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In regions with high livestock densities, the usage of antibiotics and metals for veterinary purposes or as growth promoters poses a risk in manured soils. We investigated to which degree the concentrations and depth distributions of Cu, Zn, Cr and As could be used as a tracer to discover contaminations with sulfonamides, tetracyclines and fluoroquinolones. Besides, we estimated the potential vertical translocation of antibiotics and compared the results to measured data. In the peri-urban region of Beijing, China, soil was sampled from agricultural fields and a dry riverbed contaminated by organic waste disposal. The antibiotic concentrations reached 110 μg kg(-1) sulfamethazine, 111 μg kg(-1) chlortetracycline and 62 μg kg(-1) enrofloxacin in the topsoil of agricultural fields. Intriguingly, total concentrations of Cu, Zn, Cr and As were smaller than 65, 130, 36 and 10 mg kg(-1) in surface soil, respectively, therewith fulfilling Chinese quality standards. Correlations between sulfamethazine concentrations and Cu or Zn suggest that in regions with high manure applications, one might use the frequently existing monitoring data for metals to identify potential pollution hotspots for antibiotics in topsoils. In the subsoils, we found sulfamethazine down to ≥2 m depth on agricultural sites and down to ≥4 m depth in the riverbed. As no translocation of metals was observed, subsoil antibiotic contamination could not be predicted from metal data. Nevertheless, sulfonamide stocks in the subsoil could be estimated with an accuracy of 35-200 % from fertilisation data and potential leaching rates. While this may not be sufficient for precise prediction of antibiotic exposure, it may very well be useful for the pre-identification of risk hotspots for subsequent in-depth assessment studies.

An in-depth understanding of nutrient management variability on the regional scale is urgently required due to rapid changes in cropping patterns and farmers' resource use in peri-urban areas of China. The soil surface nitrogen (N) balances of cereal, orchard and vegetable systems were studied over a 2-year period on smallholder fields in a representative peri-urban area of Beijing. Positive soil surface N balances were obtained across all three cropping systems. The mean annual N surplus of the vegetable system was 1,575 kg N ha -1 year -1 , or approximately 3 times the corresponding values in the cereal (531 kg N ha -1 year -1 ) and orchard systems (519 kg N ha -1 year -1 ). In the vegetable system, animal manure (1,443 kg N ha -1 year -1 on average) was the major source of N input (65 % of the total N input) and the factor with strongest impact on the N surplus. In the cereal system, however, about 74 % of the total N input originated from mineral fertilizer application which was the major contributor to the N surplus, while in the orchard system, the N surplus was strongly and positively correlated with both mineral fertilizer and animal manure applications. Furthermore, within each cropping system, N fertilization, crop yields and N balances showed large variations among different smallholder fields, especially in orchard and vegetable systems. This study highlights that differences in farming practices within or among cropping systems should be taken into account when calculating nutrient balances and designing strategies of integrated nutrient management on a regional scale.

Ammonia (NH 3 ) volatilization is an important N loss pathway in intensive agriculture of the North China Plain (NCP). Simulation models can help to assess complex N and water processes of agricultural soil-crop systems. Four variations (Var) of a sub-module for the deterministic, process-based HERMES model were implemented ranging from simple empirical functions (Var 3 and 4) to process-oriented approaches (Var 1 and 2) including the main processes of NH 3 volatilization, urea hydrolysis, nitrification from ammonium-based N fertilizer, and changes in soil solution pH. Ammonia volatilization, plant growth, and changes in ammonium and nitrate pools in the soil over several winter wheat-summer maize double-crop rotations at three locations in the NCP were simulated. Results were calibrated with two data sets (Dongbeiwang 1, Shunyi) and validated using two data sets (Dongbeiwang 2, Quzhou). They showed that the ammonia volatilization sub-module of the HERMES model worked well under the climatic and soil conditions of N China. Although the simpler equations, Var 3 and 4, showed lower deviations to observed volatilization across all sites and treatments with a mean absolute error (MAE) of 1.8 and 1.4 in % of applied N, respectively, compared to process-oriented approaches, Var 1 and 2, with a MAE of 2.2 and 1.9 in % of applied N, respectively. Environmental conditions were reflected better by the process-oriented approaches. Generally, simulation results were satisfying but simulated changes in topsoil pH need further verification with measurements.

A further increasing demand for animal products is anticipated owing to the growing population, rapid urbanization and improvement of living standards in China. This is leading to the development of large鄄scale livestock husbandry in peri鄄urban areas at an unprecedented rate. However, the rapid development of intensive animal production has resulted in greatly negative effects on the environment. Linking cropping and animal production systems is very important to realize the improvement of nutrient use efficiency and reduction of resource use. Consequently, a systematic research on " crop鄄livestock冶 production systems is urgently required to provide a scientific basis for reducing nutrient losses in China.In this study, three types of " crop鄄livestock冶 systems in a village typical for the peri鄄urban area of Beijing were selected. The first type was an " intensive pig farm冶 , which included pig breeding and crop production; the second type was so鄄called " ecological feeding gardens冶 consisting of 160 small pig holders; the third one was a " single cropping region冶 which had no animal production. The characteristics of nitrogen ( N) flows in these three systems were analyzed using the