Fractionation of heavy metals and distribution of organic carbon in two contaminated soils amended with humic acids

The effects of humic acids (HAs) extracted from two different organic materials on the distribution of heavy metals and on organic-C mineralisation in two contaminated soils were studied in incubation experiments. Humic acids isolated from a mature compost (HAC) and a commercial Spaghnum peat (HAP) were added to an acid soil (pH 3.4; 966 mg kg(-1) Zn and 9,229 mg kg(-1) Pb as main contaminants) and to a calcareous soil (pH 7.7; 2,602 mg kg(-1) Zn and 1,572 mg kg(-1) Pb as main contaminants) at a rate of 1.1g organic-C added per 100g soil. The mineralisation of organic-C was determined by the CO(2) released during the experiment. After 2, 8 and 28 weeks of incubation the heavy metals of the soils were fractionated by a sequential extraction procedure. After 28 weeks of incubation, the mineralisation of the organic-C added was rather low in the soils studied (<8% of TOC in the acid soil; <10% of TOC in the calcareous soil). Both humic acids caused significant Zn and Pb immobilisation (increased proportion of the residual fraction, extractable only with aqua regia) in the acid soil, while Cu and Fe were slightly mobilised (increased concentrations extractable with 0.1M CaCl(2) and/or 0.5M NaOH). In the calcareous soil there were lesser effects, and at the end of the experiment only the fraction mainly related to carbonates (EDTA-extractable) was significantly increased for Zn and decreased for Fe in the humic acids treated samples. However, HA-metal interactions provoked the flocculation of these substances, as suggested by the association of the humic acids with the sand fraction of the soil. These results indicate that humic acid-rich materials can be useful amendments for soil remediation involving stabilisation, although a concomitant slight mobilisation of Zn, Pb and Cu can be provoked in acid soils.     

Leaf litter dynamics and nitrous oxide emission in a Mediterranean riparian forest: implications for soil nitrogen dynamics

Mediterranean riparian zones can experience severe drought periods that lead to low soil moisture content, which dramatically affects their performance as nitrate removal systems. In the Mediterranean riparian zone of this study, we determined that N2O emission was practically nil. To understand the role of forest floor processes in nitrogen retention of a Mediterranean riparian area, we studied leaf litter dynamics of two tree species, London planetree [Platanus x acerifolia (Aiton) Willd.] and alder [Alnus glutinosa (L.) Gaertn.], for two years, along with soil nitrogen mineralization rates. Annual leaf litter fall equaled 562.6 +/- 10.1 (standard error) g dry wt. m(-2), 68% of which was planetree and 32% of which was alder. The temporal distribution of litterfall showed a two-peak annual cycle, one occurring in midsummer, the other in autumn. Planetree provided the major input of organic nitrogen to the forest floor, and the amount of planetree leaves remaining on the forest floor was equivalent to approximately four years of stock. Leaf litter decomposition was three times higher for alder (decay coefficient [k] = 1.13 yr(-1)) than for planetree (k = 0.365 yr(-1)). Mineralization rates showed a seasonal pattern, with the maximum rate in summer (1.92 mg N kg(-1) d(-1)). Although the forest floor was an important sink for nitrogen due to planetree leaf accumulation, 7.5% of this leaf litter was scoured to the streambed by wind. This loss was irrelevant for alder leaves. Due to the litter quality, the forest floor of this Mediterranean riparian forest acts as a nitrogen sink.     

Aerobic metabolic rates of swimming juvenile mako sharks, <Emphasis Type="Italic">Isurus oxyrinchus</Emphasis>

The shortfin mako shark, Isurus oxyrinchus, is a highly streamlined epipelagic predator that has several anatomical and physiological specializations hypothesized to increase aerobic swimming performance. A large swim-tunnel respirometer was used to measure oxygen consumption (MO₂) in juvenile mako sharks (swimming under controlled temperature and flow conditions) to test the hypothesis that the mako shark has an elevated maintenance metabolism when compared to other sharks of similar size swimming at the same water temperature. Specimen collections were conducted off the coast of southern California, USA (32.94°N and 117.37°W) in 2001-2002 at sea-surface temperatures of 16.0–21.0°C. Swimming MO₂ and tail beat frequency (TBF) were measured for nine mako sharks [77–107 cm in total length (TL) and 4.4 to 9.5 kg body mass] at speeds from 28 to 54 cm s⁻¹ (0.27–0.65 TL s⁻¹) and water temperatures of 16.5–19.5°C. Standard metabolic rate (SMR) was estimated from the extrapolation to 0-velocity of the linear regression through the LogMO₂ and swimming speed data. The estimated LogSMR (±SE) for the pooled data was 2.0937 ± 0.058 or 124 mg O₂ kg⁻¹ h⁻¹. The routine metabolic rate (RMR) calculated from seventeen MO₂ measurements from all specimens, at all test speeds was (mean ± SE) 344 ± 22 mg O₂ kg⁻¹h⁻¹ at 0.44 ± 0.03 TL s⁻¹. The maximum metabolic rate (MMR) measured for any one shark in this study was 541 mg O₂ kg⁻¹h⁻¹ at 54 cm s⁻¹ (0.65 TL s⁻¹). The mean (±SE) TBF for 39 observations of steady swimming at all test speeds was 1.00 ± 0.01 Hz, which agrees with field observations of 1.03 ± 0.03 Hz in four undisturbed free-swimming mako sharks observed during the same time period. These findings suggest that the estimate of SMR for juvenile makos is comparable to that recorded for other similar-sized, ram-ventilating shark species (when corrected for differences in experimental temperature). However, the mako RMR and MMR are apparently among the highest measured for any shark species.     

Marine aquaculture and bottlenose dolphins’ (<Emphasis Type="Italic">Tursiops truncatus</Emphasis>) social structure

In this study, we investigate association patterns of 249 bottlenose dolphin feeding groups off Sardinia Island (Italy) from January 2000–May 2007 and describe how their association behaviour is related to their response to food patches created by a marine fin fish farm. We also tested the hypothesis that dolphins have different social structures with different feeding activities: Associations should decrease during opportunistic feeding behaviours as it is easier to capture prey, and cooperation is not as necessary. Sixteen individually identified bottlenose dolphins were observed participating in both opportunistic and not opportunistic feeding activities, with a mean of 30 ± 8 times and 9.6 ± 1 times, respectively. Bottlenose dolphins show non-random social behaviour during feeding and this behaviour differs depending on their specific foraging activity. Dolphin associations during feeding can be divided into three categories: acquaintances, affiliates, and feeding associates. Association behaviour during fish farm feeding is consistent with our hypothesis that during opportunistic behaviours, benefits from cooperation decrease, as it is easier to capture prey. Group size homogeneity in both feeding activities demonstrates that the number of dolphins engaging in foraging is not necessarily related with cooperation levels. Moreover, an adult dolphin may prefer to associate with a specific individual, independent of the sex, who shares the same foraging priorities. This study is the first to show how aquaculture is not only directly affecting marine predators but could also indirectly affect their social structure and behaviour.     

The use of olive-mill waste compost to promote the plant vegetation cover in a trace-element-contaminated soil

The applicability of a mature compost as a soil amendment to promote the growth of native species for the phytorestoration of a mine-affected soil from a semi-arid area (SE Spain), contaminated with trace elements (As, Cd, Cu, Mn, Pb and Zn), was evaluated in a 2-year field experiment. The effects of an inorganic fertiliser were also determined for comparison. Bituminaria bituminosa was the selected native plant since it is a leguminous species adapted to the particular local pedoclimatic conditions. Compost addition increased total organic-C concentrations in soil with respect to the control and fertiliser treatments, maintained elevated available P concentrations throughout the duration of the experiment and stimulated soil microbial biomass, while trace elements extractability in the soil was rather low due to the calcareous nature of the soil and almost unaltered in the different treatments. Tissue concentrations of P and K in B. bituminosa increased after the addition of compost, associated with growth stimulation. Leaf Cu concentration was also increased by the amendments, although overall the trace elements concentrations can be considered non-toxic. In addition, the spontaneous colonisation of the plots by a total of 29 species of 15 different families at the end of the experiment produced a greater vegetation cover, especially in plots amended with compost. Therefore, the use of compost as a soil amendment appears to be useful for the promotion of a vegetation cover and the phytostabilisation of moderately contaminated soils under semi-arid conditions.     

Co-composting of distillery wastes with animal manures: carbon and nitrogen transformations in the evaluation of compost stability

The aim of this work was to study the viability of recycling the solid wastes generated by the winery and distillery industry by means of co-composting with animal manures, as well as to evaluate the quality of the composts obtained. Two piles, using exhausted grape marc and cattle manure or poultry manure, respectively (at ratios, on a fresh weight basis, of 70:30), were composted by the Rutgers static pile composting system. Throughout the composting process, a number of parameters were monitored, such as pH, electrical conductivity, organic matter, water-soluble carbon, water-soluble polyphenols, different forms of nitrogen (organic nitrogen, ammonium and nitrate) and humification indices (humification ratio, humification index, percentage of humic acid-like C, polymerisation ratio and cation exchange capacity), as well as the germination index. Organic matter losses followed first-order kinetics equation in both piles, the highest organic matter mineralisation rate being observed with exhausted grape marc and cow manure. On the other hand, the mixture with the lowest C/N ratio, using exhausted grape marc and poultry manure, showed the highest initial ammonium contents, probably due to the higher and more labile N content of poultry manure. The increase in the cation exchange capacity revealed the organic matter humification during composting. In contrast, other humification parameters, such as the humification ratio and the humification index, did not show the expected evolution and, thus, could not be used to assess compost maturity. Composting produced a degradation of the phytotoxic compounds, such as polyphenols, to give composts without a phytotoxic character. Therefore, composting can be considered as an efficient treatment to recycle this type of wastes, due to composts presented a stable and humified organic matter and without phytotoxic effects, which makes them suitable for their agronomic use.     

Ecological engineering with high diversity vegetation patches enhances bird activity and ecosystem services in Philippine rice fields

Regional Environmental Change - This study examines the potential for ecological engineering to enhance the beneficial ecosystem services provided by birds in tropical rice fields. Bird activities...     

Improvement of soil quality after "alperujo" compost application to two contaminated soils characterised by differing heavy metal solubility

Reclamation of trace element polluted soils often requires the improvement of the soil quality by using appropriate organic amendments. Low quality compost from municipal solid waste has been tested for reclamation of soils, but these materials can provide high amounts of heavy metals. Therefore, a high-quality compost, with low levels of heavy metals, produced from the main by-product of the Spanish olive oil extraction industry ("alperujo") was evaluated for remediation of soils affected by a pyritic mine sludge. Two contaminated soils were selected from the same area: they were characterised by differing pH values (4.6 and 7.3) and total metal concentrations, which greatly affected the fractionation of the metals. Compost was applied to soil at two rates (equivalent to 48 and 72 Tm ha(-1)) and compared with an inorganic fertiliser treatment. Compost acted as an available nutrient source (C, N and P) and showed a low mineralisation rate, suggesting a slow release of nutrients and thus favouring long term soil fertility. In addition, the liming effect of the compost led to a significant reduction of toxicity for soil microorganisms in the acidic soil and immobilisation of soil heavy metals (especially Mn and Zn), resulting in a clear increase in both soil microbial biomass and nitrification. Such positive effects were clearly greater than those provoked by the mineral fertiliser even at the lowest compost application rate, which indicates that this type of compost can be very useful for bioremediation programmes (reclamation and revegetation of polluted soils) based on phytostabilisation strategies.     

Effect of initial material bulk density and easily-degraded organic matter content on temperature changes during composting of cucumber stalk

To inactivate the potentially pathogenic microorganisms and safely utilize vegetable waste compost, ultra-high temperatures( 70°C) should be maintained during the composting without having an inhibitory effect on maturity. This study investigated the influence of bulk density(part 1) and easily-degraded organic matter content(EDOMC, part 2) on temperature evolution during vegetable waste composting: Part 1: corn straw with different particle sizes was used to achieve different bulk densities in the composting material(BD1–BD3); Part 2: partial or total substitution of the corn straw by corn starch was carried out to obtain different EDOMC(ED1–ED4). The composting experiments were conducted in a labscale reactor(1.75 kg material) and lasted for 30 d. Temperature and CO2 emission were recorded daily, and the organic matter, lignocellulose, microbial activity, germination index(GI) and C/N of the samples were measured at different stages. The highest temperature(65.7°C) in part 1 occurred in the treatment with the bulk density of 0.35 g/cm3, which also had the longest thermophilic phase. Bulk density was found to seriously influence the utilization efficiency of O2 and heat transfer through materials, rather than heat production from organic matter degradation. In experiment part 2, the highest temperature was obtained with EDOMC of 45%(71.4°C). Therefore, adjusting the bulk density to 0.35 g/cm3 and the easily-degraded organic matter content of the initial material to 45% was the best combination for reaching temperatures above 70°C during composting, with no inhibitory effect on the maturity of the compost product.