Biological productivity in many ocean regions is controlled by the availability of the nutrient phosphorus. In the Mediterranean Sea, aerosol deposition is a key source of phosphorus and understanding its composition is critical for determining its potential bioavailability. Aerosol phosphorus was investigated in European and North African air masses using phosphorus near-edge X-ray fluorescence spectroscopy (P-NEXFS). These air masses are the main source of aerosol deposition to the Mediterranean Sea. We show that European aerosols are a significant source of soluble phosphorus to the Mediterranean Sea. European aerosols deliver on average 3.5 times more soluble phosphorus than North African aerosols and furthermore are dominated by organic phosphorus compounds. The ultimate source of organic phosphorus does not stem from common primary emission sources. Rather, phosphorus associated with bacteria best explains the presence of organic phosphorus in Mediterranean aerosols.

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P‐NEXFS analysis of aerosol phosphorus delivered to the Mediterranean Sea

Nutrient analytical services laboratory standard operating procedures

Matrix-bound phosphine (PH3), a new form of phosphorus, was found in sediment of Jiaozhou Bay in December 2001. Concentration and distribution of PH3 in different layers of sediment with different stations were analyzed. The results show that PH3 concentrations are various with different layers and different stations. PH3 concentrations in the bottom layer of sediment (20-30 cm) are usually higher than those in the surface layer (0-4 cm). The highest PH3 concentration in our investigation reaches 685 ng/kg (dry), which is much higher than those in terrestrial paddy soil, marsh and landfill that have been reported up to now. The correlation analysis indicates that there is no apparent correlation between the concentrations of PH3 and inorganic phosphorus in sediment. However, the correlation between the concentrations of phosphine and organic phosphorus in the bottom layer of sediment is remarkable (R-2=0.83). It is mainly considered that PH3 in sediment of Jiaozhou Bay is produced from the decomposition of organic phosphorus in the anaerobic condition, and so PH3 concentrations are related to organic phosphorus concentration and anaerobic environment in sediment. The discovery of PH3 in sediment will give people some new ideas on the mechanisms of phosphorus supplement and biogeochemical cycle in Jiaozhou Bay.

Matrix-bound phosphine: A new form of phosphorus found in sediment of Jiaozhou Bay

. Oxygen minimum zones (OMZs) that impinge on continental margins favor the release of phosphorus (P) from the sediments to the water column, enhancing primary productivity and the maintenance or expansion of low-oxygen waters. A comprehensive field program in the Peruvian OMZ was undertaken to identify the sources of benthic P at six stations, including the analysis of particles from the water column, surface sediments, and pore fluids, as well as in situ benthic flux measurements. A major fraction of solid-phase P was bound as particulate inorganic P (PIP) both in the water column and in sediments. Sedimentary PIP increased with depth in the sediment at the expense of particulate organic P (POP). The ratio of particulate organic carbon (POC) to POP exceeded the Redfield ratio both in the water column (202 ± 29) and in surface sediments (303 ± 77). However, the POC to total particulate P (TPP = POP + PIP) ratio was close to Redfield in the water column (103 ± 9) and in sediment samples (102 ± 15). This suggests that the relative burial efficiencies of POC and TPP are similar under low-oxygen conditions and that the sediments underlying the anoxic waters on the Peru margin are not depleted in P compared to Redfield. Benthic fluxes of dissolved P were extremely high (up to 1.04 ± 0.31 mmol m−2 d−1), however, showing that a lack of oxygen promotes the intensified release of dissolved P from sediments, whilst preserving the POC / TPP burial ratio. Benthic dissolved P fluxes were always higher than the TPP rain rate to the seabed, which is proposed to be caused by transient P release by bacterial mats that had stored P during previous periods when bottom waters were less reducing. At one station located at the lower rim of the OMZ, dissolved P was taken up by the sediments, indicating ongoing phosphorite formation. This is further supported by decreasing porewater phosphate concentrations with sediment depth, whereas solid-phase P concentrations were comparatively high.

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Benthic phosphorus cycling in the Peruvian oxygen minimum zone

Several sediment samples in Lake Burullus have been affected by the discharges of heavy metals through different drains. The study aimed to analyze the chemical speciation of these metals. In particular, the chemical forms of Cd, Cu, Fe, Mn, Pb and Zn in sediments collected in spring season were studied using a sequential chemical extraction method. In general, all the elements recorded highest concentrations in the area near the discharge point. The data indicated that, the sediments were under a wide variety of environmental conditions ranging from oxic to fully anoxic conditions. Owing a wide variety of grain sizes and organic matter, these metals showed the order of abundance: Fe > Mn > Zn > Cu > Cd > Pb. Significant correlations between iron with clay, organic carbon and manganese concentrations were calculated as (r=0.685, 0.581 and 0.610, P= 0.05), respectively. This gives an idea about association of iron and manganese as main compositions of clays. In the mean time, it showed insignificant relation with total carbonate and all phosphorus forms. The metal speciation characterizes the degree to which they are potentially labile or bioavailability. It gives different fraction ratios depending on binding and sediment origin.

	 

	Key words: Heavy metals, chemical speciation, sediments, Burullus, Lake.

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Heavy metal speciation and their accumulation in sediments of Lake Burullus, Egypt

A method for the determination of iodine in plants is described. This method involves destruction of organic matter by alkaline incineration and automated spectrophotometric determination of iodide based on the Sandell and Kolthoff's reaction. The mean recovery of 131I was 93.4% (S.D. = 3.19)). For replicate analyses of different plant material, the coefficient of variation is between 3 and 5%.

Bellanger

Papers

A semi-automated method for the determination of iodine in plants.