oxygen demand (BOD₅), chemical oxygen demand (COD), phosphate (PO₄ ^2?), nitrate (NO₃ ^2?), ammonium (NH₄ ⁺), sulphate (SO₄ ^2?), lead (Pb²⁺), mercury (Hg²⁺), cadmium (Cd²⁺), aluminium (Al³⁺), and copper (Cu²⁺) using standard methods. The data showed variations it terms of the seasonal fluctuations and sampling regime as follows: temperature 12–26.5 °C; pH 5.96–8.45; turbidity 0.53–18.8 NTU; EC 15.8–5180 mS m^?1; BOD₅ 0.60–7.32 mg L^?1; COD 10.5–72.9 mg L^?1; PO₄ ^2??<?500–2,460 μg L^?1; NO₃ ^2? <0.05–4.21 mg L^?1; NH₄ ⁺?<?0.5–1.22 mg L^?1; SO₄ ^2? 3.90–2,762 mg L^?1; Pb²⁺ 0.023–0.135 mg L^?1; Hg²⁺ 0.0122–0.1231 mg L^?1 Cd²⁺ 0.068–0.416 mg L^?1; Al³⁺ 0.037–1.875 mg L^?1, and Cu²⁺0.006–0.144 mg L^?1. The concentrations of most of the investigated parameters exceeded the recommended limit of the South African Guidelines and World Health Organization tolerance limits for freshwater quality. We conclude that these water bodies are potentially hazardous to public health and this highlights the need for implementation of improved management strategies of these river catchments for continued sustainability.     

Heavy metals in the habitat and throughout the food chain of the Neotropical otter, Lontra longicaudis, in protected Mexican wetlands

Top predators like the Neotropical otter, Lontra longicaudis annectens, are usually considered good bioindicators of habitat quality. In this study, we evaluated heavy metal contamination (Hg_tot, Pb, Cd) in the riverine habitat, prey (crustaceans and fish), and otter feces in two Ramsar wetlands with contrasting upstream contamination discharges: Río Blanco and Río Caño Grande in Veracruz, Mexico, during the dry, the wet, and the nortes seasons. Most comparisons revealed no differences between sites while seasonal differences were repeatedly detected for all of the compartments. Higher concentrations of Pb during the dry season and of Cd during the wet season in otter feces mirrored differences detected in the most seasonally consumed prey. Compared with fecal methylmercury values reported for the European otter (0.25–0.75 mg kg^?1) in unprotected areas, the Hg_tot levels that we measured were lower (0.02–0.17 mg kg^?1). However, Pb (117.87 mg kg^?1) and Cd (9.14 mg kg^?1) concentrations were higher (Pb, 38.15 mg kg^?1 and Cd, 4.72 mg kg^?1) in the two Ramsar wetlands. Protected areas may shelter species, but those with water-linked diets may suffer the effect of chemicals used upstream.     

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.     

Community metabolism in a deep (stratified) tropical reservoir during a period of high water-level fluctuations

As long as lakes and reservoirs are an important component of the global carbon cycle, monitoring of their metabolism is required, especially in the tropics. In particular, the response of deep reservoirs to water-level fluctuations (WLF) is an understudied field. Here, we study community metabolism through oxygen dynamics in a deep monomictic reservoir where high WLF (~10 m) have recently occurred. Simultaneous monitoring of environmental variables and zooplankton dynamics was used to assess the effects of WLF on the metabolism of the eutrophic Valle de Bravo (VB) reservoir, where cyanobacteria blooms are frequent. Mean gross primary production (P _g) was high (2.2 g C m^?2 day^?1), but temporal variation of P _g was low except for a drastic reduction during circulation attributed to zooplankton grazing. The trophogenic layer showed net autotrophy on an annual basis, but turned to net heterotrophy during mixing, and furthermore when the whole water-column oxygen balance was calculated, considering the aphotic respiration (R _aphotic). The high total respiration resulting (3.1 g C m^?2 day^?1) is considered to be partly due to mixing enhanced by WLF. Net ecosystem production was equivalent to a net export of 3.4 mg CO₂?m^?2 day^?1 to the atmosphere. Low water levels are posed to intensify boundary-mixing events driven by the wind during the stratification in VB. Long-term monitoring showed changes in the planktonic community and a strong silicon decrease that matched with low water-level periods. The effects of low water-level on metabolism and planktonic community in VB suggest that water-level manipulation could be a useful management tool to promote phytoplankton groups other than cyanobacteria.     

An assessment of contamination of the Fusaro Lagoon (Campania Province,southern Italy) by trace metals

The Fusaro Lagoon is a shallow lagoon, located in SW Italy, largely influenced in the last decades by several anthropic impacts. The study examined the pollution status of the lagoon, during year 2011–2012 at nine sampling stations with the aim to find out proper measurements of water lagoon restoration. Concentrations of heavy metals (HMs) (aluminium [Al], barium [Ba], cadmium [Cd], copper [Cu], iron [Fe], manganese [Mn], vanadium [V] and zinc [Zn]) were examined in water, sediments and specimens of the ascidian Ciona intestinalis sp. A. Low levels of dissolved oxygen concentration were detected at many stations, with mean values of 5.2–6.4 mg L^?1. The redox potential of surface waters was also low, ?2.7 to 50.7 mV. Sediments possessed high organic matter content, 17.7–29.4 %. In sediments, the mean Zn level, 251.4 mg kg^?1, was about sixfold higher than that recorded in year 2000 (38.5 mg kg^?1) and considerably higher than that recorded in 2007 (191 mg kg^?1). The mean levels of Cd were outstandingly high, with a mean value of 70.5 mg kg^?1, about 30- and 50-fold higher than those determined in 2000 and 2007, respectively. Cadmium (Cd), Cu and nickel (Ni) appeared in excess with respect to most current guidelines, reaching significant pollution levels. C. intestinalis sp. A was detected only at few stations, with metals accumulated preferentially in the body in respect to the tunic, from 1.2 times for Zn (178 mg kg^?1) to 4.0 times for V (304 mg kg^?1). Data suggests the necessity of an immediate action of eco-compatible interventions for environmental restoration.     

Monitoring and assessing variation of sewage quality and microbial functional groups in a trunk sewer line

In this study, the variation of sewage quality was investigated and the active fraction of different microbial functional groups in biofilm was quantified in a 5.6-km trunk sewer line. The sewage quality including suspended solids, biochemical oxygen demand, total chemical oxygen demand (COD), total nitrogen, total Kjeldahl nitrogen, ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen were measured and compared with the values in literatures. The results indicated that since the wastewater treatment plant was not operated at its full capacity, the concentrations of different compounds were lower compared with the values in literatures. The values of heterotrophic growth rate constant lay between 5.6 and 8.6 day^???1. Its average value was 7.7 day^???1. The values of heterotrophic lysis rate constant lay between 0.2 and 0.4 day^???1. The active heterotrophic biomass in biofilm varied from 240 to 800 mg COD m^???2 and average value was 497 mg COD m^???2. The biofilm mass varied from 880 to 1,080 mg m^???2. The percentage of heterotroph to biofilm mass fall within the range of 24.0–90.9% and average value was 52.9%. In the oxygen uptake rate batch tests, the biomass, growth rate constant, and lysis rate constant of autotroph could not be determined because the fraction of autotroph in biofilm was relatively few. It revealed that the degradation of organic matters, nitrification, and denitrification occurred in the trunk sewer line. But the results indicate that the condition seem favorable for nitrification.     

UV/H2O2 oxidation of arsenic and terbuthylazine in drinking water

Arsenic is a widespread contaminant in the environment. The intake of water containing high concentrations of arsenic could have serious impact on human health, such as skin and lung cancer. In the European Union, thus, also in Italy, the arsenic limit in drinking water is 10 μg L^?1. Several water remediation treatment technologies are available for arsenic removal. For some processes, the removal efficiencies can be improved after an oxidation step. Most full-scale applications are based on conventional oxidation processes for chemical micropollutant removal. However, if water contains arsenic and refractory organic contaminants, the advanced oxidation processes could be considered. The aim of this work was to investigate the effectiveness of ultraviolet (UV) radiation alone and in combination with hydrogen peroxide for the oxidation of arsenic and terbuthylazine (TBA). The experimental tests were performed in groundwater at the laboratory scale (0.1 mg L^?1 As(III) and 10 μg L^?1 TBA). Hydrogen peroxide alone (15 mg L^?1) was ineffective on both arsenic and TBA oxidation; the 253.7-nm radiation alone did not oxidize arsenic(III), but photolyzed efficiently TBA (52 % removal yield at a UV dose of 1,200 mJ cm^?2). The UV/H₂O₂ advanced oxidation (UV dose 600–2,000 mJ cm^?2, 5–15 mg L^?1 H₂O₂) was the most effective process for the oxidation of both arsenic and TBA, with observed oxidation efficiencies of 85 and 94 %, respectively, with 5 mg L^?1 H₂O₂ and a UV dose of 2,000 mJ cm^?2.     

Adsorption-desorption and leaching potential of glyphosate and aminomethylphosphonic acid in acidic Malaysian soil amended with cow dung and rice husk ash

This study investigates adsorption-desorption and the leaching potential of glyphosate and aminomethylphosphonic acid (AMPA) in control and amended—addition of cow dung or rice husk ash—acidic Malaysian soil with high oxide mineral content. The addition of cow dung or rice husk ash increased the adsorptive removal of AMPA. The isotherm data of glyphosate and AMPA best fitted the Freundlich model. The constant K_f for glyphosate was high in the control soil (544.873 mg g^?1) followed by soil with cow dung (482.451 mg g^?1) then soil with rice husk ash (418.539 mg g^?1). However, for AMPA, soil with cow dung was high (166.636 mg g^?1) followed by soil with rice husk ash (137.570 mg g^?1) then the control soil (48.446 mg g^?1). The 1/n values for both glyphosate and AMPA adsorptions were <?1 indicating their strong affinity for adsorbents. Desorption of both glyphosate and AMPA occurred only in the control soil. The compounds were not detected in soils with added cow dung or rice husk ash. The addition of cow dung or rice husk ash increased glyphosate mobility. However, ground water ubiquity scores for both control and amended soils were <?2.8. This indicated glyphosate is a transitional herbicide; therefore, its leaching potential in the soil is low, despite the addition of cow dung or rice husk ash. Addition of these wastes decreased the mobility and leaching potential of AMPA. The addition of cow dung or rice husk ash could be beneficial in increasing adsorption and enhancing degradation of these compounds.     

Groundwater quality assessment in the urban-west region of Zanzibar Island

This paper highlights the levels of anions (nitrate, nitrite, sulfate, bromide, chloride, and fluoride) and cations (potassium, sodium, magnesium, and calcium) in selected springs and groundwater sources in the urban-west region of Zanzibar Island. The levels of total dissolved solids (TDS) and sodium adsorption ratio (SAR) were also studied. Thirty water samples were collected in December 2012 from various types of water sources, which included closed hand-dug wells (CHDW), open hand-dug wells (OHDW), springwater (SW), public bore wells (PBW), and bore wells owned by private individuals (BWP), and analyzed after filtration and sometimes dilution. The cations were analyzed using inductively coupled plasma-optical emission spectrometry (ICP-OES). The anions were analyzed by chemically suppressed ion chromatography (IC). The ranges of the levels of the investigated parameters were as follows: Na 13.68–3,656 mg L^?1, K 2.66–583 mg L^?1, Mg 0.63–131.10 mg L^?1, Ca 16.79–189.9 mg L^?1, Cl^? 8.61–4,340.97 mg L^?1, F^? 0–1.02 mg L^?1, Br^? 0–10.88 mg L^?1, NO₃ ^? 0.18–342.4 mg L^?1, NO₂ ^? 0–1.39, SO₄ ^2? 4.43–534.02 mg L^?1, TDS 7–6,380 mg L^?1, and SAR 0.63–50. Except fluoride, most of the studied parameters in the water samples had concentrations beyond the permissible limits of the World Health Organization (WHO). The elevated concentrations are a result of seepage of contaminated water from on-site septic tanks, pit latrines, landfill leachates, fertilizer applications, and domestic effluents. These results should alert domestic water stakeholders in Zanzibar to the urgent task of initiating a quick mitigation response to control these alarming water risks.     

Phosphorus sorption–desorption behaviour of river bed sediments in the Abshineh river, Hamedan, Iran, related to their composition

Phosphorus (P) sorption by sediments may play a vital role in buffering P concentration in the overlying water column. To characterize P sorption–desorption in the river bed sediments, 17 bed sediment samples collected from Abshineh river, in a semi arid region, Hamedan, western Iran were studied through a batch experiment and related to sediment composition. The sorbed fraction ranged from 4.4% to 5.4% and from 38.5% to 86.0% of sorption maxima when 20 and 1,500 mg P kg^?1, respectively, was added to the sediment samples. Phosphorus sorption curves were well fitted to the Langmuir model. Zero equilibrium P concentration ranged from 0.10 to 0.51 mg P l^?1 and varied with sediment characteristics. Phosphorus desorption differed strongly among the studied bed sediments and ranged from 10.8% to 80.2% when 1,500 mg P kg^?1 was added. The results of the geochemical modelling indicated that even under low P addition (2 mg l^?1), the solutions are mainly saturated with respect to hydroxyapatite and ß-tricalcium phosphate minerals and undersaturated with respect to other Ca and Mg minerals, whereas under higher P addition (150 mg l^?1), most Ca–P solid phases, except the most soluble mineral (brushite), will likely precipitate. A Langmuir sorption maximum was positively correlated with carbonate calcium. Estimated P retention capacity of the bed sediments are generally lower and zero equilibrium P concentration values higher in upstream sites than at the downstream sites, suggesting that sediments in upstream and downstream may act as source and sink of P, respectively.     

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.     

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.     

Variation of phytoplankton assemblages of Kongsfjorden in early autumn 2012: a microscopic and pigment ratio-based assessment

Phytoplankton species distribution and composition were determined by using microscopy and pigment ratios in the Kongsfjorden during early autumn 2012. Variation in sea surface temperature (SST) was minimal and matched well with satellite-derived SST. Nutrients were generally limited. Surface phytoplankton abundance ranged from 0.21?×?10³ to 10.28?×?10³ cells L^?1. Phytoplankton abundance decreased with depth and did not show any significant correlation with chlorophyll a (chl a). Column-integrated phytoplankton cell counts (PCC) ranged from 94.3?×?10⁶ cells m^?2 (Kf4) to 13.7?×?10⁶ cells m^?2 (Kf5), while chl a was lowest at inner part of the fjord (6.3 mg m^?2) and highest towards the mouth (24.83 mg m^?2). Biomass from prymnesiophytes and raphidophytes dominated at surface and 10 m, respectively. The contribution of Bacillariophyceae to biomass was low. Generally, heterotrophic dinoflagellates were great in abundance (12.82 %) and ubiquitous in nature and were major contributors to biomass. Various chl pigments (chl b, chl c, phaeopigments (phaeo)) were measured to obtain pigment/chl a ratios to ascertain phytoplankton composition. Phaeo were observed only in inner fjord. Chl b:a ratios and microscopic observations indicated dominance of Chlorophyceae at greater depths than surface. Furthermore, microscopic observations confirmed dominance of chl c containing algae throughout the fjord. The study indicates that pigment ratios can be used as a tool for preliminary identification of major phytoplankton groups. However, under the presence of a large number of heterotrophic dinoflagellates such as Gymnodinium sp. and Gyrodinium sp., pigment signatures need to be supplemented by microscopic observations.     

Metabolic degradation of imidacloprid in paddy field soil

The metabolic degradation and persistence of imidacloprid in paddy field soil were investigated following two applications of imidacloprid at 20 and 80 g a.i. ha^?1 at an interval of 10 days. The soil samples were collected at various time intervals. The limit of quantification for the analysis of imidacloprid and its metabolites was obtained at the concentration of 0.01 mg kg^?1. The initial deposits of total imidacloprid were found to be 0.44 and 1.61 mg kg^?1 following second applications. These residues could not be detected after 60 and 90 days following second applications of imidacloprid at lower and higher dosages, respectively. In soil, urea metabolite was found to be the maximum, followed by olefine, nitrosimine, 6-chloronicotinic acid, 5-hydroxy and nitroguanidine. The half-life values (t _1/2) of imidacloprid were worked out to be 12.04 and 11.14 days, respectively, when applied at lower and higher doses, respectively.     

Dissipation and residues determination of propamocarb in ginseng and soil by high-performance liquid chromatography coupled with tandem mass spectrometry

Two-year field trials were performed at two experimental sites to investigate dissipation and terminal residues of propamocarb in ginseng root, stem, leaf, and soil by high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS). Mean recoveries ranged from 80.5 to 95.6 % with relative standard deviations (RSDs) of 5.5–9.1 % at fortified levels of 0.01, 0.02, 0.05 and 0.20 mg kg^?1. The half-lives of propamocarb were 5.00–11.36 days in root, 5.07–11.46 days in stem, 6.83–11.31 days in leaf and 6.44–8.43 days in soil. The terminal residues of propamocarb were below the maximum residue limits (MRLs) of EU (0.20 mg kg^?1) and South Korea (0.50 mg kg^?1 in fresh ginseng and 1.0 mg kg^?1 in dried ginseng) over 28 days after last spraying at recommended dosage. The results provide a quantitative basis for establishing the MRL and give a suggestion of safe and reasonable use of propamocarb in ginseng.     

Persistence and risk assessment of spiromesifen on tomato in India: a multilocational study

Supervised field trials were conducted at four different agro-climatic locations of India to evaluate the dissipation pattern and risk assessment of spiromesifen on tomato. Spiromesifen 240 SC was sprayed on tomato at 150 and 300 g a.i.?ha^?1. Samples of tomato fruits were drawn at 0, 1, 3, 5, 7, 10 and 15 days after treatment and soil at 15 days after treatment. Quantification of residues was done on gas chromatograph–mass spectrophotometer in selective ion monitoring mode in the mass range of 271–274 (m/z). The limit of quantification of the method was found to be 0.05 mg kg^?1, while the limit of determination was 0.015 mg kg^?1. Residues were found below the LOQ of 0.05 mg kg^?1 in 10 days at both the doses of application at all the locations. Spiromesifen dissipated with a half-life of 0.93–1.38 days at the recommended rate of application and 1.04–1.34 days at the double the rate of application. Residues of spiromesifen in soil were detectable level (<0.05 mg kg^?1) after 15 days of treatment. A preharvest interval (PHI) of 1 day has been recommended on tomato on the basis of data generated under All India Network Project on Pesticide Residues. Spiromesifen 240 SC has been registered for its use on tomato by Central Insecticide Board and Registration Committee, Ministry of Agriculture, Government of India. The maximum residue limit (MRL) of spiromesifen on tomato has been fixed by Food Safety Standard Authority of India, Ministry of Health and Family Welfare, Government of India as 0.3 μg/g after its risk assessment.     

Evaluation of optimal conditions for determination of low selenium content in shellfish samples collected at Todos os Santos Bay,Bahia, Brazil using HG-AFS

This work proposes a procedure for the determination of total selenium content in shellfish after digestion of samples in block using cold finger system and detection using atomic fluorescent spectrometry coupled hydride generation (HG AFS). The optimal conditions for HG such as effect and volume of prereduction KBr 10 % (m/v) (1.0 and 2.0 ml) and concentration of hydrochloric acid (3.0 and 6.0 mol L^?1) were evaluated. The best results were obtained using 3 mL of HCl (6 mol L^?1) and 1 mL of KBr 10 % (m/v), followed by 30 min of prereduction for the volume of 1 mL of the digested sample. The precision and accuracy were assessed by the analysis of the Certified Reference Material NIST 1566b. Under the optimized conditions, the detection and quantification limits were 6.06 and 21.21 μg kg^?1, respectively. The developed method was applied to samples of shellfish (oysters, clams, and mussels) collected at Todos os Santos Bay, Bahia, Brazil. Selenium concentrations ranged from 0.23?±?0.02 to 3.70?±?0.27 mg kg^?1 for Mytella guyanensis and Anomalocardia brasiliana, respectively. The developed method proved to be accurate, precise, cheap, fast, and could be used for monitoring Se in shellfish samples.     

Cadmium background concentrations to establish reference quality values for soils of São Paulo State,Brazil

Proper assessment of soil cadmium (Cd) concentrations is essential to establish legislative limits. The present study aimed to assess background Cd concentrations in soils from the state of São Paulo, Brazil, and to correlate such concentrations with several soil attributes. The topsoil samples (n?=?191) were assessed for total Cd contents and for other metals using the USEPA 3051A method. The background concentration was determined according to the third quartile (75th). Principal component analysis, Spearman correlation, and multiple regressions between Cd contents and other soil attributes (pH, cation exchange capacity (CEC), clay content, sum of bases, organic matter, and total Fe, Al, Zn, and Pb levels) were performed. The mean Cd concentration of all 191 samples was 0.4 mg kg^?1, and the background concentration was 0.5 mg kg^?1. After the samples were grouped by parent material (rock origin) and soil type, the background Cd content varied, i.e., soils from igneous, metamorphic, and sedimentary rocks harbored 1.5, 0.4, and 0.2 mg kg^?1 of Cd, respectively. The background Cd content in Oxisols (0.8 mg kg^?1) was higher than in Ultisols (0.3 mg kg^?1). Multiple regression demonstrated that Fe was primarily attributed to the natural Cd contents in the soils (R ²?=?0.79). Instead of a single Cd background concentration value representing all São Paulo soils, we propose that the concentrations should be specific for at least Oxisols and Ultisols, which are the primary soil types.