Comparison of bacterial and algal utilization of orthophosphate in an estuarine environment

Bacterial utilization of orthophosphate in an estuarine environment has been differentiated from algal utilization by using flow-filters of 5.0, 1.2 and 0.45 m poresize. Examination by light microscopy showed that most of the bacterial population passed through a 5.0-m filter, whereas most algae were retained. In all experiments, bacterial and algal cell numbers and biomass were estimated. P-uptake by algae and bacteria was closely correlated with cell biomass. P-uptake by algae was high only in the summer months, whereas P-uptake by bacteria was high throughout the year. Neither algal nor bacterial P-uptake, however, was correlated with temperature or dissolved orthophosphate, total organic phosphate or total phosphate concentrations. Cell biomass of algae at a given time had a high correlation with dissolved organic phosphate levels in 2 weeks prior to sampling (r=0.830) and a low correlation in the 2 weeks following sampling (r=0.0005). Algal cell numbers had a high correlation with bacterial cell numbers (r=0.950). The biomass of algae and bacteria also had a high correlation (r=0.902). The rate of P-uptake from the water by algae and bacteria varied with season and with the species composition of the natural population.     

Nitrogen Trioxide: Key Intermediate in the Chemistry of Polluted Air?

It is proposed that peroxyacetyl nitrate and its homologues are formed in polluted air via hydrogen abstraction from the corresponding aldehyde by nitrogen trioxide, followed by (a relatively fast) combination of the resulting acyl radical with oxygen and NO₂. This mechanism provides a simple explanation for the formation of nitric acid, HNO3, as well. Nitrogen trioxide should be able to abstract hydrogen atoms from hydrocarbons, since the H-ONO₂ bond strength is about 100 kcal/mole.     

Kombinationswirkungen von Umweltchemikalien in der Ökotoxikologie

Ecosystems and biocoenoses are exposed to multiple mixtures of environmental pollutants, but the usual risk assessment of chemical toxicities is focussed only on the judgement of single substance toxicity. With the two biometrical models concentration-addition and independent action known from pharmacology and toxicology, a pragmatic way for the analysis of combined effects is possible using the experimental knowledge of single substance toxicity. A short introduction to the models is given and an appropriate experimental design for mixture toxicity analysis is outlined. The principal suitability of the concepts was verifed in two different bioassays (green alga; luminescent bacterium) with the analysis of binary and multiple mixture toxicities of environmental chemicals. In this paper we present the results obtained with the green algae bioassay. Congruent results from the bioluminescence inhibition assay can be found in Grimme (1998). The results obtained indicate that the toxicities of mixtures of chemicals can be studied experimentally, even at low concentrations of the individual components. Mixture toxicities were detected at low, statistically non-significantly acting concentrations of the single compounds. These results force one to take mixture toxicities into account when environmental standards are established.     

The sorption of Zectran on bottom sediments and peat moss

Abstract

A modified analytical method employed to determine the insecticide Zectran in natural waters frequently has resulted in erroneous data. The errors have been attributed to interferences from particulate matter in these waters. In order to evaluate analytical interferences due to sorption of Zectran on particu‐lates, a series of experiments was performed using bottom sediments and a peat moss in contact with aqueous solutions of Zectran at a pH value of 6.0 and 20°C.

Isotherm studies confirmed that Zectran sorption occurs in a direct relation to the amount of chemically oxidizable carbon present in the bottom sediments or peat moss. However, the extent of sorption was limited, which suggested that particulates may not be the primary interference in the modified analytical method.