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The distribution of Triclosan within the Hudson River Estuary can be explained by a balance among the overall effluent inputs from municipal sewage treatment facilities, dilution of Triclosan concentrations in the water column with freshwater and seawater inputs, removal of Triclosan from the water column by adsorption to particles, and loss to photodegradation. This study shows that an average water column concentration of 3+/-2 ng/l (in the lower Hudson River Estuary) is consistent with an estimate for dilution of average wastewater concentrations with seawater and calculated rates of adsorption of Triclosan to particles. An average Triclosan sediment concentration of 26+/-11 ng/g would be in equilibrium with the overlying water column if Triclosan has a particle-to-water partitioning coefficient of k(d) approximately 10(4), consistent with laboratory estimates.

Turbidity and chlorophyll introduce high uncertainty in remote sensing of Chromophoric Dissolved Organic Matter (cDoM) in riverine and coastal water. To reduce the uncertainty, we developed a functional linear model (FLM) to analyze spectral responses to GDOM concentrations observed in a cruise along two rivers and a tidal bay. The analysis was supported with the measurement of high spatial resolution underwater CDOM concentrations and concurrent in situ above-surface hyperspectral remote sensing reflectance. The functional linear model is able to explain up to 9lpercent of CDOM observations (B2 = 0.91, RMSE = 0.0206). The dummy variables of local environmental factors included in th? estimation improve CDOM assessment in coastal water. Our analysis suggests that the pattern changes of the FLM coefficient curves provide useful information for understanding the spectral signal interference from turbidity and chlorophyll. This work presents a feasibility study of in situ remote sensing of CDQM on a shipboard platform. [ABSTRACT FROM AUTHOR]

In April 2001, three instrumented surface drifters were deployed in the Mississippi River plume near the mouth of Southwest Pass. The plume was characterized by strong surface gradients of salinity, temperature, and chromophoric dissolved organic matter fluorescence (FCDOM). The drifters initially headed west and attained peak speeds of 1 m s-1 within 5 h after release. Thereafter, velocity decreased as the triad headed north in the Louisiana Bight. Linear relationships between FCDOM and salinity identified two subsurface sources of high salinity water (salinity >35) underlying the surface plume. The platforms stalled in a surface front about 40 h after deployment, and then slowly drifted south along the eastern perimeter of the plume. Shoreward of the plume front there were patches of low-salinity, high FCDOM ‘patches’ of surface waters that likely originated in the marshes, bayous, and other smaller distributaries of the delta. [Copyright &y& Elsevier]

Chromophoric dissolved organic matter (CDOM) was measured in the spring and summer in the northern Gulf of Mexico with the ECOShuttle, a towed, instrumented, undulating vehicle. A submersible pump mounted on the vehicle supplied continuously flowing, uncontaminated seawater to online instruments in the shipboard laboratory and allowed discrete samples to be taken for further analysis. CDOM in the northern Gulf of Mexico was dominated by freshwater inputs from the Mississippi River through the Birdfoot region and to the west by discharge from the Atchafalaya River. CDOM was more extensively dispersed in the high-flow period in the spring but in both time periods was limited by stratification to the upper 12 m or so. Thin, subsurface CDOM maxima were observed below the plume during the highly stratified summer period but were absent in the spring. However, there was evidence of significant in situ biological production of CDOM in both seasons.The Mississippi River freshwater end member was similar in spring and summer, while the Atchafalaya end member was significantly higher in the spring. In both time periods, the Atchafalaya was significantly higher in CDOM and dissolved organic carbon (DOC) than the Mississippi presumably due to local production and exchange within the coastal wetlands along the lower Atchafalaya which are absent along the lower Mississippi. Nearshore waters may also have higher CDOM due to outwelling from coastal wetlands. High-resolution measurements allow the differentiation of various water masses and are indicative of rapidly varying (days to weeks) source waters. Highly dynamic but conservative mixing between various freshwater and marine end members apparently dominates CDOM distributions in the area with significant in situ biological inputs (bacterial degradation of phytoplankton detritus), evidence of flocculation, and minor photobleaching effects also observed. It is clear that high-resolution measurements and adaptive sampling strategies allow a more detailed examination of the processes that control CDOM distributions in river-dominated systems. [Copyright &y& Elsevier]

Chromophoric dissolved organic matter (CDOM) fluorescence and dissolved organic carbon (DOC) were measured in the Lingdingyang Estuary, a major component of the Pearl River Delta, China, in May 2001 and November 2002. Measurements of CDOM and DOC suggest multiple sources of dissolved organic matter (DOM) in the low-salinity region of the estuary, due to the mixing of four freshwater outlets, Humen, Jiaomen, Honqimen and Hengmen, all with different freshwater endmembers and all flowing into the head of the Lingdingyang. Our 2002 cruise expanded efforts to characterize these four major outlets, allowing for the quantification of CDOM inputs within this complex watershed.DOC and CDOM appear conservative in mid-salinity (5–20) waters, suggesting that mixing dominates production and removal processes over time scales on the order of 3 days, the residence time of water in this region of the estuary. DOC and fluorescence are linearly correlated in the mid-salinity region of the estuary north of Shenzhen, suggesting that in this region, terrestrial inputs dominate both signals. However, this relationship does not continue out onto the shelf, where water masses of differing optical properties mix. The CDOM/DOC ratio decreases with increasing salinity as would be expected through phototrasformation of CDOM into non-fluorescent DOC. Additionally, this ratio at low salinity appears to vary seasonally, with a higher value in Spring (high flow) compared to Fall (low flow). [Copyright &y& Elsevier]

Variations in the concentration and inherent optical properties of colored dissolved organic matter (CDOM) in river-dominated margins provide information on the cycling of carbon and its chemical composition. Large-scale temporal and spatial variability in CDOM concentration and optical properties were observed in the Northern Gulf of Mexico in June of 2000 and April of 2001. Terrestrial CDOM from the Mississippi and Atchafalaya Rivers dominates the region. Although the primary factor controlling CDOM in this region is the quantity of fresh water runoff, strong regional variability in fresh water sources also plays a major role. Physical complexity due to changes in circulation patterns, volume of river flow and multiple river sources makes observation of biological and photochemical effects challenging in this region. We have used two approaches to distinguish between source and transformation effects: mixing models, which include the concentration and inherent optical properties of CDOM from discrete samples, and high-resolution three-dimensional mapping of multi-spectral fluorescence. [Copyright &y& Elsevier]