Browsing by Author "Sandvik, M."

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Assessment of farming practices and uses of agrochemicals in Lake Manyara basin, Tanzania
(2011-05-18) Nonga, H. E.; Mdegela, R. H.; Lie, E.; Sandvik, M.; Skaare, J. J.
This study was conducted to assess farming practices, agrochemical usage and environmental pollution in Manyara basin, Tanzania. Field surveys, interviews, questionnaires and Lake Manyara nutrient analysis were used in data collection. The highest number (95%) of households grew crops, namely, maize, rice, banana and vegetables with median farm size of 3 ha. Irrigated farming was common (75%) which enhanced cultivation on same piece of land up to 6 times a year. Farmers indiscriminately used pesticides, namely, insecticides (50%), fungicides (37.5%) and herbicides (12.5%). Uses of endosulfan in vegetable farms poses public health threats to consumers. Most respondents (85%) applied insecticides in vegetables up to 4 times per cropping season. Excessive use of pesticides and haphazard disposal of pesticide remnants and containers caused environmental pollution. The average amount of acaricides used was 1109±915 ml (mean ± SD) per livestock keeper per month per. Most farmers (78%) used inorganic fertilizers and animal manure (43.4%). Low levels of ammonium (3.6±3.1 μg/L), nitrate (1±0.8μg/L) and phosphate (36.1±42 μg/L) were recorded in the lake. Easy access to agrochemicals, limited knowledge of pesticide on environmental health and limited extension services were factors for indiscriminate uses of agrochemicals. Increasing farmers awareness and training aimed at sustainable agriculture, agrochemical uses and integrated pest management is suggested.
Conjugation of microcystins with thiols is reversible: Base-catalyzed deconjugation for chemical analysis
(Chemical Research in Toxicology, 2016-03-21) Miles, C. O.; Sandvik, M.; Nonga, H. E.; Ballot, A.; Wilkins, A. L.; Rise, F.; Jaabaek, J. A. H.; Loader, J. I.
Microcystins are potent cyclic heptapeptide toxins found in many freshwater cyanobacteria. Most microcystins contain an α,β-unsaturated amide that can react with thiolcontaining amino acids, peptides, and proteins in vivo and in vitro. While soluble conjugates formed from small peptides can be extracted and analyzed directly by LC−MS, microcystins conjugated to proteins are analyzed after oxidative cleavage of their Adda side chains, but information on which microcystin analogues were present is lost. Observations during the development of thiol-derivatization-based LC−MS methods for microcystin analysis indicated that the reaction of thiols with microcystins was reversible. The kinetics of deconjugation was investigated with mercaptoethanol as a model thiol to identify suitable reaction conditions. A range of microcystins conjugated to mercaptoethanol, methanethiol, cysteine, and glutathione were then successfully deconjugated, demonstrating the feasibility of releasing conjugated forms of microcystins for chemical analysis. Reagents for removing the released thiols or for trapping the released microcystins increased the reaction rate. Optimization of methodologies based on this reaction should increase the method’s utility for measuring free and conjugated microcystins. The results also indicate that thiol-conjugated microcystins slowly release free microcystins, even at neutral pH, with consequences for assessment of toxin exposure, metabolism, and trophic transfer. A range of other common natural and environmental toxins, such as deoxynivalenol and acrylamide, also contain α,β-unsaturated carbonyl groups and can be expected to behave in a similar manner.
Conjugation of microcystins with thiols is reversible: Base-catalyzed deconjugation for chemical analysis
(ACS Publications, 2016-03-21) Miles, C. O.; Sandvik, M.; Nonga, H. E.; Ballot, A.; Wilkins, A. L.; Rise, F.; Jaabaek, J. A. H.; Loader, J. I.
Microcystins are potent cyclic heptapeptide toxins found in many freshwater cyanobacteria. Most microcystins contain an α,β-unsaturated amide that can react with thiolcontaining amino acids, peptides, and proteins in vivo and in vitro. While soluble conjugates formed from small peptides can be extracted and analyzed directly by LC−MS, microcystins conjugated to proteins are analyzed after oxidative cleavage of their Adda side chains, but information on which microcystin analogues were present is lost. Observations during the development of thiol-derivatization-based LC−MS methods for microcystin analysis indicated that the reaction of thiols with microcystins was reversible. The kinetics of deconjugation was investigated with mercaptoethanol as a model thiol to identify suitable reaction conditions. A range of microcystins conjugated to mercaptoethanol, methanethiol, cysteine, and glutathione were then successfully deconjugated, demonstrating the feasibility of releasing conjugated forms of microcystins for chemical analysis. Reagents for removing the released thiols or for trapping the released microcystins increased the reaction rate. Optimization of methodologies based on this reaction should increase the method’s utility for measuring free and conjugated microcystins. The results also indicate that thiol-conjugated microcystins slowly release free microcystins, even at neutral pH, with consequences for assessment of toxin exposure, metabolism, and trophic transfer. A range of other common natural and environmental toxins, such as deoxynivalenol and acrylamide, also contain α,β-unsaturated carbonyl groups and can be expected to behave in a similar manner.
Cyanobacteria and cyanobacterial toxins in the alkaline-saline Lakes Natron and Momela, Tanzania
(African Journal Online, 2016-12-05) Nonga, H. E.; Mdegela, R. H.; Sandvik, M.; Lie, E.; Miles, C. O.; Skaare, J. U.
Physicochemical parameters, phytoplankton communities, microcystin (MC) concentrations and potential MC-producing cyanobacteria were investigated in Lakes Natron and Momela, Tanzania. In Lake Big Momela, concentrations of soluble reactive phosphorus, nitrate and ammonia were 7.1, 2.6 and 0.9 μg/L, respectively, while dissolved oxygen, salinity, conductivity and pH were 9.4 mg/L, 19‰, 30 mS/cm and 9.7, respectively. The concentrations of soluble reactive phosphorus, nitrate and ammonia in Lake Natron were 129.4, 8.1 and 58 μg/L, respectively, while dissolved oxygen, conductivity and pH were 8 mg/L, 52 mS/cm and 9.5 respectively. The phytoplankton communities in both lakes were dominated by cyanobacteria, particularly Arthrospira fusiformis. Navicula and Nitzschia diatoms, and Chlorella, Chlorococcum and Scenedesmus green algae were common in Lakes Momela and Natron. Liquid chromatography–mass spectrometry (LC-MS) analysis phytoplankton detected four microcystin variants namely MC-RR, -YR, -LR and -RY. The total MC concentrations in Lake Natron were 0.1–4.5 μg/mL of phytoplankton scum and in Lake Momela were below quantifiable levels. Polymerase chain reaction analysis of phytoplankton revealed presence of Microcystis and the Microcystis mcyB gene in some samples. Finding of potential MC-producing cyanobacteria and MCs in study lakes poses a health risk to Lesser Flamingo which feed on cyanobacteria.
Dioxins, PCBs, chlorinated pesticides and brominated flame retardants in free-range chicken eggs from peri-urban areas in Arusha, Tanzania: Levels and implications for human health
(Elsevier, 2016-02-03) Polder, A.; Müller, M. B.; Brynildsrud, O.B.; de Boer, J.; Hamers, T.; Kamstra, J. H.; Lie, E.; Mdegela, R. H.; Moberg, H.; Nonga, H. E.; Sandvik, M.; Skaare, J. U.; Lyche, J. L.
The environment in the northern part of Tanzania is influenced by rapid population growth, and increased urbanization. Urban agriculture is common and of economic value for low income families. In Arusha, many households sell eggs from free-ranging backyard chicken. In 2011, 159 eggs from different households in five different locations in Arusha were collected, homogenized, pooled into 28 composite samples and analyzed for a wide selection of POPs. Levels of POPs varied widely within and between the locations. The levels of dieldrin and ΣDDT ranged between 2 and 98,791 and 2 and 324 ng/g lipid weight (lw), respectively. EUMRLs of 0.02 mg/kg dieldrin for eggs were exceeded in 4/28 samples. PCBs, HCHs, chlordanes, toxaphenes and endosulfanes were found at lower frequency and levels. Brominated flame retardants (BFRs), e.g polybrominated diphenylethers (PBDEs), hexabromocyclododecane (HBCD) and 1,2-bis(2,4,6-tribromphenoxy)ethane (BTBPE) were present in 100%, 60% and 46% of the composite samples, respectively. Octa-and deca-BDEs were the dominating PBDEs and BDE 209 levels ranged between bLOQ (limit of quantification) – 312 ng/g lw. Dioxins were measured using the DRLUC bio-assay and found in levels of bLOQ – 20 pg bio-TEQs/g lw. Four samples (13%) exceeded the maximum level of 5 pg/g total WHO-TEQs for hen eggs set by the Commission Regulation (EU) No 1259/2011. The daily/weekly intake was calculated and risk was characterized for all compounds comparing with available toxicity reference values (TRVs) such as the provisional tolerable intake (PTDI) or Reference Doses (RfDs). In one sample dieldrin exceeded the PTDI (100 ng/kg bw/day). Correlation was found between bio-TEQs and lipid adjusted levels of ΣPBDEs, suggesting similar sources. Open fires in backyards may be one of the sources for contamination of eggs with BFRs and dioxins.
LC-MS analysis with thiol derivatization to differentiate [Dhb7]- from [Mdha7]‑Microcystins: Analysis of cyanobacterial blooms, planktothrix cultures and European crayfish from lake Steinsfjorden, Norway
(American Chemical Society, 2013-03-26) Miles, C. O.; Sandvik, M.; Haande, S.; Nonga, H. E.; Ballot, A.
Kinetic studies showed that [Asp3, Dhb7]MC-RR reacted with mercaptoethanol hundreds of times more slowly than MC-RR and a range of other [Mdha7]-containing microcystin congeners. The difference in reaction rate was sufficiently large that derivatization of microcystin-containing samples with mercaptoethanol, followed by LC-MS analysis, clearly discriminated between microcystins containing the isobaric [Dhb7]- and [Mdha7]-groups. Application of this approach, using LC-MS with both-ion trap and triplequadrupole mass spectrometers, to water samples and Planktothrix cultures from Lake Steinsfjorden, Norway, demonstrated the presence of [Asp3, Dhb7]MC-RR (5), [Asp3]MC-RY (14), and [Asp3]MC-LY (16), as well as analogues tentatively identified as [Asp3]MC-RR (4), [Asp3, DMAdda5, Dhb7]MC-LR (6), [Asp3, Dhb7]MC-HtyR (8), [Asp3]MC-HtyR (9), [Asp3, Dhb7]MC-LR (10), [Asp3]MC-LR (11), [Asp3, Dhb7]MC-RY (15), and [Asp3, Dhb7]MC-LY (17), together with low levels of several other analogues. This is the first use of this thiol-based LC-MS approach to identify Dhb-containing microcystins, and allowed identification of LC-MS peaks in a mixture of [Mdha7]- and [Dhb7]-congeners of [Asp3]MC-RR (4, 5), -RY (14, 15), and -LY (16, 17) in the samples from L. Steinsfjorden. This is also the first report of MC-RY-congeners outside of Africa, or in Planktothrix spp. Analysis of European crayfish (Astacus astacus) taken from L. Steinsfjorden revealed the presence of only trace levels of microcystins in the edible parts.
Levels and patterns of persistent organic pollutants (POPs) in tilapia (Oreochromis sp.) from four different lakes in Tanzania: Geographical differences and implications for human health
(Elsevier, 2014-04-22) Lie, Elisabeth; Polder, A.; Müller, M. B.; Lyche, J. L.; Mdegela, R. H.; Nonga, H. E.; Mabiki, F.; Mbise, T. J.; Skaare, J. U.; Sandvik, M.; Skjerve, E.; Lie, E.
In Tanzania fish is one of the most important protein sources for the rapidly increasing population. Wild fish is threatened by overfishing and pollution from agriculture, industries, mining, household effluents and vector control. Tomonitor possible implications for public health, the geographical differences of the occurrence and levels of persistent organic pollutants (POPs) in tilapia fish (Oreochromis sp.) from four different Tanzanian lakes were investigated in 2011. Concentrations of organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), polybrominated diphenyls (PBDEs) and hexabromocyclododecane (HBCDD) were determined in pooled samples of tilapia muscle from Lake (L) Victoria, L. Tanganyika, L. Nyasa (also called L. Malawi) and L. Babati in Tanzania in 2011. Levels of Σ-DDTs (274 ng/g lipid weight (lw)) and sum of 7 indicator PCBs (Σ-7PCBs) (17 ng/g lw) were significantly higher in tilapia from L. Tanganyika compared to the other lakes. The highest levels of Σ-endosulfan (94 ng/g lw) were detected in tilapia from L. Victoria. Toxaphenes were detected in low levels in fish from L. Tanganyika and L. Babati. Results revealed a geographic difference in the use of DDT and endosulfan between L. Victoria and L. Tanganyika. Low ratios of DDE/DDT in tilapia from L. Tanganyika indicated an on-going use of DDT in the area. Median levels of ΣBDEs, including BDE-209, were highest in L. Victoria (19.4 ng/g lw) and BDE- 209 was present in 68% of the samples from this lake. The presence of BDE-209 indicates increasing influence of imported products from heavy industrialized countries. The measured POP levels in the studied tilapia were all below MRLs of EU or were lower than recommended levels, and thus the fish is considered as safe for human consumption. They may, however, pose a risk to the fish species and threaten biodiversity.
Socio-economic values of wetland resources around lake Manyara, Tanzania: assessment of environmental threats and local community awareness on environmental degradation and their effects
(Journal of Wetlands Ecology, 2010-12-05) Nonga, H. E.; Mdegela, R. H.; Lie, E.; Sandvik, M.; Skaare, J. U.
Understanding local people’s socio-economic values of wetlands and traditional mechanisms of managing natural resources forms the basis of conserving them. Wetlands have frequently been developed for short-term economic gains that destroy their ecological values and environmental services in the long term. A study was carried out to assess socio-economic values of the wetland resources, environmental threats around Lake Manyara and local community awareness on causes of environmental changes, degradation in the wetlands and their effects using 80 respondents. Field surveys, interviews, questionnaires and direct observation were used in data collection. It was found that local community was aware on the ecosystem services accrued from the wetlands which were unsustainably used. However, environmental degradation due to unsustainable agriculture, overgrazing, deforestation, urbanization and mining was rampant which had resulted to soil erosion, reduced water availability, wildlife mortality and frequent dry up of Lake Manyara and rivers. In order to protect the lake basin; controlled human activities, land use and water resources within the catchment are to be done in cooperation between the government departments, local authorities and the general local community around.
Thiol Derivatization for LC-MS Identification of Microcystins in Complex Matrices
(ACS Publications, 2012-07-18) Miles, C. O.; Sandvik, M.; Nonga, H. E.; Rundberget, T.; Wilkins, A. L.; Rise, F.; Ballot, A.
Microcystins are a group of cyclic heptapeptides originating from cyanobacteria. Cyanobacteria also produce a range of peptides and other compounds that can result in complex chromatograms when samples are analyzed by LC-MS. Derivatization with appropriate thiols (e.g., mercaptoethanol) of the olefin in the α,β-unsaturated amide present in most microcystins was shown to simplify analysis of LC-MS chromatograms of sample extracts, making it much easier to identify peaks corresponding to candidate microcystins. Furthermore, interpretation of MS2 spectra was facilitated by addition of the mass associated with the thiol to the α,β-unsaturated amide of microcystins. Cyanotoxins containing Mdha or Dha reacted readily with thiols, whereas Mser, Ser, Mdhb, and thiol-derivatives of Mdha or Dha did not react under the conditions used. This approach therefore provides a convenient LC-MS method to obtain evidence for the presence of Mdha or Dha and can likely be used to differentiate between the isobaric amino acids Mdha and Dhb in candidate cyanotoxin peaks. When O-(2-mercaptoethyl)-O′-methyl-hexa(ethylene glycol) (MEMHEG) (Mwt. 356) was used as the thiol, the resulting derivatives eluted in an LC-MS mass window that was largely free of interferences. This approach simplifies detection of candidate microcystin analogues even in the presence of complex mixtures of coeluting components. The method was used for qualitative analysis of a Microcystis aeruginosa culture from Lake Naivasha, Kenya, and the results were verified using precursor-ion scanning and high-resolution mass spectrometry.