The voltammetric determination of phosphate and silicate in washing powders

In this work previous static and flow injection voltammetric methods for the determination of phosphate and silicate have been developed for the determination of total phosphate and soluble silicate in commercial washing powders. The method is based on the electrochemical reduction of heteropoly acids at + 0.3 v. (vs. SCE) at a glassy carbon electrode. Anionic detergents are a constituent of washing powders and are found to reduce markedly the differential pulse voltammetric peak currents obtained for 12-molybdophosphate and 12-molybdosilicate in aqueous solutions. Use of a sample solution 40–50% in ethanol was found to prevent this interference. By this method soluble silicate has been determined in unhydrolysed solutions of washing powders and total phosphate in hydrolysed solutions using both static and flow injection modes. [Continues.

Biogenic hydrocarbons in the particulate material of the water column of the Bellingshausen Sea, Antarctica, in the region of the marginal ice zone

The biogenic hydrocarbon content of particulate matter of the Bellingshausen Sea in the region of the marginal ice zone (MIZ) has been used to investigate the origins and fates of organic material in the water column in the region of a marginal ice zone. Particulates were sampled from four depths to 200 m in pack ice and at the ice edge, and from seven depths to 3000 m in open ocean. Total n-alkane concentrations associated with particulates increased from 200 ng l−1 under the pack ice to 1000 ng l−1 in the open ocean, and decreased with depth in open water to 15 ng l−1 at 3000 m. The influence of phytoplankton on particulate material was shown to be negligible under the ice but extended horizontally and vertically as the ice edge retreated. Sea-ice algae did not appear to seed the phytoplankton growth under the ice or the subsequent “bloom” at the MIZ. The alkane signature of phytoplankton from the MIZ bloom was detected at a depth of 200 m near the ice edge, at 500 m in open sea, and in surface sediments (4100 m). Zooplankton biomarkers that were at low levels in krill under the ice were higher in animals from the open ocean but were not detected in the water column or sediments. It was concluded that the majority of particulate material in the water column was algal in origin. Material in the surface sediment from under pack ice probably originated from a deep-living winter population of copepods and material in surface sediment from the ice-free ocean originated from the algal “bloom” at the MIZ

The occurrence of monounsaturated n-C21 and polyunsaturated C25 sedimentary hydrocarbons in the lipids of Antarctic marine organisms

Antarctic zooplankton have been found to be a potential source of sedimentary hydrocarbons. Monounsaturated C21 n-alkenes and highly branched polyunsaturated C25 n-alkenes were analysed in the aliphatic fraction of the lipids of Antarctic pelagic and inshore marine organisms. Cluster analysis of the species-based data set produced four main groups: phytoplankton, epipelagic herbivores, epipelagic carnivores and mesopelagic omnivores. The detailed pattern of alkenes exhibited differences within the groups and also with tissue type (krill, Euphausia superba). The origin of alkenes in Antarctic biota appeared to be either synthesis de novo or due to the condensation of smaller molecules. Formation of alkenes by the decarboxylation of fatty acids was not consistent with the hydrocarbon and fatty acid composition of Antarctic zooplankton. There was no evidence for direct assimilation of C21 and C25 alkenes by zooplankton or higher predators from their diet. Zooplankton C25 alkenes are probably transported unaltered directly to the sediment as detritus or via predators in faecal material. Sedimentary C25 alkenes are proposed as biomarkers of recent zooplankton activity in the water column

Natural and anthropogenic hydrocarbons in the Antarctic marine environment

The Antarctic marine environment contains a range of hydrocarbons at low concentrations, which are generally biogenic in origin. All major classes of hydrocarbons have been found in the Antarctic ecosystem. At present, anthropogenic input is very low and difficult to resolve from background levels. Pollution in the Antarctic is limited to only a few sources and although contamination can be locally chronic it is very restricted in extent. To date there have been few studies of hydrocarbon pollution and those available have been patchy in spatial coverage and generally lack time-series data. The low levels of natural hydrocarbons and restricted human activity make the Antarctic ecosystem suitable as an indicator of global hydrocarbon pollution

The extent of hydrocarbon contamination in the marine environment from a research station in the Antarctic

Low level hydrocarbon contamination is measurable in the vicinity of Antarctic stations, N-alkane and polycyclic aromatic hydrocarbon (PAH) concentrations in seawater and sediment at Signy Station, South Orkney Islands indicated contamination was confined to within a few hundred metres of the station. Total n-alkane concentrations in seawater decreased from 7.6 to 2.6 μg l−1 within 500 m of the station. All n-alkane values in seawater were within the limits of variation for oceanic waters proposed by cripps (1992), although the distribution pattern suggested pollution from the station. The total PAH concentration in seawater varied between 110 and 216 ng l−1. These values showed no trend with distance from the station and were all slightly higher than for the open ocean. The n-alkane and PAH concentations in the surface sediment declined to low levels within 375 m of the station. This indicates that a large proportion of the hydrocarbons entering Factory Cove was deposited from the water column. Sediment n-alkane concentrations were similar at all depths of the cores when collected more than 125 m from the station. PAH levels in the sediment appeared to be due to local input, including a small spill in 1965

Hydrocarbons in the Antarctic marine environment: monitoring and background

The Antarctic marine ecosystem is proposed as an environment in which to monitor global hydrocarbon background levels. Hydrocarbon concentrations are probably uniform throughout the Southern Ocean and it is difficult to resolve low levels of contamination against this background. Indices for identifying anthropogenic hydrocarbons have been found to be ambiguous, but principal component analysis has successfully identified potentially polluted inshore waters. Hydrocarbon contamination in the Antarctic occurs only at a small number of coastal locations and is limited in extent. This paper is a review of the work on hydrocarbons in the Southern Ocean by the British Antarctic Survey in the Bransfield Strait and Scotia Sea regions. Analytical methods are discussed and a monitoring programme is developed

Hydrocarbons in the seawater and pelagic organisms of the Southern Ocean

The aliphatic and aromatic hydrocarbon content of seawater and a selection of marine pelagic organisms from the Bransfield Strait, Antarctica were evaluated. The patterns of the hydrocarbons found indicated that their origin was biogenic and there was no evidence for anthropogenic hydrocarbons in the Antarctic marine ecosystem. Hydrocarbons which are constituents of man made materials are present throughout the region but not in the patterns characteristic of anthropogenic origin. Recent reports of an even carbon number predominance in Antarctic marine organisms were not corroborated in this study. A number of biogenic compounds were investigated as suitable markers to monitor pathways of hydrocarbons in the Antarctic food chain. Specific compounds (probably branched chain alkenes) were found to occur at more than one trophic level. Polyaromatic hydrocarbons were present in all organisms but were undetectable in 44% of the seawater samples