Estuarine environments atmospheres

In marine ecosystems, the high copper levels measured in heavily contaminated coastal areas sometimes approach the incipient lethal concentrations for some organisms (Neff and Anderson 1977). Elevated copper concentrations in marine and estuarine environments may result from atmospheric deposition, industrial and municipal wastes, urban runoff, rivers, and shoreline erosion. Chesapeake Bay, for example, receives more than 1800 kg of copper daily from these sources (Hall et al. 1988). Copper concentrations in abiotic marine materials are generally higher near shore than... 

The worlds oceans cover approximately 70% of the surface of the earth, and may play a significant role in the transport of volatile sulfur compounds from marine, coastal and estuarine environments to the atmosphere. These compounds include hydrogen sulfide, HjS, carbonyl sulfide (COS), carbon disulfide, (CSA methyl mercaptan (CH3SH), dimethyl sulfide, (CH3SCH3), (DMS), and dimethyl disulfide (CH3SSCH3) (1). Although it was initially thought that H2S was the major compound involved in this transport (2), more recent evidence indicates that DMS accounts for most of the sulmr transferred from marine environments to the atmosphere (2). 

Most data is confined to MMM which can be generated from inorganic mercurial wastes by plankton and then progressively bioaccumulated. The final concentration in animals higher up the food chain can be several orders of magnitude higher than those present in the original water. Bacterial synthesis of DMM also takes place in marine and estuarine environments. It is present there at very low levels since it is rapidly hydrolyzed to MMM or vented into the atmosphere. 

Methane is also released to the atmosphere directly from anaerobic estuarine sediments via bubble formation and injection into the water column. Although small amounts of methane from bubbles may dissolve within the water column, the relatively shallow nature of the estuarine environment results in the majority of methane in bubbles reaching the atmosphere. The quantitative release of methane via this mechanism is difficult to evaluate due to the irregular and sporadic spatial and temporal extent of ebullition. Where ebullition occurs, the flux of methane to the atmosphere is considerably higher than... 

Nitrous oxide is another important greenhouse gas that is present in elevated concentrations in estuarine environments. At present, N2O is responsible for about 5-6% of the anthropogenic greenhouse effect and is increasing in the atmosphere at a rate of about 0.25% per year. However, the role of estuaries in the global budget of the gas has only been addressed recently. 

In thermospray interfaces, the column effluent is rapidly heated in a narrow bore capillary to allow partial evaporation of the solvent. Ionisation occurs by ion-evaporation or solvent-mediated chemical ionisation initiated by electrons from a heated filament or discharge electrode. In the particle beam interface the column effluent is pneumatically nebulised in an atmospheric pressure desolvation chamber this is connected to a momentum separator where the analyte is transferred to the MS ion source and solvent molecules are pumped away. Magi and Ianni (1998) used LC-MS with a particle beam interface for the determination of tributyl tin in the marine environment. Florencio et al. (1997) compared a wide range of mass spectrometry techniques including ICP-MS for the identification of arsenic species in estuarine waters. Applications of HPLC-MS for speciation studies are given in Table 4.3. 

Evidence for the existence of a natural source of tetraalkyllead compounds comes from analysis of air from the open sea, from coastal, and from estuarine areas, since 1 to 30 ng/m tetraalkyllead was observed [61] further evidence was found from abnormally high alkyllead to total lead ratios, which have been observed in atmospheric samples in Morecambe Bay, U.K. [60]. It was speculated that these tetraalkyllead emissions arise from methylation of lead compounds in coastal and estuarine intertidal areas [61]. The hypothesis of a natural source was supported by additional measurements [132, 174] see also [46, 133, 134]. However, according to recent results on transformation rates and lifetime of alkyllead species in the atmosphere it is not necessary to invoke the hypothesis of the natural alkylation of lead to explain the enhanced alkyllead to total lead ratios [182]. Also no indication of a large-scale natural source for tetraalkyllead compounds was found in other work [22], and determination of atmospheric content of tetraalkyllead compounds gave no indication for the occurrence of natural methylation processes of lead(ll) compounds [23] see also [48, 69, 70, 73]. The origin of trialkyllead species in rural pigeons (Columba livia) was associated in part with natural sources of tetraalkyllead in the environment [135], and also the presence of small amounts of Pb(CH3)4 in fish (Coho Salmon, Yellow Perch, Sucker, Rock Bass, Sunfish) from various lakes and rivers in Ontario, Canada, was taken as an indication for the possibility of environmental methylation or in vivo methylation of lead in fish [95] see also [93]. It was considered conceivable that bacteria in fish intestines or in fish tissue could methylate lead compounds [93, 94, 101, 178]. 

Atmospheric deposition of trace metals from urban environments on the perimeter of large water bodies is a potential source to these systems. There is little data, however, to support or refute this notion. Here we discuss a study of Baltimore s urban air and its potential impact on the northern Chesapeake Bay and compare our results to those of other studies. Elevated concentrations of metals, especially lead, zinc and mercury were measured at an urban sampling site compared to a rural location. The difference was most marked for lead with the annual depositional flux almost three times higher in the city. Normalized fluxes at a rural site were mostly similar to those measured previously around the Chesapeake Bay and were also similar to those measured recently at other rural sites in Maryland and around the Great Lakes. The results of our study suggest that local atmospheric inputs from urban sources should be included in any evaluation of atmospheric deposition to lacrustrine, coastal or estuarine systems. 

For estuarine and coastal environments, direct deposition to the water s surface of some pollutants can be as important as runoff from the watershed given that the metals are strongly retained within the terrestrial environment (22, 24). Atmospheric deposition appears to be an important source to the Chesapeake Bay of metals such as Hg, Pb and Cd (3, 5, 20). However, as estimations are based on the measurements of metal deposition at rural sites, they could potentially underestimate the impact of deposition if the urban influence were significant. The present study was aimed at examining the difference in concentration and deposition in an urban and a rural setting to help address this important question. 

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