A study on the factors influencing nitrogen removal in waste water stabilization ponds was undertaken in an eight-pond series in Werribee, Australia. Nitrogen species including Kjeldahl nitrogen, total ammonia nitrogen, nitrite and nitrate were monitored monthly from March 1993 to January 1994. At the same time, pH, temperature, chlorophylla content and dissolved oxygen were also recorded. Highest nitrogen removal occurred during the period with highest levels of chlorophylla content and dissolved oxygen, but the rate of nitrogen removal was not related to temperature and pH. Enhanced photosynthetic activities resulting from an increased phytoplankton abundance due to prolonged detention time caused an increase in dissolved oxygen, and created an optimum condition for nitrification to occur. In this process, ammonia was oxidized to nitrite and nitrate which were subsequently reduced to elemental nitrogen. Apart from nitrification-denitrification which was the major nitrogen removal pathway in the study system, algal uptake of ammonium, nitrate and nitrite as nutrient sources also contributed to the nitrogen removal. The role of phytoplankton and zooplankton in the treatment process in waste stabilization ponds was discussed.

A ten year survey of water quality in 330 Massachusetts streams was conducted to examine the rate and pattern of recovery from acidification. Meta-analysis was used to combine the results of the 330 non-parametric trend tests into an overall test for trend in a variety of water quality variables including pH, acid neutralizing capacity (ANC), and major inorganic ions. Analysis of trends in the raw data indicates both pH and ANC are increasing. After detrending for variations in stream runoff, we estimate the streams are recovering from acidification at a rate of +0.021 pH units/year and +2.4μeq/L/year, for pH and ANC respectively. These trends appear to be related to declines in sulfate (−1.8μeq/L/year), while base cation trends were mixed. Meta-analysis reveals the trends are not always homogeneous between seasons or between sites.While it is commonly assumed that the low ANC systems are most ‘sensitive’ to changes in acid or base inputs, we found the greatest rates of change in ANC were associated with the high ANC systems. The greatest increases in pH were seen in the low ANC streams as expected. The results also suggest streams respond quickly to changes in precipitation inputs and stream monitoring networks may be valuable as an early detection technique for changes in environmental quality.

The effectiveness of ammonia stripping at different air flow rates (0, 1 and 5 L min⁻¹) and lime dosages (0 and 10 000 mg L⁻¹ calcium hydroxide) was investigated in aeration tanks in a laboratory as a pretreatment to remove ammoniacal-nitrogen and organic load (COD) in landfill leachate. Ammoniacal-nitrogen removal at 20 °C after one day was 70% for 0 L min⁻¹, 81% for 1 L min⁻¹ and 90% for 5 L min⁻¹ regardless of the origin of leachate. Ammonia loss was mainly due to desorption through water surface. The levels of phosphorus and COD were only reduced by lime precipitation, with 85% and 93% phosphorus removal and 24% and 47% COD removed for leachate from the Junk Bay Landfill (JB) and Gin Drinkers' Bay Landfill (GDB) respectively. The highly significant difference (P<0.05) of COD removal between JB and GDB might be due to the different age of the two landfills studied. Leachate quality and configuration of the treatment reactor were important factors affecting the efficiency of ammonia removal by stripping processes.

The Pb content in orchard soils at Mission Peninsula, Michigan was determined to assess the impact of historical lead arsenate applications. Soil samples at 72 sites located in five orchards were collected at depths of 2−, 20-, 50−, and 100 cm. Atomic absorption spectroscopy was used to quantify Pb levels (jig g⁻¹). Mean surface Pb levels at individual orchards ranged from <1–136 pg g⁻¹ and rapidly decreased with depth, to < 1-5 μg g⁻¹ at 100 cm. The impact of textural class and slope angle on Pb levels was also analyzed. Correlation coefficients linking Pb levels with textural class were weak, ranging from 0.21 to −0.07. Varying slope steepness and slope position within orchards failed to affect the spatial pattern of soil Pb.Soil Pb levels were also compared at 5 sites along local roads with varying levels of automobile traffic. Samples were collected 1 m from the roadside at the same depth intervals studied in orchards. Average daily traffic along the busiest roadsites ranged from 8200 to 16 000; these sites had Pb levels of 90–210 μg g⁻¹. Such locales had Pb levels similar to the more intensively sprayed orchards.

A new plastic-lined high-pressure squeezing device has been developed for the extraction of soil pore solutions. At a maximum pressure of 1100 kg cm⁻² the water recovery ranged between 30 and 55% of the total water content. Pressure dependent squeezing experiments showed a general increase in Si, Mn, Mg, Ca, K, Na, Al, Fe, Cd, and Zn concentrations with progressive pore water extraction and increasing pressure, indicating that micro pore solutes have the highest concentrations of solutes. Soil samples with moisture contents of more than about 15% generally provided enough water for major and trace element analyses. The data do not reveal any contamination of the pore fluids from the squeezing device. An advantage of this method is that the solution could be closely related to a specific soil horizon on a cm scale and also to the time of sampling. A further application of this squeezing method is the possibility of pressure dependent sequential squeezing to obtain fluids from different pore spaces.