Soil-plant-animal transfer models to improve soil protection guidelines: a case study from Portugal

Food chain models are essential tools to assess risks of soil contamination in view of product quality including fodder crops and animal products. Here we link soil to plant transfer (SPT) models for potentially toxic elements (PTEs) including As, Ba, Cd, Co, Cu, Hg, Ni, Pb, Sb, U and Zn with models describing accumulation in animal organs. Current EU standards for food products and acceptable daily intake levels (ADI) for humans were used as critical limits. The combined model is used to assess the impact of soil contamination on animal health, product quality and human health using data from 100 arable fields. Results indicate that 42 existing arable fields near industrial and mining sites are unsuitable for animal grazing in view of food safety due to elevated intake of Cd, Cu, Hg and Pb by cows and sheep. At 10 sites daily intake levels of As by cows exceeded threshold concentrations regarding the quality of animal products.The food chain model also was used inversely to derive soil threshold concentrations in view of EU fodder standards. Calculated threshold levels in soil for As, Cd, Cu, Pb, Hg and Zn appear to be in line with those proposed or used in other EU countries. As such the approach applied here can form a conceptual basis for a more harmonized risk assessment strategy regarding the protection of animal and human health.     

重金属污染土壤的修复方法及其在几类典型土壤修复中的应用

文中首先阐述了重金属污染土壤的途径与特点。介绍了当前几类主要的重金属污染土壤修复方法:物理化学方法、植物修复法、微生物修复法、动物修复法等的技术要点,详述了各自的技术特点及机理,并对它们的修复效能、环境友好性等进行了比较。从土壤的特性出发,区分出了3种典型的遭受重金属污染的土壤:农业土壤、城市土壤、矿区土壤,并从国内外最新的重金属污染修复实践中选取了适合各自土壤类型的修复方法进行了重金属污染土壤的治理探讨。最后,对土壤重金属污染修复技术的发展进行了展望。     

pH值对土壤吸附铜的影响分析

随着社会经济的不断进步,土壤中重金属污染问题日趋严峻,土壤中重金属污染已经受到政府相关部门和一些研究人员的高度重视。本文运用化学分析的方法研究了土壤对金属铜的吸附作用。研究土壤吸附铜的速率的方法是根据所做实验的数据进而绘制吸附量与时间之间的变化曲线,通过所得到的曲线斜率来探讨吸附动力学过程。通过实验分析我们得知:pH对土壤吸附铜的影响达到了显著水平,当其他的条件相同、土壤自身的pH增加时,土壤对铜的吸附量也随着增加,加入液pH为5.5时的吸附量显著高于pH为2.5的吸附量。表明土壤对铜的吸附作用受酸度影响较为明显,在酸度增加的情况下,土壤对铜的吸附降低,使得铜从土壤中解吸出来,进入水体对环境造成危害。因此,我们要提高预防酸雨等环境问题,防止酸雨使得土壤中重金属进入到水体。     

Reduced activity of alkaline phosphatase due to host–guest interactions with humic superstructures

Nuclear Magnetic Resonance (NMR) spectroscopy was applied to directly study the interactions between the alkaline phosphatase enzyme (AP) and two different humic acids from a volcanic soil (HA-V) and a Lignite deposit (HA-L). Addition of humic matter to enzyme solutions caused signals broadening in ¹H-NMR spectra, and progressive decrease and increase of enzyme relaxation (T₁ and T₂) and correlation (τ_C) times, respectively. Spectroscopic changes were explained with formation of ever larger weakly-bound humic–enzyme complexes, whose translational and rotational motion was increasingly restricted. NMR diffusion experiments also showed that the AP diffusive properties were progressively reduced with formation of large humic–enzyme complexes. The more hydrophobic HA-L affected spectral changes more than the more hydrophilic HA-V. ¹H-NMR spectra also showed the effect of progressively greater humic–enzyme complexes on the hydrolysis of an enzyme substrate, the 4-nitrophenyl phosphate disodium salt hexahydrate (p-NPP). While AP catalysis concomitantly decreased NMR signals of p-NPP and increased those of nitrophenol, addition of humic matter progressively and significantly slowed down the rate of change for these signals. In agreement with the observed spectral changes, the AP catalytic activity was more largely inhibited by HA-L than by HA-V. Contrary to previous studies, in which humic–enzyme interactions were only indirectly assumed from changes in spectrophotometric behavior of enzyme substrates, the direct measurements of AP behavior by NMR spectroscopy indicated that humic materials formed weakly-bound host–guest complexes with alkaline phosphatase, and the enzyme catalytic activity was thereby significantly inhibited. These results suggest that the role of extracellular enzymes in soils may be considerably reduced when they come in contact with organic matter dissolved in the soil solution.     

Characteristics of lead geochemistry and the mobility of Pb isotopes in the system of pedogenic rock–pedosphere–irrigated riverwater–cereal–atmosphere from the Yangtze River delta region,China

Knowledge of the characteristics of Pb and its isotopic transfer in different compartments is scant, especially for the mobility of Pb isotopes in the geochemical cycle. The present study characterizes differential Pb transport mechanism and the mobility of Pb isotopes in the pedogenic parent rock–pedosphere–irrigated riverwater–cereal–atmosphere system in the Yangtze River delta region, by determining Pb concentration and Pb isotopic ratios of pedogenic parent rocks, fluvial suspended particle matter, tillage soils, soil profiles, irrigated riverwater, fertilizer, Pb ore, cereal roots and grains. The results show that Pb isotopes in the geochemical cycle generally follow the equation of ²⁰⁸Pb/²⁰⁶Pb = −1.157 × ²⁰⁶Pb/²⁰⁷Pb + 3.46 (r² = 0.941). However, Pb isotopes have different mobility in different environmental matrixes. Whereas in the pedosphere, the heavier Pb (²⁰⁸Pb) usually shows stronger mobility relative to the lighter Pb, and is more likely to transfer into soil exchangeable Pb fraction and carbonates phase. The lighter Pb shows stronger transfer ability from soil to cereal grain via root compared to the heavier Pb. However, the cereal grains have lower ²⁰⁶Pb/²⁰⁷Pb and higher ²⁰⁸Pb/²⁰⁶Pb ratios than root and tillage soil, similar to the airborne Pb and anthropogenic Pb, implying that a considerable amount of Pb in cereal grains comes from the atmosphere. The estimate model shows that 16.7–52.6% (average: 33.5%) of Pb in rice grain is the airborne Pb.     

Nitrogen,Phosphorus, Carbon,and Suspended Solids Loads from Forest Clear-Cutting and Site Preparation: Long-Term Paired Catchment Studies from Eastern Finland

The long-term impacts of current forest management methods on surface water quality in Fennoscandia are largely unexplored. We studied the long-term effects of clear-cutting and site preparation on runoff and the export of total nitrogen (total N), total organic nitrogen (TON), ammonium (NH₄-N), nitrate (NO₃-N), total phosphorus (total P), phosphate (PO₄-P), total organic carbon, and suspended solids (SS) in three paired-catchments in Eastern Finland. Clear-cutting and soil preparation were carried out on 34 % (C34), 11 % (C11), and 8 % (C8) of the area of the treated catchments and wide buffer zones were left along the streams. Clear-cutting and soil preparation increased annual runoff and total N, TON, NO₃-N, PO₄-P, and SS loads, except for SS, only in C34. Runoff increased by 16 % and the annual exports of total N, TON, NO₃-N, and PO₄-P by 18, 12, 270, and 12 %, respectively, during the 14-year period after clear-cutting. SS export increased by 291 % in C34, 134 % in C11, and 16 % in C8 during the 14, 6, and 11-year periods after clear-cutting. In the C11 catchment, NO₃-N export decreased by 12 %. The results indicate that while current forest management practices can increase the export of N, P and SS from boreal catchments for many years (>10 years), the increases are only significant when the area of clear cutting exceeds 30 % of catchment area.     

Bioavailability and dissipation of fluridone under controlled conditions

Abstract

Bioavailability of fluridone, l‐methyl‐3‐phenyl‐5‐[3‐(trifluoromethyl) phenyl]‐4(1H)‐pyridinone, as affected by soil temperature, soil moisture regime, and duration of incubation was investigated in three soil types by grain sorghum (Sorghum bicolor [L.] Moench cv. Abu Sabien) chlorophyll bioassay. Initial loss of fluridone was rapid and dissipation followed first‐order kinetics under most of the incubation treatments investigated. Soil moisture, in general, had a greater impact than soil temperature on dissipation of fluridone. The herbicide dissipated faster at the fluctuating room temperature (18–24°C) than at the constant 10°C in Sonning sandy clay loam (O.M. = 1.2%) and Erl Wood sandy loam (O.M. = 2.5%) but not in Shropshire loamy peat (O.M. = 33%). In the two mineral soils, bioassay‐detectable residues from an initial rate of 1.00 μg/g were least (0.00 ‐ 0.10 μg/g) at 1/2 field capacity (FC) and greatest (0.16 ‐ 0.37 μg/g) at 1/4 FC, 400 days after treatment. At 10°C, the DT₅₀ values (days) at 1/4 FC and 1/2 FC were, respectively, 147 ± 16 and 69 ± 6 for Erl Wood soil, and 257 ± 28 and 51 ± 12 for Sonning soil. In Shropshire soil, concentrations of bioavailable fluridone were least at each bioassay date when soil moisture was maintained at FC, at both temperatures of incubation. At 10°C, herbicide concentrations in the organic soil from an initial rate of 10.00 μg/g were 0.95 and 4.69 μg/g, respectively, at FC and 1/4 FC.     

Variations annuelles de l'activite nitrifiante d'un sol evaluee au laboratoire

Abstract

The results of the experiment reported in this paper demonstrate the influence of the soil sampling date on soil nitrifying activity, estimated in the laboratory. Treatment with propamocarb leads to parallel and reduced variations of this activity.     

Book review

The Pesticide Manual ‐ A World Compendium, 8th Edition, C.R. Worthing, Editor and S.B. Walker, Assistant Editor, British Crop Protection Council, BCPC Publications Sales, Bear Farm, Binfield, Bracknell, Berkshire RG12 5QE, England. 1987, 1100 pp., UK £50; Overseas £56. ISBN 0–948404–01–9.     

Impact of repeated pesticide applications on the binding and release of methyl 14C-monocrotophos and U-ring labelled 14C-carbaryl to soil matrices under field conditions

The dissipation of (O-methyl-¹⁴C) monocrotophos and U-ring labelled ¹⁴C-carbaryl was monitored for over two years in absence and presence of other insecticides using in situ soil columns. The dissipation of ¹⁴C-monocrotophos from soil treated with methomyl and carbaryl showed a faster rate of downward movement than in a control column tagged with the labelled insecticide alone. The same trend was observed in experiments with ¹⁴C-carbaryl that dissipated more readily in soil treated with non-labelled monocrotophos and methomyl. In the presence of other insecticides the percentage of bound residues was generally lower than in control experiments. The bound residues at the top of the column are released at a low rate under conditions prevailing in the field. The overall time required for dissipation of 50% of monocrotophos and carbaryl (t₅₀) as estimated from control experiment was approximately 20 and 24 weeks, respectively. The data indicate that repeated applications of pesticides might enhance the release of ¹⁴C-bound residues.