Zueng-Sang Chen

The effects of chemical remediation treatments on the extractability and speciation of cadmium and lead in contaminated soils.

Two rural soils contaminated by cadmium (Cd) and lead (Pb) were used to evaluate the effect of different chemical treatments on changes in speciation and extractability of Cd and Pb, and in phytoavailability to wheat. Triplicates of seven chemical treatments were tested to compare and evaluate the remediation techniques for contaminated soils using pot experiments. Treatments applied were calcium carbonate, a high quantity of phosphate salt, hog composts, iron oxide, manganese oxide, zeolite, and unamended control. Wheat (Triticum aestivum) was planted in the different amended soils for a further one month to evaluate the effectiveness of treatments on uptake of Cd and Pb by the wheat shoots. Results indicated that addition of calcium carbonate, manganese oxide, or zeolite reduces the extractability of Cd or Pb in both soils, and significantly reduce the uptake of Cd and Pb by wheat shoots. Changes in the extractability and metal sequential fractionations indicate that the exchangeable (or available) form of Cd and Pb in two soils can be transformed into unavailable forms after these amendments.

Relations of soil properties to topography and vegetation in a subtropical rain forest in southern Taiwan

Soil chemical properties for a subtropical rain forest in the Nanjenshan Reserve, southern Taiwan, were examined to determine soil-landscape and soil-vegetation relationships. Soil sampling sites were separated into four groups based on landscape features and exposure to the prevailing northeasterly monsoon winds. Corresponding vegetation types were delimited along the first DCA axis. The forest showed a drastic change both in structure and floristic composition along the wind-stress gradient. Redundancy analysis (RDA) showed that both topographic variables and vegetation types were needed to explain the variation in soil data. Soil properties that differed significantly among landforms were pH, available N, CEC, exchangeable Al, K, Ca and Mg. Levels of pH, exchangeable Ca and Mg increased in a downslope direction, and exchangeable Al tended to be higher in the upper slope soils. These trends pointed to the importance of slope processes in redistribution of soil minerals. The main differences in soil properties attributed to the influence of the occupying vegetation were apparently aspect dependent. The contents of available N, exchangeable K, and CEC in the 0–40 cm depth of soils under windward low-stature (mostly sclerophyllous) forest were consistently lower compared to those under the leeward forest. For a given catena, however, soil variability associated with vegetation differences seemed to be confounded by the slope processes.

Digestion Methods for Total Heavy Metals in Sediments and Soils

The objectives of this study were to analyze the total contents of Cd, Cr, Cu, Ni, Pb, and Zn in the freshwater sediments and the arable and non-arable soils of Taiwan, and to compare the different digestion methods for their determination. Two hundred and thirty-nine freshwater sediments were collected from the Fei-Tsui Reservoir Watershed (FTRW) in northern Taiwan. Forty-two surface (0–15 cm) and subsurface (15–30 cm) soil samples were likewise collected from 21 representative arable soils derived from various parent materials and with varying weathered degrees in different regions of Taiwan. In addition, one hundred and ninety-four non-arable soils were collected from the different forest regions, industrial parks, resident areas, and commercial areas. Several digestion methods including the aquaregia and different combinations of concentrated acids (HClO4, HNO3, H2SO4, or HF) were compared. All samples were digested both by the aqua regia method and the Baker and Amacher method for Cd, Cr, Cu, Ni, Pb, and Zn. The Reisenauer method was used for Cr and the Burau method for Pb further. The results indicate that the best digestion methods to analyze the total contents of heavy metals in the sediments and soils were recommended as follows: the Baker and Amacher method for Cd, Cr,Cu, Ni, and Zn; the Reisenauer method for Cr, but for simplicity the Baker and Amacher method is also recommended as the flexible method for the total analysis of Cr; the aqua regia method for Cu, Ni, and Zn; and the Burau method for Pb.

Remediation techniques and heavy metal uptake by different rice varieties in metal-contaminated soils of Taiwan: New aspects for food safety regulation and sustainable agriculture

Abstract Rice is one of the most important staple foods worldwide. Soil contamination with heavy metals and food safety problems occur in many countries as a result of numerous human activities, particularly wastewater and solid waste disposal. This review paper provides a schematic summary of heavy metals in identification processes, transport in soil to different rice varieties, and soil remediation strategies and techniques surrounding the agro-environmental impact in paddy soils based on a description of Taiwan’s experiences and database. In terms of the soil control standard, heavy metals including As, Cd, Cr, Cu, Hg, Ni, Pb and Zn are regulated by the Soil and Ground ater Pollution Remediation Act of Taiwan. Owing to the heavy metal source from wastewater along irrigation systems, heavy metals not only accumulate in the surface soil (0–30 cm), but are also highly distributed at the main entrance of irrigation water into individual paddy fields. Moreover, sediments in the irrigation canal have to be dredged and the irrigation system needs to be isolated from the discharge system of wastewater to maintain soil quality. Cadmium in rice grains accumulates more significantly in Indica varieties than in Japonica varieties, and this accumulation exceeds the food quality standard. The best well-performing metal uptake models have been developed to predict Cd levels in rice grains for Indica and Japonica varieties using soil bioavailable Cd and Zn concentrations extracted by 0.01 mol L−1 CaCl2. Soil remediation techniques, including turnover and dilution, in situ stabilization by chemical amendments and phytoremediation, have been tested and recommended in Taiwan. Although the high background levels of As, Cr and Ni, which were higher the soil control standard in some paddy soils, are derived from andesite and serpentinites in Taiwan, rice quality and yield were not adversely affected by these metals when labile concentrations were very low. Overall, it is necessary to identify the bioavailability of heavy metals in different soil types from specific case studies to provide reliable parameters for health-based risk assessments and to further achieve the goal of food safety and sustainable agriculture.

Health risk-based assessment and management of heavy metals-contaminated soil sites in Taiwan.

Risk-based assessment is a way to evaluate the potential hazards of contaminated sites and is based on considering linkages between pollution sources, pathways, and receptors. These linkages can be broken by source reduction, pathway management, and modifying exposure of the receptors. In Taiwan, the Soil and Groundwater Pollution Remediation Act (SGWPR Act) uses one target regulation to evaluate the contamination status of soil and groundwater pollution. More than 600 sites contaminated with heavy metals (HMs) have been remediated and the costs of this process are always high. Besides using soil remediation techniques to remove contaminants from these sites, the selection of possible remediation methods to obtain rapid risk reduction is permissible and of increasing interest. This paper discusses previous soil remediation techniques applied to different sites in Taiwan and also clarified the differences of risk assessment before and after soil remediation obtained by applying different risk assessment models. This paper also includes many case studies on: (1) food safety risk assessment for brown rice growing in a HMs-contaminated site; (2) a tiered approach to health risk assessment for a contaminated site; (3) risk assessment for phytoremediation techniques applied in HMs-contaminated sites; and (4) soil remediation cost analysis for contaminated sites in Taiwan.

Cadmium and lead contamination of soils near plastic stabilizing materials producing plants in Northern Taiwan

The Cd and Pb contamination in paddy soils and rice plants of northern Taiwan was caused by the stabilizing materials for plastics produced from two chemical plants. The content of Cd in the paddy soils, brown rice, surface water, and sediments on the polluted area (about 100 ha) are 0.22 to 1,486, 0.51 to 7.94, 0.01 to 50.0, 134 to 4,700 μg g−1, respectively. The content of Pb in the paddy soils, brown rice, surface water, and sediments on the polluted area are 6.3 to 12,740,0.10 to 59.27, 0.12 to 3.59, and 23 to 44,427 μg g−1, respectively. Cadmium predominantly existed in the exchangeable and organic fractions in the polluted Udipsamment or Paleudult soils. Almost equal content (25 to 30% of total) of Pb existed in exchangeable, residual, and free oxides fractions in the polluted Udipsamment soils. A higher content of Pb existed in the residual fraction (48% of total) than that of the other soil fractions in the polluted Paleudult soils. Only trace amounts of Cd and Pb was absorbed by the brown rice. Correlation between concentration of Cd (or Pb) in the brown rice and contents of Cd (or Pb) in the polluted soils were not significant.

USING A SOIL QUALITY INDEX TO ASSESS THE EFFECTS OF APPLYING SWINE MANURE COMPOST ON SOIL QUALITY UNDER A CROP ROTATION SYSTEM IN TAIWAN

Soil quality indices (SQI) have been proposed in recent years as tools for assessing soil management practice effects on soil quality. In this paper, we report the result of our 4-year study on the use of a SQI to assess the effects of applying swine manure compost on soil quality. Cabbage (Brassica camperstris L.) and maize (Zea mays L.) were grown in rotation in plots applied with low, medium, and high rates of swine manure compost while the control received only chemical fertilizers. Selected soil physical, chemical, and biological properties (bulk density, aggregate stability, organic carbon content, soil pH, available N, P, and K, extractable Cu and Zn, and microbial biomass), all of which were identified as possible soil quality indicators, were monitored at regular intervals. Tissues of harvested crops were analyzed for Cu and Zn concentrations because they were anticipated to increase due to the high amounts of the metals in the manure compost. A SQI model was derived based on Mausbach and Seybolds research and on our soil database and research experience in Taiwan. Data from our manure application experiment were used to calculate the SQI values for the different treatments. Results revealed that application of swine manure compost improved the soil quality of surface soil as indicated by increased values of soil quality indicators, SQI, and yields of the crops. In addition, Cu and Zn levels in the soil and in the crop tissues did not increase to harmful levels. Thus, it seems that the SQI was an effective tool to assess the effects of swine manure compost application on soil quality. The soil indicators we found effective included the monitored properties except for bulk density. All of these soil properties were significantly increased by manure compost application. Long-term application of 40-60 tons ha−1 year−1 of manure compost may improve the soil quality and increase the yield of the crops without polluting the soil and crops with Cu and Zn.

Lead Contamination around a Kindergarten near a Battery Recycling Plant

Lead poisoning has been noticed for more than a thousand years. Increased lead absorption and/or impaired neurobehavioral function among children who lived nearby lead smelters were reported in many different countries. In November of 1987, a worker from a lead battery recycling smelter suffered from anemia and bilateral weakness of his extremities. He was diagnosed as lead poisoning at the National Taiwan University Hospital (NTUH). A subsequent epidemiological survey of the workers from this recycling smelter showed that 31 out of 64 who came for a medical examination suffered from lead poisoning. Since there was a kindergarten next to the factory, we performed this study to determine whether there was an increased lead absorption among children of the exposed kindergarten and its association with the extent of air and soil pollution in the surrounding area. 12 refs., 1 fig., 4 tabs.

Trait‐mediated effects of environmental filtering on tree community dynamics

Summary 1. Individual performance is a function of an individual’s traits and its environment. This function, known as an environmental filter, varies in space and affects community composition. However, filters are poorly characterized because dispersal patterns can obscure environmental effects, and few studies utilize longitudinal data linking individual performance to environment. 2. We model the effects of environmental filters on demographic rates of nearly all tree species (99) in a 25-ha subtropical rain forest plot. We develop a hierarchical Bayesian model of environmental filtering, drawing inspiration from classic studies of intraspecific natural selection. We characterize the specific environmental gradients and trait axes most important in filtering of demographic rates across species. 3. We found that stronger filtering along a given trait axis corresponded to less spatial variation in the value of favoured traits. 4. Environmental gradients associated with filtering were different for growth versus survivorship. 5. Species maximum height was under the strongest filtering for growth, with shorter species favoured on convex ridges. Shorter stature species may be favoured on ridges because trees on ridges experience higher wind damage and lower soil moisture. 6. Wood density filtering had the strongest effects on survival. Steep slopes and high available P in the soil favoured species with low-density wood. Such sites may be favourable for fast-growing species that exploit resource-rich environments. 7. Synthesis: We characterized trait-mediated environmental filters that may underlie spatial niche differentiation and life-history trade-offs, which can promote species coexistence. Filtering along trait axes with the strongest effects on local community composition, that is, traits with the strongest filtering, may necessarily have a weaker potential to promote species coexistence across the plot. The weak spatial variation in filters with strong effects on demography may result from long-term processes affecting the species pool that favour habitat generalist strategies.

Carbon and nitrogen mineralization of sewage sludge compost in soils with a different initial pH

Abstract Soil properties may affect the decomposition of added organic materials and inorganic nitrogen (N) production in agricultural soils. Three soils, Potu (Pu), Sankengtzu (Sk) and Erhlin (Eh) soils, mixed with sewage sludge compost (SSC) at application rates of 0 (control), 25, 75 and 150 Mg ha−1 were selected from Taiwan for incubation for 112 days. The aim of the present study was to examine the effects of SSC application rates on the carbon decomposition rate, N transformation and pH changes in three soils with different initial soil pH values (4.8–7.7). The results indicated that the highest peaks of the CO2 evolution rate occurred after 3 days of incubation, for all treatments. The Pu soil (pH 4.8) had a relatively low rate of CO2 evolution, total amounts of CO2 evolution and percentage of added organic C loss, all of which resulted from inhibition of microbial activity under low pH. For the Pu and Sk soils, the concentration of NH4 +-N reached its peak after 7–14 days of incubation, which indicated that ammonification might have occurred in the two soils with low initial pH values. NO3 −-N rapidly accumulated in the first 7 days of incubation in the Eh soil (pH 7.7). The direction and extent of the soil pH changes were influenced by the N in the SSC and the initial soil pH. Ammonification of organic N in the SSC caused the soil pH to increase, whereas nitrification of mineralized N caused the soil pH to decline. Consequently, the initial soil pH greatly affected the rate of carbon decomposition, ammonification and nitrification of SSC.