Fusarium species complex and mycotoxins in grain maize from maize hybrid trials and from grower's fields.

AIMS: To quantify and to compare the occurrence of Fusarium species in maize kernels and stalk pieces, to analyse mycotoxins in kernels and maize crop residues, to evaluate two approaches to obtain kernel samples and to compare two methods for mycotoxin analyses. METHODS AND RESULTS: The occurrence of Fusarium species in maize kernels and stalk pieces from a three-year maize hybrid trial and 12 kernel samples from grower's fields was assessed. Nine to 16 different Fusarium species were detected in maize kernels and stalks. In kernels, F. graminearum, F. verticillioides and F. proliferatum were the most prevalent species whereas in stalks, they were F. equiseti, F. proliferatum and F. verticillioides. In 2006, 68% of the kernel samples exceeded the recommended limit for pig feed for deoxynivalenol (DON) and 42% for zearalenone (ZON), respectively. Similarly, 75% of the samples from grower's fields exceeded the limits for DON and 50% for ZON. In maize crop residues, toxin concentrations ranged from 2.6 to 15.3 mg kg(-1) for DON and from 0.7 to 7.4 mg kg(-1) for ZON. Both approaches to obtain maize kernel samples were valid, and a strong correlation between mycotoxin analysis using ELISA and LC-MS/MS was found. CONCLUSIONS: The contamination of maize kernels, stalk pieces and remaining crop residues with various mycotoxins could pose a risk not only to animal health but also to the environment. With the hand-picked sample, the entire Fusarium complex can be estimated, whereas combine harvested samples are more representative for the mycotoxin contents in harvested goods. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first multi-year study investigating mycotoxin contamination in maize kernels as well as in crop residues. The results indicate a high need to identify cropping factors influencing the infection of maize by Fusarium species to establish recommendations for growers.

Observations of the PCB distribution within and in-between ice, snow, ice-rafted debris, ice-interstitial water, and seawater in the Barents Sea marginal ice zone and the North Pole area.

To evaluate the two hypotheses of locally elevated exposure of persistent organic pollutants (POPs) in ice-associated microenvironments and ice as a key carrier for long-range transport of POPs to the Arctic marginal ice zone (MIZ), dissolved and particulate polychlorinated biphenyls (PCBs) were analyzed in ice, snow, ice-interstitial water (IIW), seawater in the melt layer underlying the ice, and in ice-rafted sediment (IRS) from the Barents Sea MIZ to the high Arctic in the summer of 2001. Ultra-clean sampling equipment and protocols were specially developed for this expedition, including construction of a permanent clean room facility and a stainless steel seawater intake system on the I/B ODEN as well as two mobile 370 l ice-melting systems. Similar concentrations were found in several ice-associated compartments. For instance, the concentration of one of the most abundant congeners, PCB 52, was typically on the order of 0.1-0.3 pg l(-1) in the dissolved (melted) phase of the ice, snow, IIW, and underlying seawater while its particulate organic-carbon (POC) normalized concentrations were around 1-3 ng gPOC(-1) in the ice, snow, IIW, and IRS. The solid-water distribution of PCBs in ice was well correlated with and predictable from K(ow) (ice log K(oc)-log K(ow) regressions: p<0.05, r2=0.78-0.98, n=9), indicating near-equilibrium partitioning of PCBs within each local ice system. These results do generally not evidence the existence of physical microenvironments with locally elevated POP exposures. However, there were some indications that the ice-associated system had harbored local environments with higher exposure levels earlier/before the melting/vegetative season, as a few samples had PCB concentrations elevated by factors of 5-10 relative to the typical values, and the elevated levels were predominantly found at the station where melting had putatively progressed the least. The very low PCB concentrations and absence of any significant concentration gradients, both in-between different matrices and over the Eurasian Arctic basin scale, suggest that ice is not an important long-range transport purveyor of POPs to the Arctic MIZ ecosystem.

Soot-carbon influenced distribution of PCDD/Fs in the marine environment of the Grenlandsfjords, Norway.

The particle associations of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) were studied in both the water column and the surface sediments of a marine fiord system and were found to poorly obey expectations from the organic matter partitioning (OMP) paradigm. The field observations were instead consistent with the presence of a stronger sorbent subdomain such as pyrogenic soot-carbon (SC) playing an important role in affecting the environmental distribution and fate of PCDD/Fs. Solid-water distribution coefficients (Kd) of PCDD/ Fs actually observed in the water column were several orders of magnitude above predictions from a commonly used OMP model. Even when these elevated Kd values were normalized to the particulate organic carbon (POC) content (i.e., K(OC)), the variability in K(OC) for individual PCDD/ Fs at different fjord locations and seasons of factors 100-1,000 suggested that bulk organic matter was not the governing sorbent domain of the suspended particles. Further, POC-normalized particle concentrations of PCDD/ Fs (C(OC)) in a vertical profile (surface water-bottom water-surface sediment) revealed a strong increasing trend with depth. Factors of about 100 higher Coc for all PCDD/Fs in the sediment than in the surface water could not be explained by higher fugacity in the surrounding deep water nor with C:N or delta13C indexes of selective aging of the bulk organic matter. Instead this was hypothesized to reflect selective preservation of a more recalcitrant and highly sorbing, but minor, subdomain such as soot. The extent of enhanced PCDD/F sorption, above the OMP predictions, was positively correlated with the SC:POC ratio of the suspended particles in surface and deep waters. Finally, the geographical distribution of sedimentary PCDD/F concentrations were better explained by the SC content than by the bulk OC content of the sediment. Altogether, these field-based findings add to recent laboratory-based sorption studies to suggest that we need to consider both amorphous OC partitioning domains and SC particles as carriers of planar aromatic contaminants if we are to explain the environmental distribution and fate of pollutants such as PCDD/Fs.

Dynamic colloid--water partitioning of pyrene through a coastal Baltic spring bloom.

Colloidal organic particles constitute the dominant portion of particulate organic matter in surface seawater, but their influence on the phase speciation and bioavailability of hydrophobic organic compounds (HOCs) is sparsely evaluated. Studies on colloid-water partitioning have been focused on other regimes and have largely been performed on chemically defined subportions of total colloids such as the humic fraction. Available estimates of colloid-water partition coefficients (Kcoc) are highly variable and not easily explained by regularly applied Kow-Koc relationships. Here, pyrene was partitioned to bulk natural colloids isolated using cross-flow ultrafiltration techniques from the surface water of a coastal bay. A key objective was to elucidate biogeochemical controls on the changing colloid-sorbent qualities over the course of the dynamic allochtonous-autochtonous transition of a well-constrained boreal coastal spring bloom. The pyrene Kcoc was found to decrease from 12.9+/-0.9 x 10(3) Lw/kg(oc) in the terrestrial runoff dominated regime to values around 2.9+/-0.7 x 10(3) Lw/kg(oc), once phytoplankton production became the governing source of organic matter to the surface waters. The changing Kcoc was well correlated with the molar extinction coefficient at 280 nm of the colloidal organic carbon. This study supports other reports of an improved prediction of HOC phase speciation through this simple molecular proxy of the "quality" of organic sorbents. While being poor sorbents on a carbon atom basis, relative to soils and sediments, coastal marine colloids, by their shear abundance, may significantly attenuate the truly dissolved exposures of HOCs with log Kow above 5.

Ubiquitous observations of enhanced solid affinities for aromatic organochlorines in field situations: are in situ dissolved exposures overestimated by existing partitioning models?

This paper investigates the ability of the traditional organic matter partitioning (OMP) model to predict the solid-water distribution, and hence the dissolved exposures, of hydrophobic organic compounds (HOCs) in real field situations. Observed organic-carbon-normalized partitioning coefficients (Koc)obs) of polychlorinated biphenyls, polychlorinated benzenes, polychlorinated dibenzo-dioxins and -furans, and p,p'-dichlorodiphenyltrichlorethane (DDT) with metabolites were selected from the literature and compared with their respective OMP model estimates. For all compound classes and in a majority of the investigated cases, (Koc)obs values were significantly larger than predicted. This translated into factors of overestimated dissolved exposures ranging from 1 to 1,000. Various reasons are discussed for the discrepancies between predictions and actual observations, such as the effect of the diagenetic state and other properties of the particulate organic matter. The greater enhancement in (Koc)obs of planar over nonplanar compounds suggests in certain cases that efficient interactions with aromatic soot phases may be significant. For an improved predictability of (Koc)obs and dissolved exposures of HOCs in the real environment, the inclusion of soot and possibly other distinct subfractions of bulk organic carbon into an extended solid-water partitioning model may be considered.

Spherical clay conglomerates: a novel stationary phase for solid-phase extraction and "reversed-phase" liquid chromatography.

A new solid phase is presented to be used for the solid-phase extraction (SPE) of organic compounds from aqueous solutions and as a stationary phase for the separation of organic compounds in "reversed-phase" HPLC. The material consists of spherical clay conglomerates (SCCs) in the size ranges of 2-5, 5-10, and 10-20 µm. SCCs are especially well suited for the extraction and separation of aromatic compounds with electron-withdrawing substituents, because of the formation of specific electron donor-acceptor (EDA) complexes of such compounds with natural clay minerals. A series of nitroaromatic compounds (NACs), e.g., nitrophenols, and nitrotoluenes, served as probe substances for the characterization of the SPE with SCCs online coupled to a C18-HPLC-DAD system. Breakthrough volumes were > 1 L and method detection limits (MDLs) < 100 ng/L for compounds with moderate to high affinity towards clay minerals. The performance of the material is hardly affected by matrix effects and because of its excellent physical properties, i.e., regenerability and pressure-resistance, it meets the requirements for fully automated routine trace analysis of several primary pollutants, such as 6-methyl-2,4-dinitrophenol (DNOC) or 2,4,6-trinitrotoluene (TNT), in various natural waters. Offline SPE with SCCs was superior or equivalent to commercial SPE products for analysis of such compounds. Finally, SCCs are shown to be well suited as a stationary phase in reversed-phase HPLC. This opens a wide range of applications, e.g., as an easy and fast separation technique that is orthogonal to C18 reversed-phase HPLC.